engine question me109

[Kyso4ek]

F4 is allowed 1.42 ata for <1 minute
G2 isnt allowed 1.42 ata, only 1.3

I want to ask why is it so.
and which has more power?

[Hadji]

From a translated official document:

Berlin, June 18, 1942

SUBJECT: DB 605 Engine in the Bf 109 G

A number of breakdowns 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 be used. The climbing output with 1.3 Atm. and 2600 revs. may, in the case of of the older engines, be used only when operational essential.
...

So to answer your question: There was a problem with the DB 605 engine at the time which resulted in piston burn-through at higher boost pressure. I believe the root cause was bearings: Ball bearings had been replaced with roll bearings and the lubrication system was changed accordingly. With more powerful oil pumps the engine suffered from low oil pressure and lack of proper lubrication because of oil foaming.

Here is a transcript of a conversation between Reichsmarschall Göring and representants from Daimler-Benz and Junkers in September 1943:

Reichmarschall Göring : This means that with regard to the DB605, it is impossible to predict whether the engine is ever going to be a useful engine.

Eisenlohr : The engineering changes and the available test results reveal that there is a high probability that concerning the question bearings, the worst is behind us and the situation is going to improve, even if it is not going to be a robust engine, but at least one that can be run at maximum output by the frontline units with full justification. The testing at Rechlin proceeded completely well so far. Cuno reported that four weeks are still required for completion.

Reichmarschall Göring :You have the confidence in that can work out?

Eisenlohr : Yes sir.

Reichmarschall Göring : Nallinger, do you still have great confidence in your child?

Nallinger : On the basis of our latest testings we have the absolute confidence in that with the engneering changes I've reported, the engine will be fixed with regard to the bearings and the Startleistung is going to be cleared for use.

Reichmarschall Göring : What do you think, Petersen?

Petersen : I share this conviction and additionally am convinced that in conjunction with the oil centrifuge, the engine is going to be allright with regard to the bearings. That has always been the experience of the past, the maintenance people predicted that the engine is going to fail soon if the oil pressure dropped below a certain figure, below 100 atü. The new 177s with oil centrifuges have worked well so far, and no bearing failures have been suffered, so that I'm able to say: If these measures which I would like to call detail work are added, the oil centrifuge in conjection with the 605, that the bearing story can be considered to have ended.


Reichmarschall Göring : What do you say, Scheibe?

Scheibe : According to the understanding at Junkers, there should actually be no problem fixing the engine with regard to the bearings. If a far-fetched solution is necessary, then - as Nallinger elaborated - the lubrication has to be taken out of the crankshaft, if it's possible to use the example of the Jumo 211 as a reference which runs in the power-boosted forms N and P at virtually the same speeds without bearing problems.

Source: http://kurfurst.org/Engine/Boostclearances/DB605A_GLmeeting_September1943.html

[Kyso4ek]

Originally posted by 1./ZG1_El Hadji:

From a translated official document:

Berlin, June 18, 1942

SUBJECT: DB 605 Engine in the Bf 109 G

A number of breakdowns 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 be used. The climbing output with 1.3 Atm. and 2600 revs. may, in the case of of the older engines, be used only when operational essential.
...

So to answer your question: There was a problem with the DB 605 engine at the time which resulted in piston burn-through at higher boost pressure. I believe the root cause was bearings: Ball bearings had been replaced with roll bearings and the lubrication system was changed accordingly. With more powerful oil pumps the engine suffered from low oil pressure and lack of proper lubrication because of oil foaming.

Here is a transcript of a conversation between Reichsmarschall Göring and representants from Daimler-Benz and Junkers in September 1943:

Reichmarschall Göring : This means that with regard to the DB605, it is impossible to predict whether the engine is ever going to be a useful engine.

Eisenlohr : The engineering changes and the available test results reveal that there is a high probability that concerning the question bearings, the worst is behind us and the situation is going to improve, even if it is not going to be a robust engine, but at least one that can be run at maximum output by the frontline units with full justification. The testing at Rechlin proceeded completely well so far. Cuno reported that four weeks are still required for completion.

Reichmarschall Göring :You have the confidence in that can work out?

Eisenlohr : Yes sir.

Reichmarschall Göring : Nallinger, do you still have great confidence in your child?

Nallinger : On the basis of our latest testings we have the absolute confidence in that with the engneering changes I've reported, the engine will be fixed with regard to the bearings and the Startleistung is going to be cleared for use.

Reichmarschall Göring : What do you think, Petersen?

Petersen : I share this conviction and additionally am convinced that in conjunction with the oil centrifuge, the engine is going to be allright with regard to the bearings. That has always been the experience of the past, the maintenance people predicted that the engine is going to fail soon if the oil pressure dropped below a certain figure, below 100 atü. The new 177s with oil centrifuges have worked well so far, and no bearing failures have been suffered, so that I'm able to say: If these measures which I would like to call detail work are added, the oil centrifuge in conjection with the 605, that the bearing story can be considered to have ended.


Reichmarschall Göring : What do you say, Scheibe?

Scheibe : According to the understanding at Junkers, there should actually be no problem fixing the engine with regard to the bearings. If a far-fetched solution is necessary, then - as Nallinger elaborated - the lubrication has to be taken out of the crankshaft, if it's possible to use the example of the Jumo 211 as a reference which runs in the power-boosted forms N and P at virtually the same speeds without bearing problems.

Source: http://kurfurst.org/Engine/Boostclearances/DB605A_GLmeeting_September1943.html

TLDR me109g engine was only allowed 1.42 ata in the summer 1943. Ok i got this.

But F4 has a diffirent engine right? And it was more developed at the time of Stalingrad and was allowed to use 1.42 for a short period.

But which engine has more power f4 1.42 or g2 1.3?

[Hadji]

In terms of performance the F-4 and G-2 are very similiar (thanx to the boost pressure restriction).

The F-4 turns slightly better than the G-2 but the G-2 does have a slight engine advantage since you won't be flying at WEP for the most part (1200 bhp in the F-4 vs 1300 bhp in the G-2 without WEP). This makes the G-2 a bit better as a "boom-and-zoom" fighter. The G-2 is also more effective at high altitude than the F-4.