actually thats a good question i would like to know that as well ^

 

Somewhere I made a long post on how a lighter flywheel increases angular acceleration and therefore HP. Only problem is bogging off the line as others have said. Other than that performance is much better...

 

Well... I though I might put in my 2 cents.

I had 4.3 gears and a light 12.5 flywheel a few years back... Drag racing it sucked...I could not 60 ft consistantly. I put the stock one back in and settled with that. I'm still running a sequential turbo system.

But if you're running non-seq.. I think it might suit your needs better. Less lag I guess. But I think for drag racing the 4.3 gear set might be a better buy.

Autocross and road course would benefit from the lighter flywheel... the car just feels more tossable into tight corners.

 

Drag racing no, road racing yes, it is that simple

 

my 9.5lb flywheel made a real noticeable difference. pain in the *** to install it but well worth the $450

 

Here's my page with some analysis on the effects:
http://www.maxcooper.com/rx7/parts_i...eel/index.html

The estimates are not perfect, but I think they are in the ballpark.

-Max

 

Just remember that a lightweight flywheel is tougher on a stock engine at higher rpms, since the stock rotating assembly is balanced based on the weight of the factory crank pulley and flywheel, as well as the internals.

 

This isn't true, here's why:

BALANCE
-----------
The stock flywheel is counterweighted. When you install a light flywheel, you use the separate counterweight that is normally bolted to the flex plate on auto-tranny cars. As long as you use the right counterweight, the balance will be just like it was with the stock flywheel.

Also, the front pulley is not counterweighted on these cars. There is actually a separate counterweight inside the front cover. The pulley is not counter-weighted.

DAMPING
-----------
Some engines can be damaged if you use a lighter pulley (and presumably a lighter flywheel). The mass of the pulley and flywheel damp harmonic vibrations. If you go too light, you end up under-damping the vibrations and you can snap, bend, or twist the crankshaft. This is a separate issue from balance. Typically this is only an issue on engines with long crankshafts like I6s. I believe the reports for the engines they warn users about, but these warnings are not applicable to the 13B rotary. It has a short, thick main shaft with only two slightly-eccentric journals. The 13B does not depend on heavy front pulleys or flywheels to damp harmonic vibrations.

CONCLUSION
----------------
Installing a light flywheel will not hurt your 13B.

-Max

 

I don't think so.

If anything, a light flywheel will be easier on the engine because there is less drag (mass) for it to move. The counterweight takes care of any balance issues.