Stan - I'm pretty sure that in stock form, the 190mm flywheels are as heavy as boat anchors, so they would not be well suited for performance use without lightening. They have a very big weight of mass near the starter gear ring that needs to be peeled off to get their weight down. I'm pretty sure that if you can't lighten the flywheel, a 210mm setup would be the lightest, especially if you could find or make a lightweight pressure plate that can bolt onto it. I would however, turn the 210mm flywheel down to it's minimum thickenss (IE: blueprint it for lightest weight) to save as much weight there as you can.
It looks like you are allowed to bolt any pressure plate to the 210mm. Sachs racing makes a very light aluminum alloy 210mm pressure plate, however because it is ultra expensive, you may be ruling that one out. Since a 210mm flywheel and pressure plate has a different "bolt pattern" than a 190mm or 200mm setup, you'd need to use a 210mm pressure plate to go with the 210mm flywheel. You might however, be able to lighten a stock 210mm pressure plate by taking weight off the "friction ring" (IE: face it to make it thinner, and turn down it's OD to 190mm, which would work if you ran it with a 190mm clutch disc....)
For the clutch friction material, the stock material of clutch disc would work fine as long as you had it pre-loaded with enough pressure plate spring, and didn't abuse it to the point of overheating it. It also requires a lot of clutch pedal travel to completely disengage it due to it's "sprung" marcel. A 4-puck or even lighter, 3-puck clutch disc with solid (non-sprung) center would save some weight and would give more holding power than you'd need, and also since it has no sprung marcel, you can disengage it with something like 1/4 of the clutch pedal travel. This ability to get the clutch disengaged/engaged IMO makes for fewer "gear crunch - oops" shifts, so it adds reliability for shifting. Taking off from a stop, they are shakier and more prone to stalling than a stock disc, but this isn't a problem for a racer.
I'm thinking that a close-ratio transmission like one from a GTI would be ideal for your needs, assuming the fifth gear is tall enough for your needs, which will depend on how high you want to revv the motor and also how fast you go down your fastest straight.
As others have said, a bad synchro will just make it a little harder to get into that gear. If you only select 2nd gear once per racing event, and it's only during your warm-up lap when a slow shift would not effect your performance, it sounds like it might not be a problem at all! Your application sounds like it may be very hard on transmission fluid temps, and the chance of loosing fifth gear is very high if you run the transmission fluid level down too low if it leaks even a little bit, etc. Might want to ask MrDave about his low fluid warning / transmission temp sensor.
Topic: Clutch and Trans Q's (Read 4667 times)
