PPI's and Overrev results

[smit2100]

Someone may find this of use on Overrev results

Rev Range Activity....a much discussed and often misunderstood topic striking fear in to the hearts of those exploring Porsche ownership or those looking to renew or activate insurance backed warranty schemes on their vehicles.

We embraced the importance of Rev Range activity many years ago and our contribution towards a universal clarity has been significant. Our buyer Tom has become something of a specialist on the topic and to this end is regularly approached for subjective advice. In theory the principles behind Rev Range activity are simple, it’s the variation in data interpretation that causes issues.

Engines are designed to operate up to a maximum rotational speed. The manufacturer uses a rev limiter to prevent engine speeds exceeding a pre-determined point of safety. At full throttle and whilst pushing and holding the accelerator pedal down indefinitely the engine can’t and won’t exceed the rotational speed of the limiter. However, when a driver selects too low a gear relative to the speed of travel, the momentum of the car can mechanically drive the engine past a point of safety.

Rev Range data is stored in the cars ECU (engine control unit). The ECU is able to record and store engine ignitions at or past the cars limiter. On a 6 cylinder engine there are 3 ignition pulses per engine revolution. Ignitions are recorded as a cumulative total throughout a cars life.

• 986 and 996 models have 2 Rev Ranges. Rev Range 1 records ignitions at the rev limiter whilst Rev Range 2 records ignitions beyond the limiter

• 987, 997, 981 and 991 models have the ability to record ignitions in 6 different ranges. Rev Range 1 and 2 record ignitions at or just below the limiter. Ranges 3 through 6 represent increasingly higher engine speeds

Shown below are the engine speed ranges for selected models within the Porsche line-up in revolutions per minute

 

	Range 1	Range 2
996 Boxster	> 7200 and < 7800	> 7800
996 Carrera	> 7300 and < 7900	> 7900
996 Turbo and 996 GT2	> 6750 and < 7250	> 7250
996 GT3	> 8200 and < 8800	> 8800
Cayenne 3.2 (V6)	> 6700 and < 6900	> 6900
Cayenne S 4.5 (V8)	> 6900 and < 7200	> 7200
Cayenne Turbo	> 6670 and < 7000	> 7000

 

	Range 1	">Range 2	Range 3	Range 4	Range 5	Range 6
987 Boxster	> 7200 and < 7500	> 7500 and < 7700	> 7700 and < 7900	> 7900 and < 8400	> 9400 and < 9500	> 9500
997 Carrera	> 7300 and < 7500	">> 7500 and < 7700	> 7700 and < 7900	> 7900 and < 8400	> 8400 and < 9500	> 9500
997 GT3	> 9000 and < 9200	> 9200 and < 9400	> 9400 and < 9600	> 9600 and < 10000	> 10000 and < 11000	> 11000
997 Turbo	> 6800 and < 7000	> 7000 and < 7200	> 7200 and < 7400	> 7400 and < 7900	> 7900 and < 9000	> 9000

 

Until recently ignitions recorded in ranges 3 and 4 were considered by the Manufacturer to be safe with such vehicles still eligible for Porsche Extended warranty. Ignitions recorded in Ranges 5 and 6 would not be considered for warranty with existing policies invalidated at the point of over rev. Current Porsche warranty procedure considers activity in ranges 3 and 4 to be potentially problematic with compression tests and / or oil checks deemed necessary for incursions within the last 200 operating hours. However, in a pragmatic relaxation of previous protocol vehicles with activity in ranges 5 and 6 will be considered for extended warranty provided the over rev activity occurred more than 200 operating hours ago. The warranty provision is at the discretion of the importer and subject to the aforementioned compression/oil checks.

An operating hour log captures the exact moment when the most recent activity within a given rev range is recorded. The timing of the most recently recorded over rev is as significant as the over-rev itself.

When the engine rev limiter is exceeded the engine can fail or be damaged leaving it susceptible to future failure. Instant failure would normally be caused by valves hitting a piston. Subsequent or delayed failure is often caused by a compromised timing chain which can be weakened or stretched at high engine speeds. If a timing chain were to be excessively stretched failure is possible due to the abrasive effect of a slack chain against the sprocket teeth on which it runs.

Industry experts would suggest a 50 operating hour window of danger after the point of an over rev where chains or associated inter-gear can fail or develop problems leading to costly engine work / engine rebuilds.

At 911Virgin our purchase policy prevents us from considering a car with engine over rev activity beyond the rev limiter within the last 50 operating hours.

We are regularly approached to help interpret Rev Range Data. The ability to separate genuine incident from an erroneous recording is critical. In general terms we would consider the registering of less than 10 ignitions within a given range to be no cause for concern. 10 ignitions represents fractions of a second, insufficient time, in our experience to cause damage. Porsche take a different view and consider the registering of a single ignition (one third of an engine revolution) to be relevant. A single ignition recorded in rev range 3 or higher within a 200 operating hour period means that an engine compression test is deemed necessary.

