Aces High Bulletin Board
General Forums => Aircraft and Vehicles => Topic started by: Angus on November 12, 2002, 04:34:21 PM
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By starting this thread, I am basically looking for information so I can compare those two wondeful pieces of machinery. However, the best way to gather information in this place is to throw a flamer. Hmm...maybe the thread topic should have been something like "RR MERLIN BEATS DB!!!"....but...I'll skip that.
But yet, which engine was the better one? Weight to power? Durability? Maintenance? Ability to be tuned to further power output? Wear and tear?
For what it's worth, I'd put my money on the Merlin. Now, as far as I remember, the Merlin weighted less pr.hp, needed a smaller coolant surface, and would have a longer lifetime. I am not sure about maintenance, fuel consumption etc, but anyway, this is all about info, so please shoot:D
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Then again, history is written by the victor......
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Hi Angus,
>But yet, which engine was the better one?
I'd say they were perfectly matched :-)
The Rolls-Royce Merlin generally yielded a higher specific power output than the Daimler-Benz, but the DB series engines generated equivalent total power despite employing inferior alloys and lower grade fuel (not by choice, but by necessity). The key to that was greater displacement and the use of a sophisticated fuel injection system which the Merlin didn't have.
Early in the war, the DB series engines held an advantage in high-altitude power due to the variable-speed supercharger. When the two-stage supercharger was introduced, the high-altitude advantage went to the Merlin-engined fighters. On the other hand, in specialized aircraft GM-1 injection restored the Daimler-Benz superiority at extreme altitudes.
While the Merlin was capable of running at higher revolutions than the Daimler Benz, MW50 injection gave the DB engines as much or even more power. Engine life probably was greater with the Merlin engines, but the DB engines were reliable throughout their design life, even if it was shorter.
The Merlin had a small frontal area due to the supercharger being aft of the engine and not on the side as with the Daimler-Benz, which was especially pronounced when the latter was fitted with large high-altitude superchargers. On the other hand, the inverted layout of the DB engine allowed a better view over the nose, and the lateral supercharger placement allowed fitting of a ballistically favourable engine cannon.
There are probably quite a few more pros and contras for each of the two engine series, but in the end, it came down to the performance of the aircraft fitted with these engines - which was very close for most of the war, including the last few months when the DB engines reached their peak (while Merlin development continued for a while after the war.)
Actually, the comparison probably could be extended beyond the Merlin and the DB605 to the Griffon and the DB603, and yield similar results.
When the British analyzed German piston engine technology after WW2, they were impressed by some of the detail solutions, but generally found they couldn't learn much from it since both sides had achieved similar results using different methods - an obvious case of parallel evolution.
(However, they might have been more interested in the details, redundant to British technologies or not, if it hadn't been for the jet engine which obviously was destined to replace the piston engine in the near future :-)
One important technology which the Germans didn't develop and the Merlin didn't employ was the turbo supercharger. The Merlin had satisfactory high-altitude performance even on its engine-driven supercharger (plus residual exhaust thrust), and Germans were facing shortage of high-quality alloys as well as shortage of engineering man power because most of the experts with the know-how to design turbo supercharger were working on jet turbines instead.
Regards,
Henning (HoHun)
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If you want to compare the Merlin to a DB engine, the best choice would be the DB601 and DB605.
If you are interested in the DB 603 you should compare it to the Gryffon.
Generally, the two-stage Merlins were better than the later 605's. But Single stage Merlins weren't at a big advantage over the 601's and earlier 605's. The DB's had fuel injection from the start, while Merlins didn't get fuel injection until the 60 series. DB's were also designed to have a cannon firing through the prop spinner, a definite packaging advantage. I don't have any information on cooling requirements.
It would be interesting to look at the following for several versions of each engine:
Max HP
Max HP/weight
Max HP/displacement
gal/hp-hr
Highest critical altitude and power at that altitude.
Those will pretty much tell you who was the boss.
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On the other hand, in specialized aircraft GM-1 injection restored the Daimler-Benz superiority at extreme altitudes
I understand this little bit, but could one of you please explain to me what exactly "water injection" was/ is? I know this is a little off- topic with the thread, but I have read about it to a small degree in the few reference books I have and am very curious how injecting water into an engine could boost it's performance
:confused:
Thanks!
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The DC 600 series would hav ebeen a great engine if they weren't upside-down :)
J_A_B
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Originally posted by VOR
I understand this little bit, but could one of you please explain to me what exactly "water injection" was/ is? I know this is a little off- topic with the thread, but I have read about it to a small degree in the few reference books I have and am very curious how injecting water into an engine could boost it's performance
:confused:
Thanks!
Water injection allows higher supercharger boost (or compression ratio) without damage or wear on the engine. Basically it cools down the fuel/air charge and prevents detonation. Methanol was added to prevent the water from freezing at high altitudes. Systems of this sort are variously known as "water injection", "ADI", "methanol-water injection", "MW 50" and probably some other names. All are referring to the same technology.
GM-1 was something completely different. It was an injection system that used nitrous oxide. This was used to give the engine more power at high altitude.
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Thanks Funked, that's been a mystery to me for a while
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The Germans tried to run captured and restored Spitfires on DB engines, but had troubles with overheating due to the Spitfires lack of radiator surface (probably) Makes me wonder how their total frontal area including radiators compares.
As it goes for boost and robustness, 60 years old Merlins being squeezed up to a whooping 3000 HP are still running in P51's at the Reno air races.
The late DB's would wear out quite quickly, but it is most likely a result of alloy shortage rather than design.
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Originally posted by Angus
...The late DB's would wear out quite quickly, but it is most likely a result of alloy shortage rather than design.
would this make the DBs relativly more vulnerable in combat?
which engine was easier to knock out in air-to-air combat?
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http://w1.1861.telia.com/~u186104874/db605.htm
btw those "60 years old Merlins" are usually using strenghtened post-war engines / cylinder blocks which were made to be used in commercial planes after the WWII.
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The German jets were copied by the russians, and powered the Yak-15, Yak-17 and Mig-9 fighters. After the war German aircraft production was devestated, and early post-wwii the germans were forbidden to produce aircraft engines (among other things). This led to the Allied nations getting a significant lead in engine development. To give an example of the rediculous restictions forced upon a post-war german industry, they wern't even allowed to participate in auto-sports like Formula One until the '60's (or late '50's, I'm not sure), but when they did they swept the (former) allied nations away. Winning nearly every race with DB and BMW engines.
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hmm letīs see:
DB605:
- inverted engine, allowing better view, and (more important) better aerodynamics with low mounted wings
- central propeller shift, going right through the COG, allowing for very aerodynamic nose shape, while RR engines had the shaft quite high, reducing nose shape aerodynamic quality and producing pitch down moments (but allows mounting a larger propeller or shorten the gear)
- no "power hole" due to gear shift of the supercharger. Continous power in all altitudes.
