Over-rev Questions
03-13-2010, 04:07 PM
#1
Over-rev Questions
I'm having trouble getting the a consistent story/explanation on a read-out I got from the DME on my '04 GT3. Here are the facts:
23,000 miles (I bought "CPO" at 7,900). Spirited driving, but no track time, under my ownership. Have had no issues with car, doesn't use oil (can usually go btwn changes every 3-5k without adding any oil).
Operating hours counter 550.2
Number of ignitions, range 1: 111; 494.5 hours
Number of ignitions, range 2: 1,599; 143.4 hours
I've communicated with three Porsche techs and one independent race shop owner on the foregoing. Here's what I've been told.
1. Range 2 is same as Type-2 (makes sense).
2. 6/GT3 DME does not provide rpm's at which over-revs occurred and Porsche does not publish rpm break-point differentiating range 1 and range 2, but range 1 is about redline or a little below (when rev-limiter kicks in). No way to tell what max revs were in range 2.
3. 6/GT3 DME has 5 over-rev ranges and having a range 2 over-rev is not a big deal - over-revs in higher ranges is (I'm skeptical about this response - see below)
4. 6/GT3 DME has only 2 over-rev ranges. 7/GT3 has 6 over-rev ranges (direct conflict with 3., above hence my skepticism).
5. Car has been in a range 2 over-rev condition for about 4 seconds (1,599/3/133) - don't worry about it given amount of time, that it occurred early in the car's life & no issues since.
So...my questions are:
A. What is true/false in 1-5, above?
B. Do I have anything to worry about with on-going operation of the car or if I sell the car (as I likely will & of course, I'd disclose the DME report)?
C. What, if any, additional testing can be done to determine if there is/isn't an issue with the motor?
Thanks for all of your informed responses. Much appreciated, as always.
23,000 miles (I bought "CPO" at 7,900). Spirited driving, but no track time, under my ownership. Have had no issues with car, doesn't use oil (can usually go btwn changes every 3-5k without adding any oil).
Operating hours counter 550.2
Number of ignitions, range 1: 111; 494.5 hours
Number of ignitions, range 2: 1,599; 143.4 hours
I've communicated with three Porsche techs and one independent race shop owner on the foregoing. Here's what I've been told.
1. Range 2 is same as Type-2 (makes sense).
2. 6/GT3 DME does not provide rpm's at which over-revs occurred and Porsche does not publish rpm break-point differentiating range 1 and range 2, but range 1 is about redline or a little below (when rev-limiter kicks in). No way to tell what max revs were in range 2.
3. 6/GT3 DME has 5 over-rev ranges and having a range 2 over-rev is not a big deal - over-revs in higher ranges is (I'm skeptical about this response - see below)
4. 6/GT3 DME has only 2 over-rev ranges. 7/GT3 has 6 over-rev ranges (direct conflict with 3., above hence my skepticism).
5. Car has been in a range 2 over-rev condition for about 4 seconds (1,599/3/133) - don't worry about it given amount of time, that it occurred early in the car's life & no issues since.
So...my questions are:
A. What is true/false in 1-5, above?
B. Do I have anything to worry about with on-going operation of the car or if I sell the car (as I likely will & of course, I'd disclose the DME report)?
C. What, if any, additional testing can be done to determine if there is/isn't an issue with the motor?
Thanks for all of your informed responses. Much appreciated, as always.
03-13-2010, 04:21 PM
#2
Three Wheelin'
Ok :
- rev range 1 = hitting limiter.
- rev range 2 = > limiter but no categories to show you how bad (unlike 997). 1599 is a pretty low number though so I wouldn't lose a lot of sleep. If you had overrev damage I'm pretty sure it would have manifested by now. Normally fails within a few hundred miles of the overrev if it had any 'hidden' probs.
p.s. not sure how you convert the number of ignitions to time? Is that calc right as I thought 1599 was less time than that...
- rev range 1 = hitting limiter.
- rev range 2 = > limiter but no categories to show you how bad (unlike 997). 1599 is a pretty low number though so I wouldn't lose a lot of sleep. If you had overrev damage I'm pretty sure it would have manifested by now. Normally fails within a few hundred miles of the overrev if it had any 'hidden' probs.
p.s. not sure how you convert the number of ignitions to time? Is that calc right as I thought 1599 was less time than that...
