I was talkin with some of my Subaru friends and the subject of flywheels came up, eventually one guy was saying how its better for rx7 to have heavier flywheels (he was talking about for drifting purposes) for the reason of mainting high rpms/torque...my understanding is the heavier mass flywheel doesnt slow down as easily, so your rpms dont drop as fast when u get of the gas...I never took physics so thats the best i can explain my thinking...

anyways I was wonding if this same school of thought should be applied to buildign an autoX car? I surely dont plan of drifting, and im not one for drag racing where a super light fly wheel woudl be common sense.....but thats my question?

 

The tradeoff is energy stored in the flywheel vs time needed to change it's speed.

A very light flywheel will behave like a Formula 1 car: Spastic revving, but basically no power stored in it - if you drop the clutch at high RPM, you'll probably bog it down.

A very heavy flywheel stores a lot of energy, but takes a long time to rev. Think heavy diesel engine. For drag racing or drifting, this would probably be beneficial, because you can drop the clutch hard and the flywheel will dump massive amounts of energy into the rear wheels, providing a nice launch or enough energy to kick the rear end free.

For autocross, you'll probably want to go with lighter, but check the rules - changing flywheel weights may put you in a significantly different class.

-=Russ=-

 

You will thank yourself later for a lightened flywheel. If you get a lightened steel you will probably wish you got an aluminum one later . I got an aluminum flywheel in my car, let a few friends drive it, and inside a few months they both had lightened flywheels as well.

As a sidenote, if you aren't interested in drifting, take everything the drifting guys say with a grain of salt. It's a completely different form of driving and alot of stuff is done/tuned differently, especially by the DIY guys who want to turn their DD's into drift machines. If you went to a track day with one of them you'd eat them for lunch in lap times.

 

cool thnx for the advice

 

In autocross, you're not worrying all so much about the launches, more about rev matching, heal-toe, and etc, so lighter proves better. I love the 12.5lb steelies

 

I run a 12 lb Steel Flywheel from a 12a in mine and I will never go back to a factory flywheel in the car. It makes it a much more difficult car to drive on the street but you become used to it. I also have a Copper Clutch instead of an organic or such clutch.

It is certainly not legal for stock class and I don't recall if it is legal for SP or STS2.

 

I hardly ever shift out of 2nd in auto-x (except for the launch, of course).

I'd say go with light, but check the rules first.

 

I do all the time, some sections are way too tight to try to bog 2nd coming out of the corners, and considering most places I run are airport runways, it's not uncommon to be well into 3rd gear on a straight.