- optional 2nd gear (GM-1)
- better fuel consumption due to higher compression, lower RPM, and direct fuel injection.
I really canīt see advantages of the Merlin. It was already said that RR engines didnīt suffer from shortcomings ofalloys, this was the major point. Nevertheless the 605DC engine could run with 1800PS on B4 fuel (87 oct.).
But RR engines were of course very reliable. Lerche said in his book: The Rolls Royce engine run like you expect it from a Rolls Royce.
About racing engines: Before the war the 209 was powered by a DB601 engines. They just changed the compression and gear ratio, everything else remained the same. It run with 2770PS.
niklas
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Hi Oedipus,
>For instance VW still made the pre-war Beetle in post war Germany to help get the economy rolling,
In WW2, Volkswagen had turned out military vehicles based on the Beetle technology, but the Beetle itself didn't really enter mass production until after WW2. The Beetle was a technologically advanced high-quality car that competed successfully against later designs all over the globe for decades to come. The cars that got the German economy rolling were much more modest than the Beetle - and they were build by companies with names you might recognize. The Heinkel "Kabinenroller", the Messerschmitt "KR175" and "KR200", the BMW "Isetta" - they all were swept away when the economy got going and the Germans could afford expensive high-quality cars - which at that time simply meant the Beetle.
http://www.pcsystems.com/messerschmitt/mess.html
http://vintagecars.about.com/library/weekly/aa121497.htm
>Same with the German jet engines. If they had indeed been superior they would have been copied.
You don't see many jet engines today that still have radial turbines, unless you're into RC models. Radial turbines were the Allied way of building jets. Today, jet engines universally have axial flow turbines, and that's just how the German jet engines were built.
In 1945, even the Germans would not have copied the Jumo 004. The experience they had gained with the Jumo enabled them to build much better engines - and so all over the world, German engineers were working on new jet engines after 1945. The Soviet Union was lacking the basic technology as well as the German top experts, and so they copied the old WW2 jet engines (and improved them, demonstrating their untapped development potential) to get the best understanding of the new technology that was possible in the short time.
Regards,
Henning (HoHun)
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Originally posted by Oedipus
GScholz those Russian planes had poor performance at best with those copied German jet engines. It wasn't until the Mig-15 with it's RD-45 engine (which was a copy of the Rolls Royce Nene. A WWII engine from early-mid 1944) that a real threat was posed to Western air forces.
Oed
The RR Nene wasn't available for production until 1946, when the US bought a license for it and used it in the Phanter. The Soviets got it in '47 I believe. So if you mean that the development of the Nene started in '43-'44, I believe you. The development of the Jumo and BMW jets started in the late '30's.
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IMHO the DB 605 and the DB 603 were good designs and mostly par with the competion. The problem was that neither them did not really get advanced and mass produced airframes to combine with.
gripen
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Quote:
You don't see many jet engines today that still have radial turbines, unless you're into RC models. Radial turbines were the Allied way of building jets. Today, jet engines universally have axial flow turbines, and that's just how the German jet engines were built.
End quote.
The reason the main allied jet engines were "radial" was that it gave the best life span for thrust, and were easer to build given the state of the art of the time.
The axial flow type was known, hell Lockheed had started prototype development of an axial flow engine with a built on afterburner in 1940-41 to go into Kelly Johnsons' FIRST jet design. The one the government told them to stop work on, and then made them sell the engine design to a non airframe company. They did not want wasted time on "Buck Rogers" programs:rolleyes:
If I had to build a jet engine I would fly with using 1940-45 theory and production tools, the GE J-33 series made from 3,750lbs thrust (J33) up to 5,500 lbs (J33-A-35) thrust with good life spans.
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The simple fact of the matter is that the Jerrys got a jet-fighter operational in good numbers (considering their supply problems) that was a serious threat to the allies. The Brits got their jet operational too late to have an impact (proven by the fact that the 262 and the Comet never faced eachother in combat), and the Yanks never got a jet operational at all during WWII.
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Another point: A wealthy American, whos name I no longer recall, owned a 262 in the 50's, and he was BANNED from using it in a jet air-race. The US A/C manufacturers was afraid that this aging German warbird would out fly its modern US competition. Hmmmmmm :rolleyes:
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Hi MC202,
>The reason the main allied jet engines were "radial" was that it gave the best life span for thrust, and were easer to build given the state of the art of the time.
Actually, Whittle invented the jet engine as a radial turbine in an evolutionary process coming from conventional superchargers. Von Ohain skipped the evolutionary process and invented his jet engine as an axial flow turbine right away, but built the first technology demonstrator as radial turbine as well for ease of production.
The jet engine comparison is a quite complex topic as well, and Gersdorff et al. give some good information. However, I'd think we'd need a new thread for that :-)
Regards,
Henning (HoHun)
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Oopsie, we're all into jet engines now!
Well, the German way of making it was more modern, but a tad too much ahead of its time. The brits made a more sensible choice for the time, building engines that ran reasonably well, and are even still powering old birds TODAY.
Oh, and they sound so cool:)
But back to the old DB and RR. It has been pointed out that the DB has quite some things in its favour, - as a design, - it may be excused a bit for alloy shortage and lack of proper fuel. Makes one wonder WHAT IF, etc.
Oh, and as expected, Niklas pops up with his affection for german machinery, or as he puts it:
"I really canīt see advantages of the Merlin".
But the Merlin had advanages in Real Life! It was lighter, and had a smaller frontal surface for the equal or better amount of power.
That looks like an advantage to me.
However the DB had a better power output pro octane and as pointed out by Niklas, an upside-down engine gave an opening for a more aerodynamic nose.
Does a more aerodynamic nose definately make up for a shorter propeller? And do not forget that the surface was larger both because of the coolant surface and the position of the Turbine.
Hmm, don't know, - look like a pretty even pair to me.
Oh, btw, - here's a nice Merlin thread:
http://www.wwiitechpubs.com/hangar/ac-uk/ac-uk-eng-rolls-royce-merlin/ac-uk-eng-rolls-royce-merlin-br.html
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"Does a more aerodynamic nose definately make up for a shorter
propeller?"
Yes
"And do not forget that the surface was larger both because of the coolant surface and the position of the Turbine. "
The compressor was no problem, with the enlargement due to the Mg131 the fuselage had to be widen anyway.
"It was lighter..." (the merlin)
Here you are completly wrong. Donīt forget that DB and all other engine manufacors had to deliver engine sets, not engine alone. So if you compare weights you need to compare the dry weights, which are as follow:
The merlin6x had a dry weight of 1645lb, 745kg.
The 605A had a dry weight of 1585lb, 720kg.
