Aces High Bulletin Board
General Forums => Aircraft and Vehicles => Topic started by: FTJR on May 18, 2004, 02:16:06 AM
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Hi Guys,
Im away from home for a while but it just occurred to me that while the C205 has the same engine as the 109, it does not have the same amount of WEP? or does it?
Anyone care to comment.
Regards:confused:
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No, it has half the wep (like other planes). The 205 has the same engine, but I am unsure if it had MW50. That may explain it. It's the same with the Clowntail Ki ... also a DB powered plane.
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Good question, but is the real question why does the 205 have half as much time or why does the 109 have twice as much?
I don't know why the G-6 and G-2 have 10 minutes. I assume that inadvertantly migrated from the G-10 unless I've forgotten something that I used to know. The G-10 has water injection, so I believe 10 minutes is correct for that. Can anybody verify the time limit on the 605A(obviously without the early restriction on emergency power)?
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Yes, I've always wondered why all the 109s have the exact same WEP times despite having different engines. Also wondered why the Dora and 152 had the same cool down time as the 190As, but that seems to have been fixed now. The 109G6 had MW50 I believe.
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But are we sure they are the same engines?
For example the c202 has a DB601 just like Bf109E4 but the c202s engine seems to be more powerful.
So maybe the c205 did not have exactly the same DB605 as the 109Gs?
In fact I think they built their own copies of DB605 engines, their version is the Fiat RA.1050 Tifone.
Perhaps that explains the difference.
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The G6/R2 was the recce version of the G-6 equipped with the MW-50.
The serial installation of mw50 on G-6, was designated as a G-14.
G-6 with mw50 = G-14
The mw50 ran 10 on 5 off. On the K-4 mw50 lasted 26 min.
The 202 and 205 did not have mw50..
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speaking of wep...
as i recall from 2 sources (hurricane Messershmidt, and fighting aircraft of ww2) the hurricane and spitfire 1 did not have wep...ours do
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Probably means the WEP time for the F-4, G-2 and G-6 should all be shortened to 5 minutes or so(arrrrgh!)...
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Firstly, we need to know what kind of "WEP" we have modeled.
1.- WEP=110%?
2.- WEP=110%+boost (if able)?
In this case, 109 Es, Fs, G2 and G6 (thinking that we have and early one) must be in 1st option. And this mean less than 5 minutes of engine endurance.
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Can anybody verify the time limit on the 605A(obviously without the early restriction on emergency power)?
Last I saw, Butch has checked documents and come to the conclusion the Db 605A was limited to 1.3 ata until some time in 1944, which would put it beyond the service life of the G2, iirc.
as i recall from 2 sources (hurricane Messershmidt, and fighting aircraft of ww2) the hurricane and spitfire 1 did not have wep...ours do
With the introduction of 100 octane fuel to Fighter Command in March 1940, Hurricanes and Spits were allowed to use 12 lbs boost presure, up from the previous 6.25 lbs.
12 lbs should take the Spitfire I up to 310 mph at sea level, iirc (I'm on holiday and away from my sources). AH models just over 290 mph according to the help page charts, which is equivalent to 9 lbs boost on a Spitfire II.
So, AH does model some level of WEP on the Spitfire I, just not as much as it actually had available.
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Originally posted by Pyro
Can anybody verify the time limit on the 605A(obviously without the early restriction on emergency power)?
Time limit for 1.42ata was 3 minutes for 605A, the coolant could take maximum temperature for up to 10 mins. 1.3ata could be maintained 30 mins.
When MW 50 was introduced, limit rose to 10 minutes with MW50, as been stated.
British documents of captured 109G-2/trop dated the early months of 1943 already state they found engine cards in 109Gs that have 1.42ata allowed for their 605A engines.
For 601E of the 109F-4, it was 5 minute rating at 1.42ata, and same 30 min for 1.3ata. W
Pyro, If you fetch an email address, I can send the relevant docs.
But I think it should be kept in mind that the engines may be the same in different planes, but the coolant system is often not, it may have less or more cooling capacity, depending on airframe design..
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I have this (http://www.onpoi.net/ah/pics/users/245_1084986645_db605a.zip) file on the DB605A, but I'm unable to find any reference to time limits. Perhaps someone with a better understanding of the German language can be of greater assistance.
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PYRO,
every italian reference about the use of license built DB605A (i.e. the G.55 flight manual) show the early restriction on emergency power. Only God knows what pilots did of that restriction ...
BTW, you have the G.55 manual and can easily see the early time limits.
Grun,
the C.205, G.55 and Re2005 had the same engine of the G-2's and early G-6's.
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One thing: are the G2 and G6 WEP at 1.42 ata or 1.3 ata? I'm wondering about this seeing how our G2 and G6 is about as fast on WEP as Finnish and Russian G2 tests done at 1.3 ata / 7000 meters.
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Thanks for the input everybody. I can be emailed through the email link on this board.
I'm curious about the 1.42 ata restriction. I've always thought that the restriction was just a teething problem on the early G-2s. If it was not fixed until '44, exactly what was the cause and fix?
