Aces High Bulletin Board
General Forums => Aircraft and Vehicles => Topic started by: 1K3 on May 23, 2007, 04:35:05 AM
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In the radial department, nothing beats the Pratt & Whitney series. Not even the BMW radials can beat P&W.
When it comes to Inline liquid-cooled engine, which company made THE best inline engine
[ EDIT: Jumo is added to the list ]
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Rolls Royce (for versatility) Spits, Hurri's,Lancs, Mossies, Mustangs,Cromwell Tank, Comet Tank, Centurian Tank I think some Brit MTB,S AND MGB,s Merlin, Griffin and Packard Builds under Liscence.
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Allisons win the "best sound" award. ;)
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I would judge an engine by its power to weight ratio.
Does anyone have this info on engines?
1K3.. why do you consider the P&W to be the best radial?
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Originally posted by Virage
I would judge an engine by its power to weight ratio.
And reliability, fuel efficiency, in war ease of consruction, level of vibration, performance under diferent climatic conditions and altitudes, versatility, ease of maintainance, length of time in production, ease of up grade and pottential for development plus wheter it represented a significant change in technology etc lets assume
:D
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Hi,
difficult to compare engines without to consider the used fule, altitude to be used in, reliability and how(easy/difficult)) to maintain it.
I guess the Jumo 213E + MW50 + GM1 will be one of the best regarding the performence.
Otherwise RR and DB did produce(constructed) the best engines in large numbers. Sometimes DB sometimes RR was in front, at the end the better fuel probably gave RR the lead.
The winner always depends to the available fuel and additional injections, but also to the airframe and altitude to be used in. The Jumo213 didnt fit into the 109, same like the Kilmov 106 didnt fit into the smal russian fighters, or at least the needed cooling systems dont found place.
It also was difficult to place MW50 and GM1 into a 109, while the superchared planes could fight in high and low alt.
On the other hand the 109 construction did allow the mechianics to maintain the engine rather easy.
Imho, same like with the planes, there is no exact decission possible.
Greetings,
Knegel
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Jumo 213 for performance?
I vote Napier's Sabre. Nothing beats overkill :t
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Err, best engine in conditions where they were used or just engine design? Does this include only the engine design or the charging solution too?
The DB certainly had a great supercharger. The turbo had its advantages, too.
http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19930081638_1993081638.pdf
Does anybody know why Germans made their V-engines inverted? Better view from cockpit? Any disadvantages e.g. bigger oil consumption etc?
Do i remember correctly that DB had a solid block but RR could be taken into quite small pieces?
-C+
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Originally posted by leitwolf
Allisons win the "best sound" award. ;)
Nahhhhh, can't be the 109 with the super-charger whine.
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Oh yes, it can! And two of them sounds twice as good.
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i vote merlin for overall!:aok
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Charge, it might have just been to accomodate the cowl guns in the airframes of the time. Keep in mind the 109s started with only MGs in the cowling. Wing guns were added later. Then removed later. Then added later again. The nose guns always stayed.
Could be as simple as that (or, could not be).
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Originally posted by leitwolf
Jumo 213 for performance?
I vote Napier's Sabre. Nothing beats overkill :t
DING DING!!!
Nothing quite like taking two 12 cyl engines and bolting them together :D
Also getting the sleeve valve system to work was nice :)
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Originally posted by Charge
Does anybody know why Germans made their V-engines inverted? Better view from cockpit? Any disadvantages e.g. bigger oil consumption etc?
-C+
Afaik due to the lower(centered) propellor position, the thrust line goes right through the COG, this minimize the interferenz drag and allow to create a airframe with smaler front surface(smaler drag again), while the pilots forward sight remain good.
Somewhere i did read that it also was more easy to maintain the engine, cause all important parts could get reached from below and the side.
I never did read about disadvantages.
Greetings,
Knegel
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DB605 :aok
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My vote is for the JUMO.... Just because they looked sooooo cool.... The Dora9/ta152, or the UHU, or the Arrow, they had the coolest looking engine cowlings
I know pretty superficial huh....
OG
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Oh yeah, Just a little trivia!!! The beemer radials were a development of the Wright Cyclone... Ernst Udet bought them in the US before the war.... The French and Ruskies had their versions too...
OG
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Originally posted by 1K3
In the radial department, nothing beats the Pratt & Whitney series. Not even the BMW radials can beat P&W.
:rofl Oh boy. Okee-dokee.
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Originally posted by Masherbrum
:rofl Oh boy. Okee-dokee.
The P&W that powered the P-47s, F4Us, F6F, are tough and it's got not dead spots at all altitudes (except at extreme high altitudes)
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In the category of inline engines nothing comes close to the Merlin; by far the best developed and only one of these to see some civil use.
In category of radials the Hercules comes close the R-2800; infact in the terms of reliability (particularly TBO) and fuel consumption, it's better than R-2800. However, the R-2800 saw much wider use during war as well as large civil use.
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Originally posted by leitwolf
Allisons win the "best sound" award. ;)
DB 605 I beleive it is takes the cake. You ever hear that startup-scream? It will wake the dead and scare small children to death. THATS my kind of engine.
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Originally posted by gripen
In the category of inline engines nothing comes close to the Merlin; by far the best developed and only one of these to see some civil use.
In category of radials the Hercules comes close the R-2800; infact in the terms of reliability (particularly TBO) and fuel consumption, it's better than R-2800. However, the R-2800 saw much wider use during war as well as large civil use.
The Merlin???
Even the Griffon did count as more advanced, the main advantage over the DB´s was rather the fuel than the stage of development.
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The Merlin never lived long enough to win a Gold race at Reno, until someone figured out how to put Allison connecting rods in one. Merlins have too many problems for me to rate them #1. From a mechanic and engine builder's point of view anyway.
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Best? RR Griffon ;)
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Plenty of geek awards to be handed out here..
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Originally posted by Knegel
The Merlin???
Even the Griffon did count as more advanced, the main advantage over the DB´s was rather the fuel than the stage of development.
Well, the question was about the best, not about the most advanced. The Merlin was there when needed and giving very good performance. And regarding the reliability, the other inlines are far behind; even the civil version of the two stage Merlin were rated for 2000hp while the military versions of the Allisons and DBs were really hard pushed at that output.
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Which was the "best" engine is very subjective; however I nominate the DB 603. It saw service with several LW bombers and fighters from 1943 to the end of the war. Some notable planes that used the 603 were: the Me 410, He 219, Ta 152C, Do 335. The (very) late-war DB 603N with two-stage supercharger developed 2800 hp using C3 fuel (~130 octane). With B4 (~87 octane) it developed 2000 hp.
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Originally posted by 1K3
The P&W that powered the P-47s, F4Us, F6F, are tough and it's got not dead spots at all altitudes (except at extreme high altitudes)
The DB603 was better, but we all have "our own opinions". There is no point in a discussion like this, because of that.
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Originally posted by gripen
Well, the question was about the best, not about the most advanced. The Merlin was there when needed and giving very good performance. And regarding the reliability, the other inlines are far behind; even the civil version of the two stage Merlin were rated for 2000hp while the military versions of the Allisons and DBs were really hard pushed at that output.
No, the Allison was NOT hard pushed at 2000 HP. Not at all.
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So why weren't they all at 2000 hp+?
And at altitude, why bother putting a Merlin into a P51?
How about a 2000 hp P-40 instead of escorting them with Hurricanes?
(okay, the last one was a tad trollish, but it has a foot in it)
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As for the Griffon, AFAIK the final version ended with some 2400 hp, pushing the Supermarine Spiteful over the 490 mph limit, with full military load.
Weights some 900 kg's though (2000 lbs roughly)
As for reliability, the Avro Shackleton ran on Griffons, but overhauls were frequent. Well, not compared to WW2 lifetime, - top overhaul for some 400 hours, but that happens fast on long tours, and the aircraft did indeed go on very long tours.
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The USAAF downrated the Allison in the P-38L by nearly 200 HP per engine. The P-38K engines made over 1825HP, and they'd do it at nearly 30,000 feet. Try that with a Merlin.
Why wasn't the non turbocharged Allison making 2000HP, and making decent HP at high altitude? Because the USAAF and the War Production Board never allowed General Motors to develop and install a two speed two stage supercharger on the Allison. The ONLY advantage a Merlin has over an Allison is the two speed two stage supercharger. It is NOT the engine itself.
The Merlin wasn't making 2000HP, but it was close, and it sure as Hell wasn't doing it at high altitudes. By 29,000 feet, the Merlin in a P-51D isn't making ONE thousand horsepower, never mind making double that.
NO piston engine with a crank driven supercharger, even WITH a two speed two stage supercharger, makes sea level power at high altitude.
In the as produced form, the Allison has a stronger crankshaft, stronger connecting rods, a better oiling system, a larger capacity margin in the cooling system, and stronger cylinder heads.
The last piston engine powered unlimited hydroplane to win a race was Allison powered. The last competitive aircraft piston engine powered pulling tractors are Allison powered. And for AT LEAST the first 30 YEARS after the war, no Merlin could last long enough at Reno to win a competitive Gold race, and they only became a contender after one of the engine builders put Allison connecting rods in one. Even today, the most common failure in Reno is a Merlin eating the bearings.
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Originally posted by Captain Virgil Hilts
The USAAF downrated the Allison in the P-38L by nearly 200 HP per engine. The P-38K engines made over 1825HP, and they'd do it at nearly 30,000 feet. Try that with a Merlin.
This has been discused here several times, the Merlin utilizes exhaust thrust which in practice balances the situation. And the P-38K never saw service.
Besides, 2000hp Merlins saw quite wide service during war and were type tested for over 2600hp. The Allisons maxed around 1800hp during war (very limited use in the P-63).
Originally posted by Captain Virgil Hilts
The last piston engine powered unlimited hydroplane to win a race was Allison powered. The last competitive aircraft piston engine powered pulling tractors are Allison powered. And for AT LEAST the first 30 YEARS after the war, no Merlin could last long enough at Reno to win a competitive Gold race, and they only became a contender after one of the engine builders put Allison connecting rods in one. Even today, the most common failure in Reno is a Merlin eating the bearings.
The race use has pretty much nothing to do with practical service use and in the service the Merlin proved to be more powerfull and more reliable than the Allison.
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Whats the engine in the tempest?
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Originally posted by gripen
The race use has pretty much nothing to do with practical service use and in the service the Merlin proved to be more powerfull and more reliable than the Allison.
I'd have to disagree.
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Ok, let's disagree, no problem.
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There's no way that the exhaust thrust from a Merlin makes up for the fact that it is 700HP short of a turbocharged Allison at 29,000 feet. They're exhaust headers, they're not rocket boosters. Hell, the radiator installation with the boundary layer scoop on the Mustang comes closer to adding enough thrust to make up some of the difference. At 26,000 feet, a Merlin in a P-51D is down to 1100 HP or so, and at 29,000 feet, it's down to just barely 900HP. The "-30" Allison in the P-38L is still making 1725HP at 26,500 feet. And more than that at the Lockheed/Allison ratings of 80" and 3200RPM.
Exhaust thrust can offer SOME measurable gains in speed, in fact, Kelly Johnson wanted to do it with the P-38, but the increased back pressure at the turbocharger cost more HP and speed was decreased. But the exhaust thrust from an engine making 900HP or so won't make up for being short 700HP or more.
The speed of the Mustang had more to do with light weight, reduced parasitic drag, and a drastically more efficient propeller than JUST the Merlin. The Merlin only improved performance at altitude, and in fact, down low, the Allison was more than a match.
It should also be noted that the Allison developed for the P-82 Twin Mustang, with higher compression and a 12 counterweight crankshaft for higher RPM performance and durability is nearly as powerful as a turbocharged Allison from a P-38, without the turbocharger, and extremely durable. And it still didn't have a really good centrifugal supercharger (again, the USAAF and the War Production Board are the reason behind the problem) even then.
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Originally posted by gripen
Besides, 2000hp Merlins saw quite wide service during war and were type tested for over 2600hp. The Allisons maxed around 1800hp during war (very limited use in the P-63).
The race use has pretty much nothing to do with practical service use and in the service the Merlin proved to be more powerfull and more reliable than the Allison.
Actually, the use in racing has EVERYTHING to do with the quality and superiority of the engine design. The Allison had far more room to grow in power without sacrificing reliability. The Allison was rated by the manufacturer at well over 1800HP, the USAAF down rated it. Further, the same basic engine was used later with compound turbosupercharging to reliably produce around 3000HP. The only problem with that engine was the exhaust temperature was too great for the typical aircraft exhaust system. But the engine itself tested beautifully.
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Those Rolls-Royce licensed built Allisons were great!!!
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Originally posted by Wes14
Whats the engine in the tempest?
Napier Sabre, just google it...amazing engine :)
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Virgil Hilts: Please please explain to me P51 had to be powered by a merlin to get alive above 15k.
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"Actually, the use in racing has EVERYTHING to do with the quality and superiority of the engine design. The Allison had far more room to grow in power without sacrificing reliability. The Allison was rated by the manufacturer at well over 1800HP, the USAAF down rated it. Further, the same basic engine was used later with compound turbosupercharging to reliably produce around 3000HP. The only problem with that engine was the exhaust temperature was too great for the typical aircraft exhaust system. But the engine itself tested beautifully."
A factory made juiced-up Spitfire was making 3000 hp in 1939 and making nice and fast tours between places, like England-France. The engine ran beautifully, but the whole thing was perhaps not practical for military ops.
Anyway, if a starting power of an engine in development is 1800hp as easy-go (Merlin at 1030?), as well as the alt performance being spectacular, why on earth would that not be THE main mount of all western allied inline engined aircraft?????????????????????????????
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Originally posted by Furball
Those Rolls-Royce licensed built Allisons were great!!!
hehe, so were those RR license-built Packards :D
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Originally posted by Captain Virgil Hilts
Actually, the use in racing has EVERYTHING to do with the quality and superiority of the engine design. The Allison had far more room to grow in power without sacrificing reliability.
Well, you see the problem in that logic; historically the Allison had problems to do 1600hp reliably while the Merlin did quite well 2000hp. That was the situation at spring 1944.
Besides, the Allison design went towards the concepts used in the Merlin like lower compression ratio and mechanical supercharger etc. In practice the developement of the Allison was couple years behind the Merlin during war.
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Originally posted by Captain Virgil Hilts
There's no way that the exhaust thrust from a Merlin makes up for the fact that it is 700HP short of a turbocharged Allison at 29,000 feet.
I made a calculation based on 1943 USAF test here (http://www.wwiiaircraftperformance.org/mustang/p51b-12093.html). Assuming 80% prop efficiency and 250lbs exhaust thrust at FTH 29800ft, the equivalent hp increase is about 370hp ie without exhaust thrust the plane would have required about 1640hp instead the 1275hp to reach same performance. Note that this is far above the critical altitude of the P-38J/L.
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Originally posted by Angus
Virgil Hilts: Please please explain to me P51 had to be powered by a merlin to get alive above 15k.
Once again, in simple, easy to grasp terms. The Allison, as required by the USAAF and the War Production Board, was produced with a single speed supercharger. Without the ability to increase the speed of the supercharger, there was not enough boost available to make horsepower at higher altitudes.
The Merlin had a two speed supercharger. At low altitudes it ran at a low speed, and at higher altitudes it ran at a higher speed to produce more boost in the thinner air at higher altitudes. Around 20,000 feet or so, the Merlin supercharger went from low speed to high speed.
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So, The R4360 would blow them all away anyway.
So there ya go!!!!
OG
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Originally posted by gripen
Well, you see the problem in that logic; historically the Allison had problems to do 1600hp reliably while the Merlin did quite well 2000hp. That was the situation at spring 1944.
Besides, the Allison design went towards the concepts used in the Merlin like lower compression ratio and mechanical supercharger etc. In practice the developement of the Allison was couple years behind the Merlin during war.
No, the Allison, with the correct fuel, and properly tuned, could easily produce in excess of 1800HP reliably. In spring of 1944, actually winter 43-44, the P-38J had well over 1600HP at critical altitude. That was the under rated HP from the first of the J model P-38 as delivered. In late spring and early summer of 1944, the P-38L arrived, rated at 1725HP.
The Allison was designed to run with 6.6:1 compression and with a centrifugal supercharger from the beginning. It didn't "go towards Merlin concepts". It had the low static compression from the very beginning. It also had dual overhead cams, 4 valves per cylinder, pent roof combustion chambers, dual spark plugs, forged pistons, roller cams, and roller rocker arms.
And NO, the Merlin was NOT that reliable. The first P-51's delivered to the 8th AF fighter groups were notorious for cracked heads, that dumped coolant out. As soon as the head cracked and the coolant left, you had 30 seconds of power, after which it seized. They were also at least as bad if not worse for fouling spark plugs as the Allison ever was. Sorry, but the vaunted Merlin power and reliability was as big a myth as the Mustang being the plane that beat the Luftwaffe. It just ain't so. The new Merlin equipped P-51B had severe teething issues when it was introduced. Now, this is the same Merlin that you speak of, that was NOT a new engine, but rather the same engine that had already been in the war since 1939. So four years later, it was STILL cracking heads, fouling plugs, and seizing crankshafts, and on a regular basis. At least according to the guys who flew them.
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In 1940 Packard Motors of Detroit began building the two-speed Merlin V-1650-1 (Merlin 28) under license from Rolls Royce. This engine had 1170 horsepower in high blower with a critical altitude of 21,000 feet. Lockheed ran a study comparing a Merlin XX powered Lightning with a standard V-1710 powered variant. The reported speed difference was over 25 mph, favoring the Merlin powered airplane. Climb performance was similar to the Allison powered machine.
Another Merlin vs. Allison comparison in 1942 involved the V-1710-89/91 Allisons (engines used in standard P-38J) and the Packard V-1650-3 two-speed, two-stage Merlin used in the P-51B/C. Utilizing Military Power speed was almost identical.
Yet another study in 1944 compared V-1710s producing 1725 bhp and "advanced" Merlins using "special" fuel and producing 2000 bhp (no altitude specified). The Merlin powered version could supposedly attain 468 mph at 30,000 feet, which was considerably better than the Allison powered version.
These studies were all conducted by Lockheed and exhibit a certain amount of optimism in regard to maximum speed for both types, but the consensus clearly shows better performance with the Merlin powered Lightning.
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Originally posted by Captain Virgil Hilts
Actually, the use in racing has EVERYTHING to do with the quality and superiority of the engine design. The Allison had far more room to grow in power without sacrificing reliability. The Allison was rated by the manufacturer at well over 1800HP, the USAAF down rated it. Further, the same basic engine was used later with compound turbosupercharging to reliably produce around 3000HP. The only problem with that engine was the exhaust temperature was too great for the typical aircraft exhaust system. But the engine itself tested beautifully.
Should mention the Allison V-1710 Turbocompound engine.
An attempt to recover some of this energy resulted in the turbocompound V1710 shown at the bottom of the page. It was identified as the V1710‑E22 by Allison, and as the V1710‑127 by the government. A turbocompound engine collects all of the exhaust gasses and runs them through a turbine, with all of the power generated going back into the crankshaft and ultimately to the propeller. It differs from a turbosupercharged engine, which uses exhaust gas energy to increase the pressure of incoming air. Work on this engine began in about 1944 and continued until 1946, when Allison asked that it be cancelled because turbine engines had greater promise. It was the first successful turbocompound engine, and probably one of only three to ever be built. This engine was designed to power the XP63H, which, as it turned out, never flew. The V1710‑E22 had a military rating of 2320 hp, and a War Emergency Rating with water/alcohol injection of 3090 hp.
(http://www.enginehistory.org/Allison/V1710TC.jpg)
http://www.enginehistory.org/v1710tc.htm
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Woo-hoo:
"Sorry, but the vaunted Merlin power and reliability was as big a myth as the Mustang being the plane that beat the Luftwaffe. It just ain't so. The new Merlin equipped P-51B had severe teething issues when it was introduced. Now, this is the same Merlin that you speak of, that was NOT a new engine, but rather the same engine that had already been in the war since 1939. So four years later, it was STILL cracking heads, fouling plugs, and seizing crankshafts, and on a regular basis. At least according to the guys who flew them."
And the Allisons flew just very nice? Of course many more Merlins failed, after all the hours in service were many times as many. Probably many more than any inline engine.
More of reliability of the engine 4 years in service? Well, the power was pushed up from 1000 hp to close 2000, with 1700 as an easy go, and those are figures of front-line fighters in big numbers.
What of the reliability of the Allison powering the P38 in the ETO? Problems because of the atmosphere AFAIK.
BTW, a P38 smacked into a hill close to where I live. Engine failiure leading to fire. A guy dug up the engine blocks and keeps them in a secret place, or so it's told.
And:
"At least according to the guys who flew them."
Well, who? I knew one who clocked 2+ TOD's in WW2 (combat) as well as instruction, without as much as a hic-up.
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Originally posted by Wolfala
Should mention the Allison V-1710 Turbocompound engine.
**Snip text and sexy engine pic**
Got any info on how much that beast weighed? Already sounds like it'd blow a turboshaft out of the water (Pratt PT-6 being the one in mind) on power alone.
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Originally posted by Captain Virgil Hilts
No, the Allison, with the correct fuel, and properly tuned, could easily produce in excess of 1800HP reliably. In spring of 1944, actually winter 43-44, the P-38J had well over 1600HP at critical altitude. That was the under rated HP from the first of the J model P-38 as delivered. In late spring and early summer of 1944, the P-38L arrived, rated at 1725HP.
Hm... There has been several theories why the Allisons were so unreliable at high altitudes. Anyway, high altitude problems were not limited in ETO, there were similar issues with the F-5s in the MTO (see America's 100000) so fuel theory can be rejected quite easily (there were no Js before summer). IIRC Tony Levier blew something like 30 Allisons during summer 1944 when trying to solve the problem so the problem was there and apparently never fully solved because P-38s were not tried again in the high altitude operations.
Originally posted by Captain Virgil Hilts
The Allison was designed to run with 6.6:1 compression and with a centrifugal supercharger from the beginning. It didn't "go towards Merlin concepts".
Actually it did in the G-series Allisons, see the "Vee's for Victory".
Originally posted by Captain Virgil Hilts
And NO, the Merlin was NOT that reliable. The first P-51's delivered to the 8th AF fighter groups were notorious for cracked heads, that dumped coolant out. As soon as the head cracked and the coolant left, you had 30 seconds of power, after which it seized. They were also at least as bad if not worse for fouling spark plugs as the Allison ever was. Sorry, but the vaunted Merlin power and reliability was as big a myth as the Mustang being the plane that beat the Luftwaffe. It just ain't so. The new Merlin equipped P-51B had severe teething issues when it was introduced. Now, this is the same Merlin that you speak of, that was NOT a new engine, but rather the same engine that had already been in the war since 1939. So four years later, it was STILL cracking heads, fouling plugs, and seizing crankshafts, and on a regular basis. At least according to the guys who flew them.
There were problems in the beginning; the P-51B was rushed in the service due desperate need. However, the problems were soon solved, IIRC one P-38/P-51 pilot once said: "I have landed P-38 one engine running several times but I have allways landed P-51 one engine running".
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Originally posted by gripen
Well, the question was about the best, not about the most advanced. The Merlin was there when needed and giving very good performance. And regarding the reliability, the other inlines are far behind; even the civil version of the two stage Merlin were rated for 2000hp while the military versions of the Allisons and DBs were really hard pushed at that output.
So was the DB601 and DB605, despite the less good fuel, the DB engeeners always found a way to get to a very similar stage of power.
To say the "Merlin was by far the best developed" engine is not true, at least much overdone.
1st the DB601A was ahead of the MerlinII, then the brits got better fuel and the Merlin had a WEP advantage, then the germans did use better fuel and the DB601N was ahead again, then the Brits got a new engine, then the DB601E and so on.
Only in mid 1942- mid 44 there was a advantage for the merlin, cause the germans gave all the good fuel to the BMW´s. Later, with MW50 and GM1 the DB605 was on paar again, while the fuel still was the main problem(next to the typical late war production problems).
The DB603 and Jumo213 also was very good designs.
There simply is no best engine, there are airframes where the engines fit in and turn to be very good and there are tactical situations where the engine need to fit.
The high alt performence of the allied engines wasnt much worth while a tactical airwar in MTO and russia, while the great Ash82 and BMW801 was bad while interceps in high alt.
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Originally posted by gripen
Hm... There has been several theories why the Allisons were so unreliable at high altitudes. Anyway, high altitude problems were not limited in ETO, there were similar issues with the F-5s in the MTO (see America's 100000) so fuel theory can be rejected quite easily (there were no Js before summer). IIRC Tony Levier blew something like 30 Allisons during summer 1944 when trying to solve the problem so the problem was there and apparently never fully solved because P-38s were not tried again in the high altitude operations.
Actually it did in the G-series Allisons, see the "Vee's for Victory".
There were problems in the beginning; the P-51B was rushed in the service due desperate need. However, the problems were soon solved, IIRC one P-38/P-51 pilot once said: "I have landed P-38 one engine running several times but I have allways landed P-51 one engine running".
I'm not aware of Levier blowing 30 engines, and especially not during the summer of 1944. I have no idea where you got that. In fact, after Levier came to England, the engine failures were greatly reduced, as was fuel consumption. Funny you should bring up Levier, in fact. It was Levier who solved the problems with burned valves, runaway turbochargers, excessive fuel consumption, and performance at high altitude. Suggest you read "The Lockheed P-38 Lightning" by Warren Bodie, and the other version by Steve Pace. They have Levier's reports on operational issues from his tour of the 8th AF, and the causes thereof. The causes thereof happen to be: incorrect fuel mixture setting at cruise, incorrect prop pitch settings at cruise, improper adjustment of the turbocharger oil regulators and waste gate, and irregular fuel quality. After proper instruction of both the pilots and crews, pilots who had been returning from missions on one engine and with 10 gallons of fuel were returning with two healthy engines and as much as 100 gallons of fuel.
A perfect example would be Lt. Loenhert's P-38, "California Cutie" which flew some 300hours of combat on one pair of Allisons. The ones that came with the plane.
After Levier's tour, the P-38's DID in fact fly full high altitude missions in escort of the bombers. The P-51 DID NOT replace the P-38, or even equal it in numbers, until APRIL 1944. Only AFTER the P-51 reached numerical parity with the P-38 were the P-38 units completely relieved of escort duty, and released to ground attack. And the P-38 was in fact the first U.S. fighter over Berlin, and in numbers. BOTH the 20th AND the 55th made it to Berlin before a P-51 unit even came close.
The ORIGINAL V-1710 Allison had around 6:1 compression. They varied between 6:1 and 6.6:1 more or less. It was designed to be supercharged. It was ALWAYS supercharged, and had low static compression. The F series in the P-38 had 6.5:1 compression.
I hate to break this to you, but the P-38J-1-Lo entered service with the 8th AF in NOVEMBER of 1943. The P-38J, in all versions from J-1-Lo to J-25-Lo served with the 8th AF from November 1943 to July 1944. The P-38L entered service in July 1944, although most, but not all squadrons switched to the P-51 instead. Some squadrons in the ETO did not switch.
The Merlin was already supposedly a proven high altitude engine, supposedly superior to the Allison, and in service over Europe for over 3 years before an Allison equipped P-38 even arrived. But in late 43 and early 44, more than 3 YEARS after they entered combat service, they evidently weren't so superior or proven, since they blew up in P-51's on a regular basis.
Oh, and the Allison equipped P-38's were rushed into service before the P-51's, with FAR less operational training and indoctrination, with FAR fewer experienced combat pilots and officers. The 20th and 55th were rushed into service after "Black Thursday", a lot sooner than the P-51 units, and in a bigger hurry. So that excuse doesn't wash for the P-51. They had more time to go operational, and the supposedly superior engine had already BEEN in operation at high altitude over Europe for 3 years.
Yes, many P-38's returned on one engine. But P-51's that lost one engine NEVER returned at all.
If you want to quote pilots, I'll quote one for you, and give you his name. Captain Arthur Heiden, flight leader, 79th FS, 20th FG.
From Captain Heiden, who flew BOTh the P-38 and the P-51:
"P-38 units from the moment of going on initial operational status were committed to MAX EFFORT. No two ways about it. No time to shake things out, to discover your problems. You got there and zap, you were in up to your eyeballs. This meant that everything flyable went and everything that still had wings would be made flyable. No matter what. This in effect was the same as demanding, by direct order, that everyone and everything must have, immediately if not sooner, 100 percent combat capabilities. Like Casey Jones, the pressure was all the way up without any margins whatsoever."
"Despite these revolting developments, the pilots of the 8th knew that the P-38 could outturn, outclimb, outrun and outfight anybody's airplane in the air so they set about rectifying their problems."
And:
"Nothing, to these pilots, after the hard winter of 1943-44 could be more beautiful than a P-38L outrolling and tailgating a German fighter straight down, following a spin or split-S or whatever gyration a startled, panicked and doomed German might attempt to initiate. You just couldn't get away from the P-38L. Whatever the German could do, the American in the P-38L could do better."
On the P-51:
"The P-51 was a new airplane and we were eager to fly it and were happy with it. It was so easy and comfortable to fly. The P-38 had kept us on our toes and constantly busy--far more critical to fly. You never could relax with it. We were disappointed with the 51's rate of climb and concerned with the reverse stick, especially if fuel was in the fuselage tank, the rash of rough engines from fouled plugs, and cracked heads which dumped the coolant. With the 38 you could be at altitude before landfall over the continent, but with the 51 you still had a lot of climbing yet to do. The 38 was an interceptor and if both engines (were healthy), you could outclimb any other airplane, and that's what wins dog fights. When you are in a dog fight below tree tops, it is way more comfortable in a 38 with its power and stall characteristics and, for that matter at any altitude."
