devon7

I've just experienced something in my S that I've never noticed before - and I'm curious to know whether it's perfectly normal or not.

A visiting cousin had never had a ride in a 911 and asked if I would oblige, which of course I was happy to do. After a couple of miles we hit the main road, I pulled out of a junction and floored it - got great wheel spin and the tyres were smoking!

What surprised me was the clutch being depressed under my foot automatically. I assume that the PASM system detected the lack of traction and dipped the clutch for me to regain it?

After the clutch being dipped like this it suddenly popped out and we took off like a bat out of hell. It was quite spectacular and made my cousins day!

If I'm sounding like a moron who's never learnt to drive his car properly I apologize and will no doubt get a verbal beating for it. While I like to drive fast I rarely am bothered to race off the lights, and previously if I put my foot down the car would simply go. This has never happened before and reminded me of the "Launch Control" in the new M5 which I tried last year before buying the S.

Guys your comments are most welcome

dstrimbu

Careful, Devon. The 997 clutch is hydraulically actuated; attempting to dump it at high RPM can cause a nasty smoke job - and it won't be your tires that are smoking! Did you smell the clutch burning when you did this? That "top of travel hitch" in the clutch is Porsche's way of telling you that you have too many RPMs built up for proper engagment.

PSM is the stability management, PASM is the suspension. PSM will not dip the clutch; it'll modulate the brakes on a spinning wheel first, then chop the throttle if that's not sufficient.

Much better to release the clutch fast and early (2-3k RPM) and keep your foot in it. If you turn PSM off, you'll get an even better show - just make sure that you're not turning when you pull out, or an accidental throttle lift will cause an end swap.

Remember, Porsches are rear engine cars that want to be front engine cars... lifting the throttle after a hard push (with PSM off) will make the motor move to the front... <yikes!>

You can search the board for more info on optimal launch techniques for the 997...

Be safe!

-don

B-Line

Hey Devon,

I am going to teach you what is called the Porsche "cookie jar" rule.

The rule is, everytime you dump your clutch, when you get home, put $100 into the "cookie jar" -- This money will then go towards the replacement of your clutch which has been prematurely mangled.

Just remember, you got the engine behind you, not in front of you. So when you cause your wheels to spin, they got that heavy engine right above em. Something has to give, the engine weight (not!), the rubber tires (designed for grip) (not!), the clutch (ding, ding ding!!!)

B

Edgy01

Keep doing what you're doing. Porsche mechanics everywhere will thank you for it.

ChipAZ

From my first 911S in 67 I never did get what people got of out smoking the tires. It's just hard on everything.

devon7

Thanks for the feedback - maybe it was the clutch that was smoking. To be fair I didn't actually mean to smoke the tyres (or clutch) I've never experienced that before as I said, it's not really my style.

But has anyone experienced the clutch pedal dipping on its own - it definatley depressed itself somehow either electronically or mechanically.

Thanks again for the advice - I'll put a $100 in the cookie jar and hope to leave it at that!

99firehawk

clucth cannot depress it self no way not possible, if you wernt on the clutch, it likely was tire smoke, you would smell your clutch burning, it also doesnt take off so well with the cluth slipping

Edgy01

Here's what I suggest to Porsche drivers (having put about 300,000 miles on them over the years). Don't attempt to pop the clutch to show off a jack rabbit start to yourself or anyone. Porsche has equipped their cars with substantial rubber and to burn rubber in a launch is virtually impossible. As HP goes up they continue to move tire sizes up accordingly. Just take it easy and let out the clutch gently. I have often gotten over 100,000 miles on a clutch. I don't really 'punch it' until I know the clutch is fully engaged between the tranny and the engine,--then I seriously accelerate.

The most expensive smell you NEVER want to smell from the cockpit of a Porsche is clutch linings.

Queram

either your car thinks it is a BMW M

or since this is not your style, because of the adrenalin your body is doing it as a nature of racing. (what ?!?)

Moogle

Indeed, these cars are not made for launching, best "launch" is to dail up 1500-2500 rpm, let out the clutch gradually but surely, and then floor it when you know things are engaged properly.

The magazines do numbers by abusing the cars, but it's not something to do to your own.

If you want to dump the clutch, get a japanese car and a turbocharger.

UK997C2S

Hi Devon 7!

I had exactly the same thing happen to me! I agree with all the guys telling us we should be kind to the clutch, but I needed JUST ONCE to see if the rear wheels would spin on a dry road (and I was trying to impress a visiting brother!) What actually happened was the clutch pedal didn't rise until the clutch had stopped slipping; no wheelspin, just clutch slip and the burning smell! OK, cookie jar now suitably funded and I've probably used up 20,000 miles of clutch wear in 10 yards, but the it's behaving just fine now. To everyone else telling Devon7 and now me that we shouldn't be doing this, well I don't think we'll do it again, but this is my first 911 and we are all on a learning curve!

I think Devon7's question (and mine) is: what is it that keeps the pedal down in these clutch-spin circumstances when you've actually taken your foot off it?

PS to Devon7: I'm in Berkshire, UK. Maybe we should meet up!

Coochas

I agree with all of the comments in the thread. My own experience (years ago) with an Rx-7 that I heavily modded was that I would get about 15000 miles out of a clutch (which I used to dump routinely and track often). In those days I could change out the clutch myself but I'm going to guess that a 997 costs about 20 times as much moola! I have never dumped the clutch on my 4S and never plan on doing so...I'm just not the drag racing type.

For comparison, the recent Excellence tested the 997 turbo w/6-speed by dumping the clutch at 4000 rpm to achieve 0-60 mph times of 3.7 secs. Yoooucch.

cr2000

I've owned many stick-shifts and never once dumped the clutch. Seems pointless for a couple 10ths of second. But I guess I'm just not into abusing cars...

fxhomie

On a side note, the A.W.E. exhaust video shows a clutch dump on takeoff, while Fabspeed's video shows a gentle, smooth launch.

Hopefully A.W.E. doesn't treat its customers like that 911...

dstrimbu

Devon, I've been thinking about your question - "What causes the pedal to dip / stay down?" (which was the actual question in this thread, I think... <g>).

I *think* that the "slack" in the pedal is due to the fact that the clutch is not fully engaged, and since it's not, the throw-out bearing is not in it's final (engaged) position... this means that the slave cylinder isn't where it should be, either. The hydraulic system is closed, and the clutch master cylinder follows the position of the slave - therefore, the pedal is not at top of travel as you'd expect it to be had the clutch locked up properly...

Not sure, but it makes sense to me with my limited knowledge of the P-car's clutch hydraulics...

-don