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I guess Pyro just kicked a Hornet Nest. :D
As for the 1.42ata, lets only say its introduction date is highly debated.
Possible dates could be about January 1943, June 1943, automn 1943, and spring 1944. Every one these dates have supportive evidence of some sort. Personally, I tend to believe 8th of June 1943, when an official clearing was issued.
Troubles were caused by burning out piston heads.
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What was the fix?
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Not sure if that mail link is working right. My address is dougb at hitechcreations.com. Make sure you use a header that will unequivocally let me know it isn't spam. If the header is blank or ambiguous, chances are the email will be deleted without being read.
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Originally posted by Pyro
What was the fix?
Redesigned piston heads, but I think there were other fixes added as well. Trouble was iirc too little clearance between the head and the bore (not sure about correct tech terminus of English), and that the pistons burned out too quickly.
Keep in mind that the 605s were also used in the He 177, where in their interconnected design (610) they developed main bearing troubles, as seen in the RLM discussions, probably because of sync problems between the two engines, and the huge forces involved (3100 HP engine!). I guess this didnt effected 109s/110s much.
Third problem was non-engine related, founded in the varying quality of synthetic avgas, which could cause pre-ignition troubles, and was fixed with new type of spark plugs. No problem though when using 'natural' B-4 avgas, which was of better (or more like, more stable) quality.
Edit: I just sent an email 4 you, Pyro, at the given address. Hope you got it.
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I'm curious about the 1.42 ata restriction. I've always thought that the restriction was just a teething problem on the early G-2s. If it was not fixed until '44, exactly what was the cause and fix?
I went on holiday just after I first saw Butch's comments on this, so I don't know if he's found anything other documents one way or another, but there's some reference to it in this thread at Ubi:
Isegrim since you are so fond of flight manuals, could you check your copies of the following documents :
- L.Dv.T.2109 G-12/Fl which is the Bf 109G-12 Bedienungvorschrift-Fl (Stand August 1944) Ausgabe Dezember 1944
- L.Dv.T.2109 G-4/R3, G-6/R3/Fl which is the Bf 109 G-4/R3, G-6/R3 Bedienungvorschrift-Fl (Stand November 1943) Ausgabe Februar 1944
- L.Dv.T.2109 G-2, G-4, G-6/Fl which is the Bedienungsvorschrift-Fl (Stand April 1943) Ausgabe Juni 1943
You'll notice that none of those documents, which are the actual flightmanuals btw, clear the 1.42ata boost.
The only late manual i have seen so far that cleared the DB605A 1.42 boost is the DB605A-B Baureihe 0,1 u. 2 motoren-Karte (Stand April 1944) Ausgabe Juli 1944. This document replace the Motorenkarte issued in Oktober 1942 which, contrary to the earlier motorenkarten, prevented the use of the 1.42ata boost.
There were no revision between the two MotorenKarte, but a lot of modifications were done on the DB605A design in the meantine.
http://ubbxforums.ubi.com/6/ubb.x?a=tpc&s=400102&f=63110913&m=875109873&r=452107983#452107983
Futher down:
Btw the 1.42ata boost appear in various documents of mid 1943, with the followings mentions : 1 minutes setting ! hardly convenient as a boost isn't it. And with the following mentions in the Bf 110G-2 manual : "z.Z.gesperrt" which translate by "Not currently available".
Moreover i have a list of modification introduced in Oktober 1943 so as to fix the deficiencies of the DB605A.
i don't have Butch's email, but he comes here occasionally, and I believe you've had corespondence with him in the past.
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Posted by butch2k
There were three main problems with the DB605A, the last one being pre-ignition troubles when using B4 fuel at 1.42ata. It was not solved until the introduction of a new kind of sparkplug.
It seems that it was possible to run on 1.42ata but only when relying on true 87 octane fuel not the ertsatz B4. So it might explain why some aircraft could actually use 1.42ata by mid 43. [/u]
As in fact they did even a bit earlier on :
(http://www.x-plane.org/users/isegrim/109/DB605A142ata.jpg)
British report of Bf 109G-2/trop dated 8th February, 1943.
Another point of interest is the very economical fuel consumption even when high powers are involved (Merlin 66 consumed 150 gal/hour at WEP).
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If that extract is from the British report on the G-2 trop they captured and tested, that's originally how I came about the thought that the restriction was just an early teething problem with the 605.
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Hi Pyro: here's some excerpts from docs I have:
• Flugzeugmuster BF 109 G-1 mit motor DB 605A Kennblatt:
The figures indicated refer to combat and climbing power. n - 2600 U/min:Plade - 1,3 ata. Take-off and emergency power are not as yet approved for the 605/A. Die angegebenen Leistungen beziehen sich auf kampf und steigleistung. n - 2600 U/min :Plade - 1.3 ata. Start und notleistung ist für 605/A zurzeit noch nicht freigegeben
• R.L.M. message GL/C-TT No.1374/42/42 of 12.6.42 as translated by British Air Intellegence.
