Did the BMW 801D burn B4 or C3?

[Broncazonk]

Also, what fuel went into the following engines: DB 605D, Jumo 213A and DB 603A?

I apologize for these basic questions, but the issue has me confused, and my books are making it worse.

Thanks,

Bronc

[Broncazonk]

Did the BMW 801D burn B4 or C3? Answer: The BMW 801 D-2 series engines became operational in early 1942, and ran on C2/C3 100 octane fuel instead of the A/B/C/L's B4 87 octane, boosting takeoff power to 1,700 PS (1,677 hp, 1,250 kW).

DB 605D? Answer: B4 or C3, depending on the version of the engine, however, the vast majority of operationally deployed 605D engines burned B4.

Jumo 213A? Answer: B4

DB 603A? B4

Bronc

[Leo Etgen]

Hi Bronc

I believe that you are correct. Regarding the BMW 801 D-2, it did use C3 fuel and Motorleistung (pure engine power) at take-off was 1,800 PS. However, the engine was equipped with a cooling fan which necessitated 70 PS to run therefore Triebwerksleistung (power arriving at prop) at take-off was 1,730 PS. I hope this helps.

Horrido!

Leo

[Broncazonk]

DB 601 --> DB 605 engines were designed to run on B4 from the very beginning. Any DB 605 that didn't run on B4 was a developmental, prototype engine. The DB 603A was also designed to run on B4 from the beginning. Similarly, the Jumo 211 --> Jumo 213A were designed for B4 from the very beginning.

The DB 601 (from which the 605 and 603 were developed) and the Jumo 211 (from which the 213A was developed) were unrushed, pre-war developments. Why did the both companies choose 87 octane B4 for their inline engines instead of 100 octane C3?

The DB 601E for the Bf-109 F-3 and F-4 achieved 1,350 PS (1,332 HP) running on B4 with a dry weight of 590 kg (1,320 lb). What would the power output have been running on C3? (The DB 605A barely achieved 1475 PS running on B4 with a dry weight of 756 kg (1,667 lb)!!

Bronc

[ChrisMAg2]

Originally Posted by Broncazonk

... What would the power output have been running on C3? ...

That just didn't happen. German engines were designed to run on a specific grade of fuel, and to get the most of what was available and nobody would feed the engines anything else. The effort to do that would be so big, and the gain so little, that it just didn't make sense to do it. So even thinking "what if" is pointless.
Besides higher graded fuels where low on stocks, as only a rather small number of engines even demanded it.

[Kutscha]

By turning a screw, the DB605D could run either B4 or C3 fuel.

C3 couldn't have been that low in stock or late war Fw190A, F and Gs would have been sitting on the ground.

[Broncazonk]

Originally Posted by Kutscha

C3 couldn't have been that low in stock or late war Fw190A, F and Gs would have been sitting on the ground.

That's exactly what I've been thinking.

Here is the bottom line question: Did the Luftwaffe leave a lot of performance sitting on the drawing board by not insisting that their inline, water-cooled engines run on C3?

Examples: The Jumo 213A (the major production version that ran on B4 / 87 octane) put out 1,750 PS on take-off. The Jumo 213B (a 213A that ran on C3 fuel / 100 octane) put out 2,000 PS on take-off. The DB 603A (the major production version that ran on B4) put out 1,750 PS on take-off. On the other hand, the DB 603N (a prototype with a two-stage supercharger that ran on C3) put out 2,800 PS on take-off. <--That's not a typo.

Bronc

[ChrisMAg2]

Originally Posted by Kutscha

By turning a screw, the DB605D could run either B4 or C3 fuel.

C3 couldn't have been that low in stock or late war Fw190A, F and Gs would have been sitting on the ground.

This should be clarified:

As early as 1942 Daimler had also been working on an upgraded D-series engine that could run on either B4 or C3 fuel. The first of these, which appeared in late 1944, were a small series of DB 605DM, followed by the main production series, the DB 605DB/DC.[3] These engines were fitted with an adjustable screw stop which allowed the use of either B4 fuel with MW-50, or C-3 fuel without MW-50, in which case the engine was designated DB 605DB, or the use of C-3 fuel with MW-50, in which case the engine was given the -DC suffix instead.[3] In its DB-suffix form the engine generated 1,800 PS (1,775 hp) for take-off at 1.8 ata, while the DC was capable of 2,000 PS (1,973 hp) at 1.98 ata.[4] If MW-50 was not available for use with the B4 fuel the throttle was limited to 1.45 ata for the entire flight. Thus, this series was ideally suited to catering for the chaotic fuel supply situation prevalent during the last months of the Third Reich.[5] These engines were mainly used in the Bf 109G-10 and K-4 series.
Source:http://en.wikipedia.org/wiki/Daimler-Benz_DB_605

Because this means,
1. that not so many DB605DB/DC (able of selecting their fuel) were actually in use and demand for C-3 fuel. Even the DB605ASC(M) that only ran on C-3 was not that numerously around.
2. that you could and would not just switch to a higher class fuel, just because somebody wanted to do so. A lot was necessary to be done, if a switch to higher graded fuel was wanted to be done. Much more just turn a switch or press a button.

Regarding the BMW801D-2: Later in the war the fuel shortage for all fuels also grounded the planes using a BMW801D-2 at one or another time. And the improvement of the BMW801D-2 compared to the BMW801A/C/L is not (only) because of the use of C-3 fuel, but mainly because of changes in the design. The use of C-3 fuel is only one part of the change.

In the end, a simple switching to a higher graded fuel for higher performance on production engines was still just not done. Acc to an allied report, German aero engines were not designed to just improve performance by switching to a higher graded fuel.