Clutch and Flywheel

Since we had to drop the engine and pull the tranny to change the final gear, it was a good time to inspect the clutch and flywheel. We only had about 6000 miles on the car after one season, we didn't expect any problems, but since it was apart, might as well check. So we pulled the clutch and, SURPRISE, there was virtually nothing left on the Fidanza 3.2 4 puck Kevlar clutch! If fact, there was about 0.1mm left before the rivets would be at the flywheel. What was that all about? In addition, there was some scoring on the flywheel friction plate. We liked the feel of the clutch, although toward the end of the season I felt it was chattering a bit and the clutch pedal seem to engage a bit higher, thats why we went and checked it. Now, we do drive the car aggresivly, and our dual driving in Autocross probably counted up to about 250 launches, but they are nothing like a drag launch, aggressive with some tire spin, usually from second gear.

The other thing that scared us, is when we unbolted the clutch from the flywheel, the bolts were extremely loose. In fact, if you look at the picture of the flywheel, you can see some indications of the clutch starting to back off from the flywheel. So much for securely bolting the clutch onto the aluminum flywheel. A google search revealed some other complaints about the bolts backing out of aluminum flywheels.

So, we had to replace the clutch, and I was not particularly enamored with the flywheel issues. We pulled the OEM ITR flywheel out from the attic, and as we mentioned previously, this flywheel is unique to the the ITR, and if we had know this at the get go, we may have not gone with the aluminum flywheel. The ITR flywheel for the K20A is considerably lighter than the USDM K20A flywheel. It weighs in at about 10.5 lbs, vs about 15 or so for the K20A and 8 for the aluminum Fidanza. So for 2.5 lbs, we opted to go back to the ITR flywheel. A trip to our local machine shop, R&L Engines in Dover, NH, and literally 10 minutes later I walked out with a professionally resurface ITR flywheel as good as new.

Next was to choose a new clutch. We did a lot of research, and wound up going with a Clutch Masters. The question was, do we stay with the Kevlar (FX300) or go upstream to a more aggressive and less streetable ceramic FX400. The sales/technical support at Clutch Masters was outstanding, the recomendation from their end is "don't use the Kevlar for Autocross". Soooo, while we loved the streetablility of the Kevlar clutch, perhaps for more aggressive driving, it is not so cool. We really could not find any good discussion on this issue, but it is something to think about when choosing a clutch. So we ordered up a 6 puck FX400, the six puck is less aggressive then the 4 puck, it does have a sprung hub, but no marcel spring plate, so it should be less streetable,we shall see. This is also a more appropriate setup to handle the extra 100 HP or so from the Rotrex. Going back to the slightly heavier flywheel should help a bit in drivability, and I really feel more comfortable with the OEM steel flywheel for durability. We shall report back.

It should be noted, we are not knocking the Fidanaza clutch or flywheel, it might be that the kevlar clutch was a poor choice for how we drive. As for Steel vs Aluminum flywheel, you definately save weight, but there are some issues to be aware of in aluminum, in our opinion.

The 4 puck Kevlar clutch is spent. The red is the kevlar dust an pucks are worn out.
The Fidanza 3.2 Kevlar clutch was within .1mm of the rivets after only 6000 miles, beware.
The original K20A ITR steel flywheel fresh from resurfacing, looks sweet, and makes us feel more comfortable.
Fidanza aluminum flywheel showed some scoring after after 6000 miles and the clutch bolts had began to loosen.