Bf 109G-6/AS powerboost

[greybeard]

I got lost trying to find a reliable answer about the superpower system (if any) of the G-6 equipped with DB 605AS engine. Yet the latter I can not ascertain what kind it was: AS, ASB, ASC, ASM are mentioned. Some sources speak of GM-1 (for some sub-variants), others of MW 50. Wikipedia does not provide any type of superpower system.

I guess the situation at the time was confusing, hence the contradictions in the sources, but I would like to get a better idea about it.

Thank you,
GB

 

[tomo pauk]

GM-1 tank can be installed if MW 50 tank is not installed. IMO GM-1 was seldom used on with AS engines, since AS engines have had big S/C that offered good power at high altitudes.

'AS' should imply that there was no MW-50 boost.
'ASB' - AS engine that has throttle set in accordance to B4 fuel limitations (less boost allowed than with C3 fuel)
'ASC' - AS engine that needs C3 fuel
Neither of those exclude MW 50, but should be able to run without it.
'ASM' - AS engine with all modifications in place to use MW 50, and probably the Bf 109 that uses it has MW 50 system installed.

 

[eagledad]

Greybeard,

According to my sources, the G-6 /AS was either powered by the DB 605 ASB engine, using B4/87 octane fuel, or the DB 605 ASC, using C3/96 Octane fuel with GM-1 power boost. The Bf-109G-6/U2/AS, and Bf-109G-6/R4/AS were fitted with the ASC engine. Three units (III/JG1, 1/JG5, and II / JG11) employed the Bf-109G-6/AS in Defense of the Reich 1n 1944. I have no data on the total number of G-6/AS's built, or how many were equipped with the ASC engine. However, it appears that the Messerschmitt factory at Regensburg delivered 325 G-6/AS's between 1/44 and 12/44.

Eagledad

Sources: Monogram Close-Up 6, by Thomas H. Hitchcock, page 13
Messerschmitt Bf-109F-K by Willy Radinger and Wolfgang Otto, page 45. (production data)

 

[greybeard]

Gentlemen,

thanks for the prompt and kind answers. Especially Eagledad for having been substantiated. I tried to cross his data on the squadrons with those of the site:

The Luftwaffe, 1933-45

finding that only six Bf 109G-6/U2/AS were in service between September and October 1944 (two left on November) with II./JG11, while the presence of the same sub-variant in the other two squadrons is not confirmed.

I also found here:

forum.axishistory.com

that:

"... Bf 109G-6/U2/AS ... used DB-605 ASM, which had ... the MW-50 boost system... Not many were produced to this standard as they were soon replaced by Bf-109G-14/AS and Bf 109G-10"

but he does not report his sources.

 

[Denniss]

AS = basic engine version, ~1425 PS for take-off
ASM = AS with MW50 (required to run at max boost), ~1700 PS
ASB = laterwar version (or rename of ASM), performance similar to DB 605DB, requires B4+MW50 or C3 without MW50, ~1800PS?
ASC = laterwar version, performance similar to DB 605DC, ASB with higher boost, requires C3+MW50, ~2000PS ?

There may have been some special ops G-6/AS with GM-1 boost, I remember reading something about usage for Mosquito hunting (albeit not successful)

 

[Spielmann]

Hello,
It's very difficult to answer this question because engines foreseen with MW 50 could use B4 fuel but with limitations particularly in not using emergency power.
And more, GM-1 device could be modified to use MW 50...
Official production of Bf 109 G-6/AS is as follows (to 30 July 1944). Then production turned over to G-14 and G-14/AS.
Mtt-AG : 226 brandt new G-6/AS (the only ones produced by Mtt-AG. All others are modifications of G-5 and G-6) :
Erla-Leipzig : 76 G-5/AS with B4 fuel
100 G-5/R2/AS (Recce version with MW 50 on modified GM-1 device)
11 G-6/AS (B4 fuel)
118 G-6/U2/AS with GM-1 (U2 = GM-1)
1 G-6/U4/AS (B4 or C3 fuel not known) with axial MK 108)
Mimetall : 39 G-6/U2/AS with GM-1
130 G-6/U4/AS (B4 or C3 fuel not known) with axial MK 108)
Blohm und Voss : 80 G-6/U2/AS with GM-1
20 G-6/U4/AS (B4 or C3 fuel not known) with axial MK 108)

Before January 1945, there were only DB 605 AS (B4 fuel with or without GM-1) or DB 605 ASM (C3 fuel with MW 50)
From January 1945 onwards, DB 606 ASB/ASC (equivalent to DB 605 DB/DC) were for Bf 109 G-14/AS or planes repaired by the Reparatur-Industrie.
DB 605 DB = B4 fuel ; DB 605 DC = C3 fuel.

Spielmann

 

[greybeard]

Thanks for all info.

And more, GM-1 device could be modified to use MW 50...

I think this is a key point. Since a device raising rated altitude about of 2500 m (going on memory) on a fighter already rated at 8400 m seemingly makes no sense (what should do a Bf 109 around 11000 m?), I'm prone to think they replaced GM-1 with MW 50. There were many G-5/U2 and G-6/U2; it looks like they put AS engine on a frame containing U2 device and then modified this latter to be MW 50, leaving original Umrust code. But this is only my fantasy: evidence would be needed.

Mtt-AG : 226 brandt new G-6/AS (the only ones produced by Mtt-AG. All others are modifications of G-5 and G-6)

This makes me think that actually they could have done what supposed above.