Finally:
"Feb 44 we went back to Schwienfurt with acceptable loses. March 3rd the 20th & 55thFGs went to Berlin--Bombers were recalled. March, April, and May brought vicious battles, often with heavy loses. However, Germany were throwing their valuable flight instructors and 100hr students in to the battle. The Luftwaffe was at last starting to die."
"The 8th was, at last, being flooded with Mustangs and well trained pilots. The Mustang was a delight to fly, easier to maintain cheaper to build and train pilots for, and had long legs. In those respects you can rightfully call it better, but it could not do anything better than a P-38J-25 or L. Just remember who took the war to the enemy and held on under inconceivable odds. Enough of the crap."
Note The above quotes from Captain Arthur Heiden, from Dr. Carlo Kopp's article "Der Gabelschwanz Tuefel", at C. C. Jordan's "Planes and Pilot's of World War II".
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Gunther Rall flew captured allied aircraft in mock-up fights against students. He was fascinated by the Merlin, both the sound, and power as well as the engine showing little wear (with som 90 hrs on the overhaul clock) while the DB was loosing power very shortly.
That P51 he flew had a very tight engine he said, while his 109 did not, - in only 10 hours you could turn the prop easily.
Could be a material issue rather than design though, - after all it was war and 1944...
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Originally posted by Captain Virgil Hilts
I'm not aware of Levier blowing 30 engines, and especially not during the summer of 1944.
I don't remember where I got that number, however he certainly experienced several "Allison time Bombs" during his tour in Britain which ended in the beginning of June. He tried to solve problem there and the testing continued in the states as well.
Originally posted by Captain Virgil Hilts
I have no idea where you got that. In fact, after Levier came to England, the engine failures were greatly reduced, as was fuel consumption.
It's quite logical that the problems were reduced when the air temperature increased in spring and the P-38 started fly more low altitude missions.
Originally posted by Captain Virgil Hilts
The P-51 DID NOT replace the P-38, or even equal it in numbers, until APRIL 1944.
Actually it did, all P-38 units of the 8th AF converted to the P-51. And even in MTO and pacific the P-51 took over high altitude missions.
Originally posted by Captain Virgil Hilts
The ORIGINAL V-1710 Allison had around 6:1 compression. They varied between 6:1 and 6.6:1 more or less. It was designed to be supercharged. It was ALWAYS supercharged, and had low static compression. The F series in the P-38 had 6.5:1 compression.
Please read the "Vee's for Victory"; the G-series V-1710 had CR 6.00:1 ie same as in the Merlin.
Originally posted by Captain Virgil Hilts
I hate to break this to you, but the P-38J-1-Lo entered service with the 8th AF in NOVEMBER of 1943. The P-38J, in all versions from J-1-Lo to J-25-Lo served with the 8th AF from November 1943 to July 1944.
Please read my post, there were no Js (in the MTO) before summer 1944, however, there were J based F-5s in the MTO at winter 43/44 which experienced similar problems as Js in the ETO so local fuel can't explain the problems.
Originally posted by Captain Virgil Hilts
The Merlin was already supposedly a proven high altitude engine, supposedly superior to the Allison, and in service over Europe for over 3 years before an Allison equipped P-38 even arrived. But in late 43 and early 44, more than 3 YEARS after they entered combat service, they evidently weren't so superior or proven, since they blew up in P-51's on a regular basis.
Well, once introduced to the service the P-51 with Merlin quickly replaced the P-38.
Originally posted by Captain Virgil Hilts
Yes, many P-38's returned on one engine. But P-51's that lost one engine NEVER returned at all.
Well, that underlines the reliability problem of the Allison; it would have been removed from service if it had been in the single engined fighter. However, the reliability of the Merlin was certainly acceptable because it eventually replaced the P-38.
It can be said that the 8th AF found a quick fix to the high altitude problems of the P-38 (Allison was just one of the problems), the fix was called the P-51.
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Originally posted by Knegel
So was the DB601 and DB605, despite the less good fuel, the DB engeeners always found a way to get to a very similar stage of power.
Hm... The DBs had restrictions most of time and often problems to reach claimed performance also the TBO was short. Infact the DB603 was used mostly for the twins due to continous problems. There were similar problems wth the Jumos as well.
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"The DBs had restrictions most of time and often problems to reach claimed performance also the TBO was short."
Because of material problems/shortages. Technically the engine could deliver comparable power given proper fuel and plugs.
-C+
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Originally posted by gripen
Hm... The DBs had restrictions most of time and often problems to reach claimed performance also the TBO was short. Infact the DB603 was used mostly for the twins due to continous problems. There were similar problems wth the Jumos as well.
Give it up.
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I thought the DB603 was used for the twins because it was too big for a 109 :confused:
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Originally posted by gripen
I don't remember where I got that number, however he certainly experienced several "Allison time Bombs" during his tour in Britain which ended in the beginning of June. He tried to solve problem there and the testing continued in the states as well.
It's quite logical that the problems were reduced when the air temperature increased in spring and the P-38 started fly more low altitude missions.
Actually it did, all P-38 units of the 8th AF converted to the P-51. And even in MTO and pacific the P-51 took over high altitude missions.
Please read the "Vee's for Victory"; the G-series V-1710 had CR 6.00:1 ie same as in the Merlin.
Please read my post, there were no Js (in the MTO) before summer 1944, however, there were J based F-5s in the MTO at winter 43/44 which experienced similar problems as Js in the ETO so local fuel can't explain the problems.
Well, once introduced to the service the P-51 with Merlin quickly replaced the P-38.
Well, that underlines the reliability problem of the Allison; it would have been removed from service if it had been in the single engined fighter. However, the reliability of the Merlin was certainly acceptable because it eventually replaced the P-38.
It can be said that the 8th AF found a quick fix to the high altitude problems of the P-38 (Allison was just one of the problems), the fix was called the P-51.
Nothing I read in Levier's report mentions him blowing several Allisons. I'll look again.
Again, read the report from Levier where solutions to the problems were found, and note that the P-38 continued to fly high altitude missions right up until they were replaced in July of 1944. Look at the unit numbers. The 20th and 55th flew escort missions until April or May, and they flew the P-38J until JULY 1944. Never said local fuel was the ONLY problem, just that it WAS a problem.
Again, read the unit histories, the 20th AND the 55th fighter groups received the P-38J-1-Lo in NOVEMBER 1943. So you are absolutely WRONG, the P-38J DID fly in the 8th AF fighter groups in 1943 and 1944.
By the way, the temperature at 25,000 to 30,000 feet varies little, regardless of the season of the year or the location on the globe. It's about as cold at 30,000 feet over the Bismark sea, or Guadalcanal, in July, as it is over France and Germany in January.
You obviously do not grasp the concept of compression ratio. The difference between 6.0:1 compression and 6.6:1 compression is not even worth measuring, and makes no real difference at all. Production tolerances will create a difference of as much as 0.1:1. The difference between 6.0:1 and 6.6:1 will not make enough difference in the amount of boost that can be run to make it necessary to adjust either the boost, the cam timing, or the ignition timing. And I should know, I worked on Allison pulling tractor engines, and I still build racing engines for a living to this day, including supercharged and turbosupercharged engines.
Yes, the 55th and 20th found a quick fix. It was Tony Levier and the Lockheed manuals. Not to mention Jimmy Doolittle's relationship with Shell Aerofuel.
Speaking of Doolittle, he flew over Normandy on 6, June, 1944 in a P-38J, while several units of the 20th flew escort and cover missions over the incasion, and they too were in Lockheed P-38 Lightning fighters.
At this point, I'm finished here. You do not understand compression ratio, you ignore the facts that the P-38 remained in service with the 20th and 55th until June, and that the P-38J was in service in the ETO from November 1943 as a frontline escort fighter. All of which are commonly known facts, seen the the records of the units. Think what you will, between holding the history books in hand and reading them, and corresponding with over a dozen P-38 pilots with the 20th and 55th fighter groups, not to mention a few from the 5th AF in the Pacific, I'm pretty well versed in the facts of where and when the P-38 was in service, and what it's operational duties and capabilities were. Enjoy your delusions.
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A shame SaVaGe is taking gripen to the woodshed on this topic. Gripen, again, give it up. You have been wrong on alot of your "points".
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Originally posted by Captain Virgil Hilts
Nothing I read in Levier's report mentions him blowing several Allisons. I'll look again.
In his book, LeVier mentions only having had one engine fail while he was in Britain. He states that he had suffered about 10 failures previously while flying the test programs stateside.
LeVier does mention that that virtually every P-38 in the ETO suffered at least one engine failure. I know of one that didn't suffer a failure over 300 hours of combat time. However, that was the exception, not the rule.
He states that during his four months attached to the 8th AF Fighter Command, almost 2,000 Allisons were replaced. He also admits that there were serious problems with the Allisons. After March of 1944, the 8th began assigning P-38 units escort altitudes as low as possible, giving high cover assignments to the Mustangs. This, combined with unit level fixes and specially blended fuel, greatly reduced the number of engine failures. Unfortunately, the much improved P-38L arrived too late and the 8th was already committed to the P-51 as their fighter.
In the MTO, the P-38L did very well, with few engine woes as compared to the ETO. They did fly far north and thru the winter of 1944-45. Some improvement could be related to warmer temperatures, but much of it is assigned to better quality fuel and the redesigned intake manifold of the Allison engines installed in the P-38L.
Now as to engine failure rates in the MTO, which someone mentioned, the Allison powered P-38s had a failure rate no greater than the P-51s.
Of course, the P-47 proved to be the most reliable fighter of the three by a big margin. R-2800s seldom failed and most failures were attributed to scavage pump failure and carburetor diaphragms rupturing due to improper pre-soaking.
My regards,
Widewing
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Hehe, Widewing waves the magic wand :aok
Anyway, the answer that many a P47 Pilot gave to the question "what was the best thing about the P47?" would be "It was strong and the engine was tough", or something like that.
BTW, why exactly did the Allison experience problems exactly at high altitude in N-Europe? What is the difference in atmospheric conditions at high altitude, say 25K+???
There is a difference in temperature, I know, at 20K and up it is actually colder over the med, - so was the temp to high or was it a humidity issue???
And here is a sidenote about Allison Engined Mustangs.
And a little more....from history:
Geoffrey Page was involved with a pair of Allison Powered Mustangs in a deep penetration raid into France. At the time, he sais this was about the fastest low-altitude fighter in the world. They did a good run, the pair of them and finished off some unsuspecting LW aircraft. Allison was all fine, but it makes me curious that not more were kept Allison powered in this job rather than focusing on Tiffies and cropped Spitfires. BTW, were Merlin-Power Mustangs never cropped?
Then the one from history, that I finally re-discovered while looking up in my books. Page actually got into a fight with none other than Hans-Joachim Jabs, who in his 110, down and low, shot down 2 Spitfires. Page locked into his six though and shot him down. They were to become friends after the war.
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Oh, an addition to the Story, - there was a second deep-penetration sortie into France, but it went bad. The flight leader, James Maclachlan, either got hit (no flak seen) or suffered an engine failiure, and crash landed on a field in France. He died from his injuries some 2 weeks later.
Their first sortie yealded 6 kills.
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Originally posted by Angus
BTW, why exactly did the Allison experience problems exactly at high altitude in N-Europe? What is the difference in atmospheric conditions at high altitude, say 25K+???
There is a difference in temperature, I know, at 20K and up it is actually colder over the med, - so was the temp to high or was it a humidity issue???
P-38H: inefficient intercoolers... High intake temperatures leading to detonation and engine damage.
Same intake manifold as P-38J, resulting in some cylinders running too lean, leading to potential engine damage.
Lead coming out of solution in fuel (associated with intake manifold).
P-38J: Over-cooling of engine oil. Thickened oil does not flow well, sometimes causing oil pump cavitation. Thick oil is a problem for the turbo regulators which use engine oil as the fluid media. Resulted in runaway turbos, which could lead to over-boosting, or the turbo simply coming apart.
Same intake manifold issues as P-38H.
All P-38H and many P-38Js had a single generator. Loss of that engine meant the loss of electrical power, except for the battery. This means that the electric boost fuel pumps must be turned off. Without boost pumps, the P-38 cannot maintain fuel pressure for high altitude flight. It must descend. Cruise power could barely be maintained at 20,000 feet. For full MIL power, the P-38 pilot would have to get below 10,000 feet.
The loss of the generator or the engine spinning the generator created another problem. Loss of propeller control.
Art Heiden explains, "If a generator was lost or a low battery the Curtiss Electric prop would lose the dynamic brake and go to extreme low pitch. This was called a 'run-away'. It could happen on Take Off with a low battery. Since you couldn't feather it set up a lot of drag making it difficult to make it around to land.
The killer situation was to lose the generator or lose the engine with the generator on it while 2 or 3hrs into Germany. Procedure was to set the props then turn off all electrical power. Then momentarily turn it back on to reset the props as needed. Being sure everything electrical was also turned off -- No radios. The forgotten thing was you were at altitude and the OAT was -60 degrees F and the little old battery was cold soaked. Hence, dead as a dog. Result, with a lot of altitude you have less than an hour with one or two props in run-away.
I have no statistics to back me up on this, but believe, that more P-38s were lost from this than any other factor including combat. This simple problem did not receive attention until April, '44."
As you can see, the loss of an engine can often have cascading effects that can doom a pilot. Later J models and all Ls had two generators, greatly increasing overall reliability.
Since Aces High does not model reliability, the P-38J is nearly faultless and there's little to no advantage flying the P-38L. However, in the real world, the differences were very significant, because all of the major mechanical issues had been resolved or mitigated with the P-38L.
My regards,
Widewing
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Originally posted by Captain Virgil Hilts
Again, read the report from Levier where solutions to the problems were found, and note that the P-38 continued to fly high altitude missions right up until they were replaced in July of 1944. Look at the unit numbers. The 20th and 55th flew escort missions until April or May, and they flew the P-38J until JULY 1944. Never said local fuel was the ONLY problem, just that it WAS a problem.
Well, about everyone and their dog wanted the P-51 so some groups had to wait until summer and flew missions despite the poor reliability of the Allisons at high altitude.
LeVier was trying to solve the problems at May 1944 so it is obvious that the problems were not solved that time.
Originally posted by Captain Virgil Hilts
Again, read the unit histories, the 20th AND the 55th fighter groups received the P-38J-1-Lo in NOVEMBER 1943. So you are absolutely WRONG, the P-38J DID fly in the 8th AF fighter groups in 1943 and 1944.
Please read again what I said above; there were no P-38Js in the MTO (mediterranean theatre of operations, 15th AF) before summer 1944 so the the fighter groups with the P-38 (G and H) there did not have as much problems as the 8th AF which operated P-38J during winter 43/44 in ETO. However there were F-5s in the MTO which were based on the P-38J and these had very similar problems as the P-38 groups of the 8th AF. And the point is that local fuel can't explain the problems in the ETO.
Got it?
Originally posted by Captain Virgil Hilts
By the way, the temperature at 25,000 to 30,000 feet varies little, regardless of the season of the year or the location on the globe. It's about as cold at 30,000 feet over the Bismark sea, or Guadalcanal, in July, as it is over France and Germany in January.
Actually it does vary quite a lot at high altitude depending the time of the year, even at 10000m the differences can be around 20 C or more. Besides the P-38s in the Pacific rarely flew above 20k.
Originally posted by Captain Virgil Hilts
You obviously do not grasp the concept of compression ratio. The difference between 6.0:1 compression and 6.6:1 compression is not even worth measuring, and makes no real difference at all.
Well, the point was that the Allison went towards the concepts used in the Merlin and eventually they ended to the same compression ratio in the G-series as in the Merlin. They certainly had a reason to do that.
Originally posted by Captain Virgil Hilts
Speaking of Doolittle, he flew over Normandy on 6, June, 1944 in a P-38J, while several units of the 20th flew escort and cover missions over the incasion, and they too were in Lockheed P-38 Lightning fighters.
That was actually a definite fix; the P-38 fought the rest of the war in the lower altitudes.
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Regarding the amount of problems, Doolittle's letter written to Spaatz at 1 March 1944 gives some numbers (quoted from Ludwig's book):
"There have been 76 known Allison V-1710-89 and -91 engine failures in our P-38J aircraft during the few months they have been operating in this theater. It is not known how many more engine failures have occured over enemy territory and prohibited the aircraft from getting home, but the high loss rate of this type of aircraft indicates that there have been many. The engine failures have been occuring with increasing frequency and the situation is now critical."
There were two groups operating P-38Js in the ETO that time so it can be estimated that about half of the pilots had experienced "Allison time bomb" that time. Had the Allison been in a single engined fighter, that would have resulted about 25% losses due engine problems.
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(http://img.photobucket.com/albums/v424/timppa/Engmaint.jpg)
http://www.au.af.mil/au/afhra/numbered_studies/467640.pdf
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I like the DB605 :aok
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Originally posted by DaddyAck
I like the DB605 :aok
Who wouldn't? :D
Turn up the volume and listen to these two bad boys:
http://www.youtube.com/watch?v=C-16ZVyHVZU
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Merlin - for various reasons
a) Nothing sounds like it
b) The sheer number of different aircraft, not mks that used it.
c) That Rolls Royce started out with a Merlin II at 1030HP and ended up running a Merlin 66 at 2600HP for 15 mins in mid 1944.
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I'm always amazed at how often facts get twisted here. The simple reality is that the P-38 bore the brunt of the fighting in the ETO at a critical time. It's effectiveness at higher altitudes was hampered by the same stupidity that nuetered the P-39. In the ETO (like the P-39 in the PTO initially) both plane and pilot were overmatched by the task at hand. The end result is that pilots with insufficient training flew planes with significant teething issues and absorbed tremendous losses...more as a result of poor training and lack of experience then anything else. The bottom lne was/is simple...the P-38 was the 1st plane to serve as a "deep escort", it was the 1st plane over berlin and it made everything that followed possible. Many pilots were actually flying "G"'s...it gave better then it got and inflicted many casulties. Was the P-38 "better" then the mustang....probabvly not...but the L was very capable and could have handled the task. Remember that the best plane of ther war was available and not even put into service...The F7F not only could have taken the bombers to berlin and back....it could have helped flatten it:)....
Anyone who downplays the role the 38 played in the ETO either cant read or cant comprehend....in 1943...when the job needed doing the 38 was the only "tool" for the job....in mid 1944 many options (including the 38L existed). As for the Allison vs Merlin element...the merlin was simply a vision of what the allison was designed to be...but then again the US had a 400+mph fighter in 1939 and snipped its nuts....
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P-38 Groups in the 8th
1st FG
Feb 1 1942 fully equiped with P-38s
1st mission Sept 2 1942
14th FG
Feb 1942 first P-38s arrive
1st combat mission Oct 2 1942
20th FG
Jan 1943 equiped with P-38s
1st combat mission Dec 28 1943
55th FG
Feb 10 1942 equiped with P-38s
1st combat mission Oct 15 1943
78th FG
May 1942 equiped with P-38s
1st combat mission Apr 13 1943
82cd FG
Oct 1942 began training on P-38s
tranferred to the MTO Dec 1942
364th FG
training with P-38s from late 1943
1st comabt mission Mar 3 1944
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Originally posted by humble
I'm always amazed at how often facts get twisted here. The simple reality is that the P-38 bore the brunt of the fighting in the ETO at a critical time. It's effectiveness at higher altitudes was hampered by the same stupidity that nuetered the P-39. In the ETO (like the P-39 in the PTO initially) both plane and pilot were overmatched by the task at hand. The end result is that pilots with insufficient training flew planes with significant teething issues and absorbed tremendous losses...more as a result of poor training and lack of experience then anything else. The bottom lne was/is simple...the P-38 was the 1st plane to serve as a "deep escort", it was the 1st plane over berlin and it made everything that followed possible. Many pilots were actually flying "G"'s...it gave better then it got and inflicted many casulties. Was the P-38 "better" then the mustang....probabvly not...but the L was very capable and could have handled the task. Remember that the best plane of ther war was available and not even put into service...The F7F not only could have taken the bombers to berlin and back....it could have helped flatten it:)....
Anyone who downplays the role the 38 played in the ETO either cant read or cant comprehend....in 1943...when the job needed doing the 38 was the only "tool" for the job....in mid 1944 many options (including the 38L existed). As for the Allison vs Merlin element...the merlin was simply a vision of what the allison was designed to be...but then again the US had a 400+mph fighter in 1939 and snipped its nuts....
Amen brother, in reguards to the improtance of the 38 in the ETO. :D
Oh and y'all whoom love the DB605 click here and behold the manly soud.
http://www.youtube.com/watch?v=EUcENor7X_0
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Dehavilland Hornet anyone? The F7F was this a/c's ugly sister.:)
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Walter Eichhorn working the vertical:
http://www.youtube.com/watch?v=qXtb_qlk55s
Look at that 109 climb!
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Agree Humble, too many only look at the "1945 superbirds" and pretend WW2 was fought exclusively with them, and just dis everything else. "Its not a Mustang, yada yada yada..."
P-47N, Arado, 109K, Tempest, N1K2, ect ect...its a function of the MA, where you can always pick the best rides.
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Hello,
Interesting thread. Here's an interesting comparison chart I came across in a book:
DB605 Merlin XX
bore 154 137 mm
stroke 160 152 mm
displacement 35,7 27,0 l
compr. ratio 7,2:1 6,0:1
width 720 757 mm
height 1010 1046 mm
length 1740 1793 mm
frontal area 0,51 0,54 m^2
weight 745 658 kg
weight/hp 0,49 0,44 kg/hp
fuel usage 200 235 g/hp/h
oil usage 5 10 g/hp/h
fuel 87 100/130 oct
hp/litre 42,0 54,8 hp/l
hp/area of piston 0,67 0,8 hp/cm2
What points out from those stats is that the Merlin had better hp/litre ratio, altho it achieved this by using more fuel and oil. Merlin was also almost 100kg lighter but the size wise it was similar to DB605.
Also it should be pointed out that the materials and fuels that DB605 used were inferior to Merlin. For example where as 109G-2's DB605 cylinder tubes were made of cromium molybdene steel. In the G-6's DB605 they were only carbon steel. So the material shortages were hampering the development of german engines (and that severely affected their TBO intervals for the worse), as was the quality of the fuel.
[edit: my nice comparison chart were fux0red by the forum... anyone knows how to fix it?]
-teemu
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Originally posted by _733
So the material shortages were hampering the development of german engines (and that severely affected their TBO intervals for the worse), as was the quality of the fuel.-teemu
What do you mean by the 'quality of fuel'? C3 fuel was equivilent to Allied 100/130 fuel late war C3 had a rich mixture of 140.
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Oh I wish we could get C3 fuel for our 109s, even if they perked it! 2000 hp 109K would own everything!
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Originally posted by MiloMorai
What do you mean by the 'quality of fuel'? C3 fuel was equivilent to Allied 100/130 fuel late war C3 had a rich mixture of 140.
octane rating for C3 fuel was 96/100
-teemu
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Originally posted by Viking
Oh I wish we could get C3 fuel for our 109s, even if they perked it! 2000 hp 109K would own everything!
apparently DB605 DC with MW-50 gave 2200hp in G-10...
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Originally posted by Viking
Oh I wish we could get C3 fuel for our 109s, even if they perked it! 2000 hp 109K would own everything!
Oh I wish someone could actually come up with one document that proves that K-4's ever used C3.
And yes I have seen Kurfursts site, no definitive proof there either.
"Assume", "safely assume", and "probably" just don't just cut it.
OTOH we have docs showing that both the XIV and LF IX (XVI) used 150 octane from mid 44, can't get them either.
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Originally posted by Kev367th
Oh I wish someone could actually come up with one document that proves that K-4's ever used C3.
And yes I have seen Kurfursts site, no definitive proof there either.
"Assume", "safely assume", and "probably" just don't just cut it.
OTOH we have docs showing that both the XIV and LF IX (XVI) used 150 octane from mid 44, can't get them either.
*Snicker*
Kev
Bronk
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Originally posted by leitwolf
Allisons win the "best sound" award. ;)
not that this has anything to do with this thread...but i was at the reading pa airshow thisweekend.........there was a YAK9 there...and the pilot was wringing her out.....BUT.........that engine in her sounded an awful lot like an allison......any ideas therre?
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Originally posted by 1K3
In the radial department, nothing beats the Pratt & Whitney series. Not even the BMW radials can beat P&W.
When it comes to Inline liquid-cooled engine, which company made THE best inline engine
[ EDIT: Jumo is added to the list ]
another question out of curiousity??
i thought i had heard somewhere that the BMW radials were actually a pratt & whitney built under lience.....which was arranged before the war?
sounds nuts, but wondering?
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Originally posted by _733
octane rating for C3 fuel was 96/100
-teemu
Yes that is the lean mixture rating, NOT the rich mixture rating.
for your reading enjoyment,
http://www.fischer-tropsch.org/primary_documents/gvt_reports/USNAVY/tech_rpt_145_45/rpt_145_45_sec2.htm#Composition%20and%20Specifications
Please note: (The C-3 grade corresponded roughly to the U. S. grade 130 gasoline, although the octane number of C-3 was specified to be only 95 and its lean mixture performance was somewhat poorer.)
Kev, pg 174 of the Prien/Rodeike 109 book has a pic of a K-4 of 11./JG3 with the C3 decal showing clearly.
CAP1
yes it is powered by an Allison.
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If you want to bring "exotic" avgas into this, and the HP gain, then we can always talk about the 150 octane stuff that eventually became available, and the fact that using that fuel, an Allison in a P-38 could be run at 84" MAP and turned 3200RPM+. But let's leave unverified fuel and ratings out of this.
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Nothing "exotic" about C3 fuel. It was the standard fuel of the radial engined 190's and was available since before the BoB. The controversy over 109’s using C3 is that since the 190’s could only use C3 they got priority while the 109’s got the lower-grade B4 fuel.
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Exactly. There's nothing "exotic" about 150 either. Except here. There's nothing mysterious about the settings on the P-51 and P-38 when run on 150 either. Except here.
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Originally posted by MiloMorai
Kev, pg 174 of the Prien/Rodeike 109 book has a pic of a K-4 of 11./JG3 with the C3 decal showing clearly.
Even Butch said nothing too much should be read into that.
Thread on the allaboutwarfare website, and here I think also.
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Wait, "Viking" is Kurfurst? That explains everything.
Hilts, what was that quote again about Kurfurst logic? "Cleared = used by the LW = NOT used by the Allies." You're only allowed high end stuff if it's German, even if they only "might" have used it while Allied forces definitely did.
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Again your inability to read or comprehend even the simplest of texts has led you astray. I have no idea whether 150 octane fuel was used by the allies or not, and I have never commented on it.
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If the Allison was so obviously superior to the Merlin, why did nobody suggest replacing the Spitfire's Merlin with an Allison instead of the Mustang's Allison with a Merlin?
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Originally posted by Kev367th
Oh I wish someone could actually come up with one document that proves that K-4's ever used C3.
And yes I have seen Kurfursts site, no definitive proof there either.
"Assume", "safely assume", and "probably" just don't just cut it.
OTOH we have docs showing that both the XIV and LF IX (XVI) used 150 octane from mid 44, can't get them either.
What fuel 109 could use depended on what DB605 engine it had. Given the war situation late 109s could have any of these engines depending the availability:
DB605 ASM; B4 w/ MW-50, C3 w/o MW-50
DB605 ASB; B4 w/ MW-50, C3 w/o MW-50
DB605 ASC; C3 always w/ MW-50
DB605 DB; B4 w/ MW-50, C3 w/o MW-50
DB605 DC; C3 always w/ MW-50
(source: ISBN 951-95688-7-5 ; Messerschmitt BF 109 and Germany's war economy)
-teemu
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Originally posted by CAP1
another question out of curiousity??
i thought i had heard somewhere that the BMW radials were actually a pratt & whitney built under lience.....which was arranged before the war?
sounds nuts, but wondering?
from Wikipedia:
"In the 1930s, BMW took out a license to build the Pratt & Whitney Hornet engines. By the mid-30s they had introduced an improved version, the BMW 132. The 132 was widely used, most notably on the Junkers Ju 52, which it powered for much of that design's lifetime."
801 that powered 190 wasn't lisence built P&W, but i'm sure that some of the 132's useful design features were incorporated in it.
-teemy
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Originally posted by Benny Moore
Wait, "Viking" is Kurfurst? That explains everything.
Hilts, what was that quote again about Kurfurst logic? "Cleared = used by the LW = NOT used by the Allies." You're only allowed high end stuff if it's German, even if they only "might" have used it while Allied forces definitely did.
Actualy Kurfy had some good info, it was his logic that was a bit, erm,,,,, skewed.
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Originally posted by Benny Moore
Wait, "Viking" is Kurfurst? That explains everything.
Hilts, what was that quote again about Kurfurst logic? "Cleared = used by the LW = NOT used by the Allies." You're only allowed high end stuff if it's German, even if they only "might" have used it while Allied forces definitely did.
Naw, Viking ain't Kurfurst, I'll give him credit for that. Viking is GScholz.
And that quote ain't mine.
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Originally posted by Kev367th
Even Butch said nothing too much should be read into that.
