blown 87

Mike that looks really good, I really like the concentric slave cylinder.

What are the weight comparison with the stock DD for what you would recommend for a street user of say 500 RWHP?

Mike Simard

My whole setup is 16 lbs total. I also lightened the starter ring gear part to keep the moment of inertia low. I always dreamed of a big engine that revs very quickly. My 7 litre is the culmination of that hangup. With Ti rods, that clutch and the ITBs, it free revs at a silly rate, 20k-30k rpm/sec during throttle blips at rest. I was actually worried about breaking the timing belt at first but that's one of the few things that hasn't broken

So what's this 500whp? Them's big numbers! I'd really love to see what you cook up. I'm all ears!

blown 87

Mike, you have to understand, I can make really big numbers in my mind
So far in my 928 the power levels have reached close te the stock number, I hope any way.


I am hoping to make 400 RWHP with a positive displacement blower, the 500 RWHP would give me a bit of a fudge factor.
I think 400 is a number that can be made with a blower and some exhaust mods, we shall see.

I did not mean to imply I was making any where near that number now with what I have on the 928.

blown 87

Throttle response is something that just does something for me, that sharp, quick rasp in itself is worth going to a DD setup from a single for me.

I was just trying to get a idea how much faster yours would be, it has to be lighter.

SharkSkin

I think that when this doesn't do it you need to get in and first make sure that you didn't move the adjusters so far back that the IP binds the rear disk against the PP. If that's OK, and you have enough slave/arm travel and the cup on the end of the release arm is good, closely inspect the stub shaft and female splines on the disks, lube everything properly on assembly(WSM calls for 3 different lubes in the clutch). Whatever the problem, it can be found through inspection and corrected IMHO.

Disclaimer: My clutch is the only one I've had apart, though I have corrected one other clutch by adjusting, and helped a few people on the board by talking them through issues. Early on, I corrected the dragging issue after a couple rounds of adjustment. Others including Greg B have lots more experience and have had issues despite having a thorough understanding of the system. Some 928 clutches just seem haunted. YMMV.

Mike's solution looks pretty bulletproof, if you're of a mind to start over and don't mind the quirks of the setup I wouldn't try to talk you out of it.

WRT Leeroy, it probably just needs to be gone through, Stub shaft, bearings, guide tube & release arm cup.

Thanks for that - it makes this video twice as funny:

BC

Yes, I was thinking of that You-facetube (ref to Topgear) video when I posted that Corvette clutch job article.

BC

I have sort of cross posted into the original Leeroy thread about his clutch and my issues with it:

https://rennlist.com/forums/928-foru...is-here-2.html

Roy928tt

Uh, look I don't have a WSM, but looking at the DD clutch when I had it out to replace the spigot/ pilot Brg. yesterday, I couldn't see any means of adjusting it? What are you on about?

You are really unlikely to find a single plate clutch that can hold decent horsepower that can be operated by an unassisted leg!

Cheers Roy

BC

The intermediate plate has the adjustment.

SharkSkin

Some info on how it works and how to adjust it here. That link is targeted mid-page, once the images are finished loading it should settle on a section headed "Clutch Theory of Operation". If it doesn't just highlight the URL and hit "Enter".

James Bailey

The Corvette video is priceless ....well not exactly Idiot does not deserve to drive a car ...any car !

BC

I'm not quite sure how you would not be able to tell the difference between a car luridly sliding around on its burning tires - and a car just sitting there going through a couple millimeters of clutch material.

BC

I found a new clutch master cylinder - what am I measuring?

Gretch

Being devils advocate Brendan, re your original question..... You might check and see what tim Murphy is doing with clutches........ his kits are now delivering 500rwhp and I know he was thinking kevlar several years ago. I bet he has advanced way beyond that.

I have an early stage II system and it can easily over power the clutch. The math on the system works out to 475 RWHP. I have NOT had it on the dyno, but the stock clutch can barely hang on.......

BC

Thanks Gretch. Yes - if you are at around 500hp, I have little chance of a stock Porsche or upgraded stage system holding on to whatever the HP will be on this 30psi 5L. I have basically decided to use Mike Simard's Flywheel and hydraulic throw out bearing on the 78 (which allows use of the 7.25 or whatever standard size clutches tilton makes) - and try and learn to drive it properly with what is thought of as a finicky system - possibly I can get away with a more forgiving compound of clutch material on those 7.25 Tilton clutches - it may be a good compromise.