Chuck Jones

I drive a 99 996 coupe. A couple of times while getting on the freeway, I wasn't watching the tach and I hit the rev limiter....and it shut down the gas like it's supposed to do.

I assume the rev limiter's there to..limit the revs..(brilliant deduction) ...therefore it's a safety valve designed to keep the engine from over reving and keep it healthy. I would imagine that Porsche engineers built in some safety factors and actually have the limiter kick in well below the danger zone.

My question is....how unhealthy is it to hit the rev limiter...by this I mean during upshift, not downshift. If you were to take your car to Porsche and they put it on their computer and saw that you had hit the limiter several times...would that necessarily be a bad thing? My car is obviously beyond warranty...but if it were still within warranty, does hitting the rev limiter put you in a bad negotiating position with Porsche if something were to go wrong during the warranty period?

Just curious....

newport996

No....hitting the rev limiter is no big deal....EXCEPT you do have the GIAC flash, which raises the rev limiter, and how much this effects it, who knows...probably not much, but on a stock car hitting the rev limiter has no effect on the car.

Chuck Jones

I was unaware that the GIAC chip raised the rev limiter, but now that you mentioned it, I can see where it might make sense that the "performance flash" raises a number of thresholds....do you know what the factory setting on the rev limiter is versus the (??) higher setting of the GIAC chip? And along those lines...do you know what the true "danger zone" would be? I've read of folks missing a shift on downshift and overreving the engine. What is that potential overrev "blow the engine" reading?

newport996

Stock is 7200 rpm.....GIAC may raise it to 7400.....My guess is that damage to the engine would be maybe 7500? downshifting overrevs are bad as they are probably up near 8k-9k+, and the cars speed is driving the motor so it forces those revs....

Mfletch

Hi Chuck! I don't know a thing about your rev-limiter question. I just wanted to say hello. I'm looking forward to getting together...I'm waiting for a new MAF sensor in the mail. I'll call you when it's fixed and we can go for a spin.

fast1

What is that potential overrev "blow the engine" reading?

I didn't save the DME Report that the Dealer gave to me but I recall that the report had six ranges and that ranges 4 - 6 were considered likely to cause engine damage. Range 1 I believe was in the mid 7Ks and I believe that range 4 was in the mid 8K range.

hwk72

When I got my B&M SSK installed, the mechanic told me that the tricky thing with wrong downshifts is that there's no rev limiter that protects the engine, so I guess newport996 is right that these overrevs reach probably 8k+. He told me that he's seeing frequently cars with blown engines because of wrong downshifting especially with short shifters. That said it's obviously harmless to hit the rev limiter when accelerating and I've never heard of blown engines because of that.

99firehawk

I call bs.......... i have seen 3 ever, and 2 of them were massive misshifts that broke the bellhousing from the engine and snapped the crank

99firehawk

not that common to actually casue damage , and hitting the limiter when accelerationg will not hurt anything

1999Porsche911

The 3.4 can hit 8200 before the valves will begin to float.

justinmm2

Agreed - it's not revving too high in gear you need to worry about (I assume you mean "before I've shifted" by "upshifting"), it's the engine revving too high as a result of a missed downshift. In the former scenario, your engine software will save you from yourself. In the latter, it's a question of physics. You'll be dealing with revs far beyond what your software will let you get to.

hwk72

I think you're right "99firehawk". The mechanic may have exaggerated the number by saying that he frequently sees cars with blown engines because of wrong downshifting; maybe because there was a 996tt with this problem in the shop at same time I talked to him. I don't have any empirical evidence of the frequency.

Chuck Jones

Thanks guys for the clarification. I cringed every time I hit the rev limiter when upshifting and had visions of the computer readout screaming...."He hit the limiter...he hit the limiter!!" Now I feel much better and less anxious over abusing the engine.

Mark: Good to hear from you...I'm doing the LMPP or LPPM or LMMP mod...whatever it is...with the 3.6L 996 mufflers...but we can get together this next week if you like. You're employed...I'm retired so it's your call. I want to switch off and drive each other's cars to see what the mods actually feel like...then you can decide if you think it's worth it.

Call anytime you're ready.....Chuck