Rennteam 2.0 - EN - Forum - Re: Rev Limiter - Page1

Oct 8, 2006 12:30:29 PM

devo: Veteran; Loc: NY , United States; Posts: 1107, Gallery; Registered on: Jan 31, 2006

Rev Limiter

Does anyone have any information regarding the rev limter on the 997 turbo? I'm curious as to when the limiter cuts in and does it protect agaist missed shifts.
Secondly, am I correct in believing that it does not protect against improper downshifts?
I recall reading something in the manual about the cut off being more aggressive in sport mode.
Thanks for any input.

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Oct 8, 2006 7:43:53 PM

RC: Rennteam Administrator; Loc: Rennteam HQ , Germany; Posts: 59592, Gallery; Registered on: Mar 26, 2002; Reply to: devo

Re: Rev Limiter

Quote:
devo said:
Does anyone have any information regarding the rev limter on the 997 turbo? I'm curious as to when the limiter cuts in and does it protect agaist missed shifts.
Secondly, am I correct in believing that it does not protect against improper downshifts?
I recall reading something in the manual about the cut off being more aggressive in sport mode.
Thanks for any input.

1. if you forget to upshift, chances are not very high that something has been damaged, actually there are close to Zero.
2. if you downshift wrongly, meaning for example at a too high rev figure, chances are very high that you have destroyed or at least damaged something. Such bad downshifts are RECORDED in the car's ECU unit, meaning that Porsche can always prove that it was your fault.

The cut off at the rev limiter is indeed more aggressive but like I pointed out in point 1., there is no danger in that. Unfortunatley this setup doesn't "save" you from bad downshifts, damage is very likely to occur, even if your car is still driving and not making any strange noises.

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Oct 8, 2006 10:13:58 PM

devo: Veteran; Loc: NY , United States; Posts: 1107, Gallery; Registered on: Jan 31, 2006; Reply to: RC

Re: Rev Limiter

RC, thanks for the info. So is the only real danger when you over rev during a downshift? Can you tell me if the engine is protected against "missed" upward shifts?
Furthermore, can you tell me where the limiter cuts in. I realize that the red line is @ 6600 rpms, but where is the rev limiter active?
I was unable to find any info in the manual.

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Oct 8, 2006 11:00:43 PM

ADias: Rennteam Pro; Loc: Southwest USA , United States; Posts: 2495, Gallery; Registered on: Apr 9, 2004; Reply to: devo

Re: Rev Limiter

Quote:
devo said:...tell me if the engine is protected against "missed" upward shifts?...

What do you mean by "missed" upward shifts? Perhaps you mean the following scenario: suppose you are revving up in 3rd and try to shift to 4th (close to the redline), but instead engage a 2nd gear, you may overrev the engine and the rev limiter will not protect you. This will be indeed a Type 2 overrev - the bad kind.

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Oct 8, 2006 11:28:09 PM

xandi911: Senior; Loc: brasil; Posts: 688, Gallery; Registered on: Feb 14, 2006; Reply to: ADias

Re: Rev Limiter

some1 knows the perfect RPM to change gears with the 997TT?

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Oct 8, 2006 11:36:40 PM

rhino: Rennteam Pro; Loc: Island , Saint Lucia; Posts: 2866, Gallery; Registered on: Jan 26, 2006; Reply to: xandi911

Re: Rev Limiter

You're just going to have to get the feel of your new car. When going slow you should shift above 1500rpm and below 3500rpm. When halling a$$ just before redline

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Oct 9, 2006 12:10:00 AM

devo: Veteran; Loc: NY , United States; Posts: 1107, Gallery; Registered on: Jan 31, 2006; Reply to: ADias

Re: Rev Limiter

Quote:
ADias said:
Quote:
devo said:...tell me if the engine is protected against "missed" upward shifts?...

What do you mean by "missed" upward shifts? Perhaps you mean the following scenario: suppose you are revving up in 3rd and try to shift to 4th (close to the redline), but instead engage a 2nd gear, you may overrev the engine and the rev limiter will not protect you. This will be indeed a Type 2 overrev - the bad kind.

I understand the type RC explained, however, a missed shift is what I was asking about. I.E. 1st to 2nd, and you don't engage second, thinking you have, but have not, therefore "missing" the shift. When you depress the accelerator again after believing you're in second. If this happened, would the limiter work? And, if so at what rpm?