A number of cases of breakdown in the DB 605 engine as a result of pistons burning through have occured. The following must therefore be observed.
The Take-off and emergency output with a boost pressure of 1.42 atm. and 2800 revs. may not at present by used. The climbing and combat output with 1.3 atm. and 2600 revs. may in the case of the older engines (for works numbers see below), be used only when operationally essential.
• Bf109 G-2 Bedienungsvorschrift-F1 Stand Juli 1942
*Note! "start and emergency power" is blocked and may not be used. *Achtung! Die "Start und notleistung" darf nicht benutzt werden, sie ist deshalb blockiert.
• DB 605 Moteren-Karte 9 October 1942
Take-off and emergency power is closed up to revocation , thus 2650 U/min (2600 U/min +2%) may not be exceeded in any flight attitude. Die Start und Notleistung ist bis auf Widerruf gesperrt, es dürfen somit 2650 U/min (2600 U/min +2%) in keiner Fluglage überschritten werden.
• From 109 G1, G2 and G6 Meßrief - 1942 and 1943
Take off and emergency power: Provisionally closed after VT instruction Nr.2206. Start und Notleistung: Vorläufig gesperrt nach VT-Anweisung Nr.2206
• Meßrief BF 109 G-2 trop 10798
Start und Notleistung: Vorläufig gesperrt nach VT-Anweisung Nr.2206
14.12.42
• Meßrief BF 109 G-6/tp Wk Nr 16387
Start und Notleistung: Vorläufig gesperrt nach VT-Anweisung Nr.2206
Vorläufige Fluggenehmigung 9.März 1943
• Meßrief BF109G-6/tp Wk Nr 15218
Start und Notleistung: Vorläufig gesperrt nach VT-Anweisung Nr.2206
Abnahmeflug acceptance flight 18.3.1943
• Meßrief Bf 109 G-6 trop 16647
Start und Notleistung: Vorläufig gesperrt nach VT-Anweisung Nr.2206
Sonderladeplan 8.4.43
• BF 109 G-6 Wr Nr 18421 data card showing 1.3/2600 limit
• Trials Reports of Bf 109 G showing 1.3/2600 as the engine limitation
Nr 109 19 L 42 (19.9.42)
Nr 19 20 L 43 (22.1.44)
Nr 1018105428 10.5.44
• Technishe Daten Bf 109 C, D, E, F, G
Steig und Kampfleistung: zugleich startleistung
November 1943
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Yeah and make sure you read mw's "work in progress" too.
http://www.fourthfightergroup.com/eagles/spit9v109g.html
Titled: Rewriting history "How the Spitfire ruled the skies", by Mike Williams.
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but...the Spit did rule the skies, right :confused: :confused:
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Originally posted by Angus
but...the Spit did rule the skies, right :confused: :confused:
For sure, for just like teeth in a chicken's mouth, Messicraps were hard to find. The Spit, with some help, had driven the Messicraps from the sky.:rofl
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Originally posted by GScholz
Yeah and make sure you read mw's "work in progress" too.
http://www.fourthfightergroup.com/eagles/spit9v109g.html
Titled: Rewriting history "How the Spitfire ruled the skies", by Mike Williams.
And what is wrong with mw's work? He is comparing 1942-43 Spitfires and Messicraps.
There is also a line saying that the performance of later a/c increased.
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Hmm, true, those charts are basically comparing planes in a certain timeframe. Rather the operable planes it looks.
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Ever wondered why Mike`s references suddenly end in the spring of 1943 ?
(http://www.x-plane.org/users/isegrim/109/RadingerOtto142ata.jpg)
From Radinger-Otto : Me 109F-K, The world`s most produced fighter.
Of course he lists Spits on their 1943 boost, and hand picked worst performer 109Gs on their 1942 boost.
But what would you expect from Mike if not that?
BTW, as per the performance of 109G-2 in AHT, it runs at 1.3ata boost with WEP, ie. the 1942 standup.
1.3ata / 2600rpm was sustainable for 30 mins, so the WEP time should be corrected accordingly.
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So..... I guess that means I cant have more wep on my 205:eek:
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Ever wondered why Mike`s references suddenly end in the spring of 1943 ?
Just maybe, he has not got around to doing comparisons to the later Messicraps.:)
The G-5 is a bad performer??? You might be right, for with JGr25, it could not catch DH Mosquitos. It came off the assembly line from May '43 to Aug. '44. Seems Mike was comparing earlier Spits to a 1944 109.:)
When it comes to info on the 109, I would believe what Butch has to say over Issy, with his agenda, any day.
A Merlin with 15lb boost was operating at 2.02 at(29.7/14.7). With 18lb boost, it would be 2.22at(32.7/14.7). With 25lb boost, it would be 2.70at(39.7/14.7) Seems the DB engines were just a wee bit on the weak side with only a max of 5.5lb of boost.
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After giving it a more thorough check it appears that the 1.42ata boost was cleared in November 43, a revised DB605A manual (not motorenkarte) being re-issued at that time. Note that the motorenkarte was not updated until April 44 for some unknown reason.
