enginehistory.org

[jjuutinen]

Someone suggested that the reason for the different comp ration between DB 605 banks was something to do with crankshaft torsional vibration. Is this even feasible, or is it pure BS? The guy said that he has combed through hundreds of DB documents, but none of them has had any reference as to why such scheme was adopted. Thus his suggestion is speculation.

[szielinski]

Torsional vibration (should it ever be that bad to necessitate a change in CR - which I doubt), would seem to suggest that different CR's would be needed from front to back, not left to right banks.

That would be just plain weird.

Personally, the write-up on oil control problems in gallery-fed inverted V-12's in Torque Meter seems 'on the money' to me.
Bear in mind that the 605 never had articulated rods, either.

[jrussell]

The explanation in Torque Meter seems to make sense. I haven't heard anything else that does.For some time in Nascar racing the trend has been to treat the engines as eight single cylinder engines flying in " loose formation". Different compression ratios, camshaft profiles, even different intake port profiles. Honda's RC 211V V-5 engine currently has two pairs of cylinders, each sharing a single exhaust pipe, with the fifth using a single separate pipe. You would think that this would indicate that the cylinder would be tuned differently than the others. However, these are all " state of the art " competition engines, with the resultant expert care and feeding. I agree with Mr. Whitney that for a manufacturer to do this, seems an act of desperation. It's one thing to do this to a race engine, a whole 'nother thing to turn it loose on mechanics with who knows what kind of profiency!