Over-rev madness - how to interpret this data?
10-08-2008, 01:33 PM
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Over-rev madness - how to interpret this data?
There have been a few threads on red-line "violation reports", or referencing these reports as a measure of how hard a particular car has been driven. There are even reports of these being used as a foundation for warranty termination by PCNA.
Coochas had these remarks in one thread...
https://rennlist.com/forums/showthre...light=over+rev
I ran the durametric software on my car and note the following results:
Number of ignitions range 1 2023 / 443h
Number of ignitions range 2 103 / 430h
Number of ignitions range 3 7 / 392h
Number of ignitions range 4 1 / 316h
Number of ignitions range 5 1 / 316h
Number of ignitions range 6 1 / 316h
I find it interesting that a single "ignition" has been noted in each of the ranges 4,5 and 6. So that's one cylinder firing, or, at most, one third of an RPM at these values. Interesting data, not easy to conjure up a real-world situation that would produce such a result. Huge downshift error resulting in rear-wheel lock-up would be one possibility I suppose. It would also seem likely that the range 4,5 and 6 data would represent a single incident (e.g each time a range 5 field is populated, each of the 1,2,3 and 4 ranges would also be populated, and so-on)
This is where I'm left wondering how to interpret over-rev data as insight into the wear and tear on a car. It seems that over-revs can only happen on a misplaced downshift, except for the range 1 and (possibly) 2 over-revs - these can be accomplished by bumping the rev-limiter. This shouldn't be particularly troubling.
Interesting though - the range 6 over-rev on my car was in place when I bought the car and the car received CPO certification.
Coochas had these remarks in one thread...
https://rennlist.com/forums/showthre...light=over+rev
Hi Ken,
The rev limiter kicks in right around redline (7200 rpm) although I think the precise value is affected by Sport on/off and tiptronic/manual.
There is no harm in hitting the rev-limiter which you will immediately realize because it feels like the car is misfiring or hesitating. The objective is of course to avoid "bouncing off the rev-limiter" because this is only slowing you down!
The various ranges for the DME overrevs are shown below (taken from www.durametric.de). The data count the number of ignitions (i.e. sparks) in each range.I once posted a thread in which I intentionally overrevved the car in 3rd gear and generated additional range 1 ignitions.
Many people seem to get Range 2 overrevs as well in 'routine' hard driving.
I believe that since the X51 package has a higher redline (?7400) that the number of Range 1 and 2 ignitions will be significantly higher. Someone correct me if I'm wrong.
Higher range ignitions (say 4 and above) are possible by the so-called "money shift" which can happen by inappropriately selecting a lower gear (for example shifting into 2nd when going 100 mph).
There have also been many threads about the DME scans and their significance. I think it's just the high range (>4) ignitions that are a potential warranty problem.
The 6 ranges can be broken down as:
Range 1: 7300-7500 RPM
Range 2: 7500-7700 RPM
Range 3: 7700-7900 RPM
Range 4: 7900-8400 RPM
Range 5: 8400-9500 RPM
Range 6: 9500-11000 RPM
The rev limiter kicks in right around redline (7200 rpm) although I think the precise value is affected by Sport on/off and tiptronic/manual.
There is no harm in hitting the rev-limiter which you will immediately realize because it feels like the car is misfiring or hesitating. The objective is of course to avoid "bouncing off the rev-limiter" because this is only slowing you down!
The various ranges for the DME overrevs are shown below (taken from www.durametric.de). The data count the number of ignitions (i.e. sparks) in each range.I once posted a thread in which I intentionally overrevved the car in 3rd gear and generated additional range 1 ignitions.
Many people seem to get Range 2 overrevs as well in 'routine' hard driving.
I believe that since the X51 package has a higher redline (?7400) that the number of Range 1 and 2 ignitions will be significantly higher. Someone correct me if I'm wrong.
Higher range ignitions (say 4 and above) are possible by the so-called "money shift" which can happen by inappropriately selecting a lower gear (for example shifting into 2nd when going 100 mph).
There have also been many threads about the DME scans and their significance. I think it's just the high range (>4) ignitions that are a potential warranty problem.
The 6 ranges can be broken down as:
Range 1: 7300-7500 RPM
Range 2: 7500-7700 RPM
Range 3: 7700-7900 RPM
Range 4: 7900-8400 RPM
Range 5: 8400-9500 RPM
Range 6: 9500-11000 RPM
Number of ignitions range 1 2023 / 443h
Number of ignitions range 2 103 / 430h
Number of ignitions range 3 7 / 392h
Number of ignitions range 4 1 / 316h
Number of ignitions range 5 1 / 316h
Number of ignitions range 6 1 / 316h
I find it interesting that a single "ignition" has been noted in each of the ranges 4,5 and 6. So that's one cylinder firing, or, at most, one third of an RPM at these values. Interesting data, not easy to conjure up a real-world situation that would produce such a result. Huge downshift error resulting in rear-wheel lock-up would be one possibility I suppose. It would also seem likely that the range 4,5 and 6 data would represent a single incident (e.g each time a range 5 field is populated, each of the 1,2,3 and 4 ranges would also be populated, and so-on)
This is where I'm left wondering how to interpret over-rev data as insight into the wear and tear on a car. It seems that over-revs can only happen on a misplaced downshift, except for the range 1 and (possibly) 2 over-revs - these can be accomplished by bumping the rev-limiter. This shouldn't be particularly troubling.
Interesting though - the range 6 over-rev on my car was in place when I bought the car and the car received CPO certification.
