View Full Version : Bf-109E-4 boost (WEP) activation

12-06-2010, 09:41 PM
Hi guys ! I want to know if the Bf-109E-4 has a boost at all if so how to get it work. I know that the pdf aircraft guide 1946 version state that the plane has a boost 5 max or this a typo error ? Thanks in advance.


12-06-2010, 09:48 PM
No boost on the E4

The E7 has a high altitude boost but you will blow your engine if you engage it to early, from memory you need to be at 5000 metres or so before its safe to engage

12-06-2010, 09:50 PM
The UP E-4's I think show a "start- und notleistung" boost message when you have them at 110% throttle (kind of like how some US fighters say "WEP on" when you're over 100%) but I don't know if that is the same as a boost.

12-06-2010, 09:58 PM
The E-4 does not have a boost that can be switched on by pressing the (default) W-key. All you can do is pushing your lever to 110%.

The E-7/Z however has a high altitude boost (GM-1) besides it 110%. But you can only use it above 6500 metres. If you get lower than that with GM-1 still activated your engine will fail quickly.


12-06-2010, 10:09 PM
Must be an error... in the PDF it says that all of the Emils have boost with a 5 minute maximum but then it fails to mention that the G-6A/S and on have boost (it says no). Ooops!

12-06-2010, 11:10 PM
Well the nitrous (GM1) used on the E7 lasted more like 20 minutes ...

http://kurfurst.org/Performanc...kBetrA_GM1_109G.html (http://kurfurst.org/Performance_tests/109G_GM1_instructions/kBetrA_GM1_109G.html)

... and the water injection (MW50) lasted even longer.

Possibly the "5 minutes" refers to the maximum time allowed at maximum throttle ???

12-07-2010, 01:53 AM
the MW50 in the 109s in game is good for 26minutes use in total.
you can run the whole 26min with 103% power and cooler open as example........

in real in the pilotmanual there was a 5min maximum use in one time. could be use there fore 5 times (minimum) http://forums.ubi.com/groupee_common/emoticons/icon_wink.gif

ingame enginemanagment is only a small shadow of the real world enginemanagement !

and the aircraftmanual pdf is full of mistakes !
"close this book and never open it again" http://forums.ubi.com/groupee_common/emoticons/icon_frown.gif

12-07-2010, 04:20 AM
The thing is that WW2 pilots had to look after their engine's. They couldnt go out, full boost it around for 15 minutes and come back and swap it for another plane like we do.

The 5 min limit on WEP and MW50 is to preserve the engine for a reasonable amount of hours
before total overhaul, I believe.

We can 'wreck' up the engine on every mission and make it back just to replace the plane. Also the 5 min limit was a safety limit, the enigne would have run longer on WEP, but there is no telling how long. probabaly Rolls Royce knew that a new Merlin engine would give up after around 14-15 minutes constant WEP use, and gave the 5 min limit as a maximum for older worn engines.

After all, they couldnt afford for the Merlin or Griffon to pack in while over France.

So Olegs models are probably not as far off as you think. (Not saying they are totally accurate though.)

Too be honest, its one of those htings we are not likely to know for sure as all modern warbirds are flown at a very low boost rating, and certainly not with WEP on. I remember Mark Hanna was the only one who really pushed his aircraft and even he only used +9 max for rare special occassions, and usually a mx of +6 boost. (The SPit he owned is a +18 mk IX I think? (Spitfire mk IX MH434) [EDIT: I got the boost figures slightly wrong, see corrected in post below]

WHo wants to test their vintage RR Merlin of DB601 to destruction after all?

12-07-2010, 05:30 AM
MW50 in game has 28min limit. After that the water methanol tank is empty, and you cant boost the engine anymore without knocking, and at the same damage to engine.

12-07-2010, 06:29 AM
Thanks guys ! Great to know ! I was testing a throttle quadrant profile and notice that the switch I have programed fot the boost was not working at all now I know why. Yeah guess I can't rely on the manual that much. Funny thing cos the more I try to get things going on with the BF-109 the more I learn about how automated some systems are. I wanted to use 2 saitek throttle quadrant but it seems that I will need to fly another fighter to use them both loll. Thanks again

12-07-2010, 06:31 AM
I got it slightly wrong, +4 is what Mark Hanna usually used and +7 in special occassions.

Mark talks about it here discussing with old wartime vets :


12-07-2010, 10:01 PM
I remember coming across a P-47 pilot's testimony about the boost on the R-2800. There was a wire stop on the throttle. A tech said "do not go through this wire unless you absolutely must. The performance will blow you away, but we'll have to replace the engine when you get home". There was a day when he had three 109s on his tail and was in trouble. He put the throttle through the stop, and sure enough, the 47 just walked away from those 109s.

12-08-2010, 10:44 AM
Historically, the 109E had only one type of 'boost' (if we define boost as special power augmentation), that being the use of GM-1 nitrous oxide injection above ca 6-7000m for high altitude performance, on certain subtypes of (designated Bf 109E-7/Z). The F-4/Z had similiar boost, as did certain variants of the G series.

OTOH, the Bf 109E was somewhat special as far as its 'normal' emergency power outputs went. Generally maximum sustainable outputs were softly defined for apprx. 5 minutes (or in cases, 10min) of use in most contries. This had many different names, 110%/Notleistung in Germany, "Combat" in Britain, War Emergency Power in the US and 'forsazh' in the USSR. As Xia' noted, it wasn't set into stone, you could exceed it, but it would wear the engine down.

The DB 601A and 601Aa powered Emils (110C, and some bombers) were a bit of an exception. They too had a 5 minute maximum rating, Kurzleistung (Short Duration Power, later this became called Notleistung, or Emergency Power at 1.30ata (1.35ata for the 601Aa powered ones) at 2400 RPM, as above noted, with 990 (1045 for 601Aa) PS output at SL.

But, it could be increased further to 1.40 ata (1.45ata) for 1100 (1175) PS. This was an 1-minute rating, and in a very strict sense: when the throttle was pushed forward to obtain this 'boost' (really it was just giving more fuel to the engine and increasing oxygen supply accordingly), a clockwork mechanism started which disengaged it automatically after 1 minute. I guess the feature was there originally for bombers taking off with overload (the He 111 P used the same DB engines), so that a forgetful bomber pilot would not destroy an engine after taking off with max output. This is the only case I know of when max output was actually time limited.

12-09-2010, 01:00 AM