Drag Style Starts and Clutch Abuse

[RarlyL8]

I need some info from all you Drag race/0-60/Launch Pad freaks.

Just exactly how hard are these 6000 rpm holeshots on your clutch?
My 4 year old son has watched the "Mike the Mechanic" clutch abuse video about a gazillion times. He still finds it riotously funny while I cringe every time I see the tire (and clutch) smoke.

I was told by my mechanic not to even THINK about doing that with my 345s out back. What he doesn't know is that it has been succesfully pulled off a couple of times by the old 3.0 mill. Left some VERY impressive rubber. The tranny is out now and the clutch looks fine.

So we know the clutch can take it a few times. But how many? What are the weak links?

[widebody911]

When I do my 0-60 runs, I only start out at about 2500RPM or so. I shudder to think what would happen if I dumped it @ 6k!

[Undercover 3.2]

Rarly L8, From my research I been told that clutches with organic material will not last, you need some GOOD MATERIAL ,weak points are the CV Joints,but theres a company in california that make them with LIFETIME WARANTY Im just waiting for a e-mail with the address but I have another source always plan B
The bolts that hold them, the best ones are the original Porsche ones, Turbo axles are thicker and some people use them,in our project in anticipation of the abuse we replace the wheel studs with turbo type they are longer, we then install nuts torque them and the regular nuts on top and torque those too, from looking at them you will never tell,You may want to invest in a Aluminum Pressure Plate mine was 24 Pnds now is 11 pnds some HP is hide in that dept many times overlook.
Hope this helps.

[Jack Olsen]

I worry about this, too. And I hardly ever do fast starts. But I know that with my car, spinning 275's, with an 80% limited slip, has got to be transferring a lot of stress to the clutch and the rest of the drivetrain.

Without a limited slip, I'd guess it's safer, since only one tire is spinning.

[A Quiet Boom]

While I can't comment on the strong and weak points of the Porsche drivetrain, I can tell you that a 6000rpm launch is probably wrong for a P-car unless you have serious traction (read drag slicks or drag radials) An ideal drag launch is one inwhich the tires barely spin and the motor doesn't bog. Get your car to "hook" like that and you will be putting serious strain on the driveline. Here is a list of parts I've broken on my 10 second dragcar:

Toploader input shaft, twisted one snapped another.
Front U-joint, shattered all over the track
Rear U-joint, snapped in two
Twisted driveshaft
Traction lock rear end, moved to a spool after this incident
Strange Engineering wheel studs, 4 lug all 4 twisted, switched to 5 lug and drag rims after this, slicks are bolted to the rims because otherwise they slip
Driverside motor mount, switched to solid mounts
3.73 Factory ring and pinion, moved to Richmond ring and pinion

All of these parts where broken with a 5500-6500 rpm launch on a 600+HP motor and 26x10 Mickey Thompson ET Drag slicks 10-15 psi

My point here is a real good drag launch will break the weakest link in the driveline unless the driveline is stronger than the HP and traction level of the car. Spinning tires is not a good launch technique and chances are when the tires do grab traction something will break. My preferential launch technique for a car with a questionable driveline or poor traction is to "walk" the clutch out in 1st gear keeping the rpms as high as possible, then pull hard in 2nd, 3rd and 4th. A fast shift will help keep the tranny alive since the "rpm" shock won't be so great.

[RarlyL8]

Juan? Is that you? Why the name change, did you rip off Eddie Bello?

You would think that one tire spins on an "open" differential. I've got a real nice picture (someplace) of two very dark very wide black marks left on the airport tarmack of an auto-x track. Did the same thing a couple of times while testing my G-tech.
Incidentally, the widebody managed a best of 14.2 in the gizmos interpretation of the quarter mile.

Mike's video is really impressive. I just wonder how much the 915 can take.

The clutch I have for the turbo conversion is the Sachs Sport. Lightwieght and tuff without the anoying "pucks" that some race clutches use.

[Undercover 3.2]

Rarly L8,
Yes good old Juan here I was just playing around with names and NO I HAVEN'T RIP OFF BELLO Why you ask that???

[RarlyL8]

It was a joke, you know - humor.

The gag was that if someone was after you a name change would be in order. Sinse you're a drag racing guy, and our fallen hero Eddy Bellow was caught with his hand in someone elses pocket..............

Well, I guess something was lost in the translation.



SO - what clutch are you runnin' in that monster?

[juan ruiz]

I figure it was a joke but My new tuner is also the tuner of former Bellos car which is in COSTA RICA and sometimes we talk about that staff,but hey HE IS COMING BACK! 4 sure the rummors are tru the Twin Turbo 911 Alcohol is a Real Deal.

Well as you know I was going with the Clutch Master Stage 3 but when my tuner start to ask them some real good questions he offer his type which are custom, they go for $1,400 with Aluminum Pressure Plate and is a six Puck,Is been in a 800 hp street 911 for years so I figure Im safe,but if you wish to joint us and make those movies(mikes) 4 sure get a good one.

[autobonrun]

a few weeks after doing 0-60mph runs using my GtechPro, I had to replace one of my CV joints. It was probably close to going anyway. I guess the bottom line is that if any component in the drivetrain is getting close to failing, these type runs may push it over the edge. Again, it could have been a coincidence but...

[adamnitti]

ok, then, how much of a time difference are you gaining then, between a drag launch like this compared to a smoother, more progressive release of the clutch???

[1980SC]

During an autocross last weekend, I accidently launched my stock SC at 6,000 rpm's. The car didn't move. It just spun the clutch until I got off the gas, and then it hooked up. I was distracted for the rest of that run because the inside of my car stunk so bad of burnt clutch. Oops...

No idea of what type of clutch is in it. Probably a worn stock one. I wasn't even running R-compound tires that day, just some Kumoh 712's.


Rob
1980SC

[A Quiet Boom]

Originally posted by adamnitti
ok, then, how much of a time difference are you gaining then, between a drag launch like this compared to a smoother, more progressive release of the clutch???

Not sure about a P-car but a typical dragcar with sticky tires will go 1/2 second faster. Like I stated earlier though you must have good traction to pull of a launch like this, spinning tire do not propel the car forward and therefore actually slow you down. A good example of this was a kid who I taught how to launch his Mustang, he was leaving the line with the tires spinning horribly because he just dumped the clutch at a high rpm, his 60 foot times where in the 2.3-2.4 range, I got in his car, walked the clutch out at around 3500rpm and ran a 1.95sec 60 foot on street tires. On slicks with a 6000rpm launch I could have run about 1.7sec 60 foot. This translates into a lot of time at the big end of the track.

Rule of thumb, on street tires a progressive clutch release is faster as well as easier on the drivetrain. When you think about it replacing the clutch is much better than replacing the tranny.

[BlueSkyJaunte]

I always thought that 1st gear was the weak link in the chain?!?