IIRC (i'm at work) the time limit at 1.42ata had been reduced to 1 minute (1944) compared to the 3 originaly planned (1942).
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Originally posted by MiloMorai
A Merlin with 15lb boost was operating at 2.02 at(29.7/14.7). With 18lb boost, it would be 2.22at(32.7/14.7). With 25lb boost, it would be 2.70at(39.7/14.7) Seems the DB engines were just a wee bit on the weak side with only a max of 5.5lb of boost.
Interesting Milo.
It appears that, as per your data, the DB 605 developed 2000 PS at 1.98ata, whereas the Merlin at 2.02 ata (+15lbs) could develop 1340 HP.
Speaking about effiency.. :D
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I have never understood why one would compare Allied vs German engines just on the boost pressure...
It would be better to compare boost x Compression ratio... since the German relied on low boost but high CR and the Allied rather the contrary.
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Originally posted by VO101_Isegrim
Interesting Milo.
It appears that, as per your data, the DB 605 developed 2000 PS at 1.98ata, whereas the Merlin at 2.02 ata (+15lbs) could develop 1340 HP.
Speaking about effiency.. :D
Interesting indeed Issy, now what was the hp without using 'boost juice', for that is the only way they could reach that high of a hp number and boost number? Note the selective hp number stated by Issy, for the Merlin at 15lb produced ~1550hp+. Typical of him.
As can been seen in this graph, the Merlin could produce 2000hp plus, as well'.:)
(http://www.stobbe.dk/technical_literature/combustion_engines/rolls-royce/images/merlinhk.jpg)
The Griffon 65, an engine of simular displacement to the 605, produced over 2000hp without using 'boost juice'. With ADI, the power was even higher, ~2350hp+.
The Griffon 58 delivered 2455hp at low level with ADI ('boost juice') and 25lb boost.
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Originally posted by butch2k
I have never understood why one would compare Allied vs German engines just on the boost pressure...
It would be better to compare boost x Compression ratio... since the German relied on low boost but high CR and the Allied rather the contrary.
Neither I had understood such comparison in a complex matter, I just gave him some typing work and to let him waste an hour on searching the web - the world is free from him during that. ;)
To me it appears that the development at DB was a lot more systematical though, ie. swept volume, supercharger size, compression ratio, boost pressure were all increased, fuel injection, hydraulic coupling was introduced.. The main path of development seems to be more concerned about improving the engine`s overall effiency, rather than just focusing on increasing power output via MAP, as R-R did, employing an advanced supercharger technology that was perhaps not the best solution to be built into a fighter (ie. w. intercooler and it`s associated extra items).
R-Rs development reminds me of a small team of of engine tuning experts, while DB`s was more like an organised group of engineers with rather clear ideas how to develop a basic design through the years. And the difference is very clear between the approach of the two by 1945, rather identical power outputs overall, but DBs do it with less fuel, less weight, less bulk without sudden power drop characteristics of the R-R designs. Equally effective, but far more efficient.
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Typical Issy.
Actually Issy, while the 'pute was doing its number crunching, I had some free time.:) Did not catch many ambulances lately it seems since you post all day long.
FYI, Issy R-R was using fuel injection during WW2. When you start comparing weights add in the weight associated with the 'boost juice' > no big hp numbers without the 'juice'.:)
R-R knew what ADI could do and had the choice to use 'boost juice' but decided against because the extra complexity and weight were not worth the additional power. Much more logical than the complexity the Germans liked to add. Even BMWs method of injecting extra fuel was better.
Interesting that the Germans salvaged the sc gears on the Merlins because they were better than what they could make.
Oh yes the DB engineers were much more organized. One only has to look at all the dead-end/no-go engines they tried to develope from the basic engines.
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Oh my God, another Spit vs. 109 hijack. Will you guys (you know who you are) give it a rest! Argue by email if you have to argue.
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My engine is bigger than your engine ;)
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More like RR and DB tattooed dick-waving in public.
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Originally posted by GScholz
More like RR and DB tattooed dick-waving in public.
You sort of got it, for is more like pointing out, Issy's is not a big as he wishes it was. :)
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A better measure is Brake Mean Effective Pressure (BMEP), but even here you have to take into account differences in maximum RPM across engines.
At the end of the day, you want to know for the all-up weight of the engine, supercharger, boost system, oil, etc, the mass of air the engine pumps out per unit of time. Even this is a measure of gross power. You want to deduct the energy required to drive the supercharger, etc.
-Blogs
Originally posted by butch2k
I have never understood why one would compare Allied vs German engines just on the boost pressure...
It would be better to compare boost x Compression ratio... since the German relied on low boost but high CR and the Allied rather the contrary.
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Well, at least the thread produced some engine data ;)
And as usual, Milo and Issy start their scruffling.
"It appears that, as per your data, the DB 605 developed 2000 PS at 1.98ata, whereas the Merlin at 2.02 ata (+15lbs) could develop 1340 HP. "
Bear in mind that the Merlin is what, 24 litres, and the DB is what, 32 litres?
