Knegel,
"In the JaPo book on the Bf109K (p.81), Janda and Poruba mention the differences between the DB605DB and DC as being dependent not on fuel compatibility, but on maximum boost pressure. The maximum manifold pressure figures quoted are as follows:
- DB605DB: 1.80 ata at 2,800 r.p.m., giving 1,850 h.p. (no performance difference noted between B4 and C3 fuel usage)
- DB605DC: (with MW50) 1.98 ata at 2,800 r.p.m., giving 2,000 h.p
(without MW50) 1.80 ata at 2,800 r.p.m., giving 1,850 h.p
However, J.C. Mermet (p. 14, 15) quotes an official Daimler-Benz factory manual dated 5 December 1944 concerning the different designations. The B designation indicated the engine was capable of using 87 octane B4 fuel WITH MW50, or 96 octane C3 fuel WITHOUT MW50 whereas the C designation indicated the use of 96 octane C3 fuel WITH MW50.
Interestingly, the engine could be converted from a B to a C model and back again by the simple expedient of adjusting a screw valve which regulated the flow of MW50 to the engine. This would seem to be the more proper explanation, especially given the chaotic fuel situation in the Reich from 1944 onwards. It can also be seen how the different fuel configurations would account for the maximum permissible boost ratings as noted by Janda and Poruba. There is still discussion on this point, however, and further documentation may yet refine this point.
The maximum power figures between the two sources do agree, although Mermet points out that the 1.98 ata figure of the C motor was attainable only with MW50 at 110% emergency power, and operation of the B motor without MW50 would be limited to a maximum manifold pressure of 1.45 ata, and 100% power was not available anywhere within the flight regime (Note: these restrictions did not apply if MW50 was used with the B motor)"
http://109lair.hobbyvista.com/techref/systems/engine/as_vs_d/as_vs_d.htmhttp://109lair.hobbyvista.com/index1024.htmI don't see this combination mentioned > '605DB 1.98 + C3 + MW50 = 2000HP'