The DB605 was lighter.
" ...and had a smaller frontal surface"
Here u are wrong again, especially if u compare the space necessary for the installation in a aircraft with low mounted wings. Just compare the attachement. Though the G-6 is already shown with the bulges the frontal area was lower. The merlin was quite "high", just compare the height of a mustang too.
You can also see very well the steep fuselage gradient right below the propeller shaft of the spit compared to the smoth "dart" nose of the 109.
Iīd really like to see on which data your opinion is based. Please show me
Thank you
niklas
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Gsholz,
You statement about the Yanks never having a Jet by the end of the war is a little off.
The P-59 was flying in 1944 and the P-80 was in production by wars.
Few airplanes in the history of aeronautics have been as successful as the Lockheed Shooting Star. It was the first operational jet fighter in the United States when it went into service in 1945. It emerged as victor in the world's first all-jet combat, and it won the distinction of remaining in production for a full 15 years after the experimental model was first flown.
The airplane had its origin in June 1943, when Lockheed was requested to design a fighter around the De Havilland turbojet engine developed in England in response to Germany's twin-engine jet fighter, the Messerschmitt Me 262. The XP-80 was designed and built in the amazing period of only 143 days--37 days less than the original schedule. It was flown for the first time on January 8, 1944, and its performance was considered sensational.
The Army Air Force planned to build the Shooting Star in large numbers. However, only two of the machines arrived in Italy before the end of the war in Europe, and these were never used in operations. Despite the cessation of hostilities, production was continued on a reduced scale.
FYI,
At this years air race at Reno there was a Jet class. Mig 15/17 and some L-39 Albatross. The fastest Jet lap speed was slower than the Props IE P-51's and Sea Fury's.
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Originally posted by Oedipus
If the DB had been the better engine then boat and aircraft racers would have been using them the for the past 45 years or so and not the Merlin.
Maybe it's just easier to obtain parts for engines of the winning side ;)
Besides I really doubt the most used parts in the engine are half century old :>
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Niklas,
There is not much sense to compare weights of the Merlin 6X and DB605A or should we compare outputs at 10000m? Generally single stage Merlins were lighter than single stage DB605s but single stage DBs did a bit better at high altitude than single stage Merlins. It should be also noted that the high altitude DB605AS did not reach production before spring 1944 while the two stage Merlins had been around about two years by that time. Two stage DBs failed to reach more than experimental service during war. RR was able to develop engines to service stage faster than DB.
gripen
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DB 605 has from my sources the same weight as the absolute heaviest Merlins 60 series), almost to the pound. Merlins: 744-746 kg's, DB 605 730-745 KG. Dryweight of course. However that is a Two stage Merlin! At altitude it was quite superior to the DB 605 for whole two years, from spring 1942 to spring 1944.
To compare something with the same alt performance would be nearer to the Merlin 46/47 weight 628 kg's, and that is still a high level engine.
Now going back to DB 601 which was also a competitor of the Merlin, the DB 601 yealding 1175 hp weights 600 kgs while a Merlin 45 weights 628, Merlin is heavier here, but also peaks at 1515 hp! I am aware that the DB 601 was squeezed up to 1400 hp or more, but sadly have no data on how it affected the weight.
The thing about the frontal area I had from HoHun in this thread, but I'll measure your picture anyway.
What also just crossed my eye is how much bigger volume the DB engines have, DB 605 has practically the same volume as a Griffon so maybe that would be a better comparison
;)
oh, BTW, Niklas: Do you have a similar picture of a Mustang? Wonder what the overall nose area of a Mustang was, that's all.
Well, again the Mustang being faster than any 109 with the same engine size, I guess the wing-design+ prop length more than made up the drag of a bad nose, hehe.
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Hi Agnus
With your last sentence you instinctivly came to an import conclusion.
But first some technical data.
The dry weights of the 605 were:
605A 720kg
605AS 730kg
605D 740kg
The single stage merlins were no high level engines. You were wrong about the power output too.
The only single stage merlin with 1515hp in 11k was the 55A.
The 45 peaked out at 1470hp in only 9250ft
The 45M at 1585hp in only 2750ft
The 46/47 at 1415hp in 14000ft
The DB601 was available in at least 3 major variants. The most powerful was the 601E which was 30kg heavier than a 45 and could do 1320PS in 15700ft. So over 16k feet both engines put out approximatly the same.
Comparing power one must always be careful because RR engines list always highest power in critical altitude. Power at sealevel was always a bit lower.
Only the 61 was really better at high altitudes. The 65 was in 20 and 30k approximatly as good as the DB605A. The 68 again had 2k higher critical altitude, giving the advantage a bit back. Maybe it should be better compared to the early 605D which was available also in 42, at this point without the larger supercharger.
DB engines did not have 2-stage supercharger, except for the very late 605L which was mounted on 2 109 at the very end. But they did not have a single stage either. It was a multi-stage if you want, the supercharger speed was continously adjusted over 2km. This avoided the power hole.
If you reduce the question down to a power comparison, neglecting material, fuel, design, installation and other things, RR engines will lead, especially in a power/volume comparison, even if you bring them down to same RPM.
But it is really also a question of material and design. Turbo-Diesel car engines have usually a lower life expectance, because they use same power as normal engines on smaller components.
More power is wasted when the installation forces you to have more drag or weight. A merlin was build with the design philosophy of WW1 engines at the end. Donīt forget that the first spits and hurricanes didnīt even have constant speed propeller ( the first prop speed gear was used only for takeoff anyway), so a high shaft for a large propellor was necessary. Unfortunatly this cost some power due to the inferior installation.
A power to weight comparison becomes even more difficult. How much energy had to be taken away from the engine by the coolant? This would give you a hint for the necessary cooler area/weight. How heavy was the necessary propeller to drive it? Compare the fuel consumption, this means necessary weight of the fuel (lower on DB), the necessary oil (lower on DB).
So at the end it becomes really more and more a question of the whole aircraft design, what you instinctivly did in your comment.
If you compare power/volume and altitude performance the RR will lead in most cases, but the DB could get close by compensating for the inferior power due to more modern layout.
And when you include also engine managment systems, oh my... . On the other hand, the spit14 copied the german single lever system, so at this point the advantage was neutralized.
niklas
P.S Did you ever heard that they change the valve opening times in the Formula 1 cars, and recently also in the BMW 7 series? Imagaine, the 601N could do the same, using a hydraulic-mechanical system. So this idea is actually very old, and now they celebrate it as a high-tech idea :) (ok, they can adust parameters much better today of course)
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P.S Did you ever heard that they change the valve opening times in the Formula 1 cars, and recently also in the BMW 7 series? Imagaine, the 601N could do the same, using a hydraulic-mechanical system. So this idea is actually very old, and now they celebrate it as a high-tech idea (ok, they can adust parameters much better today of course)
O.K, you got me awake. Where can I found more info about this?
