In Reply to: Unfortunately does not apply to M3 or 325 (more) posted by Rich M3 on September 15, 2000 at 11:42:27:
This article is generally about lightening a stock flywheel, which cannot be done on the late model BMW 6 cylinders. There is just not enough material at the perimeter that can be removed. the article is exactly correct regarding mass and inertia, and where a flywheel should be lightened however.
The big issue with light flywheels on an M3 is that the flywheel IS the "harmonic balancer". When you remove the harmonic balancer from any motor, bad vibration things happen, and the BMW motor breaks cranks. ( as do Ford 5.0, Nissan 240z, Nissan Ka 22, etc). When you substitute an aluminum flywheel on a BMW, the weight is not exactly the issue, but rather the damping that the weight does. Several engine builders use lightened STEEL flywheels with no dual mass features and the cranks don't break then, but I think its just a little bit of luck actually. In the final analysis, especially considering the driveline damping that the stock dual mass flywheel also helps with, I like the pulleys. I have had pulleys on MANY cars, street and race, and have never felt as much of a difference as on the M3. I haven't figured out why. Signed, Rich M3