asbi

Guys.
Had a great trundle around North Wales today, sadly the camera battery failed or I would be posting some pix...

During a spirited start from rest I managed to get my clutch slipping like crazy and hit the rev limiter a couple of times in 1st gear before I could catch it. From my brief and horrified recollection the revs were hunting between 6800 and 7200 on the tacho as the limiter kicked in and then out again as the revs dropped, there was also a strong smell of distressed clutch.

Will I have done any damage?
What is the rev limit for short durations on a 1990 964? Engine runs and sounds OK.

I am pretty sure now that I will also need a new clutch soon...although it doesn't slip at any other time...
Cheers,

asbi

Just to clarify...I am concerned about possible engine rather than clutch damage.

John Boggiano

I would think if it runs OK, it's OK. After all - that's what the limiter's job is.

Different if you select a wrong gear and FORCE it to over-rev.

Anyway, it serves you right for having fun in North Wales without the rest of us!

(I'm hoping to arrange a run soon...)

P.S. I imagine it was pretty wet.

BGLeduc

For those of us that autocross or track the car, the rev limiteris our friend....

BGL

Surf Twang

I hit the rev limiter each of the last two runs I made with Khadmus/Howard and don't seem to have done any damage. Nonetheless, Howard is a bad influence...

asbi

Guys,
I am sitting here worried that I may gave damaged the car in some way (I have a way over developed mechanical empathy) should I stop worrying? I guess that these cars are designed for this stuff and hopefully there is some safety margin in the limits?

My car gets treated pretty gently, it probably can take a lot more than I throw at it, nevertheless seeing the rev counter topside of 7000 gave me a fright!
Cheers,

emilios

Asbi,

I hit the rev-limiter on quite a number of occasions, absolutely nothing to worry about - that's what it's there for anyway - so stop worrying and enjoy spirited driving in your car!

Kahdmus

yadda, yadda...Howard gets blamed if it rains these days!!

Bill Gregory

Just spinning it up and having the rev limiter kick in is OK. The only time you need to worry is when you're making a downshift at high speed, miss 4th, going into 2nd by mistake. There the rev limiter won't protect you from bent valves.

asbi

Thanks for the advice, I was really surprised when it happened, I was rolling at around 5mph, I put around 3k revs on and droppped the clutch-result a screaming engine and a strong smell of burnt clutch.

The clutch has been fine since, even accelerating hard through the gears to 6k. Is the standard clutch a little weak or is it just than my clutch is probably near the end of it's life (14 years/60K miles on original DMF)?

Thanks,

Arjan B.

If you use the rev limiter the right way by just using your gas pedal, then it's fine. If you 'mechanically' over rev the engine by selecting the wrong gear and 'brake on your engine', then you can strech your rod bolts. You will notice this not sooner then after a few trips later, they will brake........


As it happened you tell us, there is nothing wrong.

springer3

It is simple physics that you cannot launch to speed in an instant. In theory, when overwhelming force meets an immovable object, there is total obliteration. Dropping the clutch on a 964 is a physics experiment where you test this theory.

If the clutch did not slip, you likely would have bent or broken something inside the transmission or possibly twisted a drive axle. It would be better if the rear tires let go and gave you a loud and smoky burnout. However, the rear tires need a lot of bite for safe handling, and therefore are less likely to break loose when the clutch is dropped.

Dropping the clutch is more survivable in a front engine car, where the rear tires break loose easily. I suspect the Porsche factory did their usual through job by setting the clutch up to slip before something more expensive breaks. You have probably burned up some of the lining, and you risked overheating the pressure plate. As long as you avoid future abuse, the only thing you have done is shortened the clutch life by a few thousand miles.

Note that you will go faster if you drive within the limits of the machinery.

asbi

Thanks, we live and learn...