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ups , i made a mistake. It wasnt the 601N but the 603N. Big sorry. 601N was too present in my memory :)
To understand the reason to change valve opening times you need some background information.
The advantage of direct fuel injection was not mainly a better combustion due to the injection. The main reason was that you could let the inlet valve open way earlier withour risking a "backfire" (?) to the carburator, which would have had desastrous effects.
Usual engines with carburators had 20-30° angles where the outlet and inlet valve where open simultanously.
With direct fuel injection much longer time periods where possible, what increased the cleaning of the cylinder of exhaust gases a lot - so the new combustion process took place with much more clean fresh air, this way you got more power.
Now that works fine at low level with angles of equal opening up to 120° or so, BUT at high altitudes a negative effect took place: Because the chain supercharger-inlet-outlet-atmosphere was open during this period, and atmospheric pressure drops with altitude, it could happen that your cylinder wasnīt filled anymore with supercharger pressure at high altitude. So valve opening times were a compromise in direct fuel injected engines, or letīs say, direct fuel injection couldnīt be used to the maximum.
For that reason they developed an adustable system for the valve opening times (the absolut times were of course the same).
I only have this drawing in pretty bad quality, but it shows the basic concept quite well.
niklas
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Looks like a Vanos-system used in BMW's. IIRC Alfa-Romeos did use similar system already over 10 years ago where oil-pressure was changing timing of the camshaft.
http://autozine.kyul.net/technical_school/engine/vvt_3.htm
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Niklas
I bow for thee!
I must say, that:
Your information database,just as your enthusiasm in putting in data,is a great contribution to the AH community. As to myself, it is a most pleasing opportunity to be able to shoot out a thesis,based on brief assumptions, (well, not always), and through the AH community getting very professional answers or at least backed-up opinions.
I have to study your post better, and may be able to add some to it, or at least figure out a teasing new post from the material ;)
(unfortunately a bit busy at the moment)
Anyway, untill later..........and I hope we have some new stuff adding to this thread.
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Hi Niklas,
>P.S Did you ever heard that they change the valve opening times in the Formula 1 cars, and recently also in the BMW 7 series?
Here's a photograph of a Ferrari opposed 6-cylinder engine with variable inlet timing. I took the photograph at a recent visit to Maranello.
(http://members.aol.com/hohunkhan/ferrari_o6.jpg)
In front of the Official Ferrari Giftshop, I met a physicist who was designing automotive crankshafts, and it turned out he was a history freak as well, so soon we were chatting about WW2 aero engines :-) He really knew his stuff! I guess I should have asked for his email to get him onto this forum, but I was so amazed to meet someone with that level of expertise and enthusiasm regarding my favourite topic that I lacked the necessary presence of mind :-/
He wasn't particularly impressed about the above Ferrari engine, by the way, since apparently variable inlet timing was very much a standard technique when they experimented with it.
Regards,
Henning (HoHun)
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Niklas,
The competion between the Merlin and the DB 601/605 happened mostly in the supercharger arena, with the given MAP the DBs did allways better simply because they were larger (27l vs 33 or 36l).
During BoB (1940) there was not much difference between them, the DB 601A did about as well as Merlin III while the Merlin XX had a slight edge over the DB. The Merlin 45 gave a little advantage to the Merlin at spring 1941 (improved supercharger and two speed Merlins got same iprovements simultaneously). I don't see hydraulic coupling as a big advantage over fixed gear, in practice the "power hole" (or what ever) is barely noticeable in the real world data; climb and speed values do not change that much. The hydraulic coupling wastes allways some power, the pilot just can't feel it like he/she feels the gear change. Also the Merlin could use interconnected propeller and throttle levers so there was not much difference in the engine handling in the combat.
At autumn 1941 the DB 601E reached service and did about as well or bit better than Merlins at high altitude. The DB 605A came at autumn 1942 and had advantage over single stage Merlins at high altitude (again because it's a larger engine). But the single stage Merlins got higher ratings same time and had a advantage at low altitude (16lbs boost and later 18lbs). It should be noted that the DB601E was pretty much a major redesign of the DB 601A and technically closer to DB 605 (supercharger system was totally redesigned, double pump system for hydraulic coupling).
At spring 1942 the Merlin 61 reached service and had a clear advantage at high altitude, more than 200hp at 10km and also the Merlin 66 did better than DB 605A at high altitude (say more than 100hp), at low altitude it was better until DB got the MW50 (but that time, 1944, Merlin got the basta).
The DB 605AS did about as well as the Merlin 66 at high altitude, say around 1000hp at 10km. But as noted earlier, it came quite late. And the DB 605D was not available before autumn 1944 and it did about as well as the 605AS at high altitude. Again the DB605D was a major redesign of the DB 605A.
The DB 605L was a promissing engine and it did about as well as best high altitude Merlin developements. The major problem in the German WWII aviation industry was that they did not get advanced engines and airframes to the mass production. The DB 605 specially lacked an advanced airframe to combine with.
In the fuel and oil consupmtion the DBs had an advantage over the Merlin but again I don't see it as very signifiqant; the Mustang could reach berlin but the Bf 109 did have problems to reach London (well, it could but not much more). The Merlin was installed to the several advanced and mass produced airframes like the Mustang and Mosquito while the DB 605s were mostly installed to the prewar airframes like the Bf 109 and Bf 110. IMHO the Bf 109 was not a bad airfame, actually underestimated nowadays, but it could not combine required performance, armament and range like for example the Mustang did.
gripen
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A little question, or two:
With the Merlin having so much less volume, - like approx 2/3 of a DB, and (Didn't I read that somewhere?) lower pressure, how was it able to deliver about the same power? Certainly not because of the injection, - but just by using more fuel?
Also, boost comes into this. How much would one be able to boost a DB compared to a RR Merlin.
Then, I cannot but consider a little "what if" What if a DB had to run on a humble carburettor, or if a Merlin was blessed with an advanced german injection system???
hmmm.
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Angus,
The Merlin did well mostly because higher boost. This was caused by somewhat better fuels, lower compression ratio (which allowed high boost), mixture cooling by fuel itself (which did not happen in the direct fuel injection engines) and intercooler (two stage Merlins). Also strong construction helped a lot; the Merlin passed test for 2640hp at 3000rpm and +36lbs boost with water injection. Of course a bit higher rpm (smaller engine) helped a bit. Anyway, as noted earlier RR could put their advanced engines to the large scale production fast, but the competion (namely DB and Allison) had problems to put their advanced engines to production.