Thread on the allaboutwarfare website, and here I think also.
He did? Never saw such.
One can call 100/150 fuel exotic as it was only use in the ETO. Percentage wise it was produced in low quantity compared to 100/130 fuel. C3 is certainly not an exotic fuel with 2/3 of all German avgas being of the C3 grade.
Virgil, that quote is part of the sig of one called luftluuver over at the Ubi Il-2 forums:
Some dude: 'cleared' = used by the LW = NOT used by the Allies;
2 is 'quite a few ships',
112 is 'well over a hundred'
Supposidly the the Mods did not like Kurfurst name in the sig so changed it to 'some dude'.
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Originally posted by Karnak
If the Allison was so obviously superior to the Merlin, why did nobody suggest replacing the Spitfire's Merlin with an Allison instead of the Mustang's Allison with a Merlin?
LOL, good point!
Anyway, funny to see that Kuffies ghost is still haunting us :D
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There was also a proposal to replace the P-38's Allisons with Merlins. Since Allison was a division of GM, lobbying in Washington by GM had it squashed.
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I thought it was the weight? :confused:
Always wondered though :noid
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Originally posted by MiloMorai
There was also a proposal to replace the P-38's Allisons with Merlins. Since Allison was a division of GM, lobbying in Washington by GM had it squashed.
The study Lockheed did showed a reduced climb rate, and installation problems, including weight. Above 26,000 feet, the P-38 would have been slower, and suffered a serious reduction in climb. It wasn't lobbying by GM in Washington. The War Production Board wouldn't even allow Lockheed to stop production long enough to change to Hamilton Standard props, so swapping to the Merlin, even if it were a good swap, was never an option. Yes, Knudsen, who held a seat on the War Production Board, was a GM stockholder.
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On the flip side, how would the P38 have performed with a Griffon ?
Cruising on the buffering line?
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Originally posted by Angus
On the flip side, how would the P38 have performed with a Griffon ?
Cruising on the buffering line?
I don't know, and neither does anyone else that I know of. Honestly, since it was literally designed around an Allison (if you've ever seen the skin off the engine cover of a P-38 you'll know what I mean), it'd be hard to get anything else in it and not screw up the aero package or the CG, if not both. There was so much more that could have been done by simply turning up the Allison V-1710 (put the G series in it) and getting rid of the awful Curtiss props that nothing else would ever have been needed, or used. A G series V-1710, running at 3400 RPM and 84" of boost would make 2200HP at least (the unlimited hydro guys dynoed them higher than that in stock form) and a Hamilton Standard prop could have harnessed all of it, especially a 13'6" four blade. That would have made it easily possible to compress in level flight. But it would have pushed the climb rate to over 4000fpm, and made it accelerate about 15% faster, if not more.
There's no need to reinvent the wheel here, the basic combination of plane and engine is plenty sound, it just never was fully refined. All serious efforts to improve the P-38 essentially stopped with the P-38K, there were detail refinements afterward, but the WPB's decision to decline the P-38K, combined with Lockheed's resources being squandered on dead end projects, and the fact that Lockheed was building B-17's while a cargo plane company was trying unsuccessfully to build P-38's, pretty much ended real development work on the P-38, and that was April of 1943. The J was already nearing production, and the L was simply a J-25-Lo with minor detail refinements.
It's sad, really. The P-38K was a wicked plane in its own right. Figure the engine would have seen further improvements, and the Hamilton Standard props would have eventually changed from 3 to 4 blades to streamline manufacturing. So the P-38K, which was a vast improvement performance wise over both the J and L, would have been superceded by an L that was a refinement of the K and not the J.
There's no doubt the Merlin and the Griffon were excellent designs, and well executed. But the attempts to label the Allison engine as second class simply because GM/Allison was not ALLOWED to fit a two speed two stage supercharger ignore obvious facts.
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Here is a chart for most of the engines of the era
http://mysite.verizon.net/vze479py/sitebuildercontent/sitebuilderpictures/hp_wt.gif
-blogs
Originally posted by Virage
I would judge an engine by its power to weight ratio.
Does anyone have this info on engines?
1K3.. why do you consider the P&W to be the best radial?
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The BMW should be compared to Wright's R2600, but that engine was used in bombers.
The late war AshFN82 (Russian) was a pretty darn good radial engine.
-Blogs
Originally posted by Masherbrum
:rofl Oh boy. Okee-dokee.
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Bristol made excellent engines, but the Hercules is a bit small to compare to the R2800. The better comparison is the Centaurus, but it came a bit too late. - Blogs
Originally posted by gripen
In the category of inline engines nothing comes close to the Merlin; by far the best developed and only one of these to see some civil use.
In category of radials the Hercules comes close the R-2800; infact in the terms of reliability (particularly TBO) and fuel consumption, it's better than R-2800. However, the R-2800 saw much wider use during war as well as large civil use.
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Certainly differences in fuel mattered, but the Merlin was eventually developed with the most efficient of the two speed superchargers. The DB's were single stage, but benefited from fuel injection and a continuosly variable clutch.
-Blogs
Originally posted by Knegel
The Merlin???
Even the Griffon did count as more advanced, the main advantage over the DB´s was rather the fuel than the stage of development.
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That's not necessarily true. The supercharging gearing can be such that maximum horsepower cannot be developed at sea level without detonation. In fact, a lot of WW2 engines were designed exactly this way.
-Blogs
NO piston engine with a crank driven supercharger, even WITH a two speed two stage supercharger, makes sea level power at high altitude.
[/B]
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Here are the numbers for most engines of the era...
http://mysite.verizon.net/vze479py/sitebuildercontent/sitebuilderpictures/hp_disp.gif
-Blogs
Originally posted by gripen
This has been discused here several times, the Merlin utilizes exhaust thrust which in practice balances the situation. And the P-38K never saw service.
Besides, 2000hp Merlins saw quite wide service during war and were type tested for over 2600hp. The Allisons maxed around 1800hp during war (very limited use in the P-63).
The race use has pretty much nothing to do with practical service use and in the service the Merlin proved to be more powerfull and more reliable than the Allison.
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Schlaifer's history goes into great deal on this. It is not that Allison was prohibited from developing gear driven superchargers; the government was simply unwilling to pay for the development. And Allison's only customer for these engines was the government. The airforce was convinced the turbo would be ready, but they underestimated the difficulties>>>
-Blogs
Originally posted by Captain Virgil Hilts
Once again, in simple, easy to grasp terms. The Allison, as required by the USAAF and the War Production Board, was produced with a single speed supercharger. Without the ability to increase the speed of the supercharger, there was not enough boost available to make horsepower at higher altitudes.
The Merlin had a two speed supercharger. At low altitudes it ran at a low speed, and at higher altitudes it ran at a higher speed to produce more boost in the thinner air at higher altitudes. Around 20,000 feet or so, the Merlin supercharger went from low speed to high speed.
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The Germans offset lower max manifold pressures (limited by ltheir ower octane fuel) with larger displacement. Both approaches worked quite well.
-Blogs
Originally posted by Knegel
So was the DB601 and DB605, despite the less good fuel, the DB engeeners always found a way to get to a very similar stage of power.
To say the "Merlin was by far the best developed" engine is not true, at least much overdone.
1st the DB601A was ahead of the MerlinII, then the brits got better fuel and the Merlin had a WEP advantage, then the germans did use better fuel and the DB601N was ahead again, then the Brits got a new engine, then the DB601E and so on.
Only in mid 1942- mid 44 there was a advantage for the merlin, cause the germans gave all the good fuel to the BMW´s. Later, with MW50 and GM1 the DB605 was on paar again, while the fuel still was the main problem(next to the typical late war production problems).
The DB603 and Jumo213 also was very good designs.
There simply is no best engine, there are airframes where the engines fit in and turn to be very good and there are tactical situations where the engine need to fit.
The high alt performence of the allied engines wasnt much worth while a tactical airwar in MTO and russia, while the great Ash82 and BMW801 was bad while interceps in high alt.
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Here is data on compression ratios for WW2 engines:
http://mysite.verizon.net/vze479py/sitebuildercontent/sitebuilderpictures/hp_lb.gif
BTW, before the raid, Doolittle was put in charge of inspecting aircraft factories for the Air Force. He put in a critical report on the Allison factory in Indiana - way too dirty for an aircraft engine plant...
-Blogs
Originally posted by Captain Virgil Hilts
...
You obviously do not grasp the concept of compression ratio. The difference between 6.0:1 compression and 6.6:1 compression is not even worth measuring, and makes no real difference at all. Production tolerances will create a difference of as much as 0.1:1. The difference between 6.0:1 and 6.6:1 will not make enough difference in the amount of boost that can be run to make it necessary to adjust either the boost, the cam timing, or the ignition timing. And I should know, I worked on Allison pulling tractor engines, and I still build racing engines for a living to this day, including supercharged and turbosupercharged engines.
...Speaking of Doolittle, he flew over Normandy on 6, June, 1944 in a P-38J, while several units of the 20th flew escort and cover missions over the incasion, and they too were in Lockheed P-38 Lightning fighters.
ional duties and capabilities were. Enjoy your delusions.
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Originally posted by joeblogs
That's not necessarily true. The supercharging gearing can be such that maximum horsepower cannot be developed at sea level without detonation. In fact, a lot of WW2 engines were designed exactly this way.
-Blogs
In theory. In the real world, you can only spin a crank driven supercharger to a certain RPM before it begins to take WAY more power to spin than it generates. Given a fixed supercharger size, it does not take long to reach the point of diminishing returns, even with a centrifugal supercharger, with two speeds and two stages.
That's not to say you can't gear the supercharger up so it spins really fast at high altitude, and makes more power than it would at a lower speed at that same altitude, but it won't necessarily make sea level HP. You can, and some of the Merlin engines were tuned that way. You can also increase the size of the supercharger relative to the engine. However, the larger supercharger will also require more HP to spin.
There's no such thing as free HP with any supercharger of any type. You cannot keep spinning it faster and faster and get more power without penalty.
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Originally posted by joeblogs
Schlaifer's history goes into great deal on this. It is not that Allison was prohibited from developing gear driven superchargers; the government was simply unwilling to pay for the development. And Allison's only customer for these engines was the government. The airforce was convinced the turbo would be ready, but they underestimated the difficulties>>>
-Blogs
Prohibited is probably the wrong word. Let's phrase it real carefully. The War Production Board AND the USAAF/USAAC told GM/Allison, "We will not pay for development of a two stage two speed supercharger, and we will not purchase one if you develop it." So your only customer tells you they won't pay for development, and won't purchase it if you fund development on your own. What do you do?
Take it a step further. The customer says, "I want X number of product, I want Y-Z features developed and refined, that is all I will pay for, and I will fine you if you do not meet MY production and development goals". If you have limited production and R&D capacity, and need funds and time to develop something they didn't ask for, what do you do?
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Originally posted by joeblogs
Schlaifer's history goes into great deal on this. It is not that Allison was prohibited from developing gear driven superchargers; the government was simply unwilling to pay for the development. And Allison's only customer for these engines was the government. The airforce was convinced the turbo would be ready, but they underestimated the difficulties>>>
I don't have "Vees for Victory" in hand but Allison started the developement of the mechanical (variable speed) auxilary stage quite early. The problem was just that the development was slow, particularly if compared to the Merlin; two stage Merlin reached service 1942 (basicly same time as the V-1710 with exhaust driven auxilary stage) while the V-1710 with mechanical auxilary stage came about two years later and saw very little combat use.
Note that the Merlin was originally developed by the Rolls Royce as a private venture project without government support, the original project name being PV-12 (PV = private venture).
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Originally posted by joeblogs
The Germans offset lower max manifold pressures (limited by ltheir ower octane fuel) with larger displacement. Both approaches worked quite well.
-Blogs
German C3 fuel had a rich mixture rating of 130 to 140. Can you explain that comment about German fuel octane further, please?
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What I mean is that the displacement of the DB 601 and 605 were chosen assuming octanes would not be rising so much. So displacement substituted for BMEP with the german engines.
When the fuel did improve, RR was the best in developing Efficient 2 stage superchargers to exploit them. Hence the highr BMEPs.
On the fighter engines, DB did not go with a 2 dtage supercharge, but opted for alterntive boosts systems for high altitude performnce.
-Blogs
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Hi
the DB´s used with C3 fuel(DB601N and 605DC) clearly show that they wasnt behind the Merlins.
The two speed supercharger had as many advantages over the DB system like disadvantages, good for high alt and high power peaks, but a not steady powercurve and missing exhaust thrust, the weight and ammount of maintaince probably also wasnt that smal.
Of course in high alt the supercharged planes had advantages, but up to rated altitude they dont had, with GM1 the DB´s was rather even again.
btw, the BMW801 had more then 2000hp(with C3 injection) and why there is no DB605DC or Jumo213+MW50 listed in your engine performence graphic??
The DB610A was also a very powerfull engine, though heavy.
Anyway that power comparison graphic isnt much worth. Or would we compare the MerlinII(max 890hp) and DB601Aa(max 1160hp) at sealevel??
Or would we rate the Jumo213A only by its "Sondernot" power at sea level(2250PS)??
Such single point comparisons are nothing more than missleading.
Only powercurves for usefull or comparable powersettings should get listed.
What are the 1160HP of the DB601Aa worth if its only available for 1 min??
All this need to get seen in the contex of the tactical need.
What was the excelent high alt performence of the Ta152H worth in 1945, when the high alt fights stopped??
What was the great low alt power of the Ash82 and BWM801 worth in 7000m?? What was the good power of the MerlinsIII worth if the fight was in low alt?? What was the Merlins good high alt power worth in the low level tactical Airwar in Africa? etc.
The great power of the US radials, the DB610A etc also are not always that much worth cause their high weight and fuel consumption.
Powerload(in different altitudes), airframe(aerodynamical potentail of the engine, how good to maintance the engine), fuel consumtion, reliability, price and much more are needed to rate the value of a engine.
With C3 fuel the DB605 + MW50 also was in the 2000hp + class, the Jumo213 was above it with B4 fuel + MW50.
Imho RR, BMW and Junkers had the best inline engines in the war. Reliable, good powerload and fitting to the available airframes.
But also the Russian VK-105 in combination with the Yak3 airframe was very good(at least in low alt).
How important the airframe is while rating the engine, you can see if you look to the VK-107. A very nice engine, with much power, but no russian fighter airframe was able to use it(not enough space for the needed radiators).
At the end the performence of the different fighters in europe was rather similar. There was no superfighter that was supiriour in all altitudes, usefull for intercepts, dogfight and escort missions. Same like every engine brough some limitaions to the airframe, also every airfame brought limitaions to the engine.
Greetings,
Knegel
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First, I am not saying the Merlins were better than the DB or Junker inlines.
I simply observed these engines reflected a different design philosophy and these continued in their subsequent refinement. The British opted for very high manifold pressures, The Germans for more displacement.
By paying very careful attention to design, Rolls Royce came up with a very fine two stage supercharger, which made the Merlin a great high altitude engine. In the fighter engines, the Germans opted for smaller changes to their superchargers, instead focusing on boosting systems for high altitude performance. But their best solution for this problem was using bomber engines optimised for high altitude performance - hence the Dora.
Yes the BMW801 was a fine engine. Most of the thread is about the inlines however.
Yes both sides obtained better fuels than they expected before the war broke out. The effect of these improvements is to increase maximum BMEP without detonation. The chemistry does not care about the nation of origin. Remember the allies only had access to an abundant supply of 100 octane fuel becuase a guy name Jimmy Doolittle insisted the company he worked for at the time (shell) build factories in anticipation of airforce demand.
As for the data, people asked for data and I provided a good deal of it. I happen to think the data is pretty good. It has the virtue of being assembled by one source, over many editions (Wilkinson). In particular, the measurement methodology is common across engines. The disadvantage is that not all the engines are there, and there are more axis engines missing than allied ones. (Wilkinson had to wait until the end of the war to get the data on later axis models).
Now the data is maximum (gross) horsepower devleped by the engine. These are typically sealevel numbers taken off the bench, although some are reported for low altitudes (0-4k ft). Depeniding on the engine, this is either "wet" (using ADI) or not. The numbers typically correspond to maximum horsepower for take-off. These powers can only be used for a short time in any engine (typically 2-5 minutes).
Yes actual comparisons of aircraft performance are going to depend on the relative performance of the engines at different altitudes. These threads are full of such comparisons. The question is whether you want to talk about planes or powerplants. We were talking about powerplants. When the discussion is about the engines, and not the installations, the metrics I am reporting are the ones typically used by scientists and engineers. The data is only misleading if it is used in a misleading way.
As you point out, without a continuously variable clutch, multispeed superchargers result in a shark's tooth performance curver. DB avoided that, at the price of using only a single stage supercharger on the fighter engines.
-Blogs
Originally posted by Knegel
Hi
the DB´s used with C3 fuel(DB601N and 605DC) clearly show that they wasnt behind the Merlins.
The two speed supercharger had as many advantages over the DB system like disadvantages, good for high alt and high power peaks, but a not steady powercurve and missing exhaust thrust, the weight and ammount of maintaince probably also wasnt that smal.
Of course in high alt the supercharged planes had advantages, but up to rated altitude they dont had, with GM1 the DB´s was rather even again.
btw, the BMW801 had more then 2000hp(with C3 injection) and why there is no DB605DC or Jumo213+MW50 listed in your engine performence graphic??
The DB610A was also a very powerfull engine, though heavy.
Anyway that power comparison graphic isnt much worth. Or would we compare the MerlinII(max 890hp) and DB601Aa(max 1160hp) at sealevel??
Or would we rate the Jumo213A only by its "Sondernot" power at sea level(2250PS)??
Such single point comparisons are nothing more than missleading.
Only powercurves for usefull or comparable powersettings should get listed.
What are the 1160HP of the DB601Aa worth if its only available for 1 min??
All this need to get seen in the contex of the tactical need.
What was the excelent high alt performence of the Ta152H worth in 1945, when the high alt fights stopped??
What was the great low alt power of the Ash82 and BWM801 worth in 7000m?? What was the good power of the MerlinsIII worth if the fight was in low alt?? What was the Merlins good high alt power worth in the low level tactical Airwar in Africa? etc.
The great power of the US radials, the DB610A etc also are not always that much worth cause their high weight and fuel consumption.
Powerload(in different altitudes), airframe(aerodynamical potentail of the engine, how good to maintance the engine), fuel consumtion, reliability, price and much more are needed to rate the value of a engine.
With C3 fuel the DB605 + MW50 also was in the 2000hp + class, the Jumo213 was above it with B4 fuel + MW50.
Imho RR, BMW and Junkers had the best inline engines in the war. Reliable, good powerload and fitting to the available airframes.
But also the Russian VK-105 in combination with the Yak3 airframe was very good(at least in low alt).
How important the airframe is while rating the engine, you can see if you look to the VK-107. A very nice engine, with much power, but no russian fighter airframe was able to use it(not enough space for the needed radiators).
At the end the performence of the different fighters in europe was rather similar. There was no superfighter that was supiriour in all altitudes, usefull for intercepts, dogfight and escort missions. Same like every engine brough some limitaions to the airframe, also every airfame brought limitaions to the engine.
Greetings,
Knegel
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DB developed two stage mechanical superchargers but these did not reach service before the end of the war (DB 603L and DB 605L). Basicly same problem as with the V-1710 as well as with the Jumos; too little, too late.
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The DB 603L and 605L were designed for very high altitudes. The DB's already had a supercharger with a similar FTH to that of the two stage supercharged Merlins. The DB supercharger design was unique in that it was a step-less, variable speed design using a hydraulic converter to adjust the impeller speed according to altitude and engine boost. To put it in car terms the Merlin had a manual two speed gear box, while the DB a one speed automatic with roughly the same gear ratio as the Merlin’s high-gear. Using the DB 603's bigger supercharger on the DB 605 (known as the AS versions) gave the engine a FTH of more than 26,000 feet which is roughly equal to the two stage Merlins.
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Originally posted by Viking
Using the DB 603's bigger supercharger on the DB 605 (known as the AS versions) gave the engine a FTH of more than 26,000 feet which is roughly equal to the two stage Merlins.
Which merlin are you comparing this to?
Bronk
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The RR Merlin 68/ Packard Merlin V-1650-7 used by the P-51D. This engine has a FTH of 25,800 feet where it produces 1210 hp.
The DB 605AS using B4 fuel and no MW50 has a FTH of 26,200 feet (8 km) where it produces 1200 hp.
These two engines are for all intents and purposes identical in performance. Only difference being the different approach to supercharging. RR with its two-stage blower and the DB with its single-stage variable-speed blower.
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Hm... the V-1650-7 was a low altitude version of the two stage Merlin, the V-1650-3 had about 4k higher (static) FTH. The DB 605AS reached service spring 1944, nearly two years after two stage Merlin.
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The DB 605AS was a direct response to the high flying US fighters, the P-51 in particular. The DB 605A with its unique supercharger had been in service since 1942. The DB 603 with its bigger supercharger had been operational since 1943, so bolting the bigger blower onto the 605 wasn't rocket science. The LW simply hadn't had a need for the 605AS until the advent of the P-51. The Packard Merlin V-1650-3 had a FTH of 29,400 feet and was used in the P-51B and high-alt spits, mostly scouts and PR Spits. Prior to 1944 the Germans relied on GM1 for their high-alt units and the DB 605A with GM1 injection was operational in the spring of 1942. With GM1 the FTH of the DB 605A was more than 40,000 feet. Only specialized units, mostly high alt recce and scouts, used GM1 as combat at this time rarely was above 20,000 feet.
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The RR Merlin 68/ Packard Merlin V-1650-7 used by the P-51D. This engine has a FTH of 25,800 feet where it produces 1210 hp.
FTH for the V-1650-7 was far lower than that, as it was a low alt engine. FTH unrammed was under 20,000 ft.
The DB 605AS using B4 fuel and no MW50 has a FTH of 26,200 feet (8 km) where it produces 1200 hp.
A better comparison with the 605AS is the Merlin 70, the high altitude variant of the Merlin 60 series. That produced 1210 hp at 26,000 ft at reduced rpm and boost, ie at its 1 hour rating (2850 rpm, 12 lbs boost).
At 3000 rpm and increased boost, power would be higher at 26,000 ft.
(and btw, the DB 605AS produced 1200 PS, which is about 1180 HP)
These two engines are for all intents and purposes identical in performance.
No. The Merlin produces more power at what is basically a cruise setting than the DB does at maximum power. And peak power on the Merlin 70 is 1710 hp at 11,000 ft.
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"The LW simply hadn't had a need for the 605AS until the advent of the P-51."
And how about the Spit IX? When it first showed up, it was untouchable by the 109's at high altitudes. 1942 and a Merlin 61.
Ant the P47 at high alt? and the P38 perhaps?
I think they always needed higher performance engines, - well everybody did.
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I chose those two engines because they represent the two classic rivals of 1944 Western Europe: The P-51D and the Bf 109G-6AS/G-14AS. The Merlin V-1650-7 was the engine used by all blocks of P-51D. The DB 605AS(M) was the engine used by the 109G-6AS and G-14AS which were the primary German (anti)escort fighter (as opposed to bomber destroyer). I chose the non MW50 DB 605AS to better illustrate the similar power at altitude without factoring in the superior allied fuel or the German use of water injection or nitrous oxide as compensation. The DB 605ASM with MW50 produces 1800 PS and is therefore very comparable to the Merlin 70's 1710 hp. With GM1 the DB 605A is vastly superior to all versions of the Merlin at altitude, but of course this system has its drawbacks as well.
Very few Spitfires and no P-51s flew with the Merlin 70. It was mostly used by the bomber and NF Mossies.
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Wasn't aware that the P51 used the 70, but the Spit VIII used it. But I forgot the mossies of course, they needed to be caught as well ;)
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Very few Spitfires and no P-51s flew with the Merlin 70. It was mostly used by the bomber and NF Mossies.
I don't think any Mossies used the Merlin 70. 70 series engines, yes, but not the 70 itself.
As to numbers, about 1,000 Merlin 70s built, all used in Spitfires. Approx 400 Spitfire HF IXs, 160 HF VIIIs, an unknown number of PR XIs.
I chose those two engines because they represent the two classic rivals of 1944 Western Europe: The P-51D and the Bf 109G-6AS/G-14AS.
At the same time, the USAAF still had a lot of V-1650-3s in service, and the Germans had a lot of DB 605A. You have chosen a high alt German engine to compare with a low alt allied engine.
The DB 605ASM with MW50 produces 1800 PS and is therefore very comparable to the Merlin 70's 1710 hp.
And rather badly with the Merlin 70 using 100/150 fuel, which produced about 2000 hp.
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Well, the Germans had certainly a need for better high altitude performance; the DB 605AS was a stop gap solution because the DB 605D was so late.
The GM1 is more or less a red herring in fighter use, very unpractical due to slow activation etc. There were some Bf 109s with GM1 in service use as well as Spitfires with oxygen system. Both were replaced once the improved superchargers came available, in the Germany this took just much longer than in the Britain.
The P-51B with V-1650-3 (and Spitfires with Merlin 61, 63, 70 etc.) gave large performance advantage to Merlin engined planes at high altitude over the planes with the DB 605 with single stage supercharger.
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Yes.
Rolls Royce was hardly the only company to develop superchargers for high altitude performance. But they did develop the most efficient superchargers (generating more manifold pressure with less HP) than just about any other firm.
The only problem with adopting a larger single stage supercharger is that, in those day, blower efficiency falls with the diameter of the impeller. So putting in a larger impeller implies a larger penalty in HP well below the critical altitude. For gear driven superchargers this is a major problem. It was less of a problem on the DB designs because of the variable speed clutch you mentioned. Supercharger efficiency also falls off with impeller speed (at some point) so spinning the larger impeller less rapidly would mitigate some of those losses.
-Blogs
-Blogs
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Originally posted by Angus
Wasn't aware that the P51 used the 70…
They didn’t.
Originally posted by Nashwan
I don't think any Mossies used the Merlin 70. 70 series engines, yes, but not the 70 itself.
I’m sure you are correct.
Originally posted by Nashwan
As to numbers, about 1,000 Merlin 70s built, all used in Spitfires. Approx 400 Spitfire HF IXs, 160 HF VIIIs, an unknown number of PR XIs.
A very small number of Spits, as I said.
Originally posted by Nashwan
At the same time, the USAAF still had a lot of V-1650-3s in service, and the Germans had a lot of DB 605A. You have chosen a high alt German engine to compare with a low alt allied engine.
The -3 only served on P-51B’s, and many of them were later replaced with the -7 to standardize supply and maintenance. The -7 is not a low alt engine; it’s a medium alt engine. The Germans did not use DB 605A engined 109s in the West as escorts, only as bomber destroyers (with gondelwaffen and extra armor). Thousands of G-6/AS and G-14/AS saw service in 1944/45. I chose the allied Merlin engine that powered the most prolific allied fighter in the West in 1944/45 and that was the main threat to the LW at the time. You chose a Merlin that saw service with less than 1000 planes of different marks, only 400 as fighters. The proper opponent for such a rare bird would be the GM-1 equipped 109’s, and they out flew everything at high altitude.
Originally posted by Nashwan
And rather badly with the Merlin 70 using 100/150 fuel, which produced about 2000 hp.
Which compares poorly to the DB 605DC which produced 2200 hp with MW50. If you’re going to use “exotic” fuel then you must make this allowance for both sides of the argument, otherwise you’re just being dishonest. And C3 was far less exotic than 100/150 avgas, and far less problematic. One third of Germany’s avgas production was C3.
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But notice ths significant difference in Displacement between these two engines. That is what makes the comparisons so interesting.
Now RR also increased displacement for the Griffon, but I think DB was ahead of them in developing their 605 (just my opinion).
-Blogs
Originally posted by Viking
The RR Merlin 68/ Packard Merlin V-1650-7 used by the P-51D. This engine has a FTH of 25,800 feet where it produces 1210 hp.
The DB 605AS using B4 fuel and no MW50 has a FTH of 26,200 feet (8 km) where it produces 1200 hp.
These two engines are for all intents and purposes identical in performance. Only difference being the different approach to supercharging. RR with its two-stage blower and the DB with its single-stage variable-speed blower.
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Originally posted by gripen
Well, the Germans had certainly a need for better high altitude performance; the DB 605AS was a stop gap solution because the DB 605D was so late.
The DB 605D used the exact same supercharger as the DB 605AS: the supercharger developed for the DB 603. The DB 605D was an improved DB 605ASM. However the DB 605D was a real stopgap engine; the 109K was supposed to be powered by the DB 605L.
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Originally posted by joeblogs
But notice ths significant difference in Displacement between these two engines. That is what makes the comparisons so interesting.
The difference is not so big as you might think just by looking at the numbers. The DB was a high compression, low-blown engine, while the RR was a low- compression, high-blown engine. Some of the DB engine volume was used up by the higher compression ratio. The RR’s supercharger had to “make up for the slack” of the RR’s lower compression to get the same amount of fuel mix compressed in the cylinders. The higher volume also allowed the DB to produce roughly the same amount of power using 87 octane fuel as the RR did with 130 octane. It is very evident that the DB engineers were fighting an uphill battle against RR with the deteriorating availability of strategic materials and fuel. It’s a testament to their skill and ingenuity that they manage to keep pace at all.
