What’s the down side to having too light of a flywheel ...
 

assuming that it’s still strong enough? Does the car stall too easily or lose too many revs during shifting? http://www3.telus.net/public/alpine65/confused24.gif

That's about the size of it... The car gets very tricky to launch, can stall relatively easily (e.g., one misfire), and may very well stall while you are shifting... There may be other issues as well.

Most of them are not very relevant until you get to really absurdly light weights, though.

--DD

Hmmn, sounds like the new Carrera GT might suffer from this
"Although we tried our best, the Carrera is extremely hard to get off the line cleanly. The 5.7-liter V-10 engine has about zero inertia. Breathing on the gas pedal sends the revs soaring. Likewise, if you lift off, they plummet. And the engine is all too willing to overpower the rear tires".
Probably fine for a race car, though.

According to Denny, (seems like I have to say this) the excessively lightened flywheel will enhance the difficult idle of an advanced cam as well as the stall problems. These problems occur at fly wheels of less than 12.5#.
L. McC

Is that weight for 914 flywheels? Who's Denny?

Yes and Denny and Jack McNutt are the guys that bought Autocraft Engines when Ray and Bob sold Autocraft in Calif.
L. McC

Ok, thanks. One last question - how much does the stock 2.0L flywheel weigh?

More than 14lbs, judging from other comments. However, it's not the weight of the flywheel that's important nearly so much as where the weight is.

A 12" diameter flywheel that weighs 15lbs and has most of the weight out on the rim will have a far greater effect than a 12" diameter, 15lb flywheel with most of the weight near the hub. Reduce the diameter to 6" (equal weight), and you're way ahead of the game even if the weight is out on the rim.

So, just knowing the raw weight doesn't tell you much. It would be possible to reduce the weight by a very significant amount and have virtually no effect on the rotational inertia of the flywheel at all.

Ok, what is the moment of inertia of the stock 2.0L flywheel?

16#