Kerrage

I have never over revved my engine I always pay close attention on the occasion that I would rev my car close to redline....However with all the talk of over revs etc.....

Does Porsche not have a Rev limiter??? I have not pushed mine far enough to find out....but that would seem to make sense most high performance engines do...SO why not Porsche???

Just a thought

coinboy

They do have a Rev limiter. The over revving is only when you down shift to a lower gear at too high of a speed for the gear you shifted in to.

aj986s

My 944's and our Boxster all have rev limiters (fortunately, not visited often ). So I would be very surprised to discover that the 996 Turbo does not.

ADDED: As others have mentioned in this thread, the electronic rev limiter only kicks in during acceleration as redline is reached. A downshift results in RPM increases based upon rear wheel speed and gear chosen. A money shift, where selected downshift gear causes the engine to rev past its redline, is not protected by the rev limiter.

Fastboy

I think I hit my rev. limiter in the fall when I was WOT in 2nd gear coming out of a corner at the track --the car kind of "bucked" a bit--it may have been the rev limiter or it may have been the PSM kicking in. Not sure what the rev limiter would feel like when hit, so perhaps I'm mistaken. I wasnt looking at the tach at the time--busy concentrating on the track. 3rd gear was fine from there so it wasnt an engine issue.

Last930

Hitting the rev limiter while accelerating doesn't hurt anything ; it's there to stop damage from occuring under acceleration. However, if you overrev because of selecting the wrong gear while downshifting (2nd instaed of 4th for example) then you're out of luck. It's called the "money shift".

adam_

No car has a rev limiter that can prevent over-reving with a manual tranny... this is not a "porsche issue".

The DME cuts ignition if the speed exceeds the rev limit- HOWEVER, if you've shifted into 2nd gear at 120mph, no amount of computer code will slow your crankshaft down.

rdstemler

There is one of the advantages of the Tip and PDK. No money shift!!! Balance that against the control of a manual and you have the basis for an argument over which is the better tranny to have!

deckman

Sort of related question: Why does the Turbo redline at 6600 and the NA 911 redline at 7000?

No HTwo O

It seems like everyone always forgets that you can also over-rev the engine from a spin situation, in which you don't get the clutch in fast enough, and spin the engine in the opposite direction, and cause an over-rev. The rev-limiter does not protect you in this situation.

LVDell

From what I understand compression and engine internals. But I'll defer to the experts.

Macster

Many factors contribute to an engine's redline.

But generally, valve control is the biggie. While the rest of the engine may be capable of sustaining higher rpms, if the valves start to float... that's it. So the engine's redline is set to be safely below the point at which the valves begin to float. And there has to be considerable margin to account for any differences in valve spring strengths, differences in valve gear weights, and whatever effects time and heat and cycles of heat have on these items.

(A few years ago read about a European car mag writer/driver testing a (then new) Carrera GT and missing a shift with the result the CGT engine failed. A postmortum of the engine's failure found the revs touched 14K.)

Obviously too the Turbo engine is supercharged and because of this perhaps the engine designers felt additional revs not worth the extra stress the engine would be subject to. The NA engine needs more revs to produce more HP.

I believe too the racing engine platform the Turbo engine is based upon uses much higher strength rods/fasteners than the street Turbo engine fitted with. This is a cost issue, of course. Titanium rods/rod bolts or studs or whatever cost big bucks. Their absence could contribute to the lower redline of the Turbo engine to provide adequate safety margin. Again there are differences between the rods, rod fasteners, and the weight of the 6 rod/piston assemblies. The worst case has to be budgeted for.

Sincerely,

Macster.

1AS

I think there is a typo in that answer. AS

Kevin

The stock Redline for 996TT is 6750..

The rods and crank that is used in the above mentioned cars are also in the NA 993, and 993TT. Same pieces... No harm is done to increase the RPM limit to 7000 RPM's..

slant911

Quick question Kevin...........If you do increase the limiter to 7K would the DME record over revs from the stock rev limit settings?

Danyol

I've had people tell me and read that they've seen type II overrevs after bouncing off the redline. Some have sworn to have never made a "money shift". Could this be caused by engine momentum in 1st gear?