'Over rev' range incidents

[sidicks]

I understand that the RME records the number of incidents of the car being 'over revved', classifying them as:

Range 1: 7300-7500rpm
Range 2: 7500-7700
Range 3: 7700-7900
Range 4: 7900-8400
Range 5: 8400-9500
Range 6: 9500-11000

Clearly range 1 and range 2 incidents would not be exceptional and range 3 would not be totally unexpected, but ranges 4, 5 and 6 would be unexpected and a potential cause for concern.

Does anyone know what would constitute 'abnormal' and hence require further investigation before the OPC would approve a warranty extension?

This happened to me recently, my 34,000 mile 997 C4S was referred to Porsche GB due to abnormal readings which required further investigation (at my expense) before the warranty could be granted.

I want to understand if it was the range 3 records that caused the problem (27) or the range 4 and 5 readings (1 in each).

Clearly basic physics mean that it would be impossible for the engine to only have 1 ignition in range 4 before it hit range 5, and similarly it would have to hit range 4 on the way down again - clearly therefore the range 4 and 5 readings must be an error.

Any information gratefully received!

I believe that the extra investigation instigated at the request of Porsche GB was unnecessary and hence I should have the fee (circa £100) refunded.

thanks

Sidicks

 

[Rodney Naghar]

0.07th of a second in Range 3 by my calculations is a total non-event.
Absolutely correct on the Range 4,5 interpretation - impossible.

However, they may have a policy where any Range 3 incidents need to be investigated. If their policy was any R4 or R5 to be investigated then you should ask for your money back.

 

[Robin M]

Maybe it only records over-revs going up the rev range which would explain it.

 

[Terry]

My understanding is that anything in Ranges 1-4 is considered acceptable and non damaging, but any activity (except spurious single figure readings) in Ranges 5 & 6 could be a problem and will be of concern to dealers.

 

[tscaptain]

Some thoughts on the topic from another forum

http://www.renntech.org/forums/index.php/topic/31511-dme-overrevs/page__p__167215__hl__%2Bover+%2Brevs__fromsearch__1#entry167215

 

[pauljmcnulty]

There's also a similar topic on PH, running to about 5 pages. Not read it, but there might be some good advice there.

 

[Rodney Naghar]

ORIGINAL: pauljmcnulty

There's also a similar topic on PH, running to about 5 pages. Not read it, but there might be some good advice there.

It's the same OP asking the same question.

 

[sidicks]

ORIGINAL: Rodney Naghar

ORIGINAL: pauljmcnulty

There's also a similar topic on PH, running to about 5 pages. Not read it, but there might be some good advice there.

It's the same OP asking the same question.

[]

 

[sidicks]

Basic conclusion is that range 1-3 is not normally a problem, unless there were an excessive number of range 3