Toasty Clutch

Anybody have thoughts/experience with performance clutches in the Cayman? I took the Cayman out to an autocross yesterday. I just recently got all my break in miles after the 3.8 rebuild and it was the first time pushing the car. I lined up for my first run and launched by revving to 3-4k. Once I let the clutch out and got rolling, I gassed it and was immediately bouncing off the rev limiter. The clutch did not even try to hold on. No wheel spin, everyone thought I had popped out of gear or something. I let off and finished the pass using the throttle a bit more sparingly. By the time I pulled in, I'm wafting in that wonderful smell that says, "you better be careful or you're not driving this thing home today." Later runs were better, but I was very conservative with my launches, basically starting from idle and hardly ever using full throttle during the runs. Still pulled back in and could smell the clutch once or twice. I'm using a Sachs OE replacement clutch. I'm running everything stock except the 3.8 build. Stock 3.4 liter intake, headers, tune, etc. So best case scenario I may have 320 hp over the 295 stock. I would have thought the OE clutch would at least have been good enough for that. Did I just get a dud perhaps? Or maybe I just botched the first launch and burned it up? All of the previous cars I had were maybe 200 hp, so rev to 3k and full throttle once engaged worked pretty well. One thing I noted, when I bought the car, the clutch was much stiffer than anything I'd ever driven before. I don't know the history of the car, but there wasn't any indication that it would have had a performance clutch. Everything else was stock. But the Sachs unit I put on has a much softer pedal feel. Very similar to my stock Subaru BRZ that I had prior. I didn't think much of it, since the car had sat for many years before I bought it. I just thought it was a consequence of it sitting and things trying to bind up. I'm pretty sure it was a Sachs unit I took off the car. I don't remember if I compared part numbers or not, but it looked identical Anyway, it's a long post to basically ask, should I get a performance clutch, or should I just stick with stock and assume I got a bad one, or do I need to learn how to drive?

I won’t lie and pretend to be knowledgeable about engine : transmission power ratios but the first question I would ask is have you researched whether it’s safe to upgrade to the 3.8 without having to also upgrade the clutch? In other words, I’d first check whether larger engines get paired with larger clutches (although now that I think about it people do LS swaps all the time using the same transmission..)

I'll just comment: Chances are much more likely the original clutch in the car when you bought it was badly worn. When the disk gets thinner, the pressure plate moves inward, and the finger springs pressing on the pressure plate exert more resistance to relieve the pressure and disengage the clutch. Worn clutches = a heavy (or very heavy in some cases) clutch pedal. I came to this realization on the first M3 that I owned. It had a bear-trap feeling clutch, difficult enough to depress that if I tried to hold it down at a traffic light my leg would start to spasm. I sat in a brand-new M3 in the dealer's showroom and the clutch felt nothing like that. After I had the clutch replaced (disk and pressure plate, throwout bearing, fork) - it felt like the brand new car in the showroom. Easy to depress. So chances are - you had a bad clutch when you got the car. When you installed the new clutch it naturally had a much softer pedal feel. Did you change the pressure plate at the same time? Is there a reset on the pressure plate to relieve the self-adjusting feature? Was that done? If you put back a used pressure plate that had been used with a thin worn clutch disk, without relief of the self-adjusting feature (which has to do with how the fingers push the pressure plate on the disk) - chances are that's the cause of your slippage. The fix might be as easy as a new pressure plate, and while you're in the area, a new throwout bearing and possibly the clutch-release fork (those can bend or crack with age and a worn clutch..) That's where I'd be looking. When you put in the new clutch did you resurface the flywheel? A dual-mass flywheel can't be "cut" like old solid ones could - but you can de-glaze them using a palm sander and 400 grit aloxite sandpaper. You want a uniformly clean and deglazed surface, You can do it without even removing the flywheel from the engine, but DO put some sort of seal in the pilot bearing to keep grit and dirt from getting into it. Good luck! Let us know how this is resolved. BTW - thought of something else - when the new clutch was installed - how much lube was put on the clutch/transmission splines? Too much is a bad thing - it gets thrown off, often where it can get on the clutch disk, and a greased clutch disk isn't going to hold all that well. If no lube was used - there is also the possibility that the disk isn't moving fully where it should be, allowing it to slip. Clutches seem rather simple, but they actually are a bit more complex than they appear. Some experience doing one is useful when you change it. I can promise you, Porsche did not sell the car with clutches that were undersized for the power of the engines. And the additional 30HP you mention shouldn't need a performance clutch.

Thanks for the reply, all good insights. When I put everything back together, I used all new parts, including the flywheel. I'm right with you that an extra 30hp shouldn't be a problem for the stock clutch, but it let go so completely that I couldn't help but think it wasn't strong enough. It drives fine in normal conditions, even now after cooking it so thoroughly, so I'm pretty sure I didn't overdo it with the lube, but it's hard to rule that out. Are you sure the Cayman uses a self adjusting pressure plate? Or were you speaking generally? I didn't think there was any adjustments possible. I'll look into it more.

