I was wondering if there are any difficulties in getting a stock flywheel machined down a bit to get some weight savings? I'm primarily worried about damaging the balance of the motor, since the flywheel is balanced to the counterweights.

Any thoughts?

 

When you get a flywheel resurfaced, they usually grind down the grooves that stick out for a closer contact and initial grab point. I don't think that would be much weight savings though. As for grinding down any other part of it, the balance will probably get thrown off.

 

i am thinking of doing that too
my friend told me that would work well on honda
but don't know on rx7

 

ive heard of ppl grinding down the backside of a flywheel to lighten it on a brake lathe

 

i would like to hear about this as well..

 

What would it take? Probably a PHD in mathematics and a Masters in Dynamics, plus the machining experience.

It works on a Honda because the engine is internally balanced. Ours are externally balanced, and even a lightweight flywheel needs a counterweight to maintain it.

Frankly, I think buying a lightweight flywheel is a cheaper option than replacing an engine that ate it's bearings because the flywheel was lightened improperly.

 

for the most part true. the ppl that ive heard of doing this is mostly on round track cars(ford 2.3)which is internally balanced. in order to do it in your own shop at home on a rotary you would have to carefully weigh it and find the correct counterweight

 

 

The problem with the stock flywheel is the counterweight is integral to the flywheel....and its on the outer edge,the place where weight is traditionally removed due to the larger effect it has on rotating mass.
If you lathe the flywheel anywhere near the edge,youll be removing part of the counterweight "lump" which will make the rear counterweight lighter than the front and throw the whole balance off.If you machine in the center or middle of the flywheel,youll avoid taking off any of the counterweight,but it wont have nearly as much affect on rotating mass,and you run the risk of violating the flywheel's structural integrity.

 

seems like buying one from cp racing or racing beat is the only way

 

they're expensive though... anyone know a place to get 'em cheaps? how about someone setting up a group buy?

 

hmmmm. I may know someone.

 

i am definately intersted for a group buy

 

Depending on the final cost, I'm interested as well.