05.04.2009, 03:10
Here's my greatly simplified and admitedly speculative version of the 605 engine story (although assuredly it is well grounded).
The 605D was under development by the time the 605A was being fitted to the 109G as a high performance variation designed to use C2/C3 fuel and also improve altitude performance.
Development became protracted until late 1944 before it finally entered mass production in the DB and DC variants, able to use either B4 or C3 fuel. The D and D-2 were in limited production only, for development purposes.
In the meantime a stop gap was needed to improve 109G performance during early 44.
MW50 was added and the 605A was adapted for C3 fuel, but this caused serious serviceability and reliability issues.
Separately and immediately prior to this, of primary concern was the Allied bombing campaign and high altitude interceptors were needed. The D series was not yet ready for mass production and the 603 engine supercharger casing was hastily adapted to the 605A to produce the AS.
The AM describes the adaptation of 605A to use C3 fuel with a sondernotleistung setting encorporating MW50 injection. From February 1944 this engine began appearing in service as a retroactive modification to G-6 models currently in service (cited).
Soon following this the AS motor was also adapted for MW50/C3 receiving the ASM designation. Fewer of these appeared in the G-6/AS as it was not a common practise until the G-14/AS was being produced (ie. mid44).
DM is a superfluous postwar designation for the 605D development motor (limited production from 1942) as it was already equipped for C2/3 fuel usage and thus is a retroactive term only to describe MW50 fitment, which was done during 109K development. There is no Daimler document for a DM motor (my reference here is Mercedes Benz AG archival documents, please share any you have suggesting otherwise as I'd be interested to see them).
Finally the DB and DC motors, with new D series internal machinery and new D series superchargers became available late in 1944. This was wonderful but by this time it had been found by accident the 603 supercharger had performed superbly when fitted to the 605A, problems with the MW50 fitments aside.
Since the D series has a rated altitude falling between 5.5-6.5km (5.2-5.8 for the 605A) and the 605AS has a rated altitude between 6.7-8km it was decided to fit the 603/AS supercharger on the DB/DC motor during 1945. This returned a rated altitude between 6-7km with a lower fuel consumption and engine speed during cruise (both of which reflected its AS heritage in supercharger fitment) and became the best overall engine of the 605 series in either B4 (ASB) version or C3 (ASC) version.
This other business about restrictions on the DC and ASC motors I do not challenge, haven't read anything about it but sure that's entirely possible. But doesn't detract from mechanical engineering.
The 605D was under development by the time the 605A was being fitted to the 109G as a high performance variation designed to use C2/C3 fuel and also improve altitude performance.
Development became protracted until late 1944 before it finally entered mass production in the DB and DC variants, able to use either B4 or C3 fuel. The D and D-2 were in limited production only, for development purposes.
In the meantime a stop gap was needed to improve 109G performance during early 44.
MW50 was added and the 605A was adapted for C3 fuel, but this caused serious serviceability and reliability issues.
Separately and immediately prior to this, of primary concern was the Allied bombing campaign and high altitude interceptors were needed. The D series was not yet ready for mass production and the 603 engine supercharger casing was hastily adapted to the 605A to produce the AS.
The AM describes the adaptation of 605A to use C3 fuel with a sondernotleistung setting encorporating MW50 injection. From February 1944 this engine began appearing in service as a retroactive modification to G-6 models currently in service (cited).
Soon following this the AS motor was also adapted for MW50/C3 receiving the ASM designation. Fewer of these appeared in the G-6/AS as it was not a common practise until the G-14/AS was being produced (ie. mid44).
DM is a superfluous postwar designation for the 605D development motor (limited production from 1942) as it was already equipped for C2/3 fuel usage and thus is a retroactive term only to describe MW50 fitment, which was done during 109K development. There is no Daimler document for a DM motor (my reference here is Mercedes Benz AG archival documents, please share any you have suggesting otherwise as I'd be interested to see them).
Finally the DB and DC motors, with new D series internal machinery and new D series superchargers became available late in 1944. This was wonderful but by this time it had been found by accident the 603 supercharger had performed superbly when fitted to the 605A, problems with the MW50 fitments aside.
Since the D series has a rated altitude falling between 5.5-6.5km (5.2-5.8 for the 605A) and the 605AS has a rated altitude between 6.7-8km it was decided to fit the 603/AS supercharger on the DB/DC motor during 1945. This returned a rated altitude between 6-7km with a lower fuel consumption and engine speed during cruise (both of which reflected its AS heritage in supercharger fitment) and became the best overall engine of the 605 series in either B4 (ASB) version or C3 (ASC) version.
This other business about restrictions on the DC and ASC motors I do not challenge, haven't read anything about it but sure that's entirely possible. But doesn't detract from mechanical engineering.