Why am I so hard on clutches - LotusTalk - The Lotus Cars Community
 
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post #1 of 8 (permalink) Old 10-03-2017, 07:48 AM Thread Starter
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Why am I so hard on clutches

So, I have been through a number of clutches. Some of them were manufacturer related problems, some of them entirely my fault, but the commonality among them is that I am hitting the hub on the retainer pins, which means that I am overloading the hub springs, presumably when releasing the clutch on the track.

Nobody who has ridden in the car said that I am shifting particularly hard, however one very senior instructor said that I am not getting my heel toe quite right.

What are some general thoughts about driving very fast on slicks without wrecking the clutch so fast?

Here is a listing of my problems:
ACT - Hub Spring
ACT - Hub Spring
Competition clutch - Hub Springs
Competition Clutch - Hub splines (would not release or even start), hub was sticking on shaft.
Fidanza - Pressure plate failed Probably a manufactures defect
Exedy - Would not release on first install not sure why yet.

I think there is one missing along the way there but not sure.

There are dowels on both the pressure plate and transmission on this car so the normal thoughts of misalignment are gone. I have had a Fidanza flywheel with the removable plate on the car since the first ACT failure.

I plan on running a clutch delay valve once I get the car back together this time, but what can I do about technique? I got so that I was driving pretty fast (within ~1s or better of TT3 fast time of day on any given day that the car works) but I was all self taught so I seem to have missed some things.

Thoughts?

2007 Exige S with almost every track mod...
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post #2 of 8 (permalink) Old 10-03-2017, 10:10 AM
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How much power are you running, don't people[in other cars anyway] go to solid clutch plates at some point?

Or am I misunderstanding the problem?

I am thinking you are crushing the damping springs and they end up rattling or falling out and wreaking havoc
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post #3 of 8 (permalink) Old 10-03-2017, 10:35 AM Thread Starter
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Well, yes that is what happens, you can see that the hub is travelling too far from where it hits the pins as well and is wearing the pins.

However the question is how do I drive around this without losing time.

People go to solid clutch's but the problem then is that the clutch doesnt absorb shock and instead the drivetrain does, so what breaks next...

2007 Exige S with almost every track mod...
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post #4 of 8 (permalink) Old 10-09-2017, 07:10 PM Thread Starter
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2007 Exige S with almost every track mod...
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post #5 of 8 (permalink) Old 10-10-2017, 11:56 AM
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Did you change anything else on the motor? Different crank shaft? Different crank pulley?
Anything (besides the Fidanza) which would significantly change the torsional characteristics or inertias of your powertrain?

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post #6 of 8 (permalink) Old 10-10-2017, 12:11 PM Thread Starter
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Quote:
Originally Posted by Mr.C View Post
Did you change anything else on the motor? Different crank shaft? Different crank pulley?
Anything (besides the Fidanza) which would significantly change the torsional characteristics or inertias of your powertrain?

Nope, it now has the aftermarket gear-set in it from BWR, but it doesn't seem to have affected clutch life yet.

2007 Exige S with almost every track mod...
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post #7 of 8 (permalink) Old 10-10-2017, 01:16 PM
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If there was any misalignment problems between the engine and transmission, you would feel a pulsing through the clutch pedal when depressed. If the misalignment was very bad, you would be breaking transmission input shafts.

A clutch delay valve will soften the bite of the clutch...but you could go with a carbon clutch instead... A carbon clutch does not bite like a conventional clutch, it needs to heat up to bite. You will get your "soft" bite with a carbon clutch.

I would try a carbon clutch if I was not getting any pulsing through the clutch pedal. If you are getting pulsing, fix that first.

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post #8 of 8 (permalink) Old 12-06-2017, 02:09 PM
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I have had a lot of time to think about this problem recently. After I started modding my Exige S for the track, I shattered my stock clutch disc (admittedly at a VERY high-speed/open-throttle circuit). Replaced it with an ACT HDSS setup, then over the course of the last 2 1/2 years went on to grenade TWO transmissions (both 3rd gear failures), the ACT SS clutch disc (one of the hub springs broke free), and most recently, the ACT HD pressure plate (broken pivot ring).

Along the way, I did several mods that in all likelihood reduced the reliability of the drivetrain: 1- sticky R-compound tires, 2 - more aggressive brake pads, 3 - Increase in power and torque, 4 - HD pressure plate, 5 - multi-clutch type LSD (bought it because it locks up on decel, making the car more stable under hard braking). Oh, and a crazy aggressive driver on the track. All of these mods increased the magnitude of potential torque spikes to the drivetrain.

And it might not be just acceleration and upshifts that are causing the problem. I am a very late braker, and I think this can be very hard on the drivetrain during high-deceleration downshifts with braking. Granted, the gear tooth sizes on the C6x transmission and strength of the clutch assembly were all designed for the NA Celica GTS open-diff front-drive platform (which is to say, not nearly beefy enough), but anything you do to increase grip, engage the clutch faster, and insure rear axle/diff lock-up only increases the stress in both acceleration AND deceleration. BTW, going to a solid clutch disc would only make the situation worse, as the hub springs are there to soften the engagement and mitigate the torque spike when the clutch is released. In many of the newer German cars, this is what the "Dual-mass" flywheel (really two flywheels connected by elastomers) is for.

It is starting to make sense to me that Lotus never sold a 2ZZ/GE-C64 street car with more than 260hp and only a torsen LSD (which doesn't lock up on decel) as an option. And even fitted the clutch delay valves to those higher HP cars.

So the only advice I can add at this point is to also look at your downshifts under braking and try to let the clutch out more slowly. That's what I'm going to try to do next year. And assuming we don't want to reduce tire grip, brake grip, or HP/torque, maybe resign ourselves to the fact that the clutch should be the "fuse" of the drivetrain. I think some guys are switching to a pressure plate which has a clamping force closer to the stock Toyota unit, which might allow more slip in the case of a big torque spike. I can tell you although it's a pain to replace the clutch, it's still a lot easier and cheaper than rebuilding the gearbox (again)...
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