In Reply to: Engine Question posted by Rohith on October 24, 1999 at 18:30:03:
V-6s offer great packaging for today's "cab-forward" designs. They are especially well suited for front wheel drive cars. Most importantly, V-6s are often derived fron V-8s. American manufacturers often do this.
A flat six, as used by Porsche, offers a lower center of gravity. It is essentially a V-6 with 180 degrees between the cylinder banks. They offer great smoothness. This engine layout also allows for lower bodywork, although the bodywork must also be wider to accomdate the engine -- a trade off. Flat sixes are not suited very well for front-wheel drive cars (transversely mounted engines). They are just too darn wide.
The I-6 is one of the "smoothest" engine designs. The layout of the engine naturally counteracts all vibration. For some reason though, the 4.0 L straight six used in the Jeep Grand Cherokee is far from smooth. Leave it to Daimler-Chrysler to screw up an essentially smooth engine.
In addition to smoothness, I-6s, as a rule of thumb, are often torqueir than an equal sized flat- or V-6. Additionally, they allow for easy packaging in the long, narrow hood of cars like the Z3.
BMW goes so far as to counter-wieght the camshaft lobes! They want to make sure that the essentially smooth I-6 stays smooth!
Hopefully this answers your question.