It's apples and oranges really, the base design of those two are not quite exactly the same. Different approach to squeeze the power out.
The Merlin produces more power/torque for the same weight, using high grade fuel instead of MW or whatever.
The DB produces amazingly good power out of lower boost and lower grade fuel, however applying MW, which is very very bad for an engine actually.......
The Merlin could actually be squeezed up to well over 2000 hp using special juices, but it was not really worth it. Imagine the power there pro volume though. They actually fiddled with that in 1939!
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Why is using MW50 bad for the engine? Some allied late war planes used water injection. In AH the F4U4 for instance. The Merlin does not produce more power/torque for the same weight, the two engines weigh almost exactly the same.
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A lot of this is covered in the charts posted at
http://www.hitechcreations.com/forums/showthread.php?s=&threadid=106773
-Blogs
Originally posted by Angus
Well, at least the thread produced some engine data ;)
And as usual, Milo and Issy start their scruffling.
"It appears that, as per your data, the DB 605 developed 2000 PS at 1.98ata, whereas the Merlin at 2.02 ata (+15lbs) could develop 1340 HP. "
Bear in mind that the Merlin is what, 24 litres, and the DB is what, 32 litres?
It's apples and oranges really, the base design of those two are not quite exactly the same. Different approach to squeeze the power out.
The Merlin produces more power/torque for the same weight, using high grade fuel instead of MW or whatever.
The DB produces amazingly good power out of lower boost and lower grade fuel, however applying MW, which is very very bad for an engine actually.......
The Merlin could actually be squeezed up to well over 2000 hp using special juices, but it was not really worth it. Imagine the power there pro volume though. They actually fiddled with that in 1939!
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For Scholzie
"Why is using MW50 bad for the engine? Some allied late war planes used water injection. In AH the F4U4 for instance. The Merlin does not produce more power/torque for the same weight, the two engines weigh almost exactly the same."
The MW is Methan-Water right. Well, as far as I know, it's the Methan that really eats up the engine. The piston heads were the initial problem, but the thing really eats up everything, such as sleeves and valves. Using the MW would lead to either problems/inreliability, or very much maintainance, which in the late war could be a very hard task on the German side, being short of spares, engineers and facilities, - hence engines getting "old" mighty quickly.
About the Power and torque of the Merlin vs the DB, I had a close look at that actually. It was of course related to a Spit vs 109 debate, where I was trying to figure a path through so much biased data.
It is hard to figure really, - Speed, acceleration and climb do not absolutely rely on the same factor.
I picked climb as a basis for a torque measurment, calculating torque in NM/time for a given altitude. One can also have a look at the total newtons for a mass at a given speed through airflow, but it is harder to balance absolutely, for it has more curves to put in.
Anyway, a Spitfire with a similar propeller as a 109, with almost exactly the same power output, will definately pull more Newtons to altitude. It is quite more than a margin. If one levels that margin out with a different propeller for higher speed, the Spitty will in return be faster at the same power output.
(based on Spit I vs 109E3/4, both with 87 octane fuel)
Anyway, again,looking at the engines....
The Merlin is actually slightly lighter for a given power output, more or less. It is however a very marginal difference,- rating not much more at times than a fat pilot vs a thinner one. You are right, the engines do weight almost exactly the same, however, the favour tends to be a wee bit in the Merlins favour.
Torque is another issue, - as I define it, it is very much related with the boost. Remember that boost does not help so much with top speed, however drastically with climb. Why so? Torque curve maybe?
I have no Idea about the P&W. Did they use Methane as well? If they did, I am pretty sure that the US had a lot better alloys than the Germans, and bear in mind that that has nothing to do with engineering quality, just access to the alloys.
Anyway, if you have the Weight, power and climb capacity of a typical say 1942/43 109 model handy I'll gladly put it up in my algorythm and give you the climb torque as well as a co-time Merlin thingie.
Getting back to the topic, - if the 205 did not use MW, was there no other available overboost, and secondly, what about mixtures like the C-3????
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The Americans called it ADI (anti detination injection). The methanol was used as an anti-freeze while the water was the anti-detination fluid. The injected substance was a fluid not a gas which methane is. Are you thinking of nitrous oxide(GM1 by the Germans)? This is very corrosive.
Some Merlins in bombers used NOX.
The P-47 had ADI late war as did some P-51s.
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Angus check Blogs link....
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If one levels that margin out with a different propeller for higher speed, the Spitty will in return be faster at the same power output.
(based on Spit I vs 109E3/4, both with 87 octane fuel)
Thats basically the ONLY time that was true.
Bf109F4
Bf109G2
All faster for less power.
G6 is slower.
G6AS isfaster than spit 9.
G10/K4 all faster for less power than griffon spits.
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"If one levels that margin out with a different propeller for higher speed, the Spitty will in return be faster at the same power output.
(based on Spit I vs 109E3/4, both with 87 octane fuel)
Thats basically the ONLY time that was true. "
That is basically the last time a speed optimized propeller was used, - later props were more or less CS for improved climb and acceleration ;)
Anyway, the G2 is the queen of the line....