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Originally posted by Viking
Which compares poorly to the DB 605DC which produced 2200 hp with MW50. If you’re going to use “exotic” fuel then you must make this allowance for both sides of the argument, otherwise you’re just being dishonest. And C3 was far less exotic than 100/150 avgas, and far less problematic. One third of Germany’s avgas production was C3. [/B]
C3 had a rich mixture rating of 130 and late war, was pushing 140.
Some might find this of interest but no breakdown of fuel types,
(http://img.villagephotos.com/p/2005-12/1114844/Germanfuel-1.jpg)
What is of interest is that it looks like there was lots of stock, so the so called lack of fuel starting in the last half of the war could be possibly because of distribution problems.
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Viking
That was my point. There is more than one way to skin a cat.
Originally posted by Viking
The difference is not so big as you might think just by looking at the numbers. The DB was a high compression, low-blown engine, while the RR was a low- compression, high-blown engine. Some of the DB engine volume was used up by the higher compression ratio. The RR’s supercharger had to “make up for the slack” of the RR’s lower compression to get the same amount of fuel mix compressed in the cylinders. The higher volume also allowed the DB to produce roughly the same amount of power using 87 octane fuel as the RR did with 130 octane. It is very evident that the DB engineers were fighting an uphill battle against RR with the deteriorating availability of strategic materials and fuel. It’s a testament to their skill and ingenuity that they manage to keep pace at all.
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Yup, most certainly is.
Just a note to those that might think the 109G-6/AS or G-14/AS(M) were rare or "special" planes fielded only in small numbers: By late spring of 1944 the DB 605AM and DB 605AS(M), both producing 1800 hp with MW50, were the standard production engines for the 109G. The AM engines going mostly to the East where low to medium altitude performance mattered most, and the AS(M) engines to the West where high altitude performance was essential. During 1944 Germany produced over 14,000 109G's, the vast majority with 1800 hp AM or AS(M) engines.
And to quote another poster who paraphrases from a tv show that interviewed a P-51 pilot: (phew! is that even a proper sentence? ;))
Originally posted by AquaShrimp
I was watching "Wings" one day, and a P-51D pilot was talking about BF-109s being way above them (30,000+) as they were escorting bombers. He said these were special high-alt equipped 109s, and that they had much better performance than the P-51s at such altitudes.
Any idea to what type of BF-109 he was referring to?
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Originally posted by Viking
The DB 605D used the exact same supercharger as the DB 605AS: the supercharger developed for the DB 603. The DB 605D was an improved DB 605ASM. However the DB 605D was a real stopgap engine; the 109K was supposed to be powered by the DB 605L.
Actually not, the DB 605D was a whole new variant of the DB 605, it's developement started long before the DB 605AS was born. The DB 605AS was born because the delays in the DB 605D developement (for more information see Valtonen's article on DB 605AS in the SIHL).
The DB 605L was yet another 605 variant; basicly DB 605D with two stage super charger.
Originally posted by Viking
Just a note to those that might think the 109G-6/AS or G-14/AS(M) were rare or "special" planes fielded only in small numbers: By late spring of 1944 the DB 605AM and DB 605AS(M), both producing 1800 hp with MW50, were the standard production engines for the 109G. The AM engines going mostly to the East where low to medium altitude performance mattered most, and the AS(M) engines to the West where high altitude performance was essential. During 1944 Germany produced over 14,000 109G's, the vast majority with 1800 hp AM or AS(M) engines.
Well, if over the half of the BF 109s ever produced were G-6s, how can wast majority of the 1944 produced 14000 planes be with MW-50. The G-6 was produced until autumn 1944 and many of the practically similar G-14s lacked MW50.
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Can you provide a more complete citation for Valtonen's article?
Originally posted by gripen
Actually not, the DB 605D was a whole new variant of the DB 605, it's developement started long before the DB 605AS was born. The DB 605AS was born because the delays in the DB 605D developement (for more information see Valtonen's article on DB 605AS in the SIHL).
The DB 605L was yet another 605 variant; basicly DB 605D with two stage super charger.
Well, if over the half of the BF 109s ever produced were G-6s, how can wast majority of the 1944 produced 14000 planes be with MW-50. The G-6 was produced until autumn 1944 and many of the practically similar G-14s lacked MW50.
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Suomen Ilmailuhistoriallinen Lehti, 4/1995 p.15-16.
Hannu Valtonen: "Bf 109 G-6/AS, DB 605 AS moottorit Suomessa".
Written in Finnish and sources include BAMA, FAF AS papers etc.
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Originally posted by gripen
Well, if over the half of the BF 109s ever produced were G-6s, how can wast majority of the 1944 produced 14000 planes be with MW-50. The G-6 was produced until autumn 1944 and many of the practically similar G-14s lacked MW50.
A 109G-6/AS(M) is still a G-6. And I sincerely doubt any DB 605 engine was produced without MW50 after June 1944, unless with GM1.
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Out of some 17,017 new build (neubau) 109s built from Jan 1944 to wars end, only 1377 were G-14/AS and 1 G-6/AS.
The G-6AS was mostly conversions, some 686.
So only 2064 /AS 109s or 12% of 109s.
A pdf file can be found here, post by ArtieBob, http://forum.12oclockhigh.net/showthread.php?t=2462&page=3&highlight=neubau
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Thanks for posting it Milo, but downloading the attachment is only for registered users on that bbs I’m afraid. Note that I said the vast majority of 109’s produced in 1944 had AM or AS(M) engines. Some 2000+ AS(M) 109’s sounds about right. They would be the escort fighters on the Western Front. 12% of all 1944 109’s being high altitude variants is a significant number.
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Viking, I suggest you to register there. You won't regret :)
Yes, only 1377 109/AS, but also about 3600 with the 605D engine.
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2064 G-6/AS and G-14/AS plus 3600 DB 605D G-10's and K-4's. That’s 5664 high altitude 109's out of some 17,000. One in three 109's.
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Originally posted by Meyer
Viking, I suggest you to register there. You won't regret :)
Oh I think I would. I would have to give up any attempt at having a life! ;)
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Here is a data sheet on the G-10 (K-4 would be simular)
(http://img.villagephotos.com/p/2005-12/1114844/109G_10-1.jpg)
Here is a data sheet on the G-6
(http://img.villagephotos.com/p/2005-12/1114844/109G5_6_14-1.jpg)
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Thanks again! :)
(What's with you Milo? The old Milo that I knew would more likely post a picture of a burning 109 wreck and profess the absolute dominance of the Spitfire! :huh I think this new Milo scares me. ;))
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Not as fast as a Mustang, - well, overlapping.
And nowhere near a Spitfire from the same era in ROC. Except very high up?
I have one good document of a 109G. tested in 1944 (ahh, Gripen), and it's rather in the same ballpark, some 6 mins+ to 20K.
Now there is one thing about the DB that I wanted to mention. Due to material problems etc.(war situation) the legend goes that they were not up to what the design was about. So would that apply to top-notch measurements, or just the lifetime?
There are some documents about this I belive, but I got on the lead from Rall, who was not at all happy with his DB and his 109 when he had be jocking around with Allisons, Merlins and P&W's, P51, Spitty, P47 and the P38.
Anyway, there are always grayzones.
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who had the sig "A good Spitfire is a burning Spitfire" by the way? Kuffie? Or was it Niklas???
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No Viking, it is only when Barbi put on his hobnailed boots and started doing the goosestep. Someone had to counter the utter bs spewed by Barbi.
Yes Angus it was Barbi.
Here is another little trivia about German aero engines written by a German,
I don't know for shure about the alloys the Allies used for their aircraft engines - but the Germans made excessive use of ELECTRON for their engine's light-alloy-castings - that is: an alloy with up to 60 percent Magnesium to 40 percent Aluminium - throughout the entire engine.
By doing so, you can reduce the wheight of a casting down to 2/3rds of that of a sheer aluminium-alloy. Bad point is, that Electron-alloys must be coated to become oil- and water-tight, as Electron-castings tend to be porous.
Secondly, Electron-castings corrode like Hell: Electron is hysterically sensitive to water, due to it's high Magnesium-contence. The applied coating had to fight that corrosion, too. But it could do so only to a certain extent. as even the finest cracks, fissures and, punctures in the laquer-coating would allow enough humidity, if not sheer coolant liquid sip into the Electron and initiate intermolecular corrosion hat, it would render that specific casting scrap before long.
If you should ever have asked yourself, why there are so few airworthy genuine german engines from WWII left in the World - there you have the answer for this question: They are all corroded down to unairworthiness (if such a word should exist at all in English) - if not (white) dust...
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Originally posted by Viking
A 109G-6/AS(M) is still a G-6. And I sincerely doubt any DB 605 engine was produced without MW50 after June 1944, unless with GM1.
Most of the G-6/AS planes were without MW50 (at least those built/converted before June). And the production of the DB 605A (as well as standard G-6) continued until late 1944. There were large number of G-14s without MW50 as well.
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Originally posted by Nashwan
FTH for the V-1650-7 was far lower than that, as it was a low alt engine. FTH unrammed was under 20,000 ft.
A better comparison with the 605AS is the Merlin 70, the high altitude variant of the Merlin 60 series. That produced 1210 hp at 26,000 ft at reduced rpm and boost, ie at its 1 hour rating (2850 rpm, 12 lbs boost).
At 3000 rpm and increased boost, power would be higher at 26,000 ft.
(and btw, the DB 605AS produced 1200 PS, which is about 1180 HP)
Dont forget to add the exhaust thrust to the DB´s power, this is specialy important at high altitude and high speed.
Originally posted by Nashwan
No. The Merlin produces more power at what is basically a cruise setting than the DB does at maximum power. And peak power on the Merlin 70 is 1710 hp at 11,000 ft.
The DB605ASM had 1800PS at sea level, around 1850PS at 1500m(4900ft) and still 1500PS in 6500m(21000ft) + the exhaust thrust and all this for up to 10min usage. I guess it still had around 1700PS + exhaust thrust in 11000ft, while this is "only" a peak for the Merlin70, the DB has a rather constant powercurve.
Both designs had advantages and disadvantages, changing with different altitudes and speeds, but all over the result was rather similar i would say.
The used airframes of both engines got droven rather easy to their limitaions, what was pretty much in the highest class of propdriven planes with normal airfoils.
Hi Milo,
your 109G6 scan is actually rather a G14 scan.
The G6AS w/o MW50 must have been a bit faster at hight, due to less weight.
This planes wear MW50 and show the Vmax of the G14 and G14AS.
Greetings,
Knegel
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Dont forget to add the exhaust thrust to the DB´s power, this is specialy important at high altitude and high speed.
Then I'd have to add the exhaust thrust for the Merlin, too. The Merlin figures I gave are unrammed, and exclude exhaust thrust.
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The supercharger of the two stage supercharger merlin afaik did use the exhaust thrust and didnt left much, while the DB supercharger did not.
Rammed power isnt exhaust thrust, rammed simply mean that the air inlet system use the presure of highspeed aiflow to load the engine in a better way, to increase the power. This work somewhat like a supercharger. The listed DB power is also unrammed.
Greetings,
Knegel
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Umm... I don't think the Merlin's two-stage supercharger was exhaust driven. It was driven off the crankshaft, just like on the DB. You must be thinking of the turbo-supercharged Allison. However I do agree with your point on the DB’s smooth power curve vs. the Merlin’s max power being only a peak at a very narrow altitude band. That is an important point.
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Hi,
oh, i thought only the early single stage once was crankshaft droven, but probably your right.
Then of course the exhaust thrust could be there as well, depending to the exhaust.
The BMW801D for example never got the better exhaust, which did provide more power(80PS) but also more exhaust thrust(the late FW190A9´s got this feature).
Greetings,
Knegel
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Originally posted by Viking
However I do agree with your point on the DB’s smooth power curve vs. the Merlin’s max power being only a peak at a very narrow altitude band. That is an important point.
The adjustment of the hydraulic coupling in DB engines was not particularly efficient because it was not based on MAP but altitude and some degree on RAM. The phenomena can be seen in the charts which gives the "ladedruck" and "gebläsedruck"; the engine runs more or less throttled up to the FTH. Basicly large part of the theoretical advantage was lost due to this. In the 603L and 605L the throttle system was improved to reduce this problem but these never reached service.
Even in the optimal case, the hydraulic coupling gives advantage only between the 1st and 2nd FTH, in all other areas direct mechanical connection is more efficient.
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I think you exaggerate a bit, or don’t understand the workings of a supercharger. A conventional supercharger like the one on the Merlin produces a lot of overpressure at altitudes below the FTH of each stage. This overpressure is just dumped, but the engine must still use a significant amount of power to produce this overpressure. The DB design added a hydraulic converter (like on an automatic gear box) that reduced the amount of power delivered from the engine to the supercharger depending on the barometric pressure (altitude). This ensured that the supercharger produced enough pressure to feed the engine at WEP at any given altitude up to FTH, but reduced the waste of engine power used to produce unnecessary overpressure below FTH to a minimum. It could have been made even more efficient at lower throttle settings by factoring in throttle setting/manifold pressure, but to say that it was inefficient compared to a conventional supercharger is disingenuous at best.
At FTH a direct-drive supercharger is slightly more efficient since the hydraulic converter absorbs some power in the form of heat generation (again just like an automatic gear box), but at all other altitudes (below FTH) the DB supercharger is much more efficient.
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People should really read the NACA report I posted in the first page of this thread. It is about the effects of different charging methods.
-C+
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It is a good introduction to the different charging methods, and I've had the document for some time (don't know who posted it first, maybe it was you). However I'm afraid that some people will not learn because it goes against what they believe and want to be true.
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The two stage supercharger on the Merlin 60 and subsequent models was gear driven, not exhaust driven. RR may have experimented with turbo compounding but the certainly did not get it into production during the war.
-Blogs
Originally posted by Knegel
The supercharger of the two stage supercharger merlin afaik did use the exhaust thrust and didnt left much, while the DB supercharger did not.
...
Greetings,
Knegel
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Crankshaft driven centrifugal superchargers are not driven or even augmented by exhaust thrust. Any exhaust driven supercharger is either a turbine or a turbocharger. There are various forms of compound supercharging, where different types of superchargers are combined on the same engine, most commonly when some form of crank driven supercharger is combined with a turbocharger.
Crankshaft driven superchargers are tuned for various boost levels by size and drive ratio, they do not normally have any sort of dump valve, but normally have what is called a "pop off valve", intended to vent excess pressure, usually caused by a back fire. Crankshaft driven centrifugal superchargers are somewhat similar in design to turbochargers, except they have no exhaust turbine side to drive them, as they are driven by the crankshaft through a coupling and gearbox. It is necessary to spin a centrifugal supercharger at very high speeds, often in excess of 5 times the engine speed or more, because they are not positive displacement and therefore leak inside. Usually, the drive is a combination of ball bearings and planetary gears, to allow for over speed and for slippage.
The other common form of crankshaft driven supercharger is the positive displacement type, the most common version of the positive displacement supercharger is the Roots style, commonly seen on Detroit Diesel engines (first used for this by GMC trucks). This supercharger is rarely if ever seen on anything but older Detroit Diesel engines, and race engines such as drag racing or truck and tractor pulling. The ratio between the crankshaft and the supercharger is fixed, as opposed to variable. The boost is determined by drive ratio and supercharger size. They are rarely driven any more than twice the engine speed.
A turbocharger is similar to the centrifugal crank driven supercharger, but uses an exhaust turbine inside a housing to drive the compressor side. It is on the exhaust side of a turbocharger where you find a dump valve used to control boost, it is called a waste gate. When a turbocharger reaches a certain level of boost on the compressor side, the waste gate gate is opened, allowing exhaust to bypass the turbine, and slowing the turbocharger down to produce less boost. In the case of the General Electric B series turbochargers used on the Allison in the P-38, and the P&W in the P-47, as well as on some bombers, the waste gate also controls turbocharger speed, as at very high altitudes, where there is too little air to produce full boost, the turbocharger, without the load of producing full boost, will over speed. This happens around 33,000 to 35,000 feet. The waste gate on a General Electric B series turbocharger is actually controlled by an RPM governor, and actuated by oil pressure. The P-38 and P-47 had RPM indicator lights on the instrument panel so the pilot could see if he was exceeding the RPM limit. On the P-38, pilots sometimes failed to keep the engine temperatures in the correct operating range, and if the oil got too cold it would congeal, and the governor would not work, allowing the turbocharger to over speed or over pressurize.
Most high end endurance type superchargers are coupled with some sort of intercooler, since compressing air, especially enough to make serious horsepower, heats it a great deal, leading to inefficiency and detonation. Most intercoolers are "core" type, AKA heat exchanger, as seen on the K model and later P-38, and similar in construction to a radiator or oil cooler. They can be either air to air or air to liquid. Air to air types are common in aircraft, as the cooler air of high altitudes allows them to be fairly efficient. Efficiency is determined by the amount restriction they create (pressure drop across the intercooler) and the amount they lower the air temperature. A 100% efficient intercooler (very rare) will not lose any boost, the pressure before the intercooler and the pressure after the intercooler are the same, and it will lower the air charge temperature back to the ambient air temperature, the temperature the air was before the supercharger compressed it. Properly sized intercoolers are close to 100% efficient with regards to restriction, and around 50% efficient on cooling (lowers the compressed air temperature to a point half way between the temperature of the compressed air out of the supercharger and and the ambient air temperature before it is compressed).
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Originally posted by Viking
I think you exaggerate a bit, or don’t understand the workings of a supercharger. A conventional supercharger like the one on the Merlin produces a lot of overpressure at altitudes below the FTH of each stage.
Below 1st FTH the hydraulic coupling works as a fixed speed supercharger so up to this altitude there is no advantage but some disadvantage due higher losses of the hydraulic coupling and also due to power needed to run second oil pump.
Between 1st and 2nd FTH hydraulic coupling has an advantage when the second oil pump starts to increase speed of the supercharger. However, in the case of the DB, supercharger still does some overpressure because the speed of the supercharger is not adjusted according to MAP but simple barometric valve. In practice some of the theoretical advantage is lost due to this. Note that the throttle valve was located after the supercharger so the losses due to throttling were higher than in the case where the valve is before supercharger (in the L series DBs this was fixed using the spin valve before the supercharger).
Above 2nd FTH the hydraulic coupling works as a fixed speed supercharger again so there is no advantage but some disadvantage again due to higher losses of the hydraulic coupling.
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I am not sure I follow this.
My impression was there was only 1 full thottle height as their was only 1 stage, but a continuously variable speed.
-Blogs
Originally posted by gripen
Below 1st FTH the hydraulic coupling works as a fixed speed supercharger so up to this altitude there is no advantage but some disadvantage due higher losses of the hydraulic coupling and also due to power needed to run second oil pump.
Between 1st and 2nd FTH hydraulic coupling has an advantage when the second oil pump starts to increase speed of the supercharger. However, in the case of the DB, supercharger still does some overpressure because the speed of the supercharger is not adjusted according to MAP but simple barometric valve. In practice some of the theoretical advantage is lost due to this. Note that the throttle valve was located after the supercharger so the losses due to throttling were higher than in the case where the valve is before supercharger (in the L series DBs this was fixed using the spin valve before the supercharger).
Above 2nd FTH the hydraulic coupling works as a fixed speed supercharger again so there is no advantage but some disadvantage again due to higher losses of the hydraulic coupling.
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Nice summary Virgil.
I have two qualifcations. First most engines fitted with a turbo supercharger will have a single stage, single speed, gear-driven supercharger as well. It's purpose is essentially to ensure a good fuel mixture. It does not develop very high manifold pressures, since that is the job of the turbo.
Second, on the turbo-compond engines, some of the power from the turbine is returned to the drive shaft rather than being used to push air into the engine. Wright developed these after the war, as did some of the Russian design bureaus.
-Blogs
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Originally posted by joeblogs
I am not sure I follow this.
My impression was there was only 1 full thottle height as their was only 1 stage, but a continuously variable speed.
The 1st FTH is the altitude where the hydraulic coupling starts to increase the speed of the supercharger with second oil pump. Below this altitude it works like fixed speed unit because the slip of the drive was constant ie the supercharger used constant oil flow from the first oil pump.
In other words the DB supercharger was variable speed unit only at certain altitude range; between the altitude where the second oil pump started increase the speed of the supercharger and where the supercharger reached peak speed.
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Ok so below FTH 1, the only variable is the Throttle. Above this, is the throttle wide open, but the rotational speed of the supercharger increasing?
-Blogs
Originally posted by gripen
The 1st FTH is the altitude where the hydraulic coupling starts to increase the speed of the supercharger with second oil pump. Below this altitude it works like fixed speed unit because the slip of the drive was constant ie the supercharger used constant oil flow from the first oil pump.
In other words the DB supercharger was variable speed unit only at certain altitude range; between the altitude where the second oil pump started increase the speed of the supercharger and where the supercharger reached peak speed.
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Here is chart which helps to understand the issue. It's a DB 601 chart but the principle is the same. Up to 1st FTH (2100m), it works like a fixed speed unit. Between 1st FTH and 2nd FTH (5500m with 1,35ata and 2600rpm) it works like a variable speed unit. Above that it's a fixed speed unit again. If you compare that to the DVL supercharger in the NACA report, you will find out that the DBs were far from the ideal case.
(http://www.onpoi.net/ah/pics/users/852_1181653836_db.jpg)
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What are the parallel lines on the right hand side of the chart?
There is some variation in another parameter, but I know too little German to figure it out.
-Blogs
Originally posted by gripen
Here is chart which helps to understand the issue. It's a DB 601 chart but the principle is the same. Up to 1st FTH (2100m), it works like a fixed speed unit. Between 1st FTH and 2nd FTH (5500m with 1,35ata and 2600rpm) it works like a variable speed unit. Above that it's a fixed speed unit again. If you compare that to the DVL supercharger in the NACA report, you will find out that the DBs were far from the ideal case.
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Originally posted by joeblogs
What are the parallel lines on the right hand side of the chart?
Stau = Dynamic pressure (RAM)
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Errata: The FTH i have stated for the Merlin V-1650-7 of the P-51D is actually that of the V-1650-3 of the P-51B. The correct FTH's of the -7 is 7,000 feet (1st stage) and 18,000 feel (2ns stage). For comparison the FTH's of the Merlin 70 is 11,900 feet (1st stage) and 24,700 (second stage).
The DB 605AS(M) with a FTH of 7,9 km (~26,000 feet) has a higher FTH than all these Merlins.
Originally posted by Viking
The DB 603L and 605L were designed for very high altitudes. The DB's already had a supercharger with a similar FTH to that of the two stage supercharged Merlins. The DB supercharger design was unique in that it was a step-less, variable speed design using a hydraulic converter to adjust the impeller speed according to altitude and engine boost. To put it in car terms the Merlin had a manual two speed gear box, while the DB a one speed automatic with roughly the same gear ratio as the Merlin’s high-gear. Using the DB 603's bigger supercharger on the DB 605 (known as the AS versions) gave the engine a FTH of more than 26,000 feet which is roughly equal to the two stage Merlins.
Originally posted by Viking
The RR Merlin 68/ Packard Merlin V-1650-7 used by the P-51D. This engine has a FTH of 25,800 feet where it produces 1210 hp.
The DB 605AS using B4 fuel and no MW50 has a FTH of 26,200 feet (8 km) where it produces 1200 hp.
These two engines are for all intents and purposes identical in performance. Only difference being the different approach to supercharging. RR with its two-stage blower and the DB with its single-stage variable-speed blower.
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Originally posted by joeblogs
Nice summary Virgil.
I have two qualifcations. First most engines fitted with a turbo supercharger will have a single stage, single speed, gear-driven supercharger as well. It's purpose is essentially to ensure a good fuel mixture. It does not develop very high manifold pressures, since that is the job of the turbo.
Second, on the turbo-compond engines, some of the power from the turbine is returned to the drive shaft rather than being used to push air into the engine. Wright developed these after the war, as did some of the Russian design bureaus.
-Blogs
Yes, aircraft engines equipped with turbochargers will often have a crankshaft driven supercharger as well. It is actually necessary to provide boost at lower RPM and lower throttle settings as well. The same engines are often built with compression ratios of 7:1 or less. A turbocharger will only create boost under a good load, and at cruise on a high performance aircraft engine it is actually the supercharger that provides a lot of the boost, because there isn't a heavy load on the engine, nor is it at higher RPM, so there isn't enough volumes of exhaust gas to drive the turbocharger to create boost. The supercharger also creates boost when the throttles are opened quickly, creating initial acceleration, and exhaust gas to spool the turbo up.
Yes, the turbo-compound engines also use the turbine to drive the engine itself. Allison actually built a real monster based on the original V-1710 design, that made over 3400HP at the shaft. The engine and supercharging system worked fine, they had a problem with the exhaust manifold temperature, that was the only real drawback.
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so variation in RAM air can move the 2nd FTH up to 3km?
-Blogs
Originally posted by gripen
Stau = Dynamic pressure (RAM)
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Originally posted by gripen
The 1st FTH is the altitude where the hydraulic coupling starts to increase the speed of the supercharger with second oil pump. Below this altitude it works like fixed speed unit because the slip of the drive was constant ie the supercharger used constant oil flow from the first oil pump.
In other words the DB supercharger was variable speed unit only at certain altitude range; between the altitude where the second oil pump started increase the speed of the supercharger and where the supercharger reached peak speed.
The 1st FTH was at ~5000 feet so the efficiency loss below this altitude is minimal compared to the Merlin 70's supercharger which has a 1st stage FTH of 11,900 feet. The barometric pressure at 5000 feet is only 14% less than at sea level, so at sea level the DB's supercharger is only producing 14% waste pressure. The Merlin 70 otoh produces 33%-34% wasted pressure at sea level.
Originally posted by joeblogs
Ok so below FTH 1, the only variable is the Throttle. Above this, is the throttle wide open, but the rotational speed of the supercharger increasing?
-Blogs
A short description of the DB 610’s supercharger which is similar in function to the Db 605’s:
Centrifugal supercharger on port side of engine driven through a fluid coupling by a shaft at right angles to crankshaft. This shaft is driven through bevel gears from the crankshaft, variation in propeller speed secured through variable filling of fluid coupling by two-stage engine driven pump receiving lubricating oil from the main pressure filter.
First stage delivers oil direct to coupling and second stage delivery is passed in varying proportions between crankcase and coupling by piston valve controlled by a capsule which is sensitive to inlet pressure. Second stage cuts in at approximately 5,000 ft. and full delivery occurs at approximately 11,500 ft.
Butterfly throttle which is capsule controlled regulates supercharger delivery, second throttle which is pilot operated controls air supply to engine and manifold pressure, first throttle subjected to pressure between two throttles, increased boost for take-off controlled by clockwork mechanism, mixture delivered by supercharger to looped manifold by large diameter pipe, dry-sump pressure-feed lubrication, gear type oil pumps, spray of oil directed upon reduction gears, main oil pressure line feeds crankshaft bearings, secondary line feeds supercharger fluid pump.
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Originally posted by Viking
Errata: The FTH i have stated for the Merlin V-1650-7 of the P-51D is actually that of the V-1650-3 of the P-51B. The correct FTH's of the -7 is 7,000 feet (1st stage) and 18,000 feel (2ns stage). For comparison the FTH's of the Merlin 70 is 11,900 feet (1st stage) and 24,700 (second stage).
The DB 605AS(M) with a FTH of 7,9 km (~26,000 feet) has a higher FTH than all these Merlins.
Well, perhaps you should compare the reached output at altitude with RAM; say 10km:
P-51D with V-1650-7 from here (http://www.wwiiaircraftperformance.org/mustang/p51d-15342-level.jpg): about 1000hp
P-51B with V-1650-3 from here (http://www.wwiiaircraftperformance.org/mustang/p-51b-6883-level.jpg): about 1200hp
Bf 109G (GJ+FX) with DB 605AS: DB test data gives about 1,1ata at 2800rpm ie roughly about 1000hp (or ps, I used a DB 605A chart and a AS does actually a bit less).
So basicly the DB 605AS did about same as V-1650-7.
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Originally posted by Viking
The 1st FTH was at ~5000 feet so the efficiency loss below this altitude is minimal compared to the Merlin 70's supercharger which has a 1st stage FTH of 11,900 feet. The barometric pressure at 5000 feet is only 14% less than at sea level, so at sea level the DB's supercharger is only producing 14% waste pressure. The Merlin 70 otoh produces 33%-34% wasted pressure at sea level.
Pointless comparison, the Merlin 70 was a true high altitude engine.
Originally posted by Viking
A short description of the DB 610’s supercharger which is similar in function to the Db 605’s:
Well, that is about the same I have explained to you.
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The power graph looks good to me. Fairly even up to the FTH. What is wrong with it?
The ideal in that NACA report is not something you can do IRL It is lossless and the induced temperature to manifold is lower than can be normally attained. The matter is how close to that ideal you can get. The variable speed unit provides steady power output up to critical height.
-C+
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Originally posted by gripen
Well, perhaps you should compare the reached output at altitude with RAM; say 10km:
P-51D with V-1650-7 from here (http://www.wwiiaircraftperformance.org/mustang/p51d-15342-level.jpg): about 1000hp
P-51B with V-1650-3 from here (http://www.wwiiaircraftperformance.org/mustang/p-51b-6883-level.jpg): about 1200hp
Bf 109G (GJ+FX) with DB 605AS: DB test data gives about 1,1ata at 2800rpm ie roughly about 1000hp (or ps, I used a DB 605A chart and a AS does actually a bit less).
So basicly the DB 605AS did about same as V-1650-7.
I don’t have numbers at 10 km for the DB 605AS only at 8 km where it produces 1200 PS according to the Motorenblatt.