Seems that people tend to overestimate advantages of the direct fuel injectition. While it gives very exact fuel metering it does not give mixture cooling advantage which carburator and single point injection systems give (later Merlins had Bendix injection carburators or single point injection systems by SU, Hobson or RR).
gripen
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Gripen, according to my source the critical altitude of a 66 was in only 16k.
The V-1650-7 was surprisingly a bit better with 18.5k
Staga, thx for the link, i didnīt know that they used it after the war in so many cars (i didnīt wanted to say that they developed it first btw.). Most cars seem to be sports cars (?).
F1 cars of course use a completly different system, based on hydraulic control of the valvles exclusivly without a shaft, but the idea to control valve times like many other ideas go indeed back into the 20ies or 30ie of the last century.
niklas
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-Same goes with disk brakes; they were invented in the beginning of the last century but were "forgotten" 'till the ww2 when they were used in the airplanes and after that in '50s car manufacturers begun to use them again.
-Superchargers were also from WW1, iirc Daimler-Benz was one of the firsts developing them. Supercharger was mounted under ordinary engine and was having a chain-drive wrom the propellors shaft.
-Anti-lock brakes; again developed for airplanes first.
btw I believe that F-1 cars are having electric or electro-pneumatic valves, my guess is hydraulics would be little too slow to operate when engines has +17000rpm on tachometer :)
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Niklas,
Yes, the Merlin 66 did 1580hp at 16k without RAM. With RAM it did roughly 1000hp at 10km which is pretty much same as the DB 605AS did with RAM. The V-1650-7 had FS gear ratio 7,35:1 while the 66 had 7,06:1 (sources: "The Merlin in perspective" by Alec Harvey-Bailey and SIHL).
gripen
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Sorry i disagree. In case you refer to the RAM power chart that includes the 66-68 and the 1650-7 - this chart seems to be based on the 18.5K critical altitude (1650-7, 68), because 4k altitude due to Ram would be a bit high. Or the best case, when RAM changes completly into pressure what wasnīt the case.
If you draw the line down form 16k instead of 20k you īll end in 33k or 10km very close to 800PS (even a bit lower) what was very comparable to the 790PS of the 605A in 10km.
niklas
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Niklas,
Well, feel free to disagree but check for example this (http://www.fourthfightergroup.com/eagles/bs543.html) , 18k at climb and 22k at max level speed (actually FS height for +18 lbs was a bit higher because it still did +18,5 lbs at 22k).
gripen
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Originally posted by Staga
btw I believe that F-1 cars are having electric or electro-pneumatic valves, my guess is hydraulics would be little too slow to operate when engines has +17000rpm on tachometer :)
F1 cars use cams to open the valves and nitrogen to close the valves. But there are mechanisms which alter the cam profiles and camshaft phase, which are hydraulically actuated. Hydraulic power is also used for the steering, differential, and shifter on F1 cars.
Honda was the first company to use the hydraulic variable valve timing system on road cars. They had developed the system first in motorcyle and F1 racing, then on road bikes, before using it in autos.
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Niklas,
I also checked some Bf 109G data (with DB 605A) and with RAM it's FTH was about 6200m at max speed (2800rpm and 1,42ata) at climb it's FTH appears to be about same as stated in the DB 605A manual ie about 5700m. So at max speed the Merlin 66 did 1580hp at 6700m with RAM while the DB 605A did 1355hp at 6200m with RAM.
At climb speed (358km/h true) the Merlin 66 did 1580hp at 5400m with RAM while the DB 605A did (climb speed about 400km/h true) 1355hp at 5700m.
Also we can see from the test data (http://www.fourthfightergroup.com/eagles/bs543.html), the Merlin could maintain +6 lbs (MAP required for about 1000hp) up to about 32k even at climb speed.
So conclusion is that the Merlin 66 could do roughly 1000hp at 10000m with RAM while the DB 605A did roughly 800hp at 10000m with RAM. The DB 605AS did about 1000hp at 10000m with RAM so it was about equal with the Merlin 66. As for comparison the Merlin 70 could do roughly 1000hp up to 10900m even at climb speed. Late Merlin developements could do even better.
gripen
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So there you go.
Merlin eats the DB
Thanks Gripen ;)
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Well, the DB 603L and DB 605L certainly had potential to compete with the best Merlins and Griffons. But these DBs came too late and did not reach mass production and there were no mass produced advanced airframes for them.
IMHO Junkers did better than DB, the Jumo 213A reached at least more than limited production and service and the Jumo 213E did saw some service too. And there were at least some advanced airframes for them but not really mass produced (Fw 190D, Ta 152H, Ju 188 etc.).
gripen
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Hi Angus,
>So there you go. Merlin eats the DB
Nice summary :-)
The truth is: With the advent of the two-stage supercharger, the Merlin held the high-altitude advantage (ignoring GM-1 for the moment).
The operational value of this advantage is another question. The Merlin 61 was deliberately designed for a very high full throttle height, so the RAF must have been convinced that it was important.
What the Merlin 61 did not do, however, was to make the Spitfire competetive with the Fw 190A at low to medium altitudes where the Focke-Wulf was strong. The Merlin 61 improved the Spitfire above 20000 ft mainly, and superiority over the Focke-Wulf was only achieved above 25000 ft. (Compared to the Messerschmitts, the Spitfire IX was better than the Me 109F-4 above 20000 ft and better than the Me 109G-2 above 25000 ft).
This seems to collide with two popular myths ;-)
1) With the Spitfire IX, the Spitfire series matched the performance of the Focke-Wulf. (Actually, while it was superior at high altitude, the Spitfire IX didn't much to close the gap at low and medium altitude.)
2) The Messerschmitt was designed for high altitude combat. (Actually, it was a mainstream fighter. It was the Spitfire IX that was designed for high altitude combat.)
How were the fighters used operationally? Well, the Spitfire IX undoubtly flew high-altitude fighter sweeps at its optimum altitude over France. The Luftwaffe fighters were employed against the British bombers who probably flew a bit lower than the Spitfires ...
Another interesting question regarding high altitude is raised by the history of the P-51. The P-51B at first was equipped with a V-1650-3 which gave a similar performance profile as that of the Spitfire IX with Merlin 61 engine - it was the best at very high altitude. For some reason, Mustang production soon switched over to the V-1650-7 with a reduced full throttle height for the high gear, reducing high-altitude performance for a bit more performance at medium level.
I've never found a good explanation for this change, but I've been told that some pilots didn't like this change as it reduced the performance at their typical operational altitude. However, I'd speculate that such an important change was not done without a great amount of operational research justifying it, but I've never even found something like that mentioned anywhere.
At least, it seems to show that best high-altitude performance is not always results in the best overall fighter, and that the optimum is dictated by the current operational requirements.