03-13-2010, 05:23 PM
#3
Lifetime Rennlist
Member
j.,
Like you assume your #3 example is incorrect. #4 is spot on.
Just a side note here - I have no idea if it will apply. Normally you would see the Range 1 count higher than the Range 2 count, as theoretically you need to run through Range 1 to get to Range 2. Therefore you would have Range 1 totals included in any Range 2 count. But who knows.
Now, with that said... Here is the one that will throw you a loop:
This IS NOT the first Bosch DME in a 996 that I have seen record a REVERSE Range count. Meaning: If you go out and run the car up to the normal rev limiter (like we do) it will log that normal event as a Range 2. The opposite of what it should. So you in essence continue to add to the Range 2 count and the Range 1 count sits idle for the time being. If you have access to a Range reader you should try that. Jot down the Range numbers, run up to the limiter, then compare. It only takes a second or two to confirm. Again, who knows what you will see.
Lastly I have been told via-Porsche Germany that while this log is incorrect, some of the ECU's do this and they are well aware of it.
Like you assume your #3 example is incorrect. #4 is spot on.
Just a side note here - I have no idea if it will apply. Normally you would see the Range 1 count higher than the Range 2 count, as theoretically you need to run through Range 1 to get to Range 2. Therefore you would have Range 1 totals included in any Range 2 count. But who knows.
Now, with that said... Here is the one that will throw you a loop:
This IS NOT the first Bosch DME in a 996 that I have seen record a REVERSE Range count. Meaning: If you go out and run the car up to the normal rev limiter (like we do) it will log that normal event as a Range 2. The opposite of what it should. So you in essence continue to add to the Range 2 count and the Range 1 count sits idle for the time being. If you have access to a Range reader you should try that. Jot down the Range numbers, run up to the limiter, then compare. It only takes a second or two to confirm. Again, who knows what you will see.
Lastly I have been told via-Porsche Germany that while this log is incorrect, some of the ECU's do this and they are well aware of it.
03-13-2010, 08:01 PM
#4
Rennlist Member
I bought a 2000 996 C2 from a friend that had 43,000 class 1 ignitions. I sold the car in 2005 (undoubtedly with more class one's) and the car is still running strong. However 4 seconds is a long time to not step on the clutch when you've missed a shift so Michael B has a good point that the ECU might have an issue.
Generally with an over-rev I would think that if there is a problem it would have occurred immediately. The only thing I could think of that might be a lingering time bomb is cracked pin bores on the pistons. But with subsequent class one's and so many hours after the class two's happened I think that and any other problem would have shown up long ago. Possibly related issues such as broken rings, bent valves, broken valve springs or timing chain issues would show up as a noise or with a leak down test.
Given that it happened such a long time ago and nothing has shown up since I wouldn't worry about it and neither should a prospective buyer....except to beat you up on the price of course
Generally with an over-rev I would think that if there is a problem it would have occurred immediately. The only thing I could think of that might be a lingering time bomb is cracked pin bores on the pistons. But with subsequent class one's and so many hours after the class two's happened I think that and any other problem would have shown up long ago. Possibly related issues such as broken rings, bent valves, broken valve springs or timing chain issues would show up as a noise or with a leak down test.
Given that it happened such a long time ago and nothing has shown up since I wouldn't worry about it and neither should a prospective buyer....except to beat you up on the price of course
03-13-2010, 08:21 PM
#5
Race Director
I bought a 2000 996 C2 from a friend that had 43,000 class 1 ignitions. I sold the car in 2005 (undoubtedly with more class one's) and the car is still running strong. However 4 seconds is a long time to not step on the clutch when you've missed a shift so Michael B has a good point that the ECU might have an issue.
Generally with an over-rev I would think that if there is a problem it would have occurred immediately. The only thing I could think of that might be a lingering time bomb is cracked pin bores on the pistons. But with subsequent class one's and so many hours after the class two's happened I think that and any other problem would have shown up long ago. Possibly related issues such as broken rings, bent valves, broken valve springs or timing chain issues would show up as a noise or with a leak down test.