The registering and recording of a single ignition at such high engine speed, in our view, is just not possible in the same way that a single ignition in, for example, Rev Range 4 can't follow a single ignition in the previous rev range. In order to pass in to a higher bracket of engine speed the engine must complete at least a full engine revolution, a minimum of 3 ignitions.

We are regularly asked if Tiptronic and PDK equipped Porsches can record legitimate engine ignitions past the limiter; Due to the manner in which the gearbox automatically changes up a gear when the engine speed reaches a certain point it is unlikely but not impossible. We recall a 996 Tiptronic Turbo that we travelled to purchase. On the surface a beautiful car but with 313 ignitions recorded in Rev Range 2, the most recent of which recorded within the last 3 operating hours, not a car we were prepared to buy. A wasted journey, but with the benefit of hindsight a narrow escape. Two weeks later we were contacted by the owner of the car who, after our viewing, had managed to find a private buyer for his vehicle. The buyers pre-purchase inspection picked up on an engine rattle, he pulled out of the sale narrowly avoiding a large bill because a week later the inter-gear failed and the engine needed to be rebuilt. We eventually got to the bottom of how ignitions were recorded past the red line. Whilst on a final blast before attempting to sell to ourselves, a moment of indiscretion racing a group of motorbikes saw the limiter exceeded whilst at full throttle down a long steep hill. The incline caused the car to travel faster than it otherwise would have done, the cars momentum taking the engine past its limiter damaging it in the process.

The image below shows the Rev Range print out from the car in question

The print out shows 7904 ignitions recorded at the limiter (Rev range 1). The figure to the right shows when the last incident occurred. In this instance 2262.8 hours.

313 ignitions have been recorded past the limiter (Rev range 2) with the last incident also occurring at 2262.8 hours.

The significance of any over rev can only be fully understood by considering it in relation to the total operating hours for the vehicle. In this instance the car has been used for a total of 2265.7 hours meaning the last rev range 2 activity occurred just 2.9 operating hours ago well inside our suggested 50 hour danger window. We are not able to determine the number of ignitions recorded at this moment as 313 is a cumulative total from new. It could be a single ignition, it could be significantly more but in our mind it would not be worth taking the risk.

Calculating the period of time that a car has spent at the rev limiter can also be of use. Using the example of the 996 Turbo above with a rev range 1 threshold of 6750rpm the following calculation can be used

Number of igntions / 3 = number of engine revolutions

 

Number of revolutions / by rev limiter = minutes spent at limiter

 

Minutes spent at limiter x 60 = seconds spent at limiter.

 

Consequently using the above data.

 

7904 / 3 = 2634.7

 

2634.7 / 6750 = 0.39 minutes

 

0.39 x 60 = 23.4 seconds spent at the limiter as a cumulative total from new

It is not possible to accurately calculate the exact time spent past the limiter in range 2 due to us not knowing the exact engine speed reached on each occasion. We know it to be higher than 6750rpm but we can't be any more accurate than that.

The maximum number of ignitions that can be recorded is 65,535.

An understanding of the significance of Rev Range activity is important but so too is a pragmatic approach. A lack of consistency from the manufacturer has turned the subject topic in to something of a hot potato, all smoke, mirrors and mystique. Despite all this the principles are straightforward and simple to understand. A don't panic but don't dismiss approach best sums up the methodology in respect of our buying process.

We hope this overview has been of some use.

[Macca]

Wow, I have to say a very interesting read. Thank you. 

[symsy]

My calculator broke…. Just you wait till you get on that plane and drive that car of yours , I bet you will still be tempted to see if that carpet is in the way of getting that accelerator a little harder on the floor   

As for the math , just look at the rev counter a little and the speedo occasionally , whilst having one eye out in front and one in the rear mirror 

You only have 12 Demerits and the speed limit in VIC 100  , I think thats 2nd gear or possibly 1st if you over rev and take of the rev limiter 

 

[smit2100]

My calculator broke…. Just you wait till you get on that plane and drive that car of yours , I bet you will still be tempted to see if that carpet is in the way of getting that accelerator a little harder on the floor   

As for the math , just look at the rev counter a little and the speedo occasionally , whilst having one eye out in front and one in the rear mirror 

You only have 12 Demerits and the speed limit in VIC 100  , I think thats 2nd gear or possibly 1st if you over rev and take of the rev limiter 

 

I have it on pretty good authority that I will impressed with the overall drive and handling and condition of the car.  However as I suspected, I have had some degree of confirmation that I will be somewhat underwhelmed with the lack of boost / straight line speed, particularly in second and third gear / down low in the rev range from what I used to (unfortunately an over-rev event would not  be a remedy, nor will removing the carpet).  I am in the process of working on having that rectified (two phased approach - immediate and longer term) and I will be extremely disappointed if a  couple of  range 1  activity ecu records based on doing  for some 3rd gear pulls at WOT to produce some logs are not registered within two weeks of having stepped into the car for a first drive.

[Troy997.1]

Well written Smit2100, there is a lot of talk both here and overseas about the over rev report and what it means.  I don't believe there is as much concern in the USA as elsewhere.

