v12man

Porsche Centre in SA just renewed my motorplan on my Mk1 CS for it's final year - the printout from the inspection showed 3900 odd type 2 ignitions - they did not even blink at it, and considering that they are obliged to fix just about anything that goes wrong free of charge - including pads and disks that wear out - they use just about any excuse to invalidate the motorplan - and they renewed it with no complaint.

I would not worry too much about 8000 ignitions, unless it is a forced 9500 rpm plus, and there is no way to find that out from the count.

MetalSolid

How do you drive your car? May give insight into how the silver car was driven.

A mechanic told me that these type of over revs also hurt the gearbox.

I'm betting the silver car was never tracked... I have a theory, people that track their GT3s are better drivers than those with GT3s that don't, as a result the better driver rev-matches & shifts smoothly, creating less wear on engine and driveline than the guy that really prefers a PDK or automatic... Track guys may wanna adopt this theory when it comes time to sell.

GrantG

I think 8,900 overrevs is equivalent to about 10 seconds at 8,900rpm. I think it counts spark plug ignitions. So, in one minute, you would get 8,900 revolutions at 8,900rpm and since there are six ignitions per revolution, you would get 60sec/6=10sec.

I could live with that if the motor never exceeded 8,900rpm or so, but I couldn't live with a few secs at 11,000 rpm or something like that and it's impossible to tell the difference with that amount of information.

SpeedGeek

Grant will remember a forum discussion about a year ago when I missed a shift (only time in my life) and I think I hit around 9k rpm for a moment before jumping on the clutch. My ECU said 119 ignitions in rev range 2, which freaked me out. But some 15k miles later I've had no trouble, and after seeing this thread I don't feel so bad.

Holger B

Is this GT3 a two-stroke or 12 cylinder?

GrantG

Good point, so I guess it's the equivalent of 20 seconds...

GrantG

I do remember that, but I forgot that there were so few ignitions on your car. That really puts things in perspective. I guess 8,900 really is alot then (and your 119 does seem relatively benign, especially since it's been running like a top). This one is around 75 times worse (or 75 incidents like yours). Sounds like this car should be avoided...

SpeedGeek

Maybe, maybe not. The only way I can imagine having 20 secs of overrev is that the car was a track car in which the driver would often change down while still at slightly too high revs for the lower gear. That would result in a lot of overrev time, but only just overrevved - say 8400 rpm for a second per lap, lap after lap.

OTOH, my single incident may have been for only 119 ignitions, but it may have revved much higher, maybe over 9k. Which one is worse? Hard to know.

GrantG

I think it's this uncertainty which would cause me to avoid the car (without a credible explanation from the owner which might put my mind to rest). It would be helpful if the ECU could record the max rpms (it could calculate it by the rate of overrev ignitions - ignitions per second).

Although it can easily happen once or twice by accident, there is no good reason to repeatedly downshift on a track in a situation that it would put you over 8,200rpm - that would never be beneficial to a fast laptime.

JMeager

Ignition range 1: 7300-7500rpm
Ignition range 2: 7500-7700rpm
Ignition range 3: 7700-7900rpm
Ignition range 4: 7900-8400rpm
Ignition range 5: 8400-9500rpm
Ignition range 6: 9500-11000rpm
That info came from the Durametric manual. It also states as someone did before, range 1 is at the rev limiter, range 2 is over the rev limiter.

Now lets understand this. The car employs a soft rev limit meaning it begins at 7500rpm and is hard on around 7500-7700rpm. It is not possible to get anything above this as the ECU will not provide a fuel or spark above these numbers. It is impossible to have a range 3 mentioned in the ECU manual as the ECU will never spark at those revs as the rev limiter parameter will have been met.

You could have a mis-shift and rev to 10,000rpm for example but the ECU will not log this as it hasn't actually "ignitioned" at that RPM (which is what the ranges mean) - the rev limiter prevents the spark above the range 1-2 ....

So pretty much it doesn't prove too much looking at these rev limit pointers.... I suppose it does tell you someone has been making the most of the rev limiter, but hey, that's what its there for.... to limit the revs to a safe range.....about all it will tell you is if the car was driven by Miss Daisy or driven how it should be....

Cheers,
Jeff

GrantG

Interesting info. I think it may be a mistake to compare overrevs between a GT3MKI and MkII then. The car described in the V12's post is a MkI and SpeedGeek's (and car in original post) is a MkII. They have very different redlines and apparently very different definitions of a Type 2 overrev.

JMeager - are you providing info for a MkI or MkII? Sounds like MkI info?

JMeager

Actually, my apologies. I misread the manual myself! To clarify, the above limits pertain to Boxster (987), 997 and Cayman. So you will get a rundown of the ignitions within those ranges. Basically if you increased the rev limit via ECU modification you would see this reflected in the counts above....

The manual states the Boxster (986) and 996 contain the two ranges. It states that range 1 is "at the rev limiter" and range 2 is "above" the rev limiter. Obviously therefore we don't know what revs "above" is at.... It just implies above.... the ECU technically won't let it rev past a certain point so it can be assumed it's ok.

An example of this is that my car was sitting on the rev limiter for about 2 seconds at a recent track day here in the UK when I ran out of revs up to a corner. This was reflected in both the range 1 count and range 2 count based on the hour it was reported at.

v12man

Metalsolid - the cars is driven probably 50 - 70 % track.

I am sure those ignitions are from 1 specific corner - shortshifting 4th - 2nd - and are only for a fraction of a second under heavy braking, while being a bit too quick releasing the clutch - they have certainly not come from a single incident of an accidental missed shift.

I would have the car leakdown tested and compression tested, and then decide based on that evidence and the basis of it's general condition. Ask for a discount.

abg123

VERY imformative responses. Thank you all very much. So I come to my conclusion.....
It appears the car has been driven hard..and on the track. Certainly these engines are built for it. I have asked the owners to pay for a leakdown and compression test. Being the car is in excellent shape otherwise..and the Porsche PPI confirms this, If the compression and leakdown are positive I would assume this car is a candidate for purchase??

Thanks agian for all the input.

roberga

abg: that would make sense. My jaw dropped when a guy from MOTEC was talking about the revs they see in GT3s. The motors are very strong.