Given that it happened such a long time ago and nothing has shown up since I wouldn't worry about it and neither should a prospective buyer....except to beat you up on the price of course
Generally with an over-rev I would think that if there is a problem it would have occurred immediately. The only thing I could think of that might be a lingering time bomb is cracked pin bores on the pistons. But with subsequent class one's and so many hours after the class two's happened I think that and any other problem would have shown up long ago. Possibly related issues such as broken rings, bent valves, broken valve springs or timing chain issues would show up as a noise or with a leak down test.
Given that it happened such a long time ago and nothing has shown up since I wouldn't worry about it and neither should a prospective buyer....except to beat you up on the price of course
But far and away if the engine suffers any damage it is from valve float and valve and piston contact.
Just because the engine suffered an overrev doesn't mean valve float happened. There is some margin and how much varies. As we already know some engines use little oil, get better than average gas mileage, produce over advertised HP so it is not unreasonable that some engines have a higher resistance to valve float.
Sincerely,
Macster.
03-14-2010, 09:50 PM
#6
Rennlist Member
The 2004-2005 Porsche 996 GT3 Digital Motor Electronics does not record very many different types of data. Relevant to your question it provides the following.
Range 1: engine ignitions at electronic limiter
Range 2: engine ignitions over specified rpm
Cumulative total engine ignitions with time of last recording listed in hours. Range 1 count does not get included in Range 2, they are separate.
Many of us owners believe that the Range 2 are from anything other than hitting the electronic revolution limiter, typically occurring when the driver down shifts into too low a gear and the drive train forces the engine to speed up over the specified limit.
Analysis of possible engine damage from Range 2 is difficult because the maximum rpm value is not recorded. There is a factor of safety between the rpm limit and the actual rpm level where the valves “float” or some other issue occurs. As ohters stated, if the engine rpm exceeded the factor of safety range then the damage should be very apparant.
At 8200 rpm there are 410 ignitions per second
Gears 1 - 4, maximum rpm is 8200
Gears 5 - 6, maximum rpm is 8000
Your Questions:
1. I don't know
2. True
3. False
4. I think that is True
5. Cumulative time is about 4 seconds, do not know how many times that condition occurred, see above - that major damage should have been very apparant.
The Range 1 count is really low considering drivers often get carried away while accelerating and hit the electronic rev limiter. I don't know about the two being reversed as others mentioned. In general nobody should be getting Range 2 if operating the GT3 correctly but stuff happens.
Range 1: engine ignitions at electronic limiter
Range 2: engine ignitions over specified rpm
Cumulative total engine ignitions with time of last recording listed in hours. Range 1 count does not get included in Range 2, they are separate.
Many of us owners believe that the Range 2 are from anything other than hitting the electronic revolution limiter, typically occurring when the driver down shifts into too low a gear and the drive train forces the engine to speed up over the specified limit.
Analysis of possible engine damage from Range 2 is difficult because the maximum rpm value is not recorded. There is a factor of safety between the rpm limit and the actual rpm level where the valves “float” or some other issue occurs. As ohters stated, if the engine rpm exceeded the factor of safety range then the damage should be very apparant.
At 8200 rpm there are 410 ignitions per second
Gears 1 - 4, maximum rpm is 8200
Gears 5 - 6, maximum rpm is 8000
Your Questions:
1. I don't know
2. True
3. False
4. I think that is True
5. Cumulative time is about 4 seconds, do not know how many times that condition occurred, see above - that major damage should have been very apparant.
The Range 1 count is really low considering drivers often get carried away while accelerating and hit the electronic rev limiter. I don't know about the two being reversed as others mentioned. In general nobody should be getting Range 2 if operating the GT3 correctly but stuff happens.
Last edited by enthusiast; 03-14-2010 at 10:09 PM.
03-14-2010, 11:09 PM
#7
Nordschleife Master
My understanding is that the damage happens right now. Also a local Seattle shop that deals in this said that they have seen GT3 hit over 9,000 RPM on telemetry from time to time. Said more often the pressure plate or pulley take the hit.
