effect of lightweight flywheel on launches
 

A previous owner installed a lightweight steel flywheel on my car (Racing Beat, 17lbs). The stock flywheel is 28lbs so that's about a 40% decrease in mass vs stock. I'm most likely going back to a stock-style one before I get to the strip. Does anyone have any input on this or firsthand experience on how going back to a stock style flywheel will affect the launch?

After years of having a lightweight flywheel on two different Rx-7's I am getting tired of it on the street as well, especially coming off a light. I'm tired of the revs dropping so fast. I am pretty much set on ditching this lightweight flywheel because it annoys me on the street. I'm just wondering if this will make launching the car a little easier. I very rarely launch this car right now and I still need to switch to a competition diff mount (stock one is not broken).

My clutch is an ACT sprung 6 puck with heavy duty disc. Car is a T2 with a street ported engine, T04R turbo at about 16psi on straight 93 octane.

yeah I had the same problem with the exact same racing beat flywheel.. 17lbs. it sucked.. falls out of boost between gears,, launch is shit...would bog during a 2nd gear power shift after a hard launch,, put the stock back in and all my problems went away.. lightweight flywheels are great for NA cars not turbo cars... heavier flywheels more inertia or momentum equals better launching/ keeping car in boost between gear changes..

I had a similiar setup too with a GT35R at the time.. So yes it will launch way better with the stocker..

For an NA car lightier would help the launch

I agree 100% as I had the same results on a 10lb pettit flywheel. Car is so much nicer to drive/race with the stocker back in.

But unfortunatly the heavier flywheel is going to put more stress and abuse on the drivetrain and you will break more parts on the launch than you would with the lighter flywheel. NA or turbo

hey steve this eric your are right i have been using the stock flywheel and my motor is tearing up rear stationery gears but i think if i try to use the light one the car will not launch

know way in tittie hell would i trust a stock flywheel as well, i wouldn't want it to come through the floor on a big launch, IMOP stock flywheels don't belong behind High Hp engines . Its a trade of you get when you chase numbers with rotaries i suppose.
But there is a point when its too light in certain situations, but you just gotta pick your style of driving and get something to suit i suppose

There are other options for heavier aftermarket flywheels. I think McLeod engineering (or something along those lines) makes a heavy Tilton/QM clutch pattern for the 13B counterweight. When I bought my Quartermaster flywheel off 13B-RX3 I think he was switching to it.

agree though on a correctly built after market item , i just cant see a stock flywheel going into any car i have decent power and revs coming out of any time soon ;)

Stock flywheels aren't legal on a car running 11.49 or quicker in NHRA anyways, so they would be out regardless

I think the best rule of thumb is to use the lightest flywheel you can and still maintain a good launch. This can be done with gearing, more torque, etc. Once your off the line the lighter flywheel will always outperform a heavier one.

Has anyone used 4.30 gears with a lightweight flywheel? How does it compare to a lightweight flywheel and 4.10 gears? Track/street

The only problem is thats where rotaries really shine is on the starting line. For drag racing 99% of the time a heavy flywheel will do better overall.

Does anyone have any evidence that the stock flywheel is dangerous or causes reliability problems at high horsepower levels? With this 17lb steel flywheel and 6 puck clutch you really have to tach the engine way up to keep it from bogging off the line. That in itself has to be abusive. I am inclined to give an OEM part the benefit of the doubt. I'm not trying to do pass after pass of abusive hard launches. I'm trying to make the car more streetable above all. I don't take it over 8500 rpm and usually it's under 8000.

Maybe I posted in the wrong section. I don't really care about NHRA rules and I have zero plans to competitively drag race this car.

IMO you should have a scatter shield of some sort on the thing regardless of your inclination to follow rules or what flywheel you run. With that investment you will have a lot less to worry about. FWIW, I did have a ring gear detach itself from a stock flywheel on my road race car. Fortunately I found out only when I tried to restart it and the starter wouldn't engage. Could of been very bad without a scatter shield.

It doesn't matter what flywheel you're using, you should be using a scattershield on anything that you plan to rev past 8k rpms'. The OEM flywheel is solid steel so I don't see how it could fail. Maybe if the e shaft broke or the e shaft nut came loose. 99% of failures come from clutch assy's.

o ive seen accouple of them fail and it was ugly.

The point is they generally make rules in retrospect, and in order to eliminate future potential risks. What you do with your car is your business.

I don't have any verifiable evidence, but the stories I've heard about people losing legs, feet, their lives, are all enough to dissuade me from doing it, and I'll definitely be using a scattershield when I get mine on the track.

youtube mazda flywheel explosion heaps of good ones
http://www.youtube.com/watch?v=L2pz1PkhAo8

is the scatter shield a custom piece?

Usually. There was someone in PR that was selling them to fit stock trans, but not sure who.

I was just reading a thread about it, Ari and Dan Schecter just used 1/4" steel plate bent to shape, attached to the bellhousing by tabs.

0% chance I will run a scattershield. I am not competitively drag racing this car. Factory s5 n/a and Rx-8 flywheels seem to handle 8500 rpm just fine.

thats cool i wouldn't run one in your situation as well mate, i think the thread has gone off on a tangent from your original question anyway :)

also i dunno what the rules are for you guys in the states but a scatter sheild in aust must be bolted to the chassis , not the bellhousing , we have the choice of a 6mm steel bellhousing or a sfi rated one, or a 6mm complete encompassing scatter shield that extends 1 inch past the gearbox bellhousing flywheel area but must not be bolted to the engine or gearbox :nod:

I tested the stock flywheel vs a 17# RB flywheel a few years ago. The car wouldn't launch well with the RB flywheel. I managed 1.7x 60 ft times with the RB wheel and low 1.5 60 ft times with the stock one. I tested the RB wheel first and the stock one the following week at the same track in the same conditions.

How did the car run after the launch? Also, if you had a lower gear ratio in the rearend/trans. for first gear you would get a better launch from the lighter flywheel and then run quicker down the rest of the 1/4. I guarantee you pro stock cars are not running heavy flywheels. You can hear how fast their engines rev up in neutral, but they have alot of torque to help them get out of the hole. But we have high rpm's to help us get out of the hole. It's a big balancing act and you will have to play with rotational weight and gearing to get it right. Most people slap a heavy stock flywheel and call it a day because they don't have the money to invest in what it takes with gearing/suspension/etc to take advantage of a lighter flywheel and that's ok. A stock or heavier flywheel will suite most peoples needs.