Racing Clutch Question

[drbmw2002]

I recently purchased a s13 racecar and have been going through the car getting it ready to race hopefully by the end of the summer. The car has a 5.5 Quarter Master clutch with the "button flywheel". To make it work the flywheel is mated to flexplate. At one of the races the flexplate "came apart". I am not exactly sure where it come apart but it did some damage. The previous owner said it happened to another guy he knew running the same setup on a 240z. Does anyone out there have an experience with this and is there anything I can do to help prevent it from happening again? Thanks in advance.

Dan

[Matt93SE]

There's one guy I know running an EP car locally with a similar setup. Unfortunately, without knowing the cause of the failure, it's hard to help.
I'll see if he has any advice though..

[Gigapunk]

For a flexplate with a button clutch it's common for guys to just use the stock piece that came on automatic equipped cars. These are obviously not SFI approved, and aren't balanced well enough to withstand rpm greater than stock. Harmonic inbalance in the crankshaft is also damaging.

1. Get an SFI approved flexplate
2. Run a good harmonic damper

[Tower240sx]

For a flexplate with a button clutch it's common for guys to just use the stock piece that came on automatic equipped cars. These are obviously not SFI approved, and aren't balanced well enough to withstand rpm greater than stock. Harmonic inbalance in the crankshaft is also damaging.

A "flexplate" is exactly what comes on a stock automatic, what the Torque Converter bolts to...I'm sure that is what he used and also what came apart.

[Def]

The problem is that usually the button flywheels attach to the thin part of the flexplate to keep overall inertia down. Flexplates are thin due to their application (inertia prior to the torque converter makes shifts inherently rougher on an auto). Any fasteners usually go through thicker parts of the flexplate, so going through the thinner part gets things much closer to the yield strength.

As you fatigue the metal from cycling it, you will eventually get down to the point where your cycling stress exceeds the fatigue strength at that cycle and there she goes.

Seen it a few times on clutch setups like this on an autoflexplate, so it's not uncommon at all.

[Matt93SE]

Several of the ones I see for other cars actually have a tiny aluminum flywheel that bolts on top of the flexplate. The flexplate only is there for the starter. Aluminum flywheel takes all of the pressure from the clutch, but only weighs a fraction of a full size fw.

[drbmw2002]

Yes, it is a flexplate from an automatic transmission. We use the flexplate with the ring gear for the starter, like Matt said. It weighs next to nothing and then we have the tiny 5.5 "button" flywheel and small double disc clutch. I know the previous owner said the flexplate came apart. All I saw was the damage done by it coming undone not what caused it or where it "came apart". The damage actually was not too bad but you can see where it was spinning and knocking into the oil pan and rear main seal housing. A new flexplate was put on it. I was just wondering if there was a reason for it coming apart other than fatigue. Thank you Def for the explanation and the reassurance that you have seen it before. Do you think I should treat like a consumable and just replace it after x many hours of track time/races or just keep an eye out?

Matt I will shoot you a pm. I have a number for Greg, I am assuming that's the other EP car, but I think it's a New York number. I thought he use to live up there. Car is coming along. Motor back together, putting in new seat and belts this week and did some tweaking to the suspension. Then it's a bit of body work and off to the get paint. I am hoping to get it ready by the end of the summer but we will see. It all depends on how busy work gets. I can't wait to drive it! The only thing I am a little nervous about is fuel injection and getting it close (Weber sidedrafts were easy to adjust, at least once I had them working correctly). Thanks.

Dan

[Matt93SE]

What I'm talking about is one of these: http://www.quartermasterusa.com/qm/e...ch-unit-1.html

It bolts onto the back of the crank in addition to your flexplate. this removes the clutch stress from your flexplate and keeps it in the aluminum flywheel. all the flexplate does now is start the car.

the guy I'm talking about is Joel, and he lives here in Houston. Had the car for 8-10 years or so- as long as I've known him anyway.

[drbmw2002]

Yes, this is exactly what I have. Use the flexplate for the starter and then the button flywheel for the clutch and pressure plate.

Dan

[240sxTTC]

Me too!

[drbmw2002]

Here is a picture of the exact set up.

Dan

[drbmw2002]

Haha, your pictures are alot more clearer than mine but same setup.

[Matt93SE]

So what part failed in the setup? some pics of the failure would be nice. This is the first I've heard of it.

[drbmw2002]

Matt,
The failure happened with the previous owner. He replaced the flexplate, not sure if he raced it after fixing it. All I saw was the damage it did to the oil pan and and real main seal housing. When he told me about the failure I imagined it was the welds at the ring gear but after looking at the "new" one I don't think that is it at all. The flex plate itself is so thin I am wondering it is where the bolts run through to the crank? I know a EP 240z, same engine builder as my car, running the exact same setup had a similar problem two years ago. I am just trying to see if there is anything I can do to help prevent it from happening again...or at least see if there is a trick to making the set up last a little longer.
Dan

[Jason M]

Anybody care to share a parts list to make a 5.5" clutch setup work on a ka. Probably going to end up running a z32 transmission, but for now I just have the oem ka transmission.

I can CNC/modify almost anything if needed, but not sure about the clutch disc spline's & the throw out bearing setup.