So I'd be a bit more careful with summaries ;-)
Regards,
Henning (HoHun)
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Well gripen, isnīt it strange that the spitfire claim a gain of altitude due to RAM effect of 4000ft (from climb to speed), 1223m, while the germans claim only 500m? only 40%? And the air intake of the 109 was in a very good position, outside of the boundary layer, like the cooler duct of the P51.
Actually you could do a litte calculation:
Atmos. Pressure in 16k /5km: 0.54bar
in 18k: 0.505bar
in 22k: 0.428bar
Best possible RAM pressure (100%)
at 233mph in 18k: 0.0368bar
407mph in 22k: 0.1bar
now 18k: 0.505bar +0.0368bar = 0.542 = ~0.54 bar
22k: 0.428 + 0.1 = 0.538 = ~ 0.54
Can you see it? 100% efficiency in pressure gain. Sorry, they corrected for the standard day, somehow they corrected also for best RAM efficiency of 100%. Or the alittude indicator showed wrong values at those high speeds, a phenomen that can also observed for the spit14 dive tests.
6k more altitude (compared to 16k) due to RAM effect was definitly not possible for high speeds. Even the power chart lists only 2k for 400mph (assuming the base of 18k).
So i would be careful with those tests, very careful.
When the 109 tops out for climb in 5700m then it didnīt reached in this test the best critical altitude anyway.
Itīs probably better to compare strictly the engine performance charts, this one was my source
niklas
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HoHun,
Note that only the first Spitfire IXs had the Merlin 61, vast majority of production had later models ie 66, 70 etc.
For one reason or another USAAF had decided to use the Merlin powered P-51s for tactical fighter duties like the earlier Allison P-51s. So when the first P-51Bs arrived to ETO late 1943, these were allocated for 9th AF. This is probably the reason why they switched to the lower altitude engine variant.
Niklas,
I don't know if you fully understand that A&AEE test data. They simply recorded at which altitude the MAP started to decrease. There can't be big errors in altitude calculations (those were not a dive tests BTW) and you can find several other tests which confirms these results (see Morgan's and Shackladys book). Your chart combines engines with different gear ratios and appears to be somekind of calculation, not test data so it's pretty much useless for accurate comparisons.
Please prove that 6k RAM effect is impossible. Similar RAM effect is recorded for the P-51B too and actually several times.
Also note following note in the DB 605 power chart in the manual:
"Die Höhenleistungen sind abgestellt auf den Gesamtdruck (statisch + dynamisch) und ergeben sich ohne Berücksichtigung der Rückstoßenergie"
So the powerchart allready contains somekind of standard RAM effect (but not exhaust jet effect). And this RAM effect appears to be about same as at climb speed (I have test data). For max speed FTH I used again real world data, I've seen several charts and max speed FTH for DB 605A appears to be around 6-6,5km. But it had to be well over 7km to compete with the Merlin 66 because the Merlin 66 did 1580 at FTH and the DB 605A did 1355hp.
gripen
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Hi Gripen,
>Note that only the first Spitfire IXs had the Merlin 61, vast majority of production had later models ie 66, 70 etc.
I'm aware of that, but the history of the Merlin 61 nevertheless is interesting as apparently the RAF thought they could break the Fw 190 dominance with an engine with very high critical altitude.
Besides, the initial outpout of Spitfire IX aircraft seems to have been quite low so that while the Merlin 61 Spitfires were small in numbers, they were the only Spitfire IXs at all for almost a year. This underlines the importance of their role.
>For one reason or another USAAF had decided to use the Merlin powered P-51s for tactical fighter duties like the earlier Allison P-51s. So when the first P-51Bs arrived to ETO late 1943, these were allocated for 9th AF. This is probably the reason why they switched to the lower altitude engine variant.
I'm not sure this makes sense - in spite of being scheduled for low altitude duty, the P-51B arrives with a high-altitude engine that later is changes to a medium-altitude engine when the plane is used as a high altitude escort fighter, and never changed back again?
>So the powerchart allready contains somekind of standard RAM effect (but not exhaust jet effect). And this RAM effect appears to be about same as at climb speed (I have test data).
Interesting observation. I had always thought the standard charts to consider ram effect for high-speed flight. Would it perhaps be possible for you to post such a chart with the paragraph you quoted? (Sometimes "Schnellflug" appears in German documents to denote high speed flight.)
Regards,
Henning (HoHun)
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HoHun,
AFAIK Spitfires IXs with other than Merlin 61 engines started to reach units February/March 1943, 7-8 months after the first Spitfire IXs started service.
I don't know about the sense of the USAAF decisions. There were only the V-1650-3 available 1943 and production switched to the V-1650-7 sometime early 1944. I don't know exact date but according to "Rolls Royce and Mustang" decision was made late 1943. The V-1650-9 (P-51H and some late P-51Ds) was a high altitude engine again.
I don't have a scanner but gatt posted part of the DB 605 manual some time ago, see this (http://www.hitechcreations.com/forums/showthread.php?s=&threadid=27993).
gripen
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Just an idea , but could the P-51 have had its rated altitude decreased because most LW fighters were encountered at a lower altitude thus needing more power at the lower altitude.
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MiloMorai,
Yes in the case of RAF and RR, they saw Merlin powered Mustang as a solution against the Fw 190 and wanted lower altitude variant (see Rolls Royce and the Mustang). In the case of USAF I don't know definite answer; possibly they were happy with their current planes (P-38, P-47) until heavy bomber losses late 1943 turned their heads. Anyway, it's clear that in the beginning USAF allocated the P-51B for the tactical units and that was their policy at the time when the decision to change to the V-1650-7 happened (late 1943). Possibly only NAA saw the P-51 as high altitude fighter because they were developing light weight variants (F,G,H,J) for high altitude engines that time (winter 43/44).
gripen
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Originally posted by gripen
Niklas,
I don't know if you fully understand that A&AEE test data. They simply recorded at which altitude the MAP started to decrease. There can't be big errors in altitude calculations (those were not a dive tests BTW) and you can find several other tests which confirms these results (see Morgan's and Shackladys book). Your chart combines engines with different gear ratios and appears to be somekind of calculation, not test data so it's pretty much useless for accurate comparisons.
Please prove that 6k RAM effect is impossible. Similar RAM effect is recorded for the P-51B too and actually several times.
Also note following note in the DB 605 power chart in the manual:
"Die Höhenleistungen sind abgestellt auf den Gesamtdruck (statisch + dynamisch) und ergeben sich ohne Berücksichtigung der Rückstoßenergie"
So the powerchart allready contains somekind of standard RAM effect (but not exhaust jet effect). And this RAM effect appears to be about same as at climb speed (I have test data). For max speed FTH I used again real world data, I've seen several charts and max speed FTH for DB 605A appears to be around 6-6,5km. But it had to be well over 7km to compete with the Merlin 66 because the Merlin 66 did 1580 at FTH and the DB 605A did 1355hp.
gripen
Maximum gain in dynamic is rho/2 *v^2. Now you still have some pressure loss effects at the inlet, in the piping system and so on. So they didnīt reached 6k in reality for sure. This is only theoretically possible with 100% efficiency in case of the spitfire, at the given altitude and speed.