Originally posted by gripen
Pointless comparison, the Merlin 70 was a true high altitude engine.
The Merlin 70 had very similar performance to the V-1650-3.
Originally posted by gripen
Well, that is about the same I have explained to you.
Perhaps, but in better detail and without the negative connotations. In any case that part of the post was not meant for you.
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"Between 1st and 2nd FTH hydraulic coupling has an advantage when the second oil pump starts to increase speed of the supercharger. "
The flow away from the clutch is regulated in two ways. It has only one oil pressure feed. The oil pump does not rotate the charger, the engine does.
"However, in the case of the DB, supercharger still does some overpressure because the speed of the supercharger is not adjusted according to MAP but simple barometric valve. In practice some of the theoretical advantage is lost due to this."
I don't follow your logic. The pressure is controlled due to barometric conditions. How is that inaccurate considering that the aneroid is working correctly.
"Note that the throttle valve was located after the supercharger so the losses due to throttling were higher than in the case where the valve is before supercharger (in the L series DBs this was fixed using the spin valve before the supercharger)."
The throttle is supposed to cause loss -without it the plane would not stop. The point is that at what altitude you can open the throttle fully and what charger configuration will not let you do it. In DB you can open the throttle fully at any altitude and the charging control itself does not prevent it.
"Above 2nd FTH the hydraulic coupling works as a fixed speed supercharger again so there is no advantage but some disadvantage again due to higher losses of the hydraulic coupling."
Nope, the 4% loss can be compensated by simply rotating the impeller faster. The only drawback is the excess heat which needs to be get rid of.
-C+
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Originally posted by Viking
I don’t have numbers at 10 km for the DB 605AS only at 8 km where it produces 1200 PS according to the Motorenblatt.
There is plenty of charts in the site linked above.
Originally posted by Viking
The Merlin 70 had very similar performance to the V-1650-3.
The V-1650-3 was a high altitude engine like the Merlin 70.
Originally posted by Viking
Perhaps, but in better detail and without the negative connotations. In any case that part of the post was not meant for you.
Are you saying that the problems of the DBs I mentioned above are not true?
Besides, perhaps you should investigate your own claims as well...
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Originally posted by MiloMorai
No Viking, it is only when Barbi put on his hobnailed boots and started doing the goosestep. Someone had to counter the utter bs spewed by Barbi.
Yes Angus it was Barbi.
Here is another little trivia about German aero engines written by a German,
I don't know for shure about the alloys the Allies used for their aircraft engines - but the Germans made excessive use of ELECTRON for their engine's light-alloy-castings - that is: an alloy with up to 60 percent Magnesium to 40 percent Aluminium - throughout the entire engine.
By doing so, you can reduce the wheight of a casting down to 2/3rds of that of a sheer aluminium-alloy. Bad point is, that Electron-alloys must be coated to become oil- and water-tight, as Electron-castings tend to be porous.
Secondly, Electron-castings corrode like Hell: Electron is hysterically sensitive to water, due to it's high Magnesium-contence. The applied coating had to fight that corrosion, too. But it could do so only to a certain extent. as even the finest cracks, fissures and, punctures in the laquer-coating would allow enough humidity, if not sheer coolant liquid sip into the Electron and initiate intermolecular corrosion hat, it would render that specific casting scrap before long.
If you should ever have asked yourself, why there are so few airworthy genuine german engines from WWII left in the World - there you have the answer for this question: They are all corroded down to unairworthiness (if such a word should exist at all in English) - if not (white) dust...
Holy moly. So that's why. Well, makes sense to what Rall said, but what would be the cure? Wchich parts suffer and have to be refreshed? After all, he mentioned wear and loss of power after as little as 10 hours.
This also bothered me on a different quest when I was researching some claims by the 109 band. ROC.
ROC really needs a wing and power. Top speed is more like (mostly) parasite drag vs power, etc etc. So, using the Spitfire and the 109 as a comparison and calculating into NM's, they pull apart in ROC as the war proceeds, - i.e. the Spitfire gains. A Spitfire with a Merlin 66 or 70 weighting the same as a 109G will easily outclimb it. I have no other data. From SL to some 30K all combined that is.
I always tended to write that on to the wing, and not the Engine - the engines always seemed to be very very close, and since the closest match would be a Spit I (CS) and a 109E (almost same power with the 109 slightly above AFAIK), the difference in pulled Newtons was already close to 10%.
But if the DB was always being saved, or derated due to wear or tear, it upsets this a bit. I mean, why still be doing tests at 1,3/1,43 ATA still in 1944??????
:confused:
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Originally posted by Charge
"Between 1st and 2nd FTH hydraulic coupling has an advantage when the second oil pump starts to increase speed of the supercharger. "
The flow away from the clutch is regulated in two ways. It has only one oil pressure feed. The oil pump does not rotate the charger, the engine does.
Read my post please.
Originally posted by Charge
"However, in the case of the DB, supercharger still does some overpressure because the speed of the supercharger is not adjusted according to MAP but simple barometric valve. In practice some of the theoretical advantage is lost due to this."
I don't follow your logic. The pressure is controlled due to barometric conditions. How is that inaccurate considering that the aneroid is working correctly.
Needed supercharger speed (in ideal conditions) depends on MAP.
Originally posted by Charge
"Note that the throttle valve was located after the supercharger so the losses due to throttling were higher than in the case where the valve is before supercharger (in the L series DBs this was fixed using the spin valve before the supercharger)."
The throttle is supposed to cause loss -without it the plane would not stop. The point is that at what altitude you can open the throttle fully and what charger configuration will not let you do it. In DB you can open the throttle fully at any altitude and the charging control itself does not prevent it.
The problem is that the DBs did not work that way, see above.
Originally posted by Charge
"Above 2nd FTH the hydraulic coupling works as a fixed speed supercharger again so there is no advantage but some disadvantage again due to higher losses of the hydraulic coupling."
Nope, the 4% loss can be compensated by simply rotating the impeller faster. The only drawback is the excess heat which needs to be get rid of.
Please read your own text, there is 4% loss.
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Originally posted by gripen
There is plenty of charts in the site linked above.
For the DB 605AS as well? (I notice you did not post a link to a DB chart)
Originally posted by gripen
The V-1650-3 was a high altitude engine like the Merlin 70.
You chose to compare the DB 605AS with the V-1650-3 and -7 (that I compared it to earlier not realizing it actually was a -3).
Here is a piece of news that might surprise you: The DB 605AS is also a high altitude engine.
Originally posted by gripen
Are you saying that the problems of the DBs I mentioned above are not true?
Yes. They are not problems at all and the use of the word “problem” is inappropriate. You’re basically saying the supercharger had “problems” because it could have been even better than it already was.
Edit: The fact of the matter is that the DB supercharger was more efficient at a much wider altitude range than the RR supercharger. The RR supercharger was marginally (you mention 4%) more efficient at its two FTH’s, but those only peak at very narrow altitude bands.
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I don't follow the logic here.
There are lots of sources of losses in driving a supercharger. Yes one of them is spinning the supercharger at a constant multiple of engine speed and NOT opening the throttle wide open. Everyone gets that.
The losses I was referring to was the use of a single (and therefore larger) diameter impellor which is less efficient than a smaller impeller. This is offset, partially, by spinning the impeller at a smaller (but constant) multiple of engine RPM below the first throttle height if I understand what Grippen has said.
Now even a high altitude version of the Merlin is using two impellers, the smaller one at lower altitudes. That impeller will be more efficient than a larger impeller. Now with the Merlins, it is likely the engine is not running at full Throttle at sea level, and there are losses associated with spinning all this machinery and not pushing all the air you could through it.
The point is that the efficiency losses come from a variety of sources and they are all relevant to the comparisons.
-Blogs
Originally posted by Viking
The 1st FTH was at ~5000 feet so the efficiency loss below this altitude is minimal compared to the Merlin 70's supercharger which has a 1st stage FTH of 11,900 feet. The barometric pressure at 5000 feet is only 14% less than at sea level, so at sea level the DB's supercharger is only producing 14% waste pressure. The Merlin 70 otoh produces 33%-34% wasted pressure at sea level.
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Merlin 70 = high alt engine.
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Originally posted by joeblogs
The losses I was referring to was the use of a single (and therefore larger) diameter impellor which is less efficient than a smaller impeller.
The DB supercharger wasn’t that large. Remember that the DB was a low-blown high-compression engine, meaning the engine did much of the compression in the cylinders itself. The DB 605AS only runs at 1.42 ATA boost, meaning 142% of normal sea level atmosphere pressure.
Originally posted by joeblogs
Now even a high altitude version of the Merlin is using two impellers, the smaller one at lower altitudes. That impeller will be more efficient than a larger impeller. Now with the Merlins, it is likely the engine is not running at full Throttle at sea level, and there are losses associated with spinning all this machinery and not pushing all the air you could through it.
But they are pushing all the air they could though the supercharger at all times. They just dump what the engine can’t use at altitudes below the FTH’s, and that’s the source of the inefficiency. This is the inefficiency the Germans avoided by regulating how much engine power is used by the supercharger, thus reducing the “overproduction” of boost (a concept they nicked from the Polish).
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Originally posted by Angus
Merlin 70 = high alt engine.
You too?
Originally posted by Viking
Here is a piece of news that might surprise you: The DB 605AS is also a high altitude engine.
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Originally posted by Angus
A Spitfire with a Merlin 66 or 70 weighting the same as a 109G will easily outclimb it. I have no other data. From SL to some 30K all combined that is.
I don't see any data there, just a wrong assumption... the Spitfire IX was heavier than most 109G versions.
And nowhere near a Spitfire from the same era in ROC. Except very high up?
The ROC in those charts is in the Steg-Kampfleistung regime, not in maximum power....
But if the DB was always being saved, or derated due to wear or tear, it upsets this a bit. I mean, why still be doing tests at 1,3/1,43 ATA still in 1944??????
I don't know what is wrong with doing tests at "1.3/1.43ata" in 1944, but I have no idea of what are you talking about here
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I meant "IF" in the case of weight, sorry. You'd have to strip the Spit to get the lower weight.
A Spitfire Mk VIII trop from 1943 weighting more than i.e. a 109G from 1943/44 in a test (1.3/1.43 ATA) will hit 20K like some minute ahead.
I always presumed it to be mostly the wing while the engine output in the band could be similar, so I'm just scratching my head over whether there is an engine power issue as well.
The difference in NM's seems to increase as the power goes more and the aircraft heavier, so that would point a finger at the wing, but how does a 605A with 1,3/43 compare to a Merlin 66 or 70(not a cropped one)???
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Oh, and if I understand things right the DB turbo layout is then much more flexible, while the Merlins were optimized for narrower alt bands, yes?
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You may be right, I don't have the numbers in front of me. But the amount of manifold pressure a supercharger develops does not, in itself, tell you the size of the impeller.
I am not sure where this language about dumping and waste comes from when talking about gear driven superchargers. Now a turbo has a waste gate, so that is understandable. Gear driven superchargers don't have waste gates and they don't "dump" air. What ever air the supercharger takes in will go into that engine. The only question is how much air goes into that engine per stroke and per minute. Below full throttle height, manifold pressure is held back by (1) limiting RPM and (2) throttling the engine. Having expended the energy to drive the supercharger in the first place, this is wasteful.
If what you are trying to say is that by spinning the supercharger less rapidly, you can save some energy by not pushing more air per stroke as you need, that is certainly true.
-Blogs
Originally posted by Viking
The DB supercharger wasn’t that large. Remember that the DB was a low-blown high-compression engine, meaning the engine did much of the compression in the cylinders itself. The DB 605AS only runs at 1.42 ATA boost, meaning 142% of normal sea level atmosphere pressure.
But they are pushing all the air they could though the supercharger at all times. They just dump what the engine can’t use at altitudes below the FTH’s, and that’s the source of the inefficiency. This is the inefficiency the Germans avoided by regulating how much engine power is used by the supercharger, thus reducing the “overproduction” of boost (a concept they nicked from the Polish).
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Angus, Meyer’s point is valid; climb to altitude times are for the climb & combat power setting, not emergency power. And we both know the DB gets more power from emergency power setting than a similarly rated Merlin. The Merlin has a higher continuous power output, and thus a better climb rate in non-combat “friendly” climbs. Once you push that big red button on the 109’s instrument panel the 109 handily out climbs a contemporary Merlin Spit.
Edit: About the Spit's wings: Yes you're right that a Spit will out climb a 109 if they have the same power and weight. The wings were larger. The oval shape did not help however since climbing is done at low speeds.
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Originally posted by joeblogs
If what you are trying to say is that by spinning the supercharger less rapidly, you can save some energy by not pushing as much air per second as you need, that is certainly true.
That's what I have been trying to say (and what the Germans did). I thought they dumped the extra pressure through a valve/waste gate system, but I'm not sure. Just throttling the engine seems even worse since then the supercharger would have to fight the build-up of pressure.
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"Between 1st and 2nd FTH hydraulic coupling has an advantage when the second oil pump starts to increase speed of the supercharger. "
The flow away from the clutch is regulated in two ways. It has only one oil pressure feed. The oil pump does not rotate the charger, the engine does.
Read my post please.
I did. The advantage is not "when the second oil pump starts to increase speed etc. but all the way to critical altitude if need be. The choice of impeller gear ratio could be more radical but that would mean more excess heat generated by the clutch which would again need to be wasted. So it needs to be a compromise.
"However, in the case of the DB, supercharger still does some overpressure because the speed of the supercharger is not adjusted according to MAP but simple barometric valve. In practice some of the theoretical advantage is lost due to this."
I don't follow your logic. The pressure is controlled due to barometric conditions. How is that inaccurate considering that the aneroid is working correctly.
Needed supercharger speed (in ideal conditions) depends on MAP.
Yes, which again depends on barometric pressure, a very very important factor in aeroengine performance. I see no reason why it would produce overpressure unless something is not adjusted correctly.
"Note that the throttle valve was located after the supercharger so the losses due to throttling were higher than in the case where the valve is before supercharger (in the L series DBs this was fixed using the spin valve before the supercharger)."
The throttle is supposed to cause loss -without it the plane would not stop. The point is that at what altitude you can open the throttle fully and what charger configuration will not let you do it. In DB you can open the throttle fully at any altitude and the charging control itself does not prevent it.
The problem is that the DBs did not work that way, see above.
The clutch does the controlling of charge pressure, not the butterfly valve. The valve is used for other reasons, not to regulate the power as a primary function.
"Above 2nd FTH the hydraulic coupling works as a fixed speed supercharger again so there is no advantage but some disadvantage again due to higher losses of the hydraulic coupling."
Nope, the 4% loss can be compensated by simply rotating the impeller faster. The only drawback is the excess heat which needs to be get rid of.
Please read your own text, there is 4% loss.
I don't have to as I wrote it, but let me expalin a bit more: 4% slip i.e. loss of the power that is needed to turn the supercharger. Not 4% loss of the engine power because all of the engine power is not used to turn the charger.
***
The speed of the tips of the impeller is a major factor in impeller design. When the speed gets too high the air suddenly gets hotter which causes a surge in intake temperature which causes knocking which again needs to be countered by either more intercooling or by dropping the impeller speed.
If you have a big impleller it can still move air at high altitude without too much tip speed where as a smaller impeller reaches its critical tip speed and thus altitude earlier.
-C+
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Tip speed is increasing in the diameter of the impeller. Just think of the distance the tip is covering as the impeller rotates - it is the circumference of the impeller.
This is the same principal as the propeller - the end of the propeller reaches Mach 1 before the disc does. That is one reason why there is a twist on propeller blades. It is also one of the reasons for reduction gearing on engines that turn higher than 2000 RPM.
-Blogs
Originally posted by Charge
If you have a big impleller it can still move air at high altitude without too much tip speed where as a smaller impeller reaches its critical tip speed and thus altitude earlier.
-C+
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Originally posted by Viking
For the DB 605AS as well? (I notice you did not post a link to a DB chart)
The DB 605AS as well as the DB 605A charts can be found from Valtonen's article and Raunio's article in SILH 1/2005. Charts on GJ+FX can be found from TOCH.
Originally posted by Viking
You chose to compare the DB 605AS with the V-1650-3 and -7 (that I compared it to earlier not realizing it actually was a -3).
Here is a piece of news that might surprise you: The DB 605AS is also a high altitude engine.
As you can see, at 10000m so called high altitude DB was nearly equall with low altitude (or medium altitude if that suits your needs better) version of the two stage Merlin.
Originally posted by Viking
Yes. They are not problems at all and the use of the word “problem” is inappropriate. You’re basically saying the supercharger had “problems” because it could have been even better than it already was.
Have a look here (http://www.wwiiaircraftperformance.org/me109/me-109g6-16476-pg9.jpg).
Ladedruck = manifold pressure
Gebläsedruck = pressure between impeller and the throttle valve
As you can see the DB does quite large overpressure all the way up to the 2nd FTH. That means that large part of the theoretical advantage is lost.
Besides the oil system of the supercharger caused continous problems.
Originally posted by Viking
Edit: The fact of the matter is that the DB supercharger was more efficient at a much wider altitude range than the RR supercharger. The RR supercharger was marginally (you mention 4%) more efficient at its two FTH’s, but those only peak at very narrow altitude bands.
Perhaps you should actually try to understand the data posted above. Direct mechanical supercharger is more efficient everywhere else except between the 1st and 2nd FTH.
Originally posted by Charge
The advantage is not "when the second oil pump starts to increase speed etc. but all the way to critical altitude if need be. The choice of impeller gear ratio could be more radical but that would mean more excess heat generated by the clutch which would again need to be wasted. So it needs to be a compromise.
Well, the possible advantage lies only in the area where hydraulic coupling works enough effectively. The DB 605AS had 1st FTH around 2500m without RAM and around 3000m with RAM while roughly comparable V-1650-7 had 1st FTH around 1900m and around 3000m with RAM so there is no any advantage for the DB but losses due slip and heat (direct mechanical gear has no these losses).
Originally posted by Charge
I don't follow your logic. The pressure is controlled due to barometric conditions. How is that inaccurate considering that the aneroid is working correctly.
Aneroid does not measure MAP but outside pressure on it's orifice . The optimal impeller speed depends on needed MAP. See the link above giving the MAP and "Gebläsedruck".
Basicly the aneroid using outside pressure gives just rough adjustment and rest is done with throttle valve, therefore the engine is running more or less throttled up to the 2nd FTH. Just look the MAP and Gebläsedruck values in the graph linked above (there is several similar graphs in that site).
Originally posted by Charge
The throttle is supposed to cause loss -without it the plane would not stop. The point is that at what altitude you can open the throttle fully and what charger configuration will not let you do it. In DB you can open the throttle fully at any altitude and the charging control itself does not prevent it.
You see the problem; you don't understand at all how the adjustment of the hydraulic coupling and MAP worked in the DBs. That NACA report presents just optimal case which is not reality with the DBs.
Originally posted by Charge
Nope, the 4% loss can be compensated by simply rotating the impeller faster. The only drawback is the excess heat which needs to be get rid of.
Well, direct mechanical gear does the same with less power and without losses due to heat and slip. Other way to think the same issue is that at same gear ratio on direct mechanical gear spins 4% faster and without losses due to slip and heat.
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Originally posted by Viking
Angus, Meyer’s point is valid; climb to altitude times are for the climb & combat power setting, not emergency power. And we both know the DB gets more power from emergency power setting than a similarly rated Merlin. The Merlin has a higher continuous power output, and thus a better climb rate in non-combat “friendly” climbs. Once you push that big red button on the 109’s instrument panel the 109 handily out climbs a contemporary Merlin Spit.
Edit: About the Spit's wings: Yes you're right that a Spit will out climb a 109 if they have the same power and weight. The wings were larger. The oval shape did not help however since climbing is done at low speeds.
Could you tell me why I find NO SOURCE for this??????????????????????
I have been begging for 109 tests for years, yet half of what I have just popped up in this thread. While the Spitfire climbing tests give me some data and not nearly enough, they are vastly more that all combined as a good reliable source of the Db & 109.
So, need to get clearer on this, - after all, comparing MIL to WEP is a bit of a ...wop ;)
Are the Spit performance tests done at absolute peak power?
As for the wings, you are wrong. The oval shape helps overcome (lift) induced drag, which is much more noticable at lower speed or if you you prefer, larger A.o.A.. The bigger wings would then become a handicap in the end run where the biggest factor is parasite drag, - like in a dive.
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Now I am confused.
I thought that up to the 1st FTH, the impeller spun at a constant multiple of crankshaft speed. As the plane climbed, the pilot would continue to open the throttle (which I believe also regulated RPM if I understand the German automatic controls correctly) until it was wide open at the 1st FTH. Thereafter, I thought all the action was done by the clutch, which countinuously increased the multiple of crank speed until the 2nd FTH was obtained. Am I wrong?
-Blogs
Originally posted by gripen
...
Basicly the aneroid using outside pressure gives just rough adjustment and rest is done with throttle valve, therefore the engine is running more or less throttled up to the 2nd FTH. Just look the MAP and Gebläsedruck values in the graph linked above (there is several similar graphs in that site). ...
[/B]
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Originally posted by joeblogs
I thought that up to the 1st FTH, the impeller spun at a constant multiple of crankshaft speed.
Yes, the impeller runs constant speed until the second oil pump starts to increase the speed of the impeller at 1st FTH by increasing the oil flow through the hydraulic coupling which decreases the slip of the clutch.
Originally posted by joeblogs
As the plane climbed, the pilot would continue to open the throttle (which I believe also regulated RPM if I understand the German automatic controls correctly) until it was wide open at the 1st FTH.
The pilot has no direct control of the throttle valve, he just chooses the wanted MAP/RPM combination and the automatic controls does the rest (that is why throttle control stick used by pilot is called "leistung hebel" in the Bf 109).
Originally posted by joeblogs
Thereafter, I thought all the action was done by the clutch, which countinuously increased the multiple of crank speed until the 2nd FTH was obtained. Am I wrong?
You have the same misunderstanding as Charge; the aneroid has no information about the current MAP, so it just starts to reflow more oil to clutch just based on outside pressure regardless the MAP. So the automatic controls do the fine tuning of the MAP using the throttle valve between the impeller and intake manifolds. You can see the amount of throttling needed by looking the "ladedruck" and "gebläsedruck" curves linked above.
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Originally posted by gripen
Well, perhaps you should compare the reached output at altitude with RAM; say 10km:
P-51D with V-1650-7 from here (http://www.wwiiaircraftperformance.org/mustang/p51d-15342-level.jpg): about 1000hp
P-51B with V-1650-3 from here (http://www.wwiiaircraftperformance.org/mustang/p-51b-6883-level.jpg): about 1200hp
Bf 109G (GJ+FX) with DB 605AS: DB test data gives about 1,1ata at 2800rpm ie roughly about 1000hp (or ps, I used a DB 605A chart and a AS does actually a bit less).
So basicly the DB 605AS did about same as V-1650-7.
Hi.
in that chart i see the V-1650-3 with less than 1150hp at 10000m(32800ft)
The DB605AS had 1200PS @ 8000m, not rammed.
From the DB605A we know that the Vmax got reached at around 6700m altitude, so around 1000m above static FTH. The DB605AS max power with RAM @ 10000m must have been rather similar to that of the high alt Merlins, specialy when the speed and so the RAM effect was the same.
Greetings,
Knegel
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Originally posted by Knegel
,in that chart i see the V-1650-3 with less than 1150hp at 10000m(32800ft)
Well, the chart is hard to read but the value is in the ballpark anyway. The GJ+FX power value is overestimated as well because I used the DB 605A chart.
Originally posted by Knegel
The DB605AS had 1200PS @ 8000m, not rammed.
From the DB605A we know that the Vmax got reached at around 6700m altitude, so around 1000m above static FTH. The DB605AS max power with RAM @ 10000m must have been rather similar to that of the high alt Merlins, specialy when the speed and so the RAM effect was the same.
I'm refering flight tested values of the GJ+FX at high speed. Generally the DB 605s had continous problem to reach specified performance; as an example the DB 605A did it's claimed unrammed FTH at about climb speed (ie with some RAM). The GJ+FX has the highest tested FTH at the high speed of the AS data I have and it's still below the specification.
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GJ+FX? You mean this? http://kurfurst.allaboutwarfare.com/Performance_tests/109G_DB-G6AS_wMW/DB_109G6_ASM.html
How much below specification is it?
"the impeller runs constant speed until the second oil pump starts to increase the speed of the impeller at 1st FTH by increasing the oil flow through the hydraulic coupling which decreases the slip of the clutch."
There is no sense in using a specific oil pump to feed the clutch but to use the oil pressure from pump that feeds the engine and just do what ever you do to regulate the pressure after the clutch and thus control the rotation speed.
"Ladedruck = manifold pressure
Gebläsedruck = pressure between impeller and the throttle valve
As you can see the DB does quite large overpressure all the way up to the 2nd FTH. That means that large part of the theoretical advantage is lost."
I don't see such thing. The system maintains steady ATA and delivers good power at low FTH and high FTH without large fluctuations in power output. Looks good.
"Besides the oil system of the supercharger caused continuous problems."
What kind of problems? Blown engines because of over pressure or just no pressure?
The only thing I know was low engine oil pressure because of which de-aerators were installed but that did not solve the problem.
"Tip speed is increasing in the diameter of the impeller. Just think of the distance the tip is covering as the impeller rotates - it is the circumference of the impeller."
Of course, but as the impeller is larger it is capable of moving more air but it is rotated slower than a smaller one because the tip moves faster and thus reaches the speed limit earlier.
-C+
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Gripen:
No I don't have the same confusion as Charge. I know the clutch works off external atmoshperic pressure - I've seen the engineer's drawings. I am simply asking for some precision about the source of power increases above the 1st Full Throttle Height as altitude is increased.
Up to the 1st FTH, increased power with altitude can only come from increases in RPM and opening the throttle. I understand the German controls choose the combination of RPM and throttle automatically.
Now, at the 1st FTH, is it the case the engine is at maximum RPM with the throttle open or not? If the answer is yes, the only gain in power at altitudes above the 1st FTH must come from spinning the supercharger at ever increasing multiples of crankshaft speed. Tthis seems entirely possible.
But it does not have to work that way. There is no law of physics that says the engineers would set the 1st FTH where the engine is opened wide up. In that case, increases in power above the 1st FTH would come from a combination of (1) increased multiples of supercharger speed relative to crankshaft speed, (2) increased RPM, and (3) opening the throttle.
So which is it?
Originally posted by gripen
You have the same misunderstanding as Charge; the aneroid has no information about the current MAP, so it just starts to reflow more oil to clutch just based on outside pressure regardless the MAP. So the automatic controls do the fine tuning of the MAP using the throttle valve between the impeller and intake manifolds. You can see the amount of throttling needed by looking the "ladedruck" and "gebläsedruck" curves linked above. [/B]
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Originally posted by Charge
GJ+FX? You mean this? http://kurfurst.allaboutwarfare.com/Performance_tests/109G_DB-G6AS_wMW/DB_109G6_ASM.html
How much below specification is it?
The spec at 2600rpm 1,3ata is 8900m -200m while the GJ+FX did 8600m at that rating, other data gives lower values.
Originally posted by Charge
There is no sense in using a specific oil pump to feed the clutch but to use the oil pressure from pump that feeds the engine and just do what ever you do to regulate the pressure after the clutch and thus control the rotation speed.
There is two pumps feeding clutch; the first one does constant flow and another controlled by barometric valve does variable flow between the 1st and 2nd FTH. Below 1st FTH the flow of the second pump is used to increase oil cooling flow.
For further information see Von Gersdorf&co, Raunio's article and DB 605A manual (can be found from FAF museum).
Originally posted by Charge
I don't see such thing. The system maintains steady ATA and delivers good power at low FTH and high FTH without large fluctuations in power output.
Please look the picture here (http://www.wwiiaircraftperformance.org/me109/me-109g6-16476-pg9.jpg).
At the left side of the graph you can see the curves of the MAP (ladedruck) and the pressure between the impeller and the throttle valve (gebläsedruck). These are close each other only above 2nd FTH, as an example at 4000m the supercharger does about 1,55ata pressure which is throttled down to 1,3ata at intake manifolds using the throttle valve.
Originally posted by Charge
What kind of problems? Blown engines because of over pressure or just no pressure?
Mainly oil cooling problems, that was the reason why the size of the oil cooler was increased in the AS Bf 109Gs. And cooling problems set the limits for the max slip.
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Originally posted by joeblogs
No I don't have the same confusion as Charge. I know the clutch works off external atmoshperic pressure - I've seen the engineer's drawings. I am simply asking for some precision about the source of power increases above the 1st Full Throttle Height as altitude is increased.
Sorry if I understood you wrong, you wrote that "I thought all the action was done by the clutch" which led me to think that you are not aware about throttle use to fine tune the MAP.
Originally posted by joeblogs
Up to the 1st FTH, increased power with altitude can only come from increases in RPM and opening the throttle. I understand the German controls choose the combination of RPM and throttle automatically.
Below 1st FTH power increases with altitude mainly for the same reason as it increases in the any fixed speed supercharger ie when the throttle valve opens and the altitude increases, the supercharger works more efficiently and the engine gets cooler air. In addition the losses due to clutch are highest at max slip.
Originally posted by joeblogs
Now, at the 1st FTH, is it the case the engine is at maximum RPM with the throttle open or not? If the answer is yes, the only gain in power at altitudes above the 1st FTH must come from spinning the supercharger at ever increasing multiples of crankshaft speed. Tthis seems entirely possible.
