cobalt

I have a racing pressure plate in my track car. I have a bad left ankle due to tearing the ACL years ago and I find that track driving can aggravate it with such a firm pedal. In terms of pressure if it takes 35 pounds of pressure to push in my C2 clutch and 45 pounds for my turbo the track car is closer to 75 or 80 pounds so seriously stiff.

Interestingly while on track you don't notice it because you're so focused on driving but after a long track day it hurts something fierce.

So I picked up a replacement Slave cylinder from MPL. Very easy to deal with and I received it rather quickly.
http://www.mpl-tuningparts.de/english/porsche.html

they claim 30% reduction in pressure and although I was sceptical it seems to be working. Still stiff but far better.

I normally do these projects and don't post info about what it takes because I find most of anything on these cars is self explanatory but might as well share the differences. I happen to have a spare unit I used which helped.

The new cylinder is machined aluminum vs cast iron and is a very nice piece. A bit pricey considering you have to cannibalize your old unit to make it work but it gets the job done. It took about 30 min to swap the parts over and another 30 for install and bleed the system. I did spend some time cleaning the old parts since I am OCD but that is up to you.

Both have the same throw but the old cylinder measured 0.935 dia vs the MPL unit which measures 1.020. Very straight forward removal of parts and swapping them over. They supply a new retaining ring although the old one was easily removed with a screwdriver.

I would say it now takes about 55 pounds of pressure but it is a huge improvement. If you like butter soft clutch this might be worthwhile on a stock car but I don't see the need mostly for those of you using a racing pressure plate would benefit.

Here are the pictures of the differences and the parts that need to be swapped out.
very simple process

remove retaining clip, pry off with screwdriver being careful not to damage rubber boot

Remove rubber boot by pulling off.

Remove C clip, washer, spring and spring support

clean parts

Place supplied seating ring to make up for larger opening.

Reinstall parts on new shaft in same order as removed from old cylinder.

reinstall rubber boot and new retaining clip

Swap out bleeder valve from old cylinder to new

Install and bleed system

Simple and effective nice improvement which will hopefully reduce the strain on my ankle.

Spyerx

Hey Anthony - I have in my car some sort of billet slave but it's black anodized, not sure what it is, but action is almost too light (I'm used to a gt3!) It was on the car when I got it, sure it was installed by Orbit who rebuilt the engine/trans on the car right before I bought it. But, I know what you mean, 100 laps in a private track day in my RS and my leg IS tired from all the shifting, let alone my head, arms, etc lol.

Are there any other companies making these slaves?

Side question:
I'll be starting the next bit of my build. The plan was to simply go with the RS LWFW, and the rest of the bits needed to make that work. Should I consider anything else "higher performance"? I don't really need more clamping force, BUT, reliability is something I would pay for...

See ya

cobalt

I think my clutch pedal is about the same as the RS now My son does 375 pound leg presses and even he thought it was too stiff before. Amazing what a difference it made. I don't know of anyone else I am sure there are others, it is such a simple piece to make. When was the last time you bleed the clutch?

I would not overcomplicate things. The basic RS and LWF is a great setup unless you are going for lots of HP. I need to dyno this engine. HP is someplace between 430 and 450 but the torque is huge and the short gears really puts down some power.

Goughary

Just to put it out there...I haven't yet fully resolved the hanging clutch pedal issue on my 993 pedal box (haven't bothered to put any time yet into that since it functions well enough) - but, with the kinematic lever being longer than the stock 964 pedal, the clutch is WAY lighter.

So your your issue, and needing a lighter clutch pedal, it may be worth it to look into that.

If you make it to CT for the cnc new Canaan on the 17th of April, I'll toss you the keys and you can try it out and see if it may help prior to spending the money. 993 boxes are expensive.

cobalt

I was just talking to someone about that. It is supposed to help as well. I think the two combined might be what I really need. It is still far more work than my turbo or any of the GT3 clutches I have driven which are relatively stiff in comparison to a stock C2. Unfortunately the 17th is our local autocross and we have limited dates this year. Looks like we are doing a family AX day. My son wants to drive the C2 that day. I will have to see if I can allow it.

Thanks for the offer though, I am sure we will have another chance, the season is just beginning.

Goughary

Yep. Anytime...

jpar

I installed an MPL slave a while back and it definitely helped a little with my heavy clutch pedal. It's better than before, but still a too heavy for my taste. I've only driven one other 964, a 94 with the same rs clutch setup as my car and the pedal is much softer than mine. I have no idea what the difference could be. I also replaced the slave line and clutch master cylinder, and bled several times, wonder if the 993 cluster would help.

axl911

Where do you buy it? And how much???

koenig_roland

I`ve a 996TT pressure plate in my blue car and the clutch is ok. I had a judder problem recently, but it was an bent fork. Do you guys have problems with your clutch-forks when using super-hard pressure plates? I had a "stiffer" clutch pedal before i got the tt-pp with my old assembly. This was, because the needle-bearings in the clutch-fork bolt, the torque tube and the other "sliding stuff" were old and used. With replacing this stuff, i got the same clutch-effort despite double the clamb-force of the pressure plate.

Gus

I have a MPL slave for sale if interested. Installed and used for 1 week -
PM me if interested.

koenig_roland

Does anybody has numbers what the max pp-clamb force for the 964 clutch assembly is?

Here on RL is a thread somewhere, were the different pp clamp forces are named and the difference was/is huge!

cobalt

I don't know what stock clamping force is I believe it is somewhere around 360 lbs. The Sachs sport clutch for the 964 is 450 lbs. which I believe is stock 964 turbo. I am running 650 lbs turbo application.

I don't see the gain being needed or that noticeable for stock application. But to reduce the 650 down to the feel of 500 was worth it.

axl911

Pm sent.

JasonAndreas

When Porsche changed the stock (for all 964) pressure plate to the "RS" type back in MY92 they also used the pedal assembly from the turbo to reduce pedal pressure! That would be an easier solution than trying to get the 993 pedal assembly to work properly over the long term.


I know I have posted the clamping strength for the various pressure plates but I can't find them here anymore. I vaguely remember it was around the time all the aftermarket Porsche part vendors were selling 964RS pressure plates to 993 owners as a performance upgrade (dOH). So definitely include the 993 forum in your search area!

cobalt

Actually when I dismantled the car initially I went to rebuild the cluster only to find out it was practically new with all the tags showing the later part number. I believe they swapped it out when they did the clutch 10 years but only 1000 miles ago. The MPL has made it more tolerable. Only a good day at the track will let me know if I need to go further. Thx