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03-16-2010, 12:37 AM
#8
Thanks a lot for all of the feedback - very helpful. A Porsche tech was able to confirm for me, after communicating with Porsche engineering, that the range 1 counter stops when a range 2 condition is reached (i.e. the range 1 count is not cumulative and, therefore, the counts aren't reversed). I guess the last 2 questions are: Is there any reasonable, economic way to test for the valve float/piston damage; and would a compression and/or leak-down test be of any value?
03-16-2010, 12:08 PM
#9
Race Director
Thanks a lot for all of the feedback - very helpful. A Porsche tech was able to confirm for me, after communicating with Porsche engineering, that the range 1 counter stops when a range 2 condition is reached (i.e. the range 1 count is not cumulative and, therefore, the counts aren't reversed). I guess the last 2 questions are: Is there any reasonable, economic way to test for the valve float/piston damage; and would a compression and/or leak-down test be of any value?
The engine controller constantly monitors each cylinder's output -- measuring the acceleration imparted by the cyilnder's power stroke to the engine at the flywheel. If the output is too low (or too high) the engine controller sets a misfire error code and will light or flash the CEL. Thus if any cylinder had a bent valve that wasn't sealing right the engine controlller would have detected this and flagged a misfire.
If during an extended test drive -- roughly I'd suggest this be 30 miles long (it can be 15 miles with the owner driving the vehicle with you as a passenger then the same route with you driving the car and the owner as a passenger) --if the check engine light stays off (and you verified the bulb is present and the light works cause when you turn on the key you see the light come on then go off when the engine starts), the engine's ok.
The above assumes the engine starts up just fine cold, warm, or hot, exhibits no odd noises at any time, is fluid tight, pulls strongly and smoothly from just over idle to near redline, and in short just otherwise behaves itself and gives you no cause for concern.
Sincerely,
Macster.
03-19-2010, 06:49 PM
#10
The car runs just fine, including for extended periods of time. I've put 15k trouble free miles on the car. The CEL light is there at start-up but never lights up while driving, so I'm not going to worry about - we'll see what the potential buyers have to say. Thanks again for all of the insight & advice.
03-19-2010, 09:00 PM
#12
Nordschleife Master
Thanks a lot for all of the feedback - very helpful. A Porsche tech was able to confirm for me, after communicating with Porsche engineering, that the range 1 counter stops when a range 2 condition is reached (i.e. the range 1 count is not cumulative and, therefore, the counts aren't reversed). I guess the last 2 questions are: Is there any reasonable, economic way to test for the valve float/piston damage; and would a compression and/or leak-down test be of any value?
04-09-2010, 04:09 PM
#13
7th Gear
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Help with DME rev-counter question!
HELP!
I am looking at CPO 987 Boxsters, and one that I am interested in is a 2005 S, with low mileage (9500) and it is CPO'd by Porsche. I received the DME printout today Who can help me make some sense of this?
# of ignitions: Range 1 - 444, at 279.2h
Range 2: 2 ignitions @ 157.2h
Range 3: 2 ignitions @ 157.2h
Range 4: 1 ignition @ 157.2h
Range 5: 1 ignition @ 157.2h
Range 6: 1 ignition @ 157.2h
Total hours 293.4.
OK, so Range 1 doesn't bother me because that's right at redline (If I am not mistaken) and because 444 ignitions is practically nothing - a few seconds, correct? Bump the rev limiter 4 times in the car's life and you're there. Again, range 2 and 3 aren't TOO high, and the number of ignitions is so tiny. 4,5,6 are bad ranges as I'm told, but what is with just 1 ignition in each?? Is that reliable, or spurious? What do you guys make of this?
I haven't spoken to any Porsche service personnel or independent techs, about it yet.
I am looking at CPO 987 Boxsters, and one that I am interested in is a 2005 S, with low mileage (9500) and it is CPO'd by Porsche. I received the DME printout today Who can help me make some sense of this?
# of ignitions: Range 1 - 444, at 279.2h
Range 2: 2 ignitions @ 157.2h
Range 3: 2 ignitions @ 157.2h
Range 4: 1 ignition @ 157.2h
Range 5: 1 ignition @ 157.2h
Range 6: 1 ignition @ 157.2h
Total hours 293.4.