At given engine setting the engine RPM is constant at whole altitude range and the MAP is constant up to the 2nd FTH. The speed of the impeller is constant below the 1st FTH (at max slip) and above 2nd FTH (at min slip). The opening of the throttle valve follows closely the difference between the MAP and "Gebläsedruck; when these are close each other, the throttle valve is open and when the differerence is large, then the throttle valve more or less shut.
If there is power increase with altitude between 1st and 2nd FTH, it's probably caused by large difference between MAP and "gebläsedruck" ie the min slip is reached before FTH. This is probably the reason why the shape of the power curves of the DBs is quite bit different than in the case of the ideal DVL variable speed supercharger.
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If I understand the second part of your description it sounds like above the 1st FTH, there is the effect of (1) the clutch tightening up so that the supercharger is spinning faster and faster relative to crankshaft speed AND (2) continued opening up of the throttle as altitude rises (assuming the pilot is looking for maximum power).
Now does that mean there is a discrete change in the throttle around the 1st FTH, or perhaps the throttle is not wide open there in the first place?
Full Throttle height is probably the wrong term to use here. We are stealing it from the vocabulary used for superchargers with constant gearing. Here there is no necessity for the engine to be wide open at the point where the second pump begins to operate; that is if I understand you correctly.
Also if I understand what you are saying, the pilot's throttle/RPM controller acts as a governer on MAP, but the controller does not have any influence on the supercharger gearing. So it takes whatever pressure the supercharger delivers and adjusts engine RPM and the throttle to attain the MAP the pilot wants, subject to some maximum limit on MAP set by the controller?
-Blogs
Originally posted by gripen
Sorry if I understood you wrong, you wrote that "I thought all the action was done by the clutch" which led me to think that you are not aware about throttle use to fine tune the MAP.
Below 1st FTH power increases with altitude mainly for the same reason as it increases in the any fixed speed supercharger ie when the throttle valve opens and the altitude increases, the supercharger works more efficiently and the engine gets cooler air. In addition the losses due to clutch are highest at max slip.
At given engine setting the engine RPM is constant at whole altitude range and the MAP is constant up to the 2nd FTH. The speed of the impeller is constant below the 1st FTH (at max slip) and above 2nd FTH (at min slip). The opening of the throttle valve follows closely the difference between the MAP and "Gebläsedruck; when these are close each other, the throttle valve is open and when the differerence is large, then the throttle valve more or less shut.
If there is power increase with altitude between 1st and 2nd FTH, it's probably caused by large difference between MAP and "gebläsedruck" ie the min slip is reached before FTH. This is probably the reason why the shape of the power curves of the DBs is quite bit different than in the case of the ideal DVL variable speed supercharger.
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Hi,
GJ + FX is a G14AS, with DB605ASM, with the more weight due to the MW50 installation, this plain will have a disadvantage with combat climb to the 109G6AS.
The more weight will limit the speed of this plane in this high altitude, this minimize the RAM effect and power.
In the DB605ASM, the max power could get used rather long, although above rated alt the power is the similar to the normal Start/Not, the MW50 could get used as "Ladeluftkühlung" to increase the time of usage.
Therefor the GJ + FX had around 1,5 ata in 10000m alt for 2 x 10min combat.
If i compare the Speeds of the GJ + FX with the Spitfire IX BS. 551 (Merlin 70
( http://www.spitfireperformance.com/bs543.html , the other HF Spits show a rather similar result), the Vmax performences seems to be very similar.
The 109G14AS is better with Sondernot, but less good with combat climb, the RAM FTH of this Spit is a bit below that of the DB605ASM with combat climb, at 8350m.
If we take the time of usage into account, both engines seems to be rather similar in high alt.
Greetings,
Knegel
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Slightly off-topic question:
At first I thought it was a mistake: we're all talking about "V configuration" engines when the topic calls for the best "inline engine." In the car world, a V-6 and an Inline-6 are two very different types of configurations (that is, pistons arranged in a single row versus arranged in two rows canted 60 or 90 degrees toward each other.)
Yet as I look online and in my books, it seems that no distinction is made in classifying these two different configurations.
The usual distinction is simply "Radial" (and thereby aircooled) and "Inline" (meaning water-cooled.)
Anyone care to say why things are categorized this way?
-Llama
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llama, it all has to do with the position of the cylinders with respect to the crankshaft.
A V-6, V-8, V-10, V-12, V-16 are still inline engines but with a V configurartion.
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Actually a great point. Continental's Hyper engine was a straight 12 - two banks of six cylinders in the same plane. Junkers had a diesel like that.
There are a number of air-cooled inlines, typically straight sixes. The tend to have smaller displacement.
-Blogs
Originally posted by llama
Slightly off-topic question:
At first I thought it was a mistake: we're all talking about "V configuration" engines when the topic calls for the best "inline engine." In the car world, a V-6 and an Inline-6 are two very different types of configurations (that is, pistons arranged in a single row versus arranged in two rows canted 60 or 90 degrees toward each other.)
Yet as I look online and in my books, it seems that no distinction is made in classifying these two different configurations.
The usual distinction is simply "Radial" (and thereby aircooled) and "Inline" (meaning water-cooled.)
Anyone care to say why things are categorized this way?
-Llama
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Originally posted by Angus
Could you tell me why I find NO SOURCE for this??????????????????????
I have been begging for 109 tests for years, yet half of what I have just popped up in this thread. While the Spitfire climbing tests give me some data and not nearly enough, they are vastly more that all combined as a good reliable source of the Db & 109.
On page 6 of the „Kennblatt für das Flugzeugmuster Bf 109 Baureihe F1 und F2 Motor DB 601 N“ there is a speed and climb table that states time to various altitudes as well as rate of climb in m/sec. Under this table there is noted: “Die Werte die Flugleistungstabelle sind mit ‚Steig- und Kampfleistung‘, d. b. n. = 2400 U/min., P-lade= 1,3 ata (bis Fülldruckhöhe) erflogen.“ And „Die geklammerten Werte beziehen sich auf ‚Start- und Notleistung‘, d. b. n. = 2800 U/min., P-lade= 1,42 ata (bis Fülldruckhöhe).
Now, if my German serves me well this means that the rates of speed and climb in the table is flown at “climb and combat” setting with the number in parenthesis being flown at “Start and emergency” power. So the German Kennblatt of Messerschmitt aircraft lists both numbers.
If we compare this to The Aircraft Evaluation Report, U. S. Army Air Forces, German Messerschmitt 109F; the “Climb to 15,000 feet” table states 5 minutes for the 109F-1 and 109F-2. 15,000 feet is 4,572 metres and the Kennblatt states a time to altitude in “Climb and Combat” to 4 km at 4.3 minutes and 5 km at 5.4 minutes. Using “Start and Emergency” power the Kennblatt states 3.6 and 4.5 minutes respectively. It is pretty clear that the US evaluation is flying at “Climb and Combat”. It also states a time of 4.8 minutes for the 109F-4 (DB 601 E), which fits nicely with the F-4’s Climb and Combat. It is also interesting that the engine specifications listed only lists “military” and “normal cruise” power. Emergency power is not mentioned at all.
For allied documents on the performance of the Spitfire and other aircraft I can only assume that they test time to altitude in MIL power setting given the usual 5 min restriction on WEP. Also a time to altitude in WEP is of little practical value since you wouldn’t be climbing on WEP unless there was an emergency. Normal climbs to interception or air station was done at MIL. At least in this evaluation of captured 109F’s the climb tests seem to have been made at Climb and Combat.
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1k3 asked for some comparisons of water cooled engines.
Knegel pointed out (correctly) that we should look at performance at different altitudes.
Below are some charts for several manufacturers and different models of their engines.
What I plot are take-off and military (or emergency) powers at different altitudes. Other than take-off, I believe the points correspond to full throttle heights, but I can be corrected there.
There are two important disclaimers on the axis engines. First, note that the powers are not based on the best fuels, an important part of the discussion in this thread. Second, the powers at altitude are "rated" powers. Now in the allied nomenclature these are not necessarily military powers. I don't know if that is also true for the axis engines, but we have experts here that can tell the difference.
I should add that a more even handed comparison of the engines would be by specific weight or specific displacement, i.e. dividing output by the weight or size of the engine.
http://mysite.verizon.net/vze479py/sitebuildercontent/sitebuilderfiles/allison.pdf
http://mysite.verizon.net/vze479py/sitebuildercontent/sitebuilderfiles/packard_merlin.pdf
http://mysite.verizon.net/vze479py/sitebuildercontent/sitebuilderfiles/rr_merlin.pdf
http://mysite.verizon.net/vze479py/sitebuildercontent/sitebuilderfiles/rr_griffon.pdf
http://mysite.verizon.net/vze479py/sitebuildercontent/sitebuilderfiles/daimler_benz.pdf
http://mysite.verizon.net/vze479py/sitebuildercontent/sitebuilderfiles/junkers.pdf
http://mysite.verizon.net/vze479py/sitebuildercontent/sitebuilderfiles/klimov.pdf
-Blogs
Originally posted by 1K3
In the radial department, nothing beats the Pratt & Whitney series. Not even the BMW radials can beat P&W.
When it comes to Inline liquid-cooled engine, which company made THE best inline engine
[ EDIT: Jumo is added to the list ]
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Also those charts do not factor in the use of water injection (MW50) on any axis engine, and the only DB 605 listed is the 1942 model A1.
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Originally posted by joeblogs
If I understand the second part of your description it sounds like above the 1st FTH, there is the effect of (1) the clutch tightening up so that the supercharger is spinning faster and faster relative to crankshaft speed
Yes.
Originally posted by joeblogs
AND (2) continued opening up of the throttle as altitude rises (assuming the pilot is looking for maximum power).
At 1st FTH the throttle valve is nearly all open because "Gebläsedruck" is near same as MAP. Once the second oil pump starts to increase the speed of the impeller, the difference between the "gebläsedruck" and MAP increase again ie the throttle valve is closing a bit gain.
Originally posted by joeblogs
Now does that mean there is a discrete change in the throttle around the 1st FTH, or perhaps the throttle is not wide open there in the first place?
The only change at 1st FTH is that the speed of the supercharger starts to increase, the throttle system itself works similarly above and below the 1st FTH. In the ideal case, the throttle is wide open above 1st FTH because the speed of the supercharger is adjusted to give exactly needed MAP.
Originally posted by joeblogs
Full Throttle height is probably the wrong term to use here. We are stealing it from the vocabulary used for superchargers with constant gearing. Here there is no necessity for the engine to be wide open at the point where the second pump begins to operate; that is if I understand you correctly.
The term is confusing but in the ideal case it is correct. In Finnish language we say "ahtimen ensimmäinen määräkorkeus" which can be translated something like 1st rated altitude but also that is confusing as well.
Originally posted by joeblogs
Also if I understand what you are saying, the pilot's throttle/RPM controller acts as a governer on MAP, but the controller does not have any influence on the supercharger gearing. So it takes whatever pressure the supercharger delivers and adjusts engine RPM and the throttle to attain the MAP the pilot wants, subject to some maximum limit on MAP set by the controller?
Basicly the pilot has only one lever which is used to choose wanted RPM/MAP combination. The automatic system itself is quite complicated but shortly it adjusts the propeller to keep wanted RPM and the throttle valve to keep wanted MAP. Note that the engine RPM is constant at any given setting.
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Actually they do, when its available on the particualr engine tested. -
Well at least for the allied engines I am sure. But I think the numbers for the German engines should be treated cautiously. I think people have posted some better numbers than I think Wilkinson had available.
-blogs
Originally posted by Viking
Also those charts do not factor in the use of water injection (MW50) on any axis engine, and the only DB 605 listed is the 1942 model A1.
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Gripen
Thanks, I learned a lot from your posts.
-blogs
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Originally posted by joeblogs
Actually they do, when its available on the particualr engine tested.
That's the point. None of the Daimler-Benz or Junkers engines in those charts have MW50. There are no DB 605 AM, DB 605D or Junkers Jumo 213 (190D/Ta 152) engines. Only pre-1943 DB engines and Junkers bomber engines, none with MW50.
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This is true.
I do have numbers on the Jumo 213-A, but they are at normal, not military powers, so that does not help.
Wilkinson is very good with the allied engines, not so good with German engine developments after about 1941. His coverage of postwar piston engines is good, but for the German engines he jumps immediately to the jets.
-Blogs
Originally posted by Viking
That's the point. None of the Daimler-Benz or Junkers engines in those charts have MW50. There are no DB 605 AM, DB 605D or Junkers Jumo 213 (190D/Ta 152) engines. Only pre-1943 DB engines and Junkers bomber engines, none with MW50.
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Originally posted by Knegel
GJ + FX is a G14AS, with DB605ASM, with the more weight due to the MW50 installation, this plain will have a disadvantage with combat climb to the 109G6AS.
I'm refering high speed values and values are higher than other AS data at high altitude, lower at low altitude. Probably because not corrected for compressibility, the specification calculation is certainly without compressibility correction (directly said in the Mtt datasheet).
Originally posted by Knegel
Therefor the GJ + FX had around 1,5 ata in 10000m alt for 2 x 10min combat.
Hm... I read something like 1,1ata at 10000m at high speed (very hard to read again).
Originally posted by Knegel
If i compare the Speeds of the GJ + FX with the Spitfire IX BS. 551 (Merlin 70
( http://www.spitfireperformance.com/bs543.html , the other HF Spits show a rather similar result), the Vmax performences seems to be very similar.
Probably not because probably no compressibility correction.
Originally posted by Knegel
The 109G14AS is better with Sondernot, but less good with combat climb, the RAM FTH of this Spit is a bit below that of the DB605ASM with combat climb, at 8350m.
Hm... the GJ+FX had FTH 6800m with MW50 where it did 1495ps according to the specs. The BS 543 had FTH about 8350m where it did 1475hp according to the specs.
BTW there is only high speed FTHs in GJ+FX sheet.
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Originally posted by gripen
Hm... the GJ+FX had FTH 6800m with MW50 where it did 1495ps according to the specs.
Negative. The DB 605 ASM makes 1,435 PS at 1,42 ata according to the Leistungsblatt. With 2800 rpm according to the GJ+FX chart the engine was running 1.7 ata at 6.8 km. According to the same chart the engine was running on 1.3 ata at well over 9 km at 2800 rpm. The DB 605 ASM produces over 1300 PS at 1.3 ata and 2600 rpm. At 10 km it still runs on ca. 1.15 ata at 2800 rpm. And according to the Leistungsblatt for the DB 605 AS without MW50 (and thus without charge cooling) the engine was producing 925 PS at 10 km at 2800 rpm.
And according to this table the Merlin V-1650-3 was making 985 hp at 35,000 feet (10.6 km):
http://www.wwiiaircraftperformance.org/mustang/mustangtest.html
(http://www.onpoi.net/ah/pics/users/1022_1181783907_109g_605asmw50mod.jpg)
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Here is one more figure, which is a nice measure of relative performance. It plots the maximum horsepower the engine can develop (at any altitude), divided by its dry weight (i.e. without coolant):
http://mysite.verizon.net/vze479py/sitebuildercontent/sitebuilderfiles/power_wt.pdf
I have left out the German engines for the reason Viking mentioned earlier. If I did plot them, they would look average in my data. When corrected to reflect war time boost systems, they would look reasonably good. One reason why they would, as pointed out by others in this thread, is the generally higher compression ratio of the German engines.
You could draw a 45 degree vertical line through the data and see the strong, stable correlation between weight and power. Engines above that line are better, at least by this metric.
The outstanding engines in this figure are the late model Napier Sabres, the RR Griffons & Merlins. The Packard Merlins and the Allisons are about average, because they are reletively heavy (I don't know why).
I left out the Italian and Japanese liquid cooled engines; they are below average.
Some lesser known standouts include Contentinental's Hyper engine, which did not see production and Klimov's M107.
The Hisso and the Kestrel are engines of an earlier generation, but the Hisso seems ahead of its time. Some of those were also high compression engines.
Originally posted by 1K3
In the radial department, nothing beats the Pratt & Whitney series. Not even the BMW radials can beat P&W.
When it comes to Inline liquid-cooled engine, which company made THE best inline engine
[ EDIT: Jumo is added to the list ]
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From a post of George Hopp in the TOCH board
IIn response to the discussion on which fuels the DB engines could use, this is from a top secret DB internal memo on a conference of 3 Oct 44 on the Bf 109/DB 605 combo:
Motortype Brennstoff Startleistung Höhenleistung in 10km
DB 605 AM B4+MW 50 1830 PS 800 PS
DB 605 AM C3+MW 50 2000 PS 800 PS
DB 605 ASM+D B4+MW 50 1850 PS 950 PS
DB 605 ASM+D C3+MW 50 2000 PS 950 PS
DB 605 L C3+MW 50 1700 PS 1275 PS
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Originally posted by Viking
Negative. The DB 605 ASM makes 1,435 PS at 1,42 ata according to the Leistungsblatt.
That value is for sealevel. The specification is 1200ps at 1,42ata at 8000m while the GJ+FX did that at a bit over 8000m with RAM (hard to read again)
Originally posted by Viking
With 2800 rpm according to the GJ+FX chart the engine was running 1.7 ata at 6.8 km. According to the same chart the engine was running on 1.3 ata at well over 9 km at 2800 rpm. The DB 605 ASM produces over 1300 PS at 1.3 ata and 2600 rpm. At 10 km it still runs on ca. 1.15 ata at 2800 rpm.
If I put a paper following 10000m line from the above, it reaches the 2800rpm line at the point where the 2800rpm line ends ie closer to 1,1ata.
Originally posted by Viking
And according to the Leistungsblatt for the DB 605 AS without MW50 (and thus without charge cooling) the engine was producing 925 PS at 10 km at 2800 rpm.
You see the problem, the DBs had problems to live up to the specs; even assuming 1,15ata, the GJ+FX did around 1050ps at 10000m and a bit below 1000ps at 1,1ata.
Originally posted by Viking
And according to this table the Merlin V-1650-3 was making 985 hp at 35,000 feet (10.6 km):
Well, Knegel's reading was something like a bit below 1150hp at 10000m.
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BTW the V-1650-3 data there is for 11,5' diameter impeller (Merlin 61), not for the 12' impeller (Merlin 70).
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Hi,
i made a typo and was up to write 1,15, not 1,5.
With help of a paint program, by adding the ata steps, out of the 1,3 and 1,7 ata avlues, visible that its between 1,1 and 1,15.
Regarding the FTH i wrote the "combat/climb" FTH of the DB605ASM is above that of the Merlin70.
The Vmax performence of the SpitIXc HF and 109G14AS is very similar at hight, so is the engine power.
Greetings,
Knegel
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Originally posted by Knegel
With help of a paint program, by adding the ata steps, out of the 1,3 and 1,7 ata avlues, visible that its between 1,1 and 1,15.
I don't see much reason to argue about that small difference (about 0,02ata); the original claim, roughly about 1000ps is certainly at right ballpark.
Originally posted by Knegel
Regarding the FTH i wrote the "combat/climb" FTH of the DB605ASM is above that of the Merlin70.
What is the point comparing those? The Merlin 70 still does something like 150hp higher output at that altitude.
Originally posted by Knegel
The Vmax performence of the SpitIXc HF and 109G14AS is very similar at hight, so is the engine power.
Well, the GJ+FX results are probably not corrected for compressibility and the error is around 15-20km/h at FTH according to spec sheet. Otherwise the GJ+FX would had been 15-20km/h faster than spec at around 8000m despite the FTH was below the spec.
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Originally posted by gripen
Hm... the GJ+FX had FTH 6800m with MW50 where it did 1495ps according to the specs.
Originally posted by Viking
With 2800 rpm according to the GJ+FX chart the engine was running 1.7 ata at 6.8 km.
Forgive me if I'm repeating myself, but I can't seem to find your response to this. Surely the DB was producing more than 1495 PS at 1.7 ata at full pressure height? Or am I reading the chart wrong?
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Originally posted by gripen
What is the point comparing those? The Merlin 70 still does something like 150hp higher output at that altitude.
Because this particular discussion that has been going on for the last six pages was not initially about the engines’ power output but about the superchargers and the claim I made when entering this discussion:
Originally posted by Viking
… The DB's already had a supercharger with a similar FTH to that of the two stage supercharged Merlins. …
… to which there was an uproar of polite dissent.
Now I think it has been conclusively documented that the DB 605 AS(M) had a similar FTH to that of the two stage Merlins. The difference in FTH between the DB 605AS(M) and the Merlin 70 is less than 10%, and the DB 605AS(M) FTH is higher than all other two-stage Merlins.
Now, we can continue the discussion on which engine produced the most hp at altitude which is dependent on a lot more factors than supercharger performance; it is an interesting topic (and perhaps even more on-topic), but I consider my initial claim about the DB supercharger to have been validated.
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Originally posted by Viking
Forgive me if I'm repeating myself, but I can't seem to find your response to this. Surely the DB was producing more than 1495 PS at 1.7 ata at full pressure height? Or am I reading the chart wrong?
These values are taken directly from the GL/C-E data for the G-14/ASM Jäger, both values are naturally for 1,7ata:
V-hmax-NNot am boden km/h-km 560-1740
V-hmax-NNot im VH km/h-km 680-1495-7,5
You don't seem to understand that the hydraulic coupling uses increasing amount of power when the speed of the impeller increases between 1st and 2nd FTH.
And generally I forgive quite a lot.
Originally posted by Viking
Because this particular discussion that has been going on for the last six pages was not initially about the engines’ power output but about the superchargers and the claim I made when entering this discussion:
...
Now I think it has been conclusively documented that the DB 605 AS(M) had a similar FTH to that of the two stage Merlins. The difference in FTH between the DB 605AS(M) and the Merlin 70 is less than 10%, and the DB 605AS(M) FTH is higher than all other two-stage Merlins.
Now, we can continue the discussion on which engine produced the most hp at altitude which is dependent on a lot more factors than supercharger performance; it is an interesting topic (and perhaps even more on-topic), but I consider my initial claim about the DB supercharger to have been validated.
Well, there is no point at all to compare 30min rating FTH of the DB to the 5min rating FTH of the Merlin; the Merlin 70 has 30min rating FTH (IIRC +15psi, higher if lower MAP) well over 9000m with RAM. At both FTHs (combat and military rating) the Merlin 70 does clearly higher output than the DB.
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Hi,
the Vmax(RAM FTH) of the merlin 70 powered Spits, on the "Spitfire Performence testing", was @ 7700m, 8100m and 8475m, while the V-1650-3 chart at WEP show 8840m.
The RAM FTH of the GJ + FX with Start/Not (1,42ata) was in 8200m.
The V-1650-3 datas are made with around 705km/h, while the Spit and 109 speeds are good below this and therefor the RAM effect is smaler. Probably the P51 Aitframe also provide a better RAM effect, but that dont make the engine better, but confirm my thought that no engine can get seen without the airframe.
The Merlin70 in the Spitfire is very similar to the DB605ASM in the 109G, while the V-1650-3 in the P51 airframe reach better values, but with a not that long time of usage.
Greetings,
Knegel
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"You don't seem to understand that the hydraulic coupling uses increasing amount of power when the speed of the impeller increases between 1st and 2nd FTH."
Hmm... it does not "use" more power other than the normal amount of a supercharger which needs to be turned. If the heat from the clutching cannot be wasted the engine needs to be throttled and only then power is lost. It is a different thing than that of mechanical supercharger which needs to be throttled to prevent it from over boosting in nearly every other instance than at first and second FTH. That is the case where supercharger really hogs power from the engine.
I read an article where German pilots used to go up and down just at the altitude where the Spit had its gear change point and watch them struggle with gear change. ;)
-C+
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Originally posted by Knegel
the Vmax(RAM FTH) of the merlin 70 powered Spits, on the "Spitfire Performence testing", was @ 7700m, 8100m and 8475m, while the V-1650-3 chart at WEP show 8840m.
The RAM FTH of the GJ + FX with Start/Not (1,42ata) was in 8200m.
Hm... according to G-6/AS specs the DB 605AS did 1190ps at FTH with that rating (as usual tested FTH is well below spec, 9km). The Merlins you listed did around 1300hp at that altitude.
Note that in that site the AAF No. 43-12093 had a V-1650-3 with 11,5" first stage impeller while the production engine had 12" impeller. Strange thing is that the claimed power difference between the AAF No. 43-12093 and the AAF No. 43-6883 is only 22hp despite the first one runs at 60,5" and later one at 67". According to RR charts, the difference should be around 80hp.
Originally posted by Knegel
The Merlin70 in the Spitfire is very similar to the DB605ASM in the 109G, while the V-1650-3 in the P51 airframe reach better values, but with a not that long time of usage.
Well, the Merlin 70 does considerably more power at altitude and the Spitfire seem to be faster given the specs (and probably GJ+FX data as well) does not account the compressibility effects.
Originally posted by Charge
Hmm... it does not "use" more power other than the normal amount of a supercharger which needs to be turned.
Even in the ideal case the supercharger with hydraulic coupling uses more power for the given impeller RPM because the slip and the power used by the pump (in addition needed oil cooling increases drag).
In the case of the DBs (before the L version) the supercharger also produces some amount of overpressure all the way up to the 2nd FTH which also increases power consumption
Originally posted by Charge
If the heat from the clutching cannot be wasted the engine needs to be throttled and only then power is lost. It is a different thing than that of mechanical supercharger which needs to be throttled to prevent it from over boosting in nearly every other instance than at first and second FTH. That is the case where supercharger really hogs power from the engine.
Because the throttle valve is located before the impeller in the well designed engines, the main wastage is increased charge temperature due to throttling below the FTHs, there is no overpressure produced like in the DBs. It took about ten years for DB to fix this problem and the fix came too late.
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Hi,
as the very different FTH´s of the different Merlin 70 Spitfires show, also the Merlin wasnt that constant.
Using only the best chart of the Merlin vs a rather bad one of a DB605ASM, while other, also rather bad Merlin70 performences are available isnt that logical.
The speed of the GJ+FX is maybe not corrected, but even if we reduce all by 15km/h, the speed is still around the same like that of the Spitfire IXc HF, depending to the used test, a bit faster or a bit less fast.
Since GJ + FX´s RAM FTH is good below what the engine should offer, it simply dont make sence to compare it only with the best tested Spitfire/Merlin, specialy not with the P51 engine and the much greater RAM effect, due to much more speed.
Of course we also can assume that most DB605ASM´s was so much below the official datas, but we also could assume that GJ+FX dont use a DB605ASM, but a ASB, where the FTH was 600m more low.
Greetings,
Knegel
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Originally posted by Knegel
as the very different FTH´s of the different Merlin 70 Spitfires show, also the Merlin wasnt that constant.
Using only the best chart of the Merlin vs a rather bad one of a DB605ASM, while other, also rather bad Merlin70 performences are available isnt that logical.
I have used the best tested AS data I'm aware (it's from engine manufactiurer so the engine probably had been seen as OK). The Mustang data I choosed were just the first ones with certain engines when browsing the page down in the site. The others have choosed the Spitfires to look.
Note that even the lowest FTH Spitfire (BS310) you listed, did over +9psi at 33k ie better than the specification for the AS.
Originally posted by Knegel
Of course we also can assume that most DB605ASM´s was so much below the official datas, but we also could assume that GJ+FX dont use a DB605ASM, but a ASB, where the FTH was 600m more low.
The AS prototype did 8,3km at high speed with 1,3ata/2600rpm (the results were seen as good by Mtt staff), other one of the FAF G-6/AS did 8250m at the same setting.
Given the date 7.6.1944 and the designation of the engine (DB 605 A-S), it's certainly not an ASB but probably one of the first ASM engined planes in the engine manufacturers tests.
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Hi,
i have different datas for the G14AS and G6AS.
One is from a G14AS/G14-U2/K4 comparison and give
combat climb, 645km/h, 1140PS in 8800m
Sondernot, 680km/h, 1495PS in 7500m, what is 500m above GJ+FX.
Another is a G6AS, with a ASB engine(no MW50),
combat/climb, 648km/h, 1135PS in 8800m
Start/Not, 660km/h, 1190PS in 9000m
btw, the DB605D had 1140PS in 9000m, combat climb.
A good Merlin70 seems to have a bit more power than a good 605ASM above 8000m, while the 605ASM is better below this, with a more smooth curve.
Since the Spitfire speeds in all three tests got corrected to around 3200kg, it would be interesting what weight the 109s had, cause 200kg below take off weight is already 2/3 of the 109´s fuel and 200kg in 10000m is a lot.
I realy doubt that any of this Spitfires did reach 1300HP at FTH, with this smal weight they should be faster then.
The P51B probably did provide a better RAM effect, resulting in more power and a higher speed and a even better RAM effect and higher power.
Greetings,
Knegel
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Originally posted by Knegel
i have different datas for the G14AS and G6AS.
One is from a G14AS/G14-U2/K4 comparison and give
combat climb, 645km/h, 1140PS in 8800m
Sondernot, 680km/h, 1495PS in 7500m, what is 500m above GJ+FX.
These sound very much like spec calculations from A/IV/... and GL/C-E series.
Originally posted by Knegel
Another is a G6AS, with a ASB engine(no MW50),
combat/climb, 648km/h, 1135PS in 8800m
Start/Not, 660km/h, 1190PS in 9000m
I have not ever heard about the G6/AS with ASB engine, AFAIK the G-6 was about out of production when the ASB engines became available. What's the source?