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I believe that P&W engines - late war - used water injection with alcohol to prevent freezing. In otherwords - methanol. Pretty common by that point.
I had thought the issue about engine damage from WEP had to do with very high heat and bearing loads. The result - (time between overhauls) TBO falls dramatically.
P&W and Curtiss Wright had one advantage over German engine makers and all the British (except Bristol) - years of engineering experience derived from serving the largest market for high powered civilian transports. US engines had a distinct advantage in TBO and sometimes in specific fuel consumption.
-Blogs
Originally posted by Angus
For Scholzie
I have no Idea about the P&W. Did they use Methane as well? If they did, I am pretty sure that the US had a lot better alloys than the Germans, and bear in mind that that has nothing to do with engineering quality, just access to the alloys.
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Lol, noticed my typo, always calling methanol methane.
Must be all that cow work :D
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joeblogs,
IIRC Bristol Hercules sleeve valve engine had clearly longest TBO of the WWII military engines.Can't remeber the numbers but something like 50% longer TBO than PW engines.
gripen
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Gripen
That's why I excepted Bristol from my characterization.
Bristol had a great reputation with their poppet valve engines too, but they were a bit small in terms of displacement by WWII.
P&W tried, but never mastered a sleeve valve engine.
The other exception to make would be diesel aircraft engines, where the Germans had some of the best.
-Blogs
Originally posted by gripen
joeblogs,
IIRC Bristol Hercules sleeve valve engine had clearly longest TBO of the WWII military engines.Can't remeber the numbers but something like 50% longer TBO than PW engines.
gripen
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I am always amazed when I see these charts for German engines. To me the fuel consumption numbers looks like some kind of average over power ranges even though the organization of the table would suggest otherwise.
In the data here, specific fuel consumption varies from .43 lbs/hp/hr to 0.49 lbs/hp/hr. A comparable range for an American radial over the power spectrum would run from 0.42 to 1.0 or even higher. Most of the increase is explained by the switch from lean fuel mixtures to rich mixtures to prevent detontation under higher manifold pressure.
I don't see how the German engines can escape the physics here. Can it really be explained by direct fuel injection? Are the calculations done differently?
Paul Wilkinson (1945) estimated the best SFC for the DB605 A1 was 0.44 using 92 octane avgas.
-Blogs
Originally posted by VO101_Isegrim
As in fact they did even a bit earlier on :
(http://www.x-plane.org/users/isegrim/109/DB605A142ata.jpg)
British report of Bf 109G-2/trop dated 8th February, 1943.
Another point of interest is the very economical fuel consumption even when high powers are involved (Merlin 66 consumed 150 gal/hour at WEP).
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Those are Imperial gallons. Converted to US gallons the 1.42ata 2800 rpm fuel consumption reads as 123 gal/h. That would be consistent with the German documentation on the DB605A.
Here's page three of the DB605A Motoren-Karte. It says approximately (ungefär) 480 L/h (126 gal/h) on 1.42ata 2800 rpm and 400 L/h (105 gal/h) on 1.3ata 2600 rpm.
(http://www.onpoi.net/ah/pics/users/245_1086191161_db605apage3.jpg)
The Motorenmuster is more accurate and I get 473 L/h (124 gal/h) on 1.42ata and 393 L/h (103 gal/h) on 1.3ata.
(http://www.onpoi.net/ah/pics/users/245_1086191803_db605_varianten14.jpg)
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Yes I was worried about that, but that just changes the scale a bit, about 20 percent.
The odd factor that remains is that charts of American engines show a 70-100 percent increase in specific fuel consumption moving along the power curve from max cruise to take-off. When you look at tables of german or russian engines (the one's I've seen are compiled from British or German sources), you see a variation in specific fuel consumption on the order of 20-50%.
For example, using your second chart, and converting to American units, we have SFC ranging from 0.53 to 0.74, a variation of only 40 percent.
I just don't understand what explains the discrepancy unless the calculations are made under different assumptions. For example, suppose the take-off and climb numbers assume you throttle back when you hit the 10 minute or whatever limitation is specified in the pilot's manual?
-Blogs
Originally posted by GScholz
Those are Imperial gallons. Converted to US gallons the 1.42ata 2800 rpm fuel consumption reads as 123 gal/h. That would be consistent with the German documentation on the DB605A.
Here's page three of the DB605A Motoren-Karte. It says approximately (ungefär) 480 L/h (126 gal/h) on 1.42ata 2800 rpm and 400 L/h (105 gal/h) on 1.3ata 2600 rpm.
The Motorenmuster is more accurate and I get 473 L/h (124 gal/h) on 1.42ata and 393 L/h (103 gal/h) on 1.3ata.
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No they are actual fuel consumption at that power setting per hour, even if the engine couldn't be run at that setting for a whole hour. The inline engines were a lot more fuel efficient at high power than the big radials, even the Merlin with its carburettors were a lot more efficient.
