[eschaider]

Scott is describing the angular moment of inertia when he speaks to the mass moment for a rotating component. Everything he is saying is spot on.

The simple story is if you drag race with 500 to 600 horsepower, a heavy flywheel will improve your 60 ft times, assuming you can get a hold of the ground. If you do the light flywheel you will never catch him.

If you road race the smallest moment of inertia on the flywheel clutch assembly will be your friend. Read that as 7.5" or 5.5" clutch and a button flywheel. A heavy flywheel on a road race car brings nothing to the table but tears.

A road race application can get away with tiny moments inertia because the clutch doesn't not need to provide a drag race style 60 foot launch and can therefore be smaller and lighter. Once the car is underway the actual vehicle weight is effectively the flywheel for the car.

The cars we drive on city roads are neither being drag raced nor road raced (most of the time) so we want a clutch flywheel assembly heavy enough to smooth out the low speed power pulses from our 60's rock-n-roll style idles as we drive through town. That magic number is somewhere between 20 and 30 lbs.

Going light will make the car feel sluggish and non responsive and you will do more clutch slipping to get the car underway. Going above 30 lbs will make the car feel not as fast as it original was when you bought it, because you will get acclimated to the acceleration a bit more easily — it will feel more predictable. The light flywheel will actually allow the car to accelerate a whisker faster under acceleration but in a start to finish contest on the street will not likely produce the win you are expecting.

A 20 to 30 lb solution will put you closer to the optimum street combination than either of the two extremes.


Ed