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mark houghton mark houghton is offline
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Join Date: Jul 2008
Location: Central Washington State
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There have been several discussions posted on this topic, here as well as on Rennlist. Probably just as many differing opinions as well. But I think the general consensus is that the 930 has a heavy flywheel by design, to accommodate the turbo's inherent lag and the engine's relatively low compression ratio.

Yes, a lighter flywheel will allow quicker revs to build and probably would be more appreciated on a normally aspirated engine. But the 930 needs some time for the boost to build in tandem with the rpm's, so the benefit you may get with a lighter flywheel won't necessarily be in the form of faster power delivery. The proper amount of boost needs to be available when the rpm's reach their optimum power band. I suppose a person could play with different turbos with quicker spool-up to keep pace with the rpm's, but might sacrifice top end power in the long run. Also, the heavier flywheel is there to provide rotational mass, to keep things going (torque) when starting out (helps with the lower CR).

Hard to explain (I've surely butchered it) but Stephen at IA has commented on this in the past...perhaps he's listening today?
Old 12-02-2008, 05:16 PM
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