The values are the same as calculated values in the GL/C-E sheet for the standard G-6/AS with 605AS engine.
Originally posted by Knegel
btw, the DB605D had 1140PS in 9000m, combat climb.
The DB 605D did roughly same high altitude performance as the 605 ASM.
Originally posted by Knegel
A good Merlin70 seems to have a bit more power than a good 605ASM above 8000m, while the 605ASM is better below this, with a more smooth curve.
That depends how you define "a bit". IMHO 100-200hp at high altitude is quite a lot.
The Merlin 70 was cleared for the +25lbs use if low altitude performance was needed.
Originally posted by Knegel
I realy doubt that any of this Spitfires did reach 1300HP at FTH, with this smal weight they should be faster then.
The static rating of the Merlin 70 for 2nd FTH at +18psi is 1475hp at 22250ft.
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Originally posted by gripen
And generally I forgive quite a lot.
Well, don't bother. You're obviously arguing to "win", not to reason.
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More of the climb, - Viking.
(And TY for the input)
Climb seems to be measured at MIL in both camps. But the data is confusing. 109G in 1944 is still using 6 minutes to 20K, Rall also mentions the same figure. A Spitty in the same time will use some rough 5 with more weight :confused: :huh
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Hi Angus,
climb is made with combat/climb and this is smaler in the DB605AS(M) than in the DB605A, while the later 109G´s had 40- 80kg more weight.
Unfortunately i never saw a climb chart of a 109G with Sondernot.
Hi Gripen,
its from a chart from the "General Luftzeugmeister/C-E2 13 Aug. and 01. Nov1944.
Since this plane had the typical low ground level performence of the AS and no MW50, i only can guess that this is a writing error and should be the AS, not ASB.
Also the high rated altitude is above that of the ASB.
The DB605D had 1565PS in 7500m and 1140PS in 9000m
Thats 70PS more Sondernot in FTH and a 200m higher FTH for climb/combat.
I never saw a powercurve of the DB605D, but its not much of a guess that the power with Start/Not would have been above 1140PS in 9000m, therefor i would say the DB605D had good advantages over the DB604AS(M) in high alt and was at least even to the Merlin70.
Also the service ceiling of the DB605D powered 109´s was 500m above the AS and only 600m below that of the good HF Spits and 300m(Spits with 3200kg), while one of the three tested HF Spits had the same service ceiling.
I realy cant see a huge advantage of the RR engines at all, specialy not, if i take into account that the DB605D´s and ASM´s had a rather constant range of power, from sea level up to service ceiling, not to talk about GM1.
Greetings,
Knegel
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Originally posted by Knegel
its from a chart from the "General Luftzeugmeister/C-E2 13 Aug. and 01. Nov1944.
Since this plane had the typical low ground level performence of the AS and no MW50, i only can guess that this is a writing error and should be the AS, not ASB.
Also the high rated altitude is above that of the ASB.
The lower 2nd FTH ASB if compared to the ASM is caused by higher MAP (1,8ata). These are mostly the same engines, the ASB is just a later version with higher CR etc. The output difference is very small.
Originally posted by Knegel
The DB605D had 1565PS in 7500m and 1140PS in 9000m
Thats 70PS more Sondernot in FTH and a 200m higher FTH for climb/combat.
These are with RAM and the differences are mostly caused by higher MAP too as well due to higher RAM of the K-4. The static difference in the specification above FTH is 5-20ps between the AS and D depending on data (actually some data show advantage for the AS).
Note that all these are calculations (before production began in the case K-4). And there is no compressibility effects accounted in the calculation.
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"Even in the ideal case the supercharger with hydraulic coupling uses more power for the given impeller RPM because the slip and the power used by the pump (in addition needed oil cooling increases drag)."
The pump does not cause a noticeable need of power. The power need comes directly from transmission from crankshaft to impeller, the power need for auxiliary equipment such as alternator and oil-pump is constant. In some two speed supercharged planes the cooling of the engine alone causes a lot of the drag...
"In the case of the DBs (before the L version) the supercharger also produces some amount of overpressure all the way up to the 2nd FTH which also increases power consumption"
So you have claimed. I haven't seen evidence of any noticeable overpressure which would cause the need for throttling. First there is "slip" and then there is "overpressure". The engineers at DB obviously could not design superchargers with small enough output... ;)
"Because the throttle valve is located before the impeller in the well designed engines, the main wastage is increased charge temperature due to throttling below the FTHs, there is no overpressure produced like in the DBs. It took about ten years for DB to fix this problem and the fix came too late."
In well designed engines the impeller speed can be controlled so there is no need for rotating the supercharger needlessly and thus regulating the air feed to the charger.
-C+
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Originally posted by Charge
The pump does not cause a noticeable need of power. The power need comes directly from transmission from crankshaft to impeller, the power need for auxiliary equipment such as alternator and oil-pump is constant. In some two speed supercharged planes the cooling of the engine alone causes a lot of the drag...
-C+
Yea I'm no AC expert. However I do have some auto experience. There is a noticeable difference HP/Torque loss in manual vs auto trans car at the rear wheels.
If you have a tech sheet with identical engines. One with a hydraulic driven SC the other mechanically driven that proves it. I'd like to see it.
Bronk
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Originally posted by Charge
The pump does not cause a noticeable need of power. The power need comes directly from transmission from crankshaft to impeller, the power need for auxiliary equipment such as alternator and oil-pump is constant. In some two speed supercharged planes the cooling of the engine alone causes a lot of the drag...
Your original argument was that "it does not "use" more power other than the normal amount of a supercharger which needs to be turned". I don't know how much power did the two pumps use, but certainly these used some power. Von Gersdorf&co book has a graph which shows that at max oil flow, 2,5% slip, there is 5% performance loss (p. 149 in the edition I have), more at higher slip.
AFAIK all engines discused here needed quite a lot cooling but Von Gersdorf&co claim that the hydraulic coupling caused ca max 30% increase to needed oil cooling.
Originally posted by Charge
So you have claimed. I haven't seen evidence of any noticeable overpressure which would cause the need for throttling. First there is "slip" and then there is "overpressure". The engineers at DB obviously could not design superchargers with small enough output... ;)
Just look the picture below, in this case at sealevel it did about 30% overpressure and between the 1st and 2nd FTH max overpressure was a bit over 15%. The pictures of the throttle system of the DB 605 can be found from the manual and there is a picture of system of the L in the Gersdorf&co.
(http://www.onpoi.net/ah/pics/users/852_1182140163_geb.jpg)
Originally posted by Charge
In well designed engines the impeller speed can be controlled so there is no need for rotating the supercharger needlessly and thus regulating the air feed to the charger.
Well, the problem of the DB could not produce that kind of system. Basicly large part of the advantages of the hydraulic coupling was lost due to unaccurate adjustment of the supercharger speed and location of the throttle valve. If you compare curves of the DBs and the ideal DVL variable speed supercharger in the NACA paper, you can see that the loss is tens of ps between the 1st and 2nd FTH.
Below the 1st FTH the rate of the loss is also higher in the DBs than in the better designed engines. As an example the BMW 801D lost about 25-30ps/km while the DB 605A lost about 40-50ps/km; the BMW had throttle valves located before impeller while the DB had the throttle valve after the impeller.
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"There is a noticeable difference HP/Torque loss in manual vs auto trans car at the rear wheels. "
That would be the case if the propeller was run on hydraulic clutch. It is not run by it directly but "secondarily" which means that the possible losses can be overcome without the solution having to cause power loss. In this case by simply rotating the impeller a bit faster but not so fast that it exceeds the limiting tip speed.
"I don't know how much power did the two pumps use"
I don't have any pictures of the system or functional descriptions so I don't know how it actually looks and but I don't understand why it would need two pumps. Just one input from the main pump and one or two regulating systems depending of how well it is done. Of course the pump needs to be able to support both the engine's pressure and coupling pressure so it needs to develop more pressure than that of the same engine with two stage charger -and that pressure in not free, but I doubt the increase is significant enough to show.
"AFAIK all engines discused here needed quite a lot cooling but Von Gersdorf&co claim that the hydraulic coupling caused ca max 30% increase to needed oil cooling."
That is a fact with variable speed unit. It surprises me that the additional cooling needed is that small after all. I thought it would be bigger since the NACA requests for 50% bigger oil displacement.
"Just look the picture below, in this case at sealevel it did about 30% overpressure and between the 1st and 2nd FTH max overpressure was a bit over 15%."
I see that the Gebläsedrück is higher after the first FTH but the Ladedrück remains constant. If the GBD would be less after the FTH we could prolly see a notch in LDD i.e. less power.
"Basicly large part of the advantages of the hydraulic coupling was lost due to unaccurate adjustment of the supercharger speed and location of the throttle valve."
Probably more because of worse fuel and unclean aerodynamics...
"Below the 1st FTH the rate of the loss is also higher in the DBs than in the better designed engines. As an example the BMW 801D lost about 25-30ps/km while the DB 605A lost about 40-50ps/km; the BMW had throttle valves located before impeller while the DB had the throttle valve after the impeller."
Well, the choice of the impeller size and gear ratio dictates the power at first FTH and the second FTH and the choice can be made more freely if you have two stages as in FW and as the NACA report states the the biggest power gain in two stage charger happens in first FTH and thats where it IS better than other solutions. The bigger the power gain in First FTH the smaller the deck speed and vice versa. But after the first FTH the power begins to drop and the depth of the drop is determined of how high the second stage has its FTH. If it is very high the notch is very big, and that is where the variable speed keeps on pumping. It is visible in speed charts too. I don't see how much better the DBs could have done given the fuel they had to use.
Note: There are pros and cons in all systems and I am not claiming the variable speed system being superior to other systems. I think it was a good choice for that size and use of an aeroplane 109 was. Light and mechanically simple but requiring some automation stuff to make it work. With DBs engine construction it would have been much worse with either a turbo or a two stage charger because the weight gain would have been bigger than the gain in power. P47 and P38 could afford to run on turbo as the size of the aeroplane was so big and both Spit and Ponies had more leeway due to bigger wings and thus more load carrying capability although the weight gain of two stage is not so big over the variable speed than that of turbo system over them both.
-C+
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Originally posted by Charge
I don't have any pictures of the system or functional descriptions so I don't know how it actually looks and but I don't understand why it would need two pumps.
You can find pictures of the system from the DDB 605 manual. There is a diagram showing how the oil flow of the second pump is regulated by the barometric valve.
I don't know what the DB engineers where thinking but they probably choosed two pump system for the increased cooling flow; the second pump is used to increase cooling flow when not used for the coupling.
Originally posted by Charge
That is a fact with variable speed unit. It surprises me that the additional cooling needed is that small after all. I thought it would be bigger since the NACA requests for 50% bigger oil displacement.
Cooling need was seen as a problem. As an documented example, just take a look to the PDF on Kawasaki DB developements Mike just posted to the thread on Russian and Japanese engines.
Originally posted by Charge
I see that the Gebläsedrück is higher after the first FTH but the Ladedrück remains constant. If the GBD would be less after the FTH we could prolly see a notch in LDD i.e. less power.
The "Gebläsedruck" is practically allways a bit higher than the "ladedruck" (MAP) due to pressure losses caused by the throttle valve and other control valves (three valves all together which restrict air flow somewhat).
If the "gebläsedruck" drops below the certain level, the MAP starts to drop despite it's lower than the "gebläsedruck". A good example can be seen here (http://www.wwiiaircraftperformance.org/me109/14026pg7.jpg).
Originally posted by Charge
Probably more because of worse fuel and unclean aerodynamics...
This has absolute nothing to do with fuels nor unclean aerodynamics; the overpressure and performance losses were caused simply by unaccurate adjustment of the hydraulic coupling and the location of the throttle valve.
Originally posted by Charge
Well, the choice of the impeller size and gear ratio dictates the power at first FTH and the second FTH and the choice can be made more freely if you have two stages as in FW and as the NACA report states the the biggest power gain in two stage charger happens in first FTH and thats where it IS better than other solutions.
Hm... I quess you mean the two speed supercharger instead the two stage, right?
The DBs were variable speed systems only between 1st and 2nd FTH (the DVL system was variable speed from sealevel to it's FTH so its not the same), so it had advantage only at that altitude range, everywhere else the direct mechanical gearing is more efficient (above 2nd FTH it's even better than ideal DVL system).
Originally posted by Charge
I don't see how much better the DBs could have done given the fuel they had to use.
Just compare the concave shape of the power curve of the ideal DVL system to the convex shape of the DB power curves between 1st and 2nd FTH. And as noted above, this has absolute nothing to do with the fuels.
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Originally posted by gripen
The lower 2nd FTH ASB if compared to the ASM is caused by higher MAP (1,8ata). These are mostly the same engines, the ASB is just a later version with higher CR etc. The output difference is very small.
These are with RAM and the differences are mostly caused by higher MAP too as well due to higher RAM of the K-4. The static difference in the specification above FTH is 5-20ps between the AS and D depending on data (actually some data show advantage for the AS).
Note that all these are calculations (before production began in the case K-4). And there is no compressibility effects accounted in the calculation.
Hi,
according to my datas of the static power, i get this picture:
DB605AS:
Kurzleistung(combat/climb): fth 7800m, 1150PS
Dauerleistung: fth 7700m 1050PS
DB605ASM:
Kurzleistung: fth 7800m, 1150PS
Dauerleistung: fth 7100m, 1040PS
DB605ASB: (c3 fuel or MW50injection)
Kurzleistung: fth 6800m, 1285PS
Dauerleistung: fth 6500m, 1200PS
AS and ASB/M use different Spark plugs and ignition systems, who knows what else. All DB605 engines was rather similar, the different was the different between AS/ASB/ASM and D was in a different max usable presure and RPM. The D could run on higher rpm for longer time.
The DB605D datas are also from the 109G10, not only K4, but of course its the power with RAM, thats what we just compare(the Merlin datas are also with RAM and a even higher one, from the P51).
Combat power at 9000m is 1140PS with 653km/h. The K4 show the G10 engine datas, but 670km/h.
The K4 tests(not corrected?), show the plane with 690km/h in 9000m with combat climb, therefor i guess 670km/h(K4), 653(G10) and the related power are corrected.
Greetings,
Knegel
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Originally posted by Knegel
according to my datas of the static power, i get this picture:
DB605AS:
Kurzleistung(combat/climb): fth 7800m, 1150PS
Dauerleistung: fth 7700m 1050PS
DB605ASM:
Kurzleistung: fth 7800m, 1150PS
Dauerleistung: fth 7100m, 1040PS
These seem to be from here (http://mitglied.lycos.de/luftwaffe1/aircraft/lw/DB605_varianten.pdf). These differences are most probably typos; there is no sense to have same output at certain altitude and different at another given that the engine is practically same except MW50 (not used for these power settings).
Originally posted by Knegel
DB605ASB: (c3 fuel or MW50injection)
Kurzleistung: fth 6800m, 1285PS
Dauerleistung: fth 6500m, 1200PS
This is a later model than the AS or ASM with different ratings and other differences like higher CR.
Originally posted by Knegel
AS and ASB/M...
Never heard about ASB/M, what's the source for this? And I can't find the reference for the G-6/AS with ASB you claimed, the sheet you claimed seem to contain standard G-6/AS Jäger with the DB 605AS.
Originally posted by Knegel
All DB605 engines was rather similar, the different was the different between AS/ASB/ASM and D was in a different max usable presure and RPM. The D could run on higher rpm for longer time.
There is considerable differences between the A and D series engine engines; as an example lubrication system was partially redesigned in the D.
Originally posted by Knegel
The DB605D datas are also from the 109G10, not only K4, but of course its the power with RAM, thats what we just compare(the Merlin datas are also with RAM and a even higher one, from the P51).
The difference here is that the values for the Mustang are measured but the values you want to use for the Bf 109s are calculations. And there is plenty of evidence on problems with DBs to reach claimed performance.
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Originally posted by Angus
More of the climb, - Viking.
(And TY for the input)
Climb seems to be measured at MIL in both camps. But the data is confusing. 109G in 1944 is still using 6 minutes to 20K, Rall also mentions the same figure. A Spitty in the same time will use some rough 5 with more weight :confused: :huh
I have no problem believing a late-war Spitfire could climb better than a contemporary 109 at MIL power. Remember that while the Merlin's whole power range (cruise, MIL and WEP) increased during the war, due to limitation in materials and fuel (having to use anti-knocking agents like MW50) the DB 605 mostly just increased in WEP power. The Spitfire's bigger wing also made up for some of the greater weight.
If we look at the planes in AH we can see that the Spit XVI does indeed out climb 109G-14 on MIL power. It even matches the K-4 on MIL power.
http://www.gonzoville.com/ahcharts/index.php
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Originally posted by gripen
These seem to be from here (http://mitglied.lycos.de/luftwaffe1/aircraft/lw/DB605_varianten.pdf). These differences are most probably typos; there is no sense to have same output at certain altitude and different at another given that the engine is practically same except MW50 (not used for these power settings).
Yep, right, iam aware of this, but made the same typo, i was up to point to the different to the ASB, where you wrote before that its very similar to the AS and ASM.
Originally posted by gripen
This is a later model than the AS or ASM with different ratings and other differences like higher CR.
Yes, and same like the DB605D it had a different output.
Originally posted by gripen
Never heard about ASB/M, what's the source for this? And I can't find the reference for the G-6/AS with ASB you claimed, the sheet you claimed seem to contain standard G-6/AS Jäger with the DB 605AS.
AS, ASM+B would have been less confusing,eh?
(http://www.raf-roy.com/share/knegel/Screenes/109g.jpeg)
As i wrote before, i thinks thats a typo and should be AS.
Originally posted by gripen
There is considerable differences between the A and D series engine engines; as an example lubrication system was partially redesigned in the D.
Yes, and this different also brough a different poweroutput.
Originally posted by gripen
The difference here is that the values for the Mustang are measured but the values you want to use for the Bf 109s are calculations. And there is plenty of evidence on problems with DBs to reach claimed performance.
The 109K4 tests show a smaler FTH, but the performence is avove the calculated one and the SpitfireIXc tests dont show the great power output of the P51B engine. With "Drehzahlsteigerung" the K4´s best combat power(also max power) speed in 9km alt is around 705km/h(maybe not corrected, with a new propeller). Even with correction and the default propeller, the Vmax is still above that of the best Spitfire HF, despite the K4 is as heavy as the Spits and the heavy wingload also dont will be a advantage in this hight.
Thats why i still think its more the P51 airframe that provide better circumstances for the engine, than the engine itslef.
The big airinlet of the P51 probably provide a better RAM effect and this provide the outstanding power and highspeed performence of the P51B in high alt, despite its high wingload.
I guess the DB605D or AS in the P51 airframe would provide same results.
Greetings,
Knegel
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Originally posted by Knegel
Yep, right, iam aware of this, but made the same typo, i was up to point to the different to the ASB, where you wrote before that its very similar to the AS and ASM.
What I wrote above is that the AS and the D performed very similarly at high altitude and that the differences between earlier AS engines (AS and ASM) and later AS engines (ASB, ASC) are caused by different ratings. Just read the later pages of the same doc where the static output at 10km is given for 2800rpm:
AS 925ps
D 930ps
That means that there is no practical difference at high altitude between the AS (any model) and D (production model with large supercharger).
Originally posted by Knegel
AS, ASM+B would have been less confusing,eh?
...
As i wrote before, i thinks thats a typo and should be AS.
That is from the Monogram Close-Up series with typo, the original (from NASM microfilms) states clearly AS.
Please don't invent new designations.
Originally posted by Knegel
The 109K4 tests show a smaler FTH, but the performence is avove the calculated one and the SpitfireIXc tests dont show the great power output of the P51B engine. With "Drehzahlsteigerung" the K4´s best combat power(also max power) speed in 9km alt is around 705km/h(maybe not corrected, with a new propeller). Even with correction and the default propeller, the Vmax is still above that of the best Spitfire HF, despite the K4 is as heavy as the Spits and the heavy wingload also dont will be a advantage in this hight.
I don't see any properly corrected tests on the K-4 here. The compressibility correction for the 705km/h at 9km at can be more than 50km/h depending on conditions (edited for calculation error).
BTW what's the source and the FTH in the tests?
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"The "Gebläsedruck" is practically allways a bit higher than the "ladedruck" (MAP) due to pressure losses caused by the throttle valve and other control valves (three valves all together which restrict air flow somewhat).
If the "gebläsedruck" drops below the certain level, the MAP starts to drop despite it's lower than the "gebläsedruck". A good example can be seen here."
That looks abnormal. This (http://www.wwiiaircraftperformance.org/me109/14026pg8.jpg) looks normal.
"This has absolute nothing to do with fuels nor unclean aerodynamics; the overpressure and performance losses were caused simply by unaccurate adjustment of the hydraulic coupling and the location of the throttle valve."
Yes, that is what you keep saying, I don't buy it.
"Hm... I quess you mean the two speed supercharger instead the two stage, right?"
Yes. I wasn't aware that there were actual two-stage chargers but they actually existed. They have the advantage of better designed impellers for both critical altitudes but they are heavier designs.
"The DBs were variable speed systems only between 1st and 2nd FTH (the DVL system was variable speed from sealevel to it's FTH so its not the same), so it had advantage only at that altitude range, everywhere else the direct mechanical gearing is more efficient (above 2nd FTH it's even better than ideal DVL system)."
Of course, the DB has a single stage and thus its performance is that of a generously designed (altitude optimized) single stage with the option that its charge pressure does not need to be restricted but of course it is possible to put such impeller into two speed system that exceeds the power output of a variable speed system -but it comes with a price. There is a surge of inlet temperature rise in two stage system that calls for the drop in charging pressure in a two speed system, causing the notch in powercurve, a defect that a variable speed system does not have. Clearly seen in NACA document, too.
"Just compare the concave shape of the power curve of the ideal DVL system to the convex shape of the DB power curves between 1st and 2nd FTH. And as noted above, this has absolute nothing to do with the fuels."
Actually I think that with 130-150 grade fuel the performance and design of DB or any German aeroengine could have been quite a bit different. With 100 octane or less they had to stick with larger displacement and thus larger engine which dictated that all the auxiliaries needed to be light and thus the variable speed unit was absolutely a correct choice for DB fit in 109s. A drawback was the larger oil-cooler requirement but in turn it needed less cooler capacity than higher charged engines. E.g. Jumo213 had a two-speed charger and the weight was almost 200kg more (the 190D9 seems to have smaller notch in speed curve that both Spit and Pony have?).
In case I didn't need extreme high altitude speed I'd take variable speed unit anytime. No need for LFs or HFs or whatever... :cool:
-C+
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Originally posted by Charge
That looks abnormal.
That is exactly how it should theoretically be. Note that there is measured point at 3000m where the MAP drops and gebläsedruck is at lowest point.
Originally posted by Charge
This (http://www.wwiiaircraftperformance.org/me109/14026pg8.jpg) looks normal.
That is a drawing error at 2500m, there is no measured point at that altitude. Above 2nd FTH there is logical difference between the MAP and gebläsedruck just like in the several other graphs in the same data set.
Originally posted by Charge
Yes, that is what you keep saying, I don't buy it.
This is an impeller speed adjustment issue, it's there regardsless the fuel used or the aerodynamic condition of the plane.
We can simply disagree, if you don't want to believe me. No problem.
Originally posted by Charge
Yes. I wasn't aware that there were actual two-stage chargers but they actually existed. They have the advantage of better designed impellers for both critical altitudes but they are heavier designs.
Hm... the weight difference between single speed and two speed systems seem to be generally around 20-30kg if I look Merlin and some Radials. So the difference is quite small. It's difficult to figure out the weight of the hydraulic coupling + other needed gear but I quess it's in the same ballpark.
Originally posted by Charge
Of course, the DB has a single stage and thus its performance is that of a generously designed (altitude optimized) single stage with the option that its charge pressure does not need to be restricted but of course it is possible to put such impeller into two speed system that exceeds the power output of a variable speed system -but it comes with a price. There is a surge of inlet temperature rise in two stage system that calls for the drop in charging pressure in a two speed system, causing the notch in powercurve, a defect that a variable speed system does not have. Clearly seen in NACA document, too.
I don't know how many times it should be pointed out to you:
The ideal DVL variable speed supercharger in the NACA paper is continously adjustable at whole altitude range and the speed of the supercharger is supposed to be exactly needed below the FTH. Therefore the DVL supercharger runs at full throttle at entire adjustment range.
The DB supercharger is adjustable only at certain altitude range and there is no mechanism to adjust supercharger speed to match needed MAP. Therefore the DBs run more or less throttled up to the (near) 2nd FTH as the gebläsedruck curves show. Below 1st FTH the DB had the same losses as direct mechanical connection and in addition location of the throttle valve and coupling itself caused some more.
Originally posted by Charge
Actually I think that with 130-150 grade fuel the performance....
This has absolute nothing to do with the fuels...
Originally posted by Charge
E.g. Jumo213 had a two-speed charger and the weight was almost 200kg more (the 190D9 seems to have smaller notch in speed curve that both Spit and Pony have?).
The reason is that the Jumo 213 utilized spin type throttle (copied from the Mikulin AM-35 series) as was planned for the L series DBs. In addition the Jumo 213 did not run at constant MAP.
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Originally posted by gripen
What I wrote above is that the AS and the D performed very similarly at high altitude and that the differences between earlier AS engines (AS and ASM) and later AS engines (ASB, ASC) are caused by different ratings. Just read the later pages of the same doc where the static output at 10km is given for 2800rpm:
AS 925ps
D 930ps
That means that there is no practical difference at high altitude between the AS (any model) and D (production model with large supercharger).
As far as i understand there is a significant different in the time to use this powersetting. Further more 5PS static power will result in a higher RAM power different.
Originally posted by gripen
I don't see any properly corrected tests on the K-4 here. The compressibility correction for the 705km/h at 9km at can be more than 50km/h depending on conditions (edited for calculation error).
BTW what's the source and the FTH in the tests?
The source is the 109K4 speed curve from 19.01.45 for the DB605d/ASB mit MW50, mit Dünnblattschraube 9-12199.
Afaik thats the only available 109K4 test.
Vmax @9km with the default propeller is 690-695km/h, thats still 25-50km/h faster than the HF Spits in this altitude, despite the heavy wingload of the 109K4(same T/O weight like the Spits).
Of course we could assume that engeeners of the nation, who did develop planes like the 252, 163, flying wing , who had highspeed windtunnels etc made speed curves with a mistake of 50km/h, otherwise we also could assume the DB605D was pretty even or maybe better than the Merlin70 in the Spitfire.
Greetings,
Knegel
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Originally posted by Knegel
As far as i understand there is a significant different in the time to use this powersetting. Further more 5PS static power will result in a higher RAM power different.
Given that the tolerance for the DBs was 2,5%, the 5ps difference is neglible.
Originally posted by Knegel
The source is the 109K4 speed curve from 19.01.45 for the DB605d/ASB mit MW50, mit Dünnblattschraube 9-12199.
Hm... that sounds a lot like the A/IV/42/44; those are calculations, not test data and not accounting the drag rise due to compressibility (not the same thing as compressibility correction of the test data). Note that in these later calculations they use somewhat more realistic FTH, another story is if the engines reached claimed performance (even these lower specs).
BTW this thread is about the engines and the test data is used just to check out if the engines were up to the specs. However, for one reason or another you tend to bring in plane related arguments just like you did in Stoney's thread on airplane design.
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Hi,
actually you came up with the RAM power of the Merlin70/V-1650-3, and RAM power is in big degree related to the airframe.
If we talk about the engines only static power is valid, or we need to use the same or a similar airframe for the comparison.
I brought in the Spitfire HF performence and 109K4 performence to show that the engine power is very much related to the used airframe.
The datas say:
V-1650-3:
combat/climb: 1055HP at 8231m
max power: 1380HP at 7100m,
DB605AS:
combat/climb: 1150PS at 7800m
max power: 1200PS at 8000m
DB605D:
combat/climb: 1200HP at 7400m
max power: 1280PS at 7600m
Again its not that easy to compare this values, it simply depends to the time of usage and altitude. The Merlin have a the known high peak, but at a rather low altitude, while the DB´s have a good combat climb power.
Imho thats rather similar.
Greetings,
Knegel
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Originally posted by Knegel
actually you came up with the RAM power of the Merlin70/V-1650-3, and RAM power is in big degree related to the airframe.
That is simply because the test data shows if an engine delivers claimed performance. Note that even the lowest performing Merlin 70 you choosed gave closer to specs performance than the tested DBs.
Originally posted by Knegel
If we talk about the engines only static power is valid, or we need to use the same or a similar airframe for the comparison.
The problem with that is the chronic tendency of the DBs to not live up to the specs. Therefore test data gives better picture.
Originally posted by Knegel
I brought in the Spitfire HF performence and 109K4 performence to show that the engine power is very much related to the used airframe.
You brought in calculated data (accounts no drag rise due to compressibility) which you claimed to be flight tested.
Besides even the lowest performing Merlin 70 test data you choosed delivers higher output at high altitude than the calcudated data for the DBs.
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"That is exactly how it should theoretically be. Note that there is measured point at 3000m where the MAP drops and gebläsedruck is at lowest point."
Nope. That notch is not normal IMO.
"This is an impeller speed adjustment issue, it's there regardsless the fuel used or the aerodynamic condition of the plane.
We can simply disagree, if you don't want to believe me. No problem."
