lart951

best combo ever for the 2.5L old school high boost guys, Kep stage I + 930 clutch disc + stock flywheel good up to 400 rwhp

V2Rocket

Tom splits his time between polishing his paint and hitting the leg-press...google "quadrisaurus rex" for a photo of Tom in action

Tom M'Guinn

I can confirm the KEP1/Cup holds well over 400rwhp/t. I haven't found where it slips yet, but it is something north of 450 dynojet hp and torque.... Can't imagine the 930 disk changes that much.

I went from an '85 911 to the 951, and still remember thinking how light the clutch felt in the 951 by comparison. Maybe not a Honda, but I guess it's all relative....

333pg333

Try a Ferrari 512BB...that does require some Olympian level squat thighs. Sat in one years ago. Thought I'd pressed the brake pedal.

Tom M'Guinn

I have and you're right. My most lasting memory of that car, however, was how the gear shifter seemed to occupy the space where my leg was supposed to be -- basically in line with the gas pedal. Exotic cars were just more "exotic" back then I guess...

333pg333

Yes, exactly. They were imperfect in many ways and one of the reasons we loved them more. But harder to drive and you really had to learn the best way to extract their utmost performance. 951 was easy by comparison.

PF

Try a -89 928 GT in a 2 hour traffic jam outside Hamburg and you will know what a manly clutch is all about! And yes all my 951 clutches has been childplay in comparison

Laust Pedersen

Manly vs. wimpy clutch ... depends very much on the condition of your left leg, so let's get some numbers.

I have measured the following cars with "highly scientific" equipment consisting of a bathroom scale and a piece of wood:

1988 Porsche 951, 45 lb, OE pressure plate (PP), 930 disc *
1985 Lambo Jalpa, 45 lb, OE PP, 5-puck Centerforce disc
1972 Lambo Espada, 55 lb, Centerforce PP, Centerforce disc (550 ft-lb capacity claimed)
1994 Lambo Diablo VT, 90 lb, likely aftermarket clutch

* very early (dis-) engagement, so pedal helper spring doesn't help much.

I don't know the max power or torque of my 951 often checked at 25psi boost. however, it is enough to break the OE disc and make me worried about the gearbox, but no clutch slippage at all.

Laust

Dave W.

Thanks Laust, that's good info. It reminded me of another page I saw. Here's more info to compare with other cars;

http://www.roadraceengineering.com/clutchpressure.htm

I wonder if there were different assist springs for the 944 turbo? I know the non-turbo and 968 had different assist springs.
I also have the KEP stage 1 PP with 930 disc. It's holding 425TQ on a Mustang dyno. I find the pedal pressure to be firm yet very tolerable in stop and go city traffic. It's my DD. One of the reasons I can handle it is because the entire clutch system has very low friction.

rlm328

Here is KEP's page that discusses stock vs various KEP stages

http://www.kennedyenginc.com/Pages/PorscheClutches.aspx


As you can see the stock clutch is good to 378 ft-lbs.

Tom M'Guinn

I assume those numbers refer to flywheel torque, rather than dynojet wheel torque. If so, my stock clutch did a little better than they say, since it held up to almost 350rwt before spinning. I can vouch for the KEP1 holding at least the advertised 530 ft lbs. (assuming that's at the flywheel) and I'm quite sure I've exceeded that from time to time with no slipping... I'm guessing those values are honest, accurate minimums, and that my results are probably more a function of overly optimistic dynojets.

rlm328

As the original torque at the flywheel for a 944 Turbo S was in the 260 ft-lb range they added approximately 50% overkill to account for instantaneous torque. The instantaneous is where you will get the slip, i.e. when you power shift.

V2Rocket

yea the 378 number is a very convenient 150% of the turbo S 250lb/ft torque rating...

Monstrous4Banger

Of course...if you really want a clutch that can take the power...