entire article here
http://www.edmunds.com/insideline/do...ticleId=121767. talks about the new M3 a M3 CLS and the M division
How do you decide which engine to develop for each car?
We're looking for the best performance for the type of car. For the M5 and M6 we use a V10, and for the M3 we use a V8.
If you only develop one engine for all your cars, then you cannot have the perfect car. If the engine in the smaller car is too big, you will not have the right harmony.