Exactly why this is I don't know, but I have a hunch it is because of cooling. The air-cooled radials must have used a very rich mixture at high power setting just for cooling purposes. I know this is so for the F4U4 which has awful fuel consumption at MIL power, but because of the water injection its WEP consumes much less fuel. The liquid cooled engines were not so vulnerable to overheating parts of the engine (cylinder tops, piston heads, valves etc.).
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Scratching my head here....
Well, in princip, an inline engine has a systematic cooling pattern for the price of a more vulnerable design perhaps? The Radial cooling is simple and brutal.
How about the BMW radial then? or the russian engines?
Oh, BTW, which engines had sleeves and which not?
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I have done a similar caclulation for the Allison v12. It's still the case that above 65% rated power fuel consumption increases dramatically.
In other words the levels at different power settings may vary, but the steepness of the consumption curve really shouldn't. I don't know why we don't see that in the European charts.
My numbers also say that water cooled engines are not always as fuel efficient and the reason is quite simple - they are typically run at higher RPM. The benefit of a water cooling is really seen in the smaller displacement, higher compression ratio (sometimes) and lower dry weight rather than in the fuel economy.
The most fuel efficient engines are models of the cyclone, twin wasp, and Bristol Hercules - all air cooled.
It is still true that that the P&W R2800 engine was more thirsty for gas than Wright's at high power settings. There is some evidence this was due to the carburetor and not the engine. Very late war models corrected this problem.
-Blogs
Originally posted by GScholz
No they are actual fuel consumption at that power setting per hour, even if the engine couldn't be run at that setting for a whole hour. The inline engines were a lot more fuel efficient at high power than the big radials, even the Merlin with its carburettors were a lot more efficient.
Exactly why this is I don't know, but I have a hunch it is because of cooling. The air-cooled radials must have used a very rich mixture at high power setting just for cooling purposes. I know this is so for the F4U4 which has awful fuel consumption at MIL power, but because of the water injection its WEP consumes much less fuel. The liquid cooled engines were not so vulnerable to overheating parts of the engine (cylinder tops, piston heads, valves etc.).
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Pyro on the F4U4:
Originally posted by Pyro
As counter-intuitive as it may be, that's actually not a bug. It really did suck a lot less gas in wep than it did in military. The reason for that is because the engine had to run a very rich mixture at military but at wep it's using water injection and doesn't require such a rich mixture. As a result, when the water started to flow, it closed a jet in the carburetor and weakened the mixture which cut down the fuel flow considerably.
The air-cooled radials were designed to operate at cruise or normal power, just like any other engine. However they were less suited for emergency power because they easily overheated. A liquid-cooled engine has a rather large engine block made of metal that the cylinders are bored into. Metal is very effective in transferring heat away from the cylinders and transferring it to the coolant through the coolant-loop.
An air-cooled radial only has a thin skin of metal with cooling fins surrounding the cylinders, which is easily overheated compared to the massive engine block of an inline engine. That's why I believe they had to use very rich mixtures at high power settings to help cool the cylinders, piston heads, valves etc.
The Radials were somewhat fuel efficient on low power settings, but still I have not seen any data on a radial that matches the efficiency of the DB and Merlin or indeed any other inline. The radials were favoured for their reliability, toughness and low weight.
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In principal you are right Gscholz. The primary benefit of water cooling over air cooling is the minimization of hot spots in the cylinder.
But everthing I've read says that a piston engine run at anything near rated power must be run in a rich fuel mixture, water or air cooled. That doubles the amount of fuel used per pound of air introduced into the cylinder.
It could be the case that fuel consumption at max horsepower (without wep) with a water cooled engine will be less than an air cooled one, but I've not seen any data on US engines to confirm the difference is dramatic.
As I said, the Allison liquid cooled v12 experiences a significant increase in fuel consumption at higher output settings precisely because the fuel mixture goes to auto rich. You also see this with specific engine charts for the P51 using the Merlin.
Here is an example of curves from US specific engine charts:
(http://mysite.verizon.net/vze479py/sitebuildercontent/sitebuilderpictures/turbos.gif)
In this chart (before the carburetor change) the R2800 is a hog at high outputs. The increase for the Allison is about 50% and for the cyclone about 80%. These are rough numbers as the cyclone data is from the Curtiss Wright manual and does not incorporate the installation. The Allison is for the P-38. At peak outputs, the advantage in specific fuel consumption for the Allison over the Twin Wasp is only about 13% and for the Cyclone it is only about 8%. Even for the R2800, the disadvantage is only about 18%.
On the other side of the ocean, if you look at engine charts, such as the ones posted in this thread, you see fuel consumption curves that are much flatter than for US charts. It's true for air cooled engines too. I've seen charts on the BMW 801 and the ASH82 FNV that exhibit the same characteristics.
Fact is that no one during the war ever said that the Germans or Russians had engines that were twice as fuel efficient at rated power as the American engines (let alone Bristol or RR). So I have to wonder if the method of calculation is different than for the US charts.
