930 Clutch slipping.

justinforden · 11-04-2015, 12:45 PM

Hi all,
I have owned my first Porsche, a 1987 3.3 930, for just over 3 years now and the clutch has started slipping on boost.
I don't know a lot about the performance mods but the previous owner has installed a bigger turbo along with a bigger intercooler and played with the fuelling apparently to suit these upgrades.
It is running a G50 gearbox wich I believe is unusual for a car of this age.
I presumed that the friction plate was worn but I have pulled it apart today and it looks pretty good and has 9.5 mm thickness. The pressure plate and flywheel also look good with no scoring.
The slave cylinder let go around 2 years ago and dumped its fluid in the bellhousing but didn't seem to effect the clutch at the time. I had a year or so with no slipping after this.
Could it be possible that the pressure plate has just lost its clamping force?
I'm at a loss on this one and wondered if anyone had experienced slipping for apparently no reason.
Thanks in advance for your input.

quattrorunner · quattrorunner's Garage

Colder weather makes more power with these cars. Is it possible you're at the limit of it's clamping force and with cooler weather it's letting go? Also perhaps the pressure plate is weak?

icemann427 · 11-04-2015, 01:59 PM

Since you already have it apart, just go buy some new parts....A stronger high performance clutch package. Maybe a lightweight flywheel.

kenikh · 11-04-2015, 05:26 PM

Sachs BTR clutch. All other high power clutches are money wasted, even at a quarter the price.

justinforden · 04:18 AM

Thanks for the input so far.
I am looking into upgrading the clutch now but would really like to know why the existing has failed when there is so much meat left on the friction plate which is 9.5mm thick and 240mm diameter.
This all points to the clamping pressure on the pressure plate. I'm now wondering if after speaking to a helpful specialist near me the pressure plate may be a 3.2 n/a version from a G50 equipped car?
The only numbers on the plate are cast in and are:

FICHTEL&SACHS
TYP GMFZ 240
3032107098

The fingers on the pressure plate are 3.5mm in thicknes if this makes a difference and the plate was held in place with 9 m8 allen head bolts.
Also the pressure plate is the rubber centre type rather than sprung.
Is there any major differences between the clutches fitted to the turbo or n/a cars fitted with the G50 gearboxes?
Thanks again for your help.

T77911S · 11-05-2015, 05:17 AM

if ther disc is finme, nothing is broken, i would suspect the pressure plate is weak.

a turbo and IC is not enough to over power the stock clutch.

DONT FORGET TO SWAP THE RING GEAR TO THE NEW CLUTCH!!!! its reall really sucks when you dont.

Andy 930 · 11-06-2015, 03:03 AM

To say all other clutches are a waste of money is a bit harsh... My car makes 530 flywheel and i use the kep stage one. Light weight,smooth,reliable and just a all round nice thing to drive in heavy traffic aswell as tough enough at the strip to fend off most of the loud smelly v8 things....

justinforden · 11-06-2015, 05:49 AM

We have now established that it is actually running a stock 3.2 clutch and flywheel for some reason.
Not ideal on an engine making turbo power! And hence the eventual slippage.
I'm now faced with the option of trying to locate the correct G50/turbo flywheel and clutch which is going to be painfully costly.
Or hopefully stick with my existing 3.2 flywheel and find an updated 3.2/G50 set up to take the tuned 3.3 engine.
Does anyone have any part numbers or links that may help me on my search?
Cheers.

justinforden · 12:31 PM

I seem to have a couple of options for a 3.2 flywheeled performance clutch set up but nothing in the uk. I've drawn a total blank with Sachs as they don't seem to reply to enquireries!
Kennedy Engineering do their stage 1 that will cope with 536ft.lb. that will set me back $930 or the other option will be a Centerforce clutch kit DF021015 that is $1384.
Has anyone any experience with either of these companies?
I also looked into going the 1989 turbo flywheel and clutch route but I believe that as my gearbox is a 1987 3.2 950/00 code rather than the 1989 turbo G50/50 then the bellhousing will be too short to accommodate the bigger clutch set up. Anyone have any info to add to these findings?
Cheers.

Tippy · 11-18-2015, 12:26 PM

Quote:

Originally Posted by kenikh

Sachs BTR clutch. All other high power clutches are money wasted, even at a quarter the price.

Say whauh?

KEP works great.

kenikh · 11-18-2015, 12:29 PM

KEP is great for a G50 and hydraulic pedal. Cable actuated? This better be you:

justinforden · 11-18-2015, 01:43 PM

That's encouraging news.
It is a G50 hydraulic set up so hopefully will be manageable.
Just have to work out postage and import duties now!

kenikh · 11-18-2015, 03:03 PM

G50, KEP is the setup

justinforden · 12-07-2015, 07:45 AM

Kennedy engineering stage one clutch should be here tomorrow, not that I will need it anytime soon.
Unfortunately I've discovered a bit of a disaster in the form of 2 head studs missing. A previous owner obviously decided they couldn't justify the expense and just popped the covers back on!
Some people eh.
Strange thing is it's been like it since I've owned the car (3yrs) but now I know I can't bring myself not to sort it out.