OK, so Range 1 doesn't bother me because that's right at redline (If I am not mistaken) and because 444 ignitions is practically nothing - a few seconds, correct? Bump the rev limiter 4 times in the car's life and you're there. Again, range 2 and 3 aren't TOO high, and the number of ignitions is so tiny. 4,5,6 are bad ranges as I'm told, but what is with just 1 ignition in each?? Is that reliable, or spurious? What do you guys make of this?
I haven't spoken to any Porsche service personnel or independent techs, about it yet.
04-09-2010, 07:29 PM
#14
Race Director
HELP!
I am looking at CPO 987 Boxsters, and one that I am interested in is a 2005 S, with low mileage (9500) and it is CPO'd by Porsche. I received the DME printout today Who can help me make some sense of this?
# of ignitions: Range 1 - 444, at 279.2h
Range 2: 2 ignitions @ 157.2h
Range 3: 2 ignitions @ 157.2h
Range 4: 1 ignition @ 157.2h
Range 5: 1 ignition @ 157.2h
Range 6: 1 ignition @ 157.2h
Total hours 293.4.
OK, so Range 1 doesn't bother me because that's right at redline (If I am not mistaken) and because 444 ignitions is practically nothing - a few seconds, correct? Bump the rev limiter 4 times in the car's life and you're there. Again, range 2 and 3 aren't TOO high, and the number of ignitions is so tiny. 4,5,6 are bad ranges as I'm told, but what is with just 1 ignition in each?? Is that reliable, or spurious? What do you guys make of this?
I haven't spoken to any Porsche service personnel or independent techs, about it yet.
I am looking at CPO 987 Boxsters, and one that I am interested in is a 2005 S, with low mileage (9500) and it is CPO'd by Porsche. I received the DME printout today Who can help me make some sense of this?
# of ignitions: Range 1 - 444, at 279.2h
Range 2: 2 ignitions @ 157.2h
Range 3: 2 ignitions @ 157.2h
Range 4: 1 ignition @ 157.2h
Range 5: 1 ignition @ 157.2h
Range 6: 1 ignition @ 157.2h
Total hours 293.4.
OK, so Range 1 doesn't bother me because that's right at redline (If I am not mistaken) and because 444 ignitions is practically nothing - a few seconds, correct? Bump the rev limiter 4 times in the car's life and you're there. Again, range 2 and 3 aren't TOO high, and the number of ignitions is so tiny. 4,5,6 are bad ranges as I'm told, but what is with just 1 ignition in each?? Is that reliable, or spurious? What do you guys make of this?
I haven't spoken to any Porsche service personnel or independent techs, about it yet.
Note the engine has nearly 300 hours of run time and the "overrevs" occured at 157.2 hours so the engine's run nearly 150 hours since these events and apparently still runs just fine and is not emitting any error codes (misfires) or exhibiting any signs of a sick engine.
If so, then the numbers mean nothing, are not real, or if real (and I doubt it), the over revs didn't result in any damage to the engine.
The possible concern that came up is if someone bought a car with these spurious numbers (assuming they are spurious) and something did happen would perhaps the dealer or the factory or even a 3rd party warranty (extended service) provider reject any engine related claim cause the presence of the even single ignitions in the higher over rev ranges. That is would these numbers still be classified as spurious is some serious money was on the line?
Unfortunately I don't recall what if anything was decided.
But I note in your car's case the car has apparently received a CPO classification and this even with the over rev numbers so someone doesn't seem to think those numbers are significant.
As long as you have paperwork that shows the CPO classification awarded the car and with the dealer and I assume the factory in possession of those numbers then that would I think protect you should the engine exhibit problems and you have to file a claim against the CPO coverage. As long as you didn't add to the more serious over rev range counts of course.
But I will sit back and see what others have to say.
Sincerely,
Macster.
04-10-2010, 12:20 AM
#15
7th Gear
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Thanks, Macster - I am thinking along the same lines...I have the over-rev sheet, it's dated, the car is certified, and I have not yet taken ownership as of the date of the printout - so as long as I don' t add to it later...and I too vaguely remember seeing something about the '1' ignition being some sort of an artifact. If that's the case, then the counter suggests this car has actually been kind of babied, for the most part.