For example in the P51-B / F4U comparison the critical altitude was 29k feet, this is some reasonable 2.5k feet higher than the "static" critical altitude of 26.5k. Ok, that was a 1650-3, but the P51 was flying much faster than the spitfire up there.
AH has the P51B in 29k too.
The topspeed of the P51-B in Rechlin was in 8km.
The remark in the german manual seems to be taken out of context. Do you have the whole manual, all pages? 5.7km - and this is the listed critical altitude - did not include the dynamic pressure, this altitude is listed in all DB-manuals who simply could NOT know at what speed the aircraft will fly, what influnces dynamic pressure of course.
Maybe this sentence refer to another picture in the book that we canīt see, maybe itīs just an error, maybe dynamic pressure is something different than RAM effects - i donīt know.
niklas
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Niklas,
We don't know the area of the inlet nor aerodynamic qualities of the inlet (it was a boundary layer scoop system BTW, Spitfire and Hurricane had it long time before Bf 109) and it's a dynamic system. So there is no simply way to calculate max possible RAM effect. What we have is several sets of test data which all claim that the Merlin 66 powered had high speed FTH around 20-22k at +18lbs boost, actually even 18k would give a clear advantage over the DB 605A and is enough to make it about equall with the DB 605AS. Try to live with that.
The V-1650-3 had critical altitude around 23-24k without RAM depending on source (P-51 manual, RR lists etc.). Again there is several sets of data which claim that the P-51B had high speed FTH around 28-29k.
There is an original DB 605A manual in a museum nearby and I have copied it. It seems that DB listed FTHs with somekind of standard RAM effect and this is what manual text says. Comparison with test data shows this clearly or another possibility is that they gave "optimistic"values about the output of their products.
gripen
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According to my source the V-1650-3 topped out in 26.5k while the 61 topped out in 24k.
But well, 24k would explain the results from Rechlin.
There exist a page in the net whith flight manuals for spit-V - XIV and also P-51, but i donīt find it anymore. Do you or anybody else know the link? What P-51 manual do you mean?
The air inlet depends also a lot from the distance to the frame. The inlet of the 109 was much more outside. For the Do335 they found out than increasing the distance of the inlet from 80mm to 120mm brought a significant increase in critical altitude.
The german engine table is definitly not for RAM effect, because in case you should have the G-6, G6/R2 and G6/AS table you can see that for topspeed slightly lower power numbers are listed (1260PS compared to 1310 at sealevel for combat, 1440 compared to 1475 for emergency power).
If you use the chart i posted, start at 16 with a parallel line downwards, and interpolate it to 33k (a bit difficult due to the log-scale) then you will end very close to 800PS in 33k.
Everything else (flight test, error correction) becomes difficult to compare because noone knows how the individual tests were corrected in each country. And i already said: In Rechlin the P-51 topped out in "only" 8km.
Maybe "dynamic" pressure simply characterizes the pressure due to the massflow in the piping system, what is a function of the velocity (RPM, Volume) and density , and not RAM pressure.
Edit: It should be noted that for the Mc.205 topspeed is listed at 7.5km (605A) in some sources. Donīt ask me why it was so high, but this allows a much better comparison with the spit tests.
niklas
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Niklas,
My numbers come from USAF P-51D manual which contain ratings with and without RAM for the V-1650-3 and -7 and these are supported by RR data, Wright field test data and A&Aee data. In addition AHT contains some data (some values there are mixed). BTW what is your source? IIRC a German report stated that the supercharger of a tested P-51 was not working correctly. One possibility is that they were not using RAM air but another intake.
The Merlin 61 is physically different if compared to the V-1650-3. The diameter of the first rotor in the charger is 10,1 inch in the 61 while it is 12 inch in the V-1650-3. And FS gear ratios are different; 8,03:1 vs 8,095:1. Also ratings are different, the Merlin 61 was rated at +15lbs while the V-1650-3 was rated at about +18lbs (67"). And the FS gear FTHs without RAM are following (RR data):
Merlin 61 1390hp at 23500ft +15lbs
V-1650-3 1330hp at 23300ft 67"
I don't know why you are continously trying to argue with a chart which appear to mix together Merlin variants with different supercharger gearings and which appear to contain just calculations? Generally there is lot of good and reliable test flight data available and it's mostly created by professional and experienced test organisations.
About air inlet it should be noted that the Merlin powered Mustang did not have a boundary layer scoop for intake air but somewhat larger area intlet which did pretty well as test data shows. Also piping was quite long but again it did well despite this. BTW the Bf 109G6/AS with the DB 605AS had a larger inlet scoop than the G6 with the DB 605A, quess why...
I don't know if you fully understand why max power ratings of the DB 605AS decreased if compared to the DB 605A. The DB 605AS had simply a larger diameter supercharger from the DB603 and therefore it was able keep wanted MAP at higher altitude. But larger rotor used more power and therefore max power ratings decreased. Also the altitude where the variable speed system started to work increased a bit (from about 2km to say 2,3 km, I don't know exact height, the chart is unaccurate) because the supercharger was able to keep wanted MAP up to higher altitude at it's min speed (max slip). So if you think this carefully, you might be able to figure it out... BTW this phenomena has pretty little to do with the RAM effect, it is there with and without RAM.
So how you explain the text in the DB 605A manual and test flight data which contains also MAP graph (Finnish Bf 109G-2 test and several German charts roughly support these)? These show quite clearly that the output chart contain some RAM effect or the service engines could not reach unrammed FTH height claimed by manufacturer without some RAM. For me the first explanation is far more believeable.
I don't know about the Mc.205 but in the FAF tests the performance of the Fiat G.50 was quite far from the performance promissed by manufacturer. While performance of the Bf 109G-2 in FAF tests was pretty much exactly same as claimed by manufacturer and tested by LW.
gripen
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Gripen:
Niklas will argue to the death. You have to understand: 109 + 109's engine rule all. Wing design, engine, armament, whatever.
If there is any data indicating something else, it is either wrong, or 109 is porked in AH.
In case of that not being good enough, 190 will enter the fray.
Hence the
"niklas
__________________
only a burning spitfire is a good spitfire"
;:D:D:D:D:D
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Angus,
So far this has been just a bit of fun; if the arguments are in the level like that DB 605A vs DB 605AS stuff presented above, they are pretty easy to shot down ;)
gripen
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Gripen:
Nothing brings out a better reflection of things than a little "teaser", or as in the core of a good essay, a thesis.