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Oct 9, 2006 12:12:21 AM

devo: Veteran; Loc: NY , United States; Posts: 1107, Gallery; Registered on: Jan 31, 2006; Reply to: rhino

Re: Rev Limiter

Quote:
rhino said:
You're just going to have to get the feel of your new car. When going slow you should shift above 1500rpm and below 3500rpm. When halling a$$ just before redline

Done that, it's great. But, what if you missed the redline shift; going up in sequence, not down.

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Oct 9, 2006 12:15:22 AM

devo: Veteran; Loc: NY , United States; Posts: 1107, Gallery; Registered on: Jan 31, 2006; Reply to: devo

Re: Rev Limiter

I believe that the reason that downshifts are not protected is because the drivetrain is forcing the revs to match the wheels/gears speed, thereby forcing the revs past the limiter.

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Oct 9, 2006 12:22:18 AM

Scotty A: Senior; Loc: New Jersey; Posts: 606, Gallery; Registered on: May 31, 2006; Reply to: devo

Re: Rev Limiter

If the question is: will the rev limiter work while the trannie is in neutral? then the answer is: yes. The rev limiter cuts off the fuel based on the engine speed and has nothing to do with ground speed, wheel speed, etc.

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Oct 9, 2006 12:34:35 AM

devo: Veteran; Loc: NY , United States; Posts: 1107, Gallery; Registered on: Jan 31, 2006; Reply to: Scotty A

Re: Rev Limiter

Quote:
Scotty A said:
If the question is: will the rev limiter work while the trannie is in neutral? then the answer is: yes. The rev limiter cuts off the fuel based on the engine speed and has nothing to do with ground speed, wheel speed, etc.

Yes, that's my question. Thank you. Do you know at what rpm it cuts in?
Regarding wheel speed, I was refering to the other type of over revs, when you downshift. I was saying that i thought the reason the downshifts are not protected is because of wheel speed; just speculation, maybe I'm wrong.

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Oct 9, 2006 1:13:38 AM

ADias: Rennteam Pro; Loc: Southwest USA , United States; Posts: 2495, Gallery; Registered on: Apr 9, 2004; Reply to: devo

Re: Rev Limiter

Quote:
devo said:
Quote:
Scotty A said:
If the question is: will the rev limiter work while the trannie is in neutral? then the answer is: yes. The rev limiter cuts off the fuel based on the engine speed and has nothing to do with ground speed, wheel speed, etc.

Yes, that's my question. Thank you. Do you know at what rpm it cuts in?
Regarding wheel speed, I was refering to the other type of over revs, when you downshift. I was saying that i thought the reason the downshifts are not protected is because of wheel speed; just speculation, maybe I'm wrong.

OK you could have explained your meaning of missed upshift... yes, if in neutral and you floor it, it will hit redline and the rev limiter will intervene. The rev limiter should kick in very close to 6600RPM on the Turbo, maybe 6700RPM.

Yes, downshift misses are caused by the wheels/transmission overreving the engine. You can mitigate the error by clutching very fast.

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Oct 9, 2006 1:22:18 AM

devo: Veteran; Loc: NY , United States; Posts: 1107, Gallery; Registered on: Jan 31, 2006; Reply to: ADias

Re: Rev Limiter

Quote:
ADias said:
Quote:
devo said:
Quote:
Scotty A said:
If the question is: will the rev limiter work while the trannie is in neutral? then the answer is: yes. The rev limiter cuts off the fuel based on the engine speed and has nothing to do with ground speed, wheel speed, etc.

Yes, that's my question. Thank you. Do you know at what rpm it cuts in?
Regarding wheel speed, I was refering to the other type of over revs, when you downshift. I was saying that i thought the reason the downshifts are not protected is because of wheel speed; just speculation, maybe I'm wrong.

OK you could have explained your meaning of missed upshift... yes, if in neutral and you floor it, it will hit redline and the rev limiter will intervene. The rev limiter should kick in very close to 6600RPM on the Turbo, maybe 6700RPM.

Yes, downshift misses are caused by the wheels/transmission overreving the engine. You can mitigate the error by clutching very fast.

Nice to know; clutching fast could save a lot of headaches. Anyway, I thought I explained myself pretty well, but, thanks so much for the info.

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