Yes we do, fine for me too. I'll study this matter more if I can and let you know if I discover I was wrong.
"Hm... the weight difference between single speed and two speed systems seem to be generally around 20-30kg if I look Merlin and some Radials. So the difference is quite small. It's difficult to figure out the weight of the hydraulic coupling + other needed gear but I quess it's in the same ballpark."
I have no idea of the weight gain, only that that NACA doc claims there is some. It could well be insignificant depending on how it is done, though.
"I don't know how many times it should be pointed out to you:
The ideal DVL variable speed supercharger in the NACA paper is continously adjustable at whole altitude range and the speed of the supercharger is supposed to be exactly needed below the FTH. Therefore the DVL supercharger runs at full throttle at entire adjustment range."
The DB charger provides steady ATA from the deck to the highest FTH. I think it performs quite well looking the speed figures too. Maybe it could have been better, maybe not -but for a long time it certainly was good enough.
"The DB supercharger is adjustable only at certain altitude range and there is no mechanism to adjust supercharger speed to match needed MAP. Therefore the DBs run more or less throttled up to the (near) 2nd FTH as the gebläsedruck curves show. Below 1st FTH the DB had the same losses as direct mechanical connection and in addition location of the throttle valve and coupling itself caused some more."
It seems so. It also appears that DB did not have such abrupt temp rise as the two speed units had requiring not as radical throttling between speed change point to prevent detonation. The arch troubles me though and it is a potential place for throttling, but I don't understand why it is there. But even there the Ladendrück remains even so it does not effect speed negatively.
"This has absolute nothing to do with the fuels..."
The fuel dictated the path DB and German engine designers had to stay on. More displacement for more power and more ATA only if proper materials and fuel were available. More displacement generally means more power and thus more weight unless the engine can be lightened from some place. Wiht heavily charged engines there is not such pressures to increase displacement but the make the engine withstand more stress from increased charging pressures.
"The reason is that the Jumo 213 utilized spin type throttle (copied from the Mikulin AM-35 series) as was planned for the L series DBs. In addition the Jumo 213 did not run at constant MAP."
The point was that Jumo was heavier than DB, maybe because of its charger arrangement or again maybe not, and that its two speed charger was maybe better done than those of its allied contemporaries. That is visible in TA152s speed figure too. Two stages, three speeds and the speed of the a/c does not drop at gear/speed change, maybe because off less radical temperature changes in charged air or less sensitiveness to those changes.
-C+
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Charge, can you use italics for you quotes to help with the reading.
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Originally posted by Charge
Nope. That notch is not normal IMO.
The point was to show the relation between the gebläsedruck and MAP ie the gebläsedruck is practically allways higher than MAP.
Do you disagree?
Originally posted by Charge
Yes we do, fine for me too. I'll study this matter more if I can and let you know if I discover I was wrong.
OK. I have given the the sources to look for, most sources can be found from FAF museum library (Von Gersdorf&co there is my former copy).
Originally posted by Charge
The DB charger provides steady ATA from the deck to the highest FTH. I think it performs quite well looking the speed figures too. Maybe it could have been better, maybe not -but for a long time it certainly was good enough.
Generally it does steady MAP up to the 2nd FTH but there is no direct connection between barometric valve and MAP control so the system rarely runs impeller at optimal speed below 2nd FTH.
If barometric valve starts to redirect flow from the second pump too late, the MAP drops just like in the case discused above.
If barometric valve redirects flow too early or too much oil from the the second pump, the impeller spins too fast and throttling is needed (supercharger does overpressure) . As can be seen from the gebläsedruck curves, that is the situation most of time below the 2nd FTH.
Originally posted by Charge
It seems so. It also appears that DB did not have such abrupt temp rise as the two speed units had requiring not as radical throttling between speed change point to prevent detonation. The arch troubles me though and it is a potential place for throttling, but I don't understand why it is there. But even there the Ladendrück remains even so it does not effect speed negatively.
As pointed out by comparing the power curves of the BMW 801D and DB 605A, the losses due to throttling are higher in the case of the DB due to location of the throttle valve. In the L series engines the throttle valve was relocated before the impeller and the throttle was changed to the spin type like in the Jumo 213 (there is a picture of the system in the Von Gersdorf&co).
Originally posted by Charge
The fuel dictated the path DB and German engine desig...
The points discused above are there regardless the used fuel, in other words the fuels has nothing to do with this.
Originally posted by Charge
The point was that Jumo was heavier than DB...
I just pointed out the reason for the properties of the power curve.
The DB 605 is more comparable with the Jumo 211 than the Jumo 213, roughly same weight and roughly same output as used in service before mid 1944 (later DB got MW50 etc. but that time Junkers was focused to the more advanced Jumo 213).
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I just want to throw out a few things raised in the last few posts:
Two stage superchargers do add a significant amount of weight. It is not just the weight of the second blower itself, it is the weight and drag associated with an intercooler. The accessory drive also has to be redesigned to manage the effects of a second, more highly geared blower. And at lower altitudes all this weight is added for little purpose. It only becomes useful at higher altitudes.
As an example, the two stage blown Twin Wasp on the F4f was a fine engine for good high altittude performance (once the kinks were worked out), but for low altitudes better performance was attained using a lighter Cyclone with a single stage supercharfer (hence the FM version of the Wildcat)
Second there are sometimes differences in engine performance when comparing charts for a particular engine and looking at numbers for that same engine in a particular airplane. That does not mean that an engine chart without reference to a particular plane is necessarily reporting only "static" power. RAM air is easily simulated on the test bed and this was often done. There are plenty of P&W engine charts that include data with RAM air. Now whether a particular plane can deliver this RAM air to the engine is a different question and that is one reason why there can be differences in the charts I alluded to above (another is differences in cooling).
-Blogs
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The DB was going towards the two stage concept in high altitude engines; atleast in paper the DB 605L is comparable to the best 100 series Merlins at high altitude. The weight difference between the DB 605D and the L seem to be rather low (30-40kg depending on source) if compared to the Merlins (about 90kg). That might be partially explained by aftercooler of the Merlin. The concept of the two stage supercharger in the L was similar as seen in the Merlin and Jumo213; integral unit featuring two impellers in series in the same axle.
The American system was to use external auxilary stage (turbo or mechanical) for two stage engines. This is less compact and probably somewhat heavier arrangement. However, production wise the american system was much easier because the base engine is practically unchanged regardless the supercharging used.
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Sounds about right. The difference in the dry weight of a single stage vs. A two stage supercharged Twin Wasp is about 51kg, a 7.5 percent increase in weight.
-Blogs
Originally posted by gripen
... The weight difference between the DB 605D and the L seem to be rather low (30-40kg depending on source) if compared to the Merlins (about 90kg). That might be partially explained by aftercooler of the Merlin. ...
.
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For the double wasp, the weight increase between otherwise comparable models with single or two stage supercharging appears to be about 95kg, or roughly a 9 percent increase in engine weight.
Originally posted by joeblogs
Sounds about right. The difference in the dry weight of a single stage vs. A two stage supercharged Twin Wasp is about 51kg, a 7.5 percent increase in weight.
-Blogs
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Originally posted by gripen
That is simply because the test data shows if an engine delivers claimed performance. Note that even the lowest performing Merlin 70 you choosed gave closer to specs performance than the tested DBs.
The problem with that is the chronic tendency of the DBs to not live up to the specs. Therefore test data gives better picture.
You brought in calculated data (accounts no drag rise due to compressibility) which you claimed to be flight tested.
Besides even the lowest performing Merlin 70 test data you choosed delivers higher output at high altitude than the calcudated data for the DBs.
Hi,
actually i didnt claim the K4 is flight tested, i took the only availabe K4 (DB605D) datas i know.
Testdatas with RAM only show, if a engine in the particular airframe delivers claimed performance.
Actually i never saw a DB605D test and the tested ASM seems to delivers claimed performance.
DB605ASM
FTH static
Sondernot: 6400m
Start/Not: 8000m
Steig/Kampf: 7800m
FTH RAM
Sondernot: 6800m 400m above static fth
Start/Not: 8700m(roundabout) 700m above static fth
Steig/Kampf: 8600m 800m above static fth
Merlin 70/V-1650-3:
Static FTH
combat/climb: 1055HP at 8231m
max power: 1380HP at 7100m( found a other source with 7450m),
FTH RAM of the three HF Spitfires:
8475m (with a weight of 3218kg) 1025-1375m above static fth
8100m (with a weight of 3218kg) 650-1000m above static fth
7743m (with a weight of 3160kg) 300-650m above static fth
Dont look that bad for the AS.
Are there more datas to the GJ-FX test available?? Are this tested or calculated performences?
Are there any other tests available?
Even if we reduce the GJ-FX speed by 40km/h, in 9000m its still as fast as the slowest Spit in test, with 15km/h correction its still as fast as the fastest Spitfire, despite the smal weight of the Spits in test.
Once again i only see very similar performing engines.
All arguments against this currently base on assumtions, which are sooooo bad and wrong, if Kurfi use them.
Greetings,
Knegel
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Originally posted by Knegel
actually i didnt claim the K4 is flight tested, i took the only availabe K4 (DB605D) datas i know.
You did (actually several times), your post 06-19-2007 06:47 AM:
"The 109K4 tests show..."
Originally posted by Knegel
Testdatas with RAM only show, if a engine in the particular airframe delivers claimed performance.
The flight test data for the Merlin shows quite steady RAM response and close to spec performance:
Static ratings for 2nd FTH at WER from RR specifications (note that aircraft cards contain a lot of errors on ratings):
V-1650-3 1330hp at 23300ft
Merlin 70 1475hp at 22250ft
FTH with high speed RAM from the specs:
P-51B 29000ft (US spec)
P-51B 28000ft (UK spec)
HF IX 27500ft
Tested FTHs and difference to the spec:
AAF No. 43-6883 29400ft +400ft to US spec +1400ft to UK spec
FX953 28000ft -1000ft to US spec 0ft to UK spec
BS551 27800ft +300ft
EN524 26600ft -900ft
BS310 25400ft -2100ft (640m)
As for comparison the best performing AS plane (GJ+FX) was 700m below the spec at similar rating.
Originally posted by Knegel
Are there more datas to the GJ-FX test available?? Are this tested or calculated performences?
Are there any other tests available?
The GJ+FX data is flight tested, I have given the sources for other data above.
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Hi,
do you know other tested 109´s with AS engine, or why do you talk about the best AS plane??
And in your datas i cant see that the tested DB605AS RAM power FTH is below the Spitfire Merlin70, its also in a normal way above the static power.
The difference between the Spitfire and Mustang show how important the airframe was(for the RAm power), therefor its simply not good possible to compare the engines by the RAM power.
I cant see that the DB´s are below what they should do, therefor the static power are the datas to use to compare the engines.
Otherwise you compare the planes + engine.
Greetings,
Knegel
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Originally posted by Knegel
do you know other tested 109�s with AS engine, or why do you talk about the best AS plane??
There is two other tested AS planes claimed above, the reached FTH was about 300m less than in the case of the GJ+FX at 1,3ata 2600rpm.
Originally posted by Knegel
And in your datas i cant see that the tested DB605AS RAM power FTH is below the Spitfire Merlin70, its also in a normal way above the static power.
The FTHs with RAM are discused here to check if the tested engines lived up to the specification. If the static power had been tested, the results would have followed the trend of the FTHs with RAM (the speed differences cause rather small variation as will be shown below).
The static FTH for the DB 605 ASM is 6400m in the specs and tested FTH with RAM in the best case was 6800m ie 400m increase due to RAM over the spec.
The static FTH of the Merlin 70 is 22250ft (6782m) in the specs and tested FTH in the worst case was 25400ft (7742m) ie 960m increase due to RAM (note that even using wrong values like you did above, the increase would had been 655m over the spec).
Originally posted by Knegel
The difference between the Spitfire and Mustang show how important the airframe was(for the RAm power), therefor its simply not good possible to compare the engines by the RAM power.
The best P-51B shows 1860m increase over the spec static FTH, the best HF IX shows 1690m over the spec FTH ie the difference 150m. Given that the difference between even the worst Merlin 70 and the best DB 605AS is in hunreds of meters (even using wrong values like you did ), it is obvious that the speed and RAM combinations does not make large error here.
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Hi,
i found one of the other tested AS engines(on Kurfis page), it was to new to fly with combat climb in low level, a to new engine is a good reason for a rather bad performence and the whole configuration was a prototype.
If the Merlin70 was so advanced, do you have a idea why the heavy wingloaded 109G14 did fly that fast in 9000m and why the K4 was even faster in a higher alt?
I already wrote that the DB605ASM with Sondernot had only a 400m higher RAM FTH than static FTH, but on the other hand the Start/Not and Steig/Kampf FTH is good above the static FTH.
And the speedcurve of GJ+FX show a Sondernot FTH of 7000m, while they write 6800m on the right side.
The RAM effect dont have to be the same between different plane types.
Maybe the static power FTH´s are optimistic, but even with some hundret meters less, the power is pretty even to the static Merlin 70.
It also can be the other way around, the Spitfire airframe could provide a better RAM effect than the 109 Airframe, nevertheless the planeperformences show that the RAM power output must have been rather similar.
A US plane comparison show a static FTH for the V 1650-3 of 23300ft.
btw, iam absolutly not sure that the K4 datas with the default propeller are calculated. The calculation could be only related to the new propeller. At this time they should have had enough testdatas for the "normal" K4 to get around a calculation.
But of course we also could assume that all G10 and K4 datas in the comparison tables are only Nazi propaganda, based on horrible calculations, without to look to the tested datas they had.
Greetings,
Knegel
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Originally posted by Knegel
i found one of the other tested AS engines(on Kurfis page), it was to new to fly with combat climb in low level, a to new engine is a good reason for a rather bad performence and the whole configuration was a prototype.
Pure speculation and the difference to the GJ+FX is not big.
Originally posted by Knegel
If the Merlin70 was so advanced, do you have a idea why the heavy wingloaded 109G14 did fly that fast in 9000m and why the K4 was even faster in a higher alt?
This thread is about engines. Bring in better documented and properly corrected data and start a new thread if you want to discuss about airframes.
Originally posted by Knegel
I already wrote that the DB605ASM with Sondernot had only a 400m higher RAM FTH than static FTH, but on the other hand the Start/Not and Steig/Kampf FTH is good above the static FTH.
It's still below spec and even using the 30min power the best AS plane has lower RAM response than the worst HF IX at 5min power. Besides the output difference is even wider in that case.
Originally posted by Knegel
The RAM effect dont have to be the same between different plane types.
Maybe the static power FTH´s are optimistic, but even with some hundret meters less, the power is pretty even to the static Merlin 70.
Well, I quess you will try to twist numbers for ever but the spec output (1500ps at 6400m) does not make the AS even with the Merlin 70 at high altitude (1475hp at 6780m).
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Hi,
Originally posted by gripen
Pure speculation and the difference to the GJ+FX is not big.
Its not a speculation that a very new engine dont bring the power of a engine that did run the needed hours to be able to fly with full power.
And its no speculation that the engine was very new.
Originally posted by gripen
This thread is about engines. Bring in better documented and properly corrected data and start a new thread if you want to discuss about airframes.
Since we dont have many documents for the german engines, its imho needed and valid to take the available plane performences to estimate the engine performence.
Originally posted by gripen
It's still below spec and even using the 30min power the best AS plane has lower RAM response than the worst HF IX at 5min power. Besides the output difference is even wider in that case.
Iam not realy sure if thats right, cause i think you dont use the right power settings and fth´s for the Merlin70. You use the 25lb boost power and FTH´s and mix them up with the tested 18 lib boost fth´s.
Originally posted by gripen
Well, I quess you will try to twist numbers for ever but the spec output (1500ps at 6400m) does not make the AS even with the Merlin 70 at high altitude (1475hp at 6780m).
Thats true, but i think the Spitfires and P51B got tested with this:
(http://www.raf-roy.com/share/knegel/Screenes/V16503150oct.jpg)
(http://www.raf-roy.com/share/knegel/Screenes/MSWF4UDATA_11_0001.jpg)
Greetings,
Knegel
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Originally posted by Knegel
Its not a speculation that a very new engine dont bring the power of a engine that did run the needed hours to be able to fly with full power.
And its no speculation that the engine was very new.
The tested plane was faster than the GJ+FX at low altitude so there certainly was no large difference in output. Note that conditions in the GJ+FX data are slightly warmer than standard at FTH so the pressure altitude is lower than the density altitude.
Originally posted by Knegel
Since we dont have many documents for the german engines, its imho needed and valid to take the available plane performences to estimate the engine performence.
As has been pointed out above, the tested engine performance (measured MAP and altitude) in the planes show that even in the best case the output of the DB 605AS was well below the worst case Merlin 70 (or V-1650-3) at high altitude. Infact, even the worst Merlin 70 does higher output than specification for the DB 605AS.
Bring in better documented and properly corrected data and start a new thread if you want to discuss about airframes.
Originally posted by Knegel
Iam not realy sure if thats right, cause i think you dont use the right power settings and fth´s for the Merlin70. You use the 25lb boost power and FTH´s and mix them up with the tested 18 lib boost fth´s.
I'm quoting +18psi values for the Merlin 70 directly from the RR specifications (can be found from "The Merlin in Perspective – the Combat Years" by A. Harvey-Bailey). And the test data discused earlier, list directly the altitudes and the corresponding MAP so there is no way to mix up the values.
Originally posted by Knegel
Thats true, but i think the Spitfires and P51B got tested with this:
Neither of the papers you linked is tested data nor the specification (note the 61" MAP for the V-1650-3). Basicly you desperately throw in argument after argument regardless the sense of the argument.
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Hi,
61" MAP for the V-1650-3 is probably a typo, in the US plane comparison and in the tested datas you brought in the engine show a similar result with 67".
If the Spitfires Melin70 should have 1475hp at 6780m with 18lb boost, its MUCH below the specs in the test, not regarding the fth, but regarding the power.
At the current stage we dont have tested power datas for the Merlin70 in the Spitfire, neighter for the DB605AS or D, as result we cant get around to look to the plane performence to get an idea of the power output.
While the tested P51B power dont get close to 1475HP at hight and i have no doubt that the P51B airframe got more RAM power out of this engine.
To me it seems the Merlin 70 stand below its spec regarding the power, while the DB605 dont reach the FTH.
At the end the plane performences make me believe the engines was rather similar.
Where the AS was a bit below the Merlin70 and the D even up to 9000m, while its a bit worse above this.
Of course there is no exact prrof for this, but same there is even less a proof for a so much advances Merlin70 in the Spitfire like you say it was.
Therefor i dont see a sence to go on with this, until new datas appear.
Greetings,
Knegel
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The V-1650-3 and V-1650-7 got the RR designations M68 and M69 respectively.
blower gear ratios:
V-1650-3: 6.391:1 (low), 8.095:1 (high)
V-1650-7: 5.802:1 (low), 7.349:1 (high)
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Originally posted by Knegel
61" MAP for the V-1650-3 is probably a typo, in the US plane comparison and in the tested datas you brought in the engine show a similar result with 67".
The specification static 2nd FTH values for the V-1650-3 are 1330/3000/23300 (hp/rpm/altitude) at +18,25psi. Note that the V-1650-3 is based on R.M.8.S.M. generation (Merlin 61) except the 12" impeller.
Originally posted by Knegel
If the Spitfires Melin70 should have 1475hp at 6780m with 18lb boost, its MUCH below the specs in the test, not regarding the fth, but regarding the power.
The specification static 2nd FTH values for the Merlin 70 are 1475/3000/22250 (hp/rpm/altitude) at +18psi. Note that the Merlin 70 is based on R.M.11.S.M. design ie it's later generation engine than the V-1650-3.
Basicly the Merlin 70 had lower 2nd FTH for a bit lower MAP but higher output. There might have been improved versions of the V-1650-3 but if you look power values from the AAF No. 43-6883 report, you can see that these follow quite close RR specs.
Originally posted by Knegel
At the current stage we dont have tested power datas for the Merlin70 in the Spitfire, neighter for the DB605AS.
There is 3 datasets on the Merlin 70 and 3 datasets on the DB 605AS. The output can be estimated fairly accurately based on MAP (error due to RAM is rather small).
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Originally posted by MiloMorai
The V-1650-3 and V-1650-7 got the RR designations M68 and M69 respectively.
blower gear ratios:
V-1650-3: 6.391:1 (low), 8.095:1 (high)
V-1650-7: 5.802:1 (low), 7.349:1 (high)
Yes, the Merlin 70 had gear ratios 6.39:1 (low) and 8.03:1 (high) ie the high gear ratio was lower than in the V-1650-3. The 1st stage impeller of the Merlin 70 was improved if compared to the earlier generations. It's possible that later production V-1650-3s got improved impeller as well, the V-1650-9 had the same SC gear ratios and many features of the improved two stage Merlins.
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Hi,
Originally posted by gripen
There is 3 datasets on the Merlin 70 and 3 datasets on the DB 605AS. The output can be estimated fairly accurately based on MAP (error due to RAM is rather small).
So you realy will sell that the Merlin70 had 1475HP in 27800ft??
Ok, lets see, the P51B had around 1370hp there, a similar wingarea, 1000kg more weight and a speed of 435-440mph.
While the Spitfire with 100HP more, but 1000kg less weight just reach 415mph(best case)??
The service ceiling of the P51B(42000ft) also wasnt that much below that of the Spitfire(43100ft, best case) to believe such a power advantage. The 1000kg more weight are already more than enough to explain that different and to make believe that the Merlin70 was rather less powerfull.
On the other hand the people claim that the Spitfire had the highest critical mach and the light wingload was a huge advantage in high alt.
Realy, if the Merlin70 had such a power output inside the Spit airframe, the SpitfireIXc airframe must have been the most worse in the war, or the tested planes all did fly with a damaged propeller.
Yae, the Spitfire was a plane full of miracles. :D
btw, it wasnt me who came up with the V-1650-3 power to discuss the merlin high alt performence.
Greetings,
Knegel
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Originally posted by Knegel
So you realy will sell that the Merlin70 had 1475HP in 27800ft??
I'm not selling anything, I merely quote the specification ie static output 1475hp at 22250ft for +18psi and 3000rpm. The real output with RAM depends on conditions, for one reason or another you refer now the FTH of the BS551 which still did +18,5psi at that altitude running 2960rpm.
Originally posted by Knegel
Ok, lets see, the P51B...
I'm not comparing the planes but just looking if the engines lived up to the specifications. The output can be calculated quite accurately from the MAP and the P-51B, HF IX and Gj+FX data can be easily used to check the output of the engines because the altitude and MAP combinations are given in the data. The error caused by RAM is rather small as can be seen by comparing the FTHs of tested Merlins
Originally posted by Knegel
btw, it wasnt me who came up with the V-1650-3 power to discuss the merlin high alt performence.
It was Viking who started to compare FTHs and I used the test data to point out that it's the reached output which matters. Later you started to compare DB specs vs tested Merlins and so on... Your argument has changed quite a bit since that and not just once.
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Hi,
of course my argumetation have changed, cause i look to the same problem from different sides, while you remain to try to estimate power values out of a few curves, where we dont know exact in what way they got recalculated, without to look to the plane performeneces, which can give a good hint, if the estimated engine performences are possible or not.
Interesting is that when Viking came with FTH´s, you came with the best available Merlin test regarding the FTH. But when i come with the static power, you say your prevoious stated engine is not nearly a Merlin70 and the Merlin70 was much more powerfull, while the plane performences of the P51B and the Spitfire HF´s show that this simply cant be.
And you always claim that the DB´s dont reach their specs, while the speeds of the planes show very good performences, but of course we safely can assume that this speeds can be up to 50km/h to fast, cause the german engeeners like to offer absolut useless comparison sheets.
Of course this explain how the heavy Bf109K4, G10 and G14AS could be faster than the HF Spit up to 9000m, while the Merlin70 power must have been good above the DB605AS + D´s power.
But maybe also the P51B Speeds are without mach correction and so it didnt fly 440mph@9km, but only 410mph, what actually still would be very fast for a so powerless plane with a 1000kg disadvantage(in comparison to the Merlin70 powered Spitfire).
Of course its easy and usefull for your argumentation to wear blinders and to relay on the available engine datas, while we actually dont have any tested DB605 and Merlin70 power curve.
To mix up the good FTH´s of the tested Spit´s, with the static power stats simply dont fit to the tested flight performences.
My conclusion remain that the Merlin70 didnt reach the specs regarding the power, while the DB´s didnt reach the specs regarding the FTH, resulting in a rather close match regarding the power in hight.
Greetings,
Knegel
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Originally posted by Knegel
of course my argumetation have changed, cause i look to the...
Please, save your words; if your argument fails you come back with another.
Originally posted by Knegel
Interesting is that when Viking came with FTH´s, you came with the best available Merlin test regarding the FTH.
Those were the first ones with production engines in the site. Besides, maybe you should check Vikings argumentation first as well as your own.
Originally posted by Knegel
But when i come with the static power, you say your prevoious stated engine is not nearly a Merlin70 and the Merlin70 was much more powerfull, while the plane performences of the P51B and the Spitfire HF´s show that this simply cant be.
Start a new thread on this. There is RR calculations on this in Harvey-Baileys book and these match well tested speeds and if I put the values to my spreadsheet I got similar results; the Cd0 I got is close to other data (there appear to be about 5% variation).
Originally posted by Knegel
And you always claim that the DB´s dont reach their specs...
There is plenty of evidence of DBs not reaching claimed performance (just search the sources claimed in this thread)
Originally posted by Knegel
Of course this explain how the heavy Bf...
Start a new thread if you want to talk about the planes.
Originally posted by Knegel
But maybe also the P51B Speeds are without mach correction...
The used corrections of the Eglin Field and A&AEE P-51B tests are documented and the performance is close to the Wright field data.
BTW Start a new thread if you want to talk about the planes.
Originally posted by Knegel
Of course its easy and usefull for your argumentation to wear blinders and to relay on the available engine datas, while we actually dont have any tested DB605 and Merlin70 power curve.
I've got several of these. Besides good estimates can be calculated simply from the MAP using the specs.
Originally posted by Knegel
To mix up the good FTH´s of the tested Spit´s, with the static power stats simply dont fit to the tested flight performences.
I don't see such thing here. Have you actually calculated something? If so, start a new thread.
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Originally posted by gripen
There is RR calculations on this in Harvey-Baileys book...
Correction: The calculations are presented in "Rolls-Royce and the Mustang" by D. Birch.
Power curves (tested) for the Merlin 70 and many other Merlin developements can be found from an article "Developement of the Rolls-Royce Merlin from 1939 to 1945" by A. C. Lovesey published in "Aircraft Engineering" July 1946.
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Knegel: absolute power shows better in ROC than top speed.
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BTW, I have a sheet to calculate weight and time to alt into NM per time unit. Used it to compare similar aircraft from actual tests.
The Spit and 109 are basically so similar, that it is a delight to compare them. Power being even more similar than weight. So, this might be useful, and I will mail the sheet to you if you like :)
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http://en.wikipedia.org/wiki/Horsepower
Interesting...
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Only 1.4% difference between imperial and metric though...
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PS. Why don't you start a new thread Gripen? One of your own with a topic you see fit and not going around telling people to start a new thread if they discuss something that you are not interested in.
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Originally posted by Charge
PS. Why don't you start a new thread Gripen? One of your own with a topic you see fit and not going around telling people to start a new thread if they discuss something that you are not interested in.
Why should I start a new thread? I have tried to stay on the engines which is the subject of the thread. Some others have tried to pull the discussion off topic (drag, fuels etc.) when it appears that their original argument failed.
Regarding the ps/hp issue, if you look above, you can see that I have tried to use ps ratings for the DBs and hp ratings for the Merlins.
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"Some others have tried to pull the discussion off topic (drag, fuels etc.) when it appears that their original argument failed."
Fuel? You claimed that the fuel did not have anything to do with how German aeroengines were developed. It affected the weight and charging method and actually the lack of decent materials was one main the reason why e.g. turbos were not taken into use in German planes. Irrelevant? I don't think so and I don't remember anybody else claiming it irrelevant but you. Not your personal playground, BTW.
"Regarding the ps/hp issue, if you look above, you can see that I have tried to use ps ratings for the DBs and hp ratings for the Merlins."
My comment on that had absolutely nothing to do with YOU. It was an issue that I had completely forgotten and thought of bringing it to everybody that power was measured differently in "metric countries". My bad, but again not your personal playground.
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Originally posted by Charge
Fuel? You claimed that the fuel did not have anything to do with how German aeroengines were developed.
Please don't put words to my mouth, when we were talking about the adjustment of the hydraulic coupling in the DBs and location of the throttle valve I just pointed out that the issues (operation of the barometric valve and the location of the throttle valve) are there regardless the used fuel or the aerodynamics. Lets quote your posting (06-18-2007 01:45 PM) from above (my quoted text is in the parenthesis):
Originally posted by Charge
"Basicly large part of the advantages of the hydraulic coupling was lost due to unaccurate adjustment of the supercharger speed and location of the throttle valve."
Probably more because of worse fuel and unclean aerodynamics...
In your next post (06-19-2007 01:20 PM) you tried to turn the same issue to the fuels again.
Originally posted by Charge
My comment on that had absolutely nothing to do with YOU. It was an issue that I had completely forgotten and thought of bringing it to everybody that power was measured differently in "metric countries". My bad, but again not your personal playground.
I merely noted that I have tried to use original units and I did not see your note on ps/hp issue as an offense.