Especially in this excellent forum of AH.
I once put up a post named "WW2 Powerplants", where I was asking for information about ww2 airplane engines, - I got no reply at all.
Now, post something like "DB sucks" and I will have a floodwave of DB information. Post "109 sucks" and I will het a megatsunami of various information (statements, charts, quotations, diagrams, pictures and links) indicating that not only does the 109 NOT SUCK, but indeed RULE.
So, Indeed, a humble "A vs B" thread is maybe the best thing. This thread was quite a success, with you and Niklas, also HoHun contributing a very good amount of data, - something worthy of an essay really.
I am very grateful for being able to access this kind of community, so a big "S!" to you all.
P.S. The DB sucks anyway :D
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My 1650-3 data was for +16lb this explains the higher altitude.
Iīd really like to know how a supercharger that is connected to an engine with a fixed gear canīt work correctly.
Test flight data is an aircraft comparison. To compare engines we have to leave that out.
You said yourself the 66 tops out in 16k. Now how much power would be available in33k withour RAM.
I still doubt that engine performance is given for a kind of RAM effect in case of the DB605. Noone would know the climb speed, the aircraft and so on. RAM effect has very low influence at lower speeds, naturally. And the propeller disturbs the airflow even more actually.
But itīs an interesting aspect, i wonīt forget it.
The G6 table lists climb in crit. alt at 5.8km - some lousy 100m more, but itīs a bit more.
The max slip altitude was not a inlet/supercharger size problem. It was determined by the maximum oil temperature, and could be adjusted afaik.
The larger air intake of the AS can contribute to the higher mass flow at high altitudes and/or at higher boost, because MW-50 was almost standard now.
niklas
P.S Ok, it took the allieds 6 years to beat germans fighting in completly inferior material and numbers. Somehow i could also live with the conclusion you can draw out of this point of view :)
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If i remember robbie coltrains programme on TV on this very subject correctly it was agreed the DB had a better form of/designed supercharger mechanism but the merlin was the better engine and also the fuel injection system was far better for maneouvering than the merlins version (neg G effects)although there were quoted some benefits to the spits version in cold weather I think it was.great programme and ive probably remembered it all wrong but it goes right through the developement of both engines and speaks to restorers of these engines and the ones used in racing cars of the time(very similar).
wish i had it on tape but its bound to come on again on satalite.
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Quoting Niklas here:
"P.S Ok, it took the allieds 6 years to beat germans fighting in completly inferior material and numbers. Somehow i could also live with the conclusion you can draw out of this point of view"
Well there.
This is stupid Niklas, and does not belong to this thread. Stupid in definition, stupid in material and stupid in conclusion. Like the de-limbed black knight swearing and threatening with the words " come back you coward, I will bite your heels" you try to hold your pride whatever the cost.
You skid out of the debate and into another. Maybe time to start another thread with your header?
puhhh
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It sounds like Angus didn't get kind of answer he liked to hear :)
O.K...
Merlin is best aero engine ever built.
There :D
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Niklas,
I wonder what data you have on the V-1650-3, late P-51Bs had the V-1650-7 which fits your (questionable) data better. With +16lbs boost V-1650-3 did probably around 26k without RAM and around 30k with RAM. There is several good source books available and mentioned above, please get some of them to avoid continous mixups with the ratings.
The report I saw stated that the supercharger of the P-51 (no model specified) was "out of comission" and therefore they could not do high altitude tests (I have no idea what that means).
I don't know if you fully understand the word "test" it is not same thing as "comparison". We can use test data for comparisons but the values should be comparable.
Yes, RR lists critical altitude of the Merlin 66 as 16k without RAM and that means that at 10km it would produce roughly 800hp. But it appears that the values in the DB 605A manual are given with some sort of RAM effect (actually some German reports on the BMW 801 give unrammed and somekind of rammed output in the charts, see Bingham's book). So values appear to be not comparable.
But in the case of the test flight data we have very well comparable data because the planes operate roughly at same speed range. Even intake systems were quite similar. To put it shortly; in the real world conditions the Merlin 66 outperformed the DB 605A clearly at all altitudes.
And I wonder your comment: "Noone would know the climb speed, the aircraft and so on." Well, I have very similar and actually even more detailed data (conditions, MAP curves etc.) on the Bf 109G-2 than the above mentioned data on Spitfire IX. This data is for 1,3ata because 1,42ata boost was not used in the FAF G-2s. And in this data FTH of the climb speed is pretty much exactly same as mentioned for the 1,3ata in the DB 605 manual. And all this is roughly supported by several german measurements and actually by the DB 605 manual which you don't want believe or another possibility is that you are not able to understand it (after reading your theories about the DB605AS, it seems that later possiblity is more likely).
As noted in my last post, the slip of the supercharger or the lower peak output curves of the DB 605AS has very little to with the RAM effect as you tried to argue in your earlier post. The size of the inlet was increased simply to get a better RAM effect; you talked about the DB 605AS not about the DB 605ASM.
What next?
gripen
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"Yes, RR lists critical altitude of the Merlin 66 as 16k without RAM and that means that at 10km it would produce roughly 800hp"
Thank you.
"But it appears that the values in the DB 605A manual are given with some sort of RAM effect (actually some German reports on the BMW 801 give unrammed and somekind of rammed output in the charts"
I have this 801 chart, but with dynamic pressure crit. alt is over 6km, while engine tops out in all sources below 6000. Strangely the power listed in most sources go along with the dynamic pressure curve. So most sources list "bad" altitude and "bad" power.
But even in german sources you wonīt find the 801 listed with an altitude of over 6km, so this actually confirms my opinion that the DB is listed also without RAM.
With the climb speed i wanted to say that the 605 also was used in slower flying bombers or so (Say He-177 in the double engine variant).
"The size of the inlet was increased simply to get a better RAM effect"
Sure about this? Actually i doubt that. Because pressure is independent from the inlet size. In same way you have at the bottom of vessel filled with liquid always the same pressure at a given level, regardless of the shape.
No no, it was really a problem that at high altitudes the volume flow for the new engine consuming more air up there became to high.
niklas
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Niklas,
Why did you not thank at first time? I gave you a source and all the needed information.
The chart in the DB manual claims dynamic pressure just as the BMW chart ie it means that the DB chart is with some sort of RAM effect just like the other curve in the BMW chart.
The test flight data also clearly proves that the DB chart contains some RAM effect because the total RAM effect is certainly more than 100m, at climb speed (about 400km/h true at FTH) it should be more than 500m. Another possibility is that the inlet system of the Bf 109G was far inferior if compared to the inlet system of the Spitfire. Later possibility is quite unlikely.
You don't seem to have much idea about dynamic airflow in the inlet. It's not a static system as you argue.
gripen