So a total of 625 G-6/AS were built (237 of which with U2 device) and only 176 G-5/AS (100 of which with powerboost).

100 G-5/R2/AS (Recce version with MW 50 on modified GM-1 device)

BTW, what do you mean with "modified GM-1 device"?

DB 606 ASB/ASC (equivalent to DB 605 DB/DC)

I guess 606 is a typo... About AS and D engines relationship, in the early mentioned forum I read also:

"DB-605 AS, AM and ASM were adopted because DB-605 DB and DC were not ready yet for service in spring 1944. AM and ASM were somewhat troublesome engines, because they were not designed to operate at these high boost levels. They were replaced with DB-605 ASB and ASC, which adopted most modifications made for DB-605 DB and DC (B versions used the lower octane fuel B-4, C versions used higher octane C-3 fuel). DB-605 ASB and ASC were kept in production in parallel with DB and DC versions, in order to increase production. "

I would just recall that AS and D differed substantially for compression ratio (7.3/7.5 for AS and 8.3/8.5 for D).

 

[Denniss]

Mtt AG did produce 325 G-6/AS as new aircraft, not 226
The Erla AS conversion were (mostly) done at Antwerp until the fac was captured by allies
ASM was B4 + MW50 OR just C-3, for 1800PS you won't need C-3 + MW50. Just like the DB605AM it may have been used after initial introduction but testing proved it could be safely run with B4+MW50 providing the MW50 does not run out while on max boost.

 

[P-39 Expert]

Thanks for all info.



I think this is a key point. Since a device raising rated altitude about of 2500 m (going on memory) on a fighter already rated at 8400 m seemingly makes no sense (what should do a Bf 109 around 11000 m?), I'm prone to think they replaced GM-1 with MW 50. There were many G-5/U2 and G-6/U2; it looks like they put AS engine on a frame containing U2 device and then modified this latter to be MW 50, leaving original Umrust code. But this is only my fantasy: evidence would be needed.



This makes me think that actually they could have done what supposed above.

So a total of 625 G-6/AS were built (237 of which with U2 device) and only 176 G-5/AS (100 of which with powerboost).



BTW, what do you mean with "modified GM-1 device"?



I guess 606 is a typo... About AS and D engines relationship, in the early mentioned forum I read also:

"DB-605 AS, AM and ASM were adopted because DB-605 DB and DC were not ready yet for service in spring 1944. AM and ASM were somewhat troublesome engines, because they were not designed to operate at these high boost levels. They were replaced with DB-605 ASB and ASC, which adopted most modifications made for DB-605 DB and DC (B versions used the lower octane fuel B-4, C versions used higher octane C-3 fuel). DB-605 ASB and ASC were kept in production in parallel with DB and DC versions, in order to increase production. "

I would just recall that AS and D differed substantially for compression ratio (7.3/7.5 for AS and 8.3/8.5 for D).

Wonder why only 625 were built? Seems like a worthwhile power increase.

 

[Denniss]

replaced by G-14/AS (G-6/AS with MW-50), G-10 (same airframe but DB605D engine) and K-4 (different airframe + DB605D)

 

[greybeard]

ASM was B4 + MW50 OR just C-3, for 1800PS you won't need C-3 + MW50.

Indeed, this looks to be common opinion, reported on English sources. But would be curious to have exact translation of what follows:

"Das Triebwerk Daimler Benz DB 605 ASM entsprach dem Ausgangmuster DB 605 AS, wurde jedoch im Gegensatz zu diesem Verbesserung der Start-
und Notleistung mit dem Sonderkraftstoff C 3 und zusätzlicher Wasser Methanol-Einspritzung geflogen (MW 50)."

picked from this document. Since it seems to state that DB 605 ASM did have same output pattern of DB 605 AS but take-off and emergency power, got with the help of C-3 and MW-50.

 

[Denniss]

So was the DB605AM which was later declared safe to use with B4+MW50.
Common to both types on B4 use: if MW50 runs out while still using emergency boost it would kill the engine, C3 would have prevented this but it was in high demand by Fw 190 units

 

[greybeard]

A German friend kindly gave me exact translation of what reported at reply #11:

"The powerplant Daimler Benz DB 605 ASM was equivalent* to the basic type DB 605 AS; however, to improve take-off and emergency power it was, contrary to the latter, operated using the special fuel C 3 and additional water-methanol injection."

*"entsprach" is less than "was identical to", and much more than "was analog to" [Translator's Note]

All in, personally I would conclude that:

1). Bf 109G-6/AS was powered either by DB 605 AS (more common) or DB 605 ASM. This latter was coupled always with the use use of C3 fuel and MW50 powerboost.

2). DB 605 ASB and ASC are probably historical distortions diffused only on Allied sources. The ASC, though, was never coupled with GM-1; this news derives from use of naming Bf 109G-6/U2/AS to indicate what was actually an MW50 powerboosted engine.

 

[Denniss]

Transition from G-6 to G-14 was some kind of fluid so you may find G-6 with AM/ASM engine which later became G-14s
I vaguely remember of reading in some book that the plumbing for GM1 in the /U2 modification was also usable for MW50, just another tank was required thus several /U2 a/c were later modified to MW50 birds

 

[kettbo]

see my thread from 1 MAR 2019 "GUSTAV question" for some add details on what one can do with that system.