Yeah, Demon, I thought about this some more after I posted and realised a bit more of what you are saying. I was considering acceleration of the engine and not really of the car. So yes, since the engine is spinning at say 2000 rpm before you launch a heavier flywheel will transmit more stored energy to the wheels than a lighter one, however once the car is accelerating proportionally to the engine speed a lighter flywheel will allow it to accelerate at a faster rate.
