George D

I'm posting to say how valuable this forum is. I met Sean, a recent Mechanical Engineering grad here. He is visiting his family in Tucson, and came over yesterday to help install a new Under Pressure Performance clutch on my 89 951.

He's doing it in my garage, and I get to help. What a job! I had no idea how much work goes into a clutch change on these cars. Sean is a great guy and I appreciate having a forum like this to help me learn about these cars.

I took him out in my car yesterday so he could see how badly 400whp slips a cup clutch. There won't be any more of that with this new clutch and flywheel setup.

George

Guns951

Congrats! This place is full of great people and valuable info. If it wasn't for Rennlist I wouldn't be doing my project!

special tool

Exellent to hear this!!!

Dyno sheet please, if you have a chance.

RolexNJ

Bump. I think george said he was making in the neighborhood of 425? But don't quote me on that, lets see what he says, and the PSI level too.

333pg333

Hi George, could you tell the details of the clutch upgrade you've chosen and why? Also approx. costs if you don't mind. There are a few people on here who are going up in power and will need to do something similar. Thanks.

RolexNJ

You may be interested in knowing this Patrick. If I'm not mistaken, below is what Special Tool runs on that butt ugly, but very fast 2.5L of his. But let him elaborate or clarify on it for you since I could be wrong?




ST's Clutch Set-Up:

Kep Stage 2 with Woody Weiss copper/ceramic 6 -puc, no springs.

George D

I've used the Kennedy PP with a 930 disc in the past on a 330rwh car and liked it. It lasted years of abuse.

This car has other plans and I wanted a clutch that would be able to hold much more power. I looked at the Spec stuff, and some other options out there.

I contacted Scott Gomes at Under Pressure Performance because of his custom work using a highly modified stock pressure plate in racing conditions. He has been building 951 race cars for 15+ years, and I figured he's seen what works well and what works OK. Most of the kits available out there will work OK as long as your intentions are matched to the kits.

I purchased his lightened flywheel, street/race four puck disc, and his modified stock pressure plate. I can take some pictures of it if you like, as it's sitting on my garage floor waiting to be bolted in.

I'll give you real feedback once it's installed.

Regards,

George

George D

The Under Pressure Clutch that I purchased is the same as the other kits out there for 400-700tq 951's. I paid around $1550 with a core on the flywheel.

My cup pressure plate has only 5K on it, if anyone is interested.

George

George D

Car hit 427hp and 350tq on a dynojet at 22psi. I've run the car at 24psi just for fun in the early morning cool air here in Tucson, AZ. I'm sort-of trying to break this 2.5 so I have an excuse to build a 3.0 or 3.2 for this car.

George

shiners780

I nominate this as the Rennlist Quote of the Day!

azmi951

George, thanks for the kind words. But then again, I get fed beer and food while working so it is not a bad gig.

His 89 is NICE!!!!! Also very fast. What a car.

Tom M'Guinn

Very interested to hear how the Under Pressure parts feel on the road once it's done. That's the last piece I have to source for the new motor 3 liter I am building (still). I've been leaning toward the KEP/930 combo based on what people say here, but curious to hear to you moving away from it. How was that combo for street driving? Smooth or on/off switch? I'm looking for something very streetable for a motor usually run on pump gas in the mid to high 300rwhp range, with occassional race gas/dyno fun days in the 400's.

I have been pushing my 2.5 too to make way for the new motor, but it just keeps making more power. I'm somewhere north of 355 now. I actually thought my bone stock clutch was slipping the other night, but it may have been the tires.... hard to say, but I figure I am on borrowed time anyway with the stock (only 40k) PP and disk...

George D

This clutch was simply awesome for THAT 951 and it's HP and TQ numbers. It felt close to stock, but held extremely well at 350whp and 360wheel tq. It took whatever I gave it for about four years.

I trust Scott. He knows his stuff and backs up what he builds. There is something about modifying what Porsche desinged to work on cars that have over twice the hp that the original part was designed for.

If your current car is hitting 300 tq numbers, your stock clutch is slipping along with your tires.

I will post feedback on this clutch. It's overkill for my current numbers, but that will pass.

Sean, Get Your But Over Here!

George

rberry951

Turn the boost up to 30psi, it'll blow eventually

RolexNJ