Before I brought my Porsche, I had a PPI done by PCM. When speaking with the Porsche guy, he went thru all the items they had picked up, lucky no action was required. He then said there had been one over rev in range 5. He implied this was a big deal and I should look at walking away. I then spent the next 24 hours reading as much as I could to do with over revs. I came to the conclusion, that no over revs the range above 2 are great and a range 5 over rev could damage the engine, however how long ago was it?  I'd read the real thing to consider was the time since the over rev and that after 50 hours - 100hrs of use there is no real problem. I went back to the P guy and asked the question "how long ago" over 1500 hrs was the reply. To my surprise he said there was no real danger due to the time since the over rev??

Also consider this, a Porsche is a car to be owned and driven as intended. If you want to keep you Porsche in cotton wool, so the next owner can really enjoy it. 

Let me know when you're ready to sell.

 

 

[MezgerMan]

The information @smit2100 has helpfully posted was sourced from 911 Virgin. From another page of their web site it's clear they're very particular about which vehicles they accept for resale.

[Raven]

I Recently purchased a durametric diagnostic tool  for my 06 997,s with close to 46000 klm on the dial and spent a little time today with the laptop plug into the car just to get my head around it and see what I could learn as you do,,,one thing that has got me stumped is the cars Ignition range figure  ....?

So these are my ignition range figure below  and was after some different opinions on what you guys think about the cars ignition range history ,,,,,I do drive the car to its full potential and can honesty understand the the figures in the first 3 ranges but the one figure in ranges 4 , 5 , 6  at 1018.4 hr has got me baffled as the above information claims that either I or the previous owner have Rev the engine to 9500rpm on a down shift ...

Are these figure correct and is it even possible to do that to an M97 with out and engine failure or damage of some kind ....also keep in mine this event happened some 360 hrs ago ,,I have had the car for  2.5  years and done almost 6000 klm of driving in that time ,,,prior to purchasing I had a PPI and there was no mention of this over rev that surely would have show up in the PPI ,,,,,,as far as I am concerned the engine runs and performs as flawlessly as the day I got it so I am putting this out to you guys what do you think of these figure ,,, Correct or some sort of anomaly 

 

Number of ignitions range 1		2247 / 1374h
Number of ignitions range 2		222 / 1367h
Number of ignitions range 3		12 / 1366.9h
Number of ignitions range 4		1 / 1018.4h
Number of ignitions range 5		1 / 1018.4h
Number of ignitions range 6		1 / 1018.4h
Operating hours counter		1374.8

[Coastr]

Full throttle down an incline in a 996t?  Yikes I'm guessing he beat the bikes.   Anyway back on topic.

[9r]

I Recently purchased a durametric diagnostic tool  for my 06 997,s with close to 46000 klm on the dial and spent a little time today with the laptop plug into the car just to get my head around it and see what I could learn as you do,,,one thing that has got me stumped is the cars Ignition range figure  ....?

So these are my ignition range figure below  and was after some different opinions on what you guys think about the cars ignition range history ,,,,,I do drive the car to its full potential and can honesty understand the the figures in the first 3 ranges but the one figure in ranges 4 , 5 , 6  at 1018.4 hr has got me baffled as the above information claims that either I or the previous owner have Rev the engine to 9500rpm on a down shift ...

Are these figure correct and is it even possible to do that to an M97 with out and engine failure or damage of some kind ....also keep in mine this event happened some 360 hrs ago ,,I have had the car for  2.5  years and done almost 6000 klm of driving in that time ,,,prior to purchasing I had a PPI and there was no mention of this over rev that surely would have show up in the PPI ,,,,,,as far as I am concerned the engine runs and performs as flawlessly as the day I got it so I am putting this out to you guys what do you think of these figure ,,, Correct or some sort of anomaly 

 

Number of ignitions range 1		2247 / 1374h
Number of ignitions range 2		222 / 1367h
Number of ignitions range 3		12 / 1366.9h
Number of ignitions range 4		1 / 1018.4h
Number of ignitions range 5		1 / 1018.4h
Number of ignitions range 6		1 / 1018.4h
Operating hours counter		1374.8

They have to be erroneous figures as it is not physically possible to have 1 ignition in those ranges, the engine can't spin up that quick in 1/3 of a vevolution

[Raven]

Yeh I agree it has to be some sort of glitch or false reading as you said it is impossible to take the engine to that rpm even on a bad down shift into the wrong gear,,,I just found the figures interesting and wanted to hear some different opinions and views on what members thought this could be ...or if any one had all so experienced a similar set of False figures in those ignition ranges .......  

[Peter M]

And if it was true wouldn't the range 1, 2 and 3 also be time clocked at 1018 hours too?  (actually the time on these would be less than or equal to 1018 hours but since there hasn't been any readings in these ranges since 1018 you can doubly write the 4, 5 & 6 off as glitches)

[Pokiou]

I'd be interested to see what i get on mine? I doubt i have done any over revs but i have hit the red line when driving on the limit but never when down shifting. 

 

You need the Porsche Diagnostic tool for this right? you can use just any obd2 reader and any basic software ?

[sleazius]

Mmmmm ... money shift.