-blogs
Originally posted by GScholz
Pyro on the F4U4:
The air-cooled radials were designed to operate at cruise or normal power, just like any other engine. However they were less suited for emergency power because they easily overheated. A liquid-cooled engine has a rather large engine block made of metal that the cylinders are bored into. Metal is very effective in transferring heat away from the cylinders and transferring it to the coolant through the coolant-loop.
An air-cooled radial only has a thin skin of metal with cooling fins surrounding the cylinders, which is easily overheated compared to the massive engine block of an inline engine. That's why I believe they had to use very rich mixtures at high power settings to help cool the cylinders, piston heads, valves etc.
The Radials were somewhat fuel efficient on low power settings, but still I have not seen any data on a radial that matches the efficiency of the DB and Merlin or indeed any other inline. The radials were favoured for their reliability, toughness and low weight.
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Well like I said, I don't really know, I'm just reasoning. All I do know is that the DB's fuel efficiency was notable, and both German and Allied documents attest to it. Like the British report Isegrim posted and you quoted. I don't specifically remember a US test on the DB/109, but I'm sure there were several. Perhaps you can find one and see if the US tests are any different?
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It's all a question of degree. The DBs are reletively efficient engines and I can think of at least two reasons why: high compression ratios and a single stage supercharger operating on a continuously variable clutch. Given the low octane fuels it was rated on, its especially efficient. I just wonder how it's fuel consumption at rated output can really be below 0.7 lbs/hp/hr.
Even my chart shows a water cooled engine that does better at high output than three good air cooled radials.
-blogs
Originally posted by GScholz
Well like I said, I don't really know, I'm just reasoning. All I do know is that the DB's fuel efficiency was notable, and both German and Allied documents attest to it. Like the British report Isegrim posted and you quoted. I don't specifically remember a US test on the DB/109, but I'm sure there were several. Perhaps you can find one and see if the US tests are any different?
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Eh ... isn't the Allison in your chart below 0.7 at max power?
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I mean rated power, not WEP.
Originally posted by GScholz
Eh ... isn't the Allison in your chart below 0.7 at max power?
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Well the Allison in your chart was at 0.70 or below at any power setting. Why do you find it strange that the DB used less than the Allison considering the variable speed blower, high compression ratio, direct fuel injection etc.?
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The puzzler is how the top end can be reletively low when the bottom end is about 20 percent high relative to the Allison.
But I must concede your DB chart is a lot more plausible than the earlier one in this thread, which shows almost no variation in specific fuel consumption.
-Blogs
Originally posted by GScholz
Well the Allison in your chart was at 0.70 or below at any power setting. Why do you find it strange that the DB used less than the Allison considering the variable speed blower, high compression ratio, direct fuel injection etc.?
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Originally posted by GScholz
The air-cooled radials were designed to operate at cruise or normal power, just like any other engine. However they were less suited for emergency power because they easily overheated. A liquid-cooled engine has a rather large engine block made of metal that the cylinders are bored into. Metal is very effective in transferring heat away from the cylinders and transferring it to the coolant through the coolant-loop.
An air-cooled radial only has a thin skin of metal with cooling fins surrounding the cylinders, which is easily overheated compared to the massive engine block of an inline engine. That's why I believe they had to use very rich mixtures at high power settings to help cool the cylinders, piston heads, valves etc.
But inline engines are enclosed in the fuselage with no air flowing past the block to help disapate the heat radiating from the block. The block can become saturated with heat. Radials on the other hand, have cold air passing over the multitude of fins on the cylinders and directly on the crankcase. (P-47s in the ETO had at one time an overcooling problem)These fins also help disapate the heat from the oil which on an inline must go to an oil cooler(radials have an oil cooler as well).
Angus
All aluminium engines have sleeves or cylinder liners. The Bristol radials and Napier Hs used sleeve valves.
how sleeve valves work
http://www.geocities.com/kiwiengineer2002/sleeve.html
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So all of the main WW2 engines had cylinder sleeves right? The P&W, RR, DB, BMW, Allison, Wright, Bristol, etc etc?
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For a time, the Allisons in the P38 were non-functional in Nothern Europe because they were over-cooled at high altitudes. The problem was eventually fixed, but not until after the P51 had replaced their role.
I'm not sure why cylinder liners have much to do with all this. The liners are there primarily for strength and durability relative to aluminum. Yes they are there. Yes, steel or Iron liners have different heat entropy properties. But so what?
-Blogs
Originally posted by MiloMorai
But inline engines are enclosed in the fuselage with no air flowing past the block to help disapate the heat radiating from the block. The block can become saturated with heat. Radials on the other hand, have cold air passing over the multitude of fins on the cylinders and directly on the crankcase. (P-47s in the ETO had at one time an overcooling problem)These fins also help disapate the heat from the oil which on an inline must go to an oil cooler(radials have an oil cooler as well).
Angus
All aluminium engines have sleeves or cylinder liners. The Bristol radials and Napier Hs used sleeve valves.
how sleeve valves work
http://www.geocities.com/kiwiengineer2002/sleeve.html
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Joe, the liners were mentioned because Angus asked about them; nothing to do with the rest of the post.