@customyota - I took a look in the service manual (AllDataDIY) at the clutch assembly and replacement instructions, nothing was mentioned about a self-adjusting pressure plate. I guess just BMW went down that complex path with their Sach's M3 clutches. So with everything being new - aside from lube of some sort getting on the disk - or weakening the pressure plate spring by overheating it - I can't account for why it now slips. You say it drives fine now - once cooled off. I wonder if like BMW - there is a hidden clutch delay valve (CVD) in the hydraulic circuit that limits engagement speed? That was another bug-a-boo a lot of BMW owners removed, only to find their rear-subframes tearing out of the body due to peak torque loadings on the subframe mounts that had formerly been controlled by the "CDV"... The "CDV" was a simple in-line fitting with just a small orifice through it that limited the fluid speed when releasing the clutch. Not even any moving parts, and never documented by BMW in any service literature I could find. The purpose of it was to limit peak shock loads on the driveline - which when experienced too much caused metal fatigue around the rear subframe mounting points to the body (which were really underdesigned to begin with - but that might have been a crash-test result..) There is no mention of one in the AllDataDIY - but there is a suspicious item shown in their illustration of the under frunk-hood plumbing for the clutch master-cylinder: That looks a lot like the BMW one - which could be removed by just unscrewing the two ends, and the remaining fittings screwed right together - like this one looks like.. More thinking update.. the image above is from the AllData section on clutch hydraulics specifically for the 987.2 2.9L engine. If Porsche thought this was important and needed on the 2.9L, I can imagine the original 3.4L needed it even more. With the 3.8L you might have reached the point where there is enough torque that the designed in slippage in the clutch due to the CDV is enough to actually make the clutch slip and keep slipping (possibly by the buildup of hot gases between the clutch disk and the metal surfaces it contacts with.) It might be telling you not to try to launch the car.. since if it was needed for the 2.9L to avoid chassis damage, it would be needed in spades for the 3.8L you now have in there. Just rambling thoughts.. but it would account for your symptoms.

In my experience the oem Sachs clutch is still very worthy of running a 3.8… and measuring hp at the motor where the clutch is you should be closer to 380-400hp depending on various internals… sounds like an old clutch tho… might be worth investing, I certainly wouldn’t hammer on it until

The stock clutch was worn out. The clutches in these cars are self adjusting and getting heavier as they are worn out. My 2011 Cayman 6MT had a super heavy clutch pedal and it was much lighter when I replaced it with the OEM Sachs kit. HP isn't the real concern here. It's torque. You've add 0.4 liters of displacement with a bit more torque in the lower rpms. The clutches in the 3.8 Porsches are beefier/stronger than those used in the 2.7-3.4 motors. The extra torque compounded with the hard launch is likely why it got smoked. The stock 3.4 clutch may not be cut out for hard launches with the 3.8 motor.

So is that why it’s slipping? You’re still running a clutch for 3.4? I’m running the clutch from 997.2 Carrera S since mine is also a 3.8. I wasn’t aware what you were running

I think people are loosing track here of the original posting.. he has a new clutch. It's "stock" so I'd assume it was stock for the 3.4L engine. It slipped badly after a "launch". Only after he was moving did he apply full power to the engine. It worked fine the rest of the day with some minor smells coming from it Things we might want to consider The very real possibility of a flow limiting "valve" (AKA Clutch Delay Valve - CDV) in the hydraulic circuit designed to control the engagement speed of the clutch assembly. I say "very real" since I can't think of anything else the item in the red box in the illustration above could be. Can you? He has done "break-in" miles on the car (no details as to what this consisted of) - were they enough to also bed in a new clutch assembly? Dunno. OK - continue discussing...

I thought my question was appropriate regarding,”is it a 3.4 clutch”… no?😆

It's a Sachs unit sold as an OEM replacement for the 3.4 Cayman S. As far as I'm aware, it is the same clutch that the factory installs. It looked identical to the one I pulled out of the car when I rebuilt the engine. I haven't been able to find anything about a CDV being installed on the Cayman, and the parts diagrams just list it as a "threaded joint". There's multiple in the line, so I don't think it's a valve. I drove the car for about 3k miles of normal driving prior to the autocross. I would think that should have been enough to make sure it was set in. It drives around normally, so I'm going to run it for now, there's another autocross in a few months that I may jump in and see what happens. If I have more problems, I'll pull it out and probably just replace it with another stock unit, under the assumption that either I botched the install and got grease on it, or it's just a bad unit somehow. If that doesn't work, I'll start looking at other options. I appreciate everyone's thoughts and insight into the matter. Thanks!

I would use a lower RPM to start. The staring box to the timing light is about 20 feet, so just get the rear end hooked up. If you have a LSD, then you could use a higher rpm to spin both wheels a little. Unless you are at the top of your class in time, I would worry about attacking the course more. During your normal driving do you notice any clutch slippage? Usually in a higher gear, does it hook up well. My opinion is just to let your newer clutch disc break in rather than causing heat scarring of both the pressure plate and fly wheel. You can look up what Sacks clutch kit the 3.8 911 use. It maybe the same clutch kit.

I'm sorry to hear about your clutch trouble but glad you weren't stranded at the event like this guy.

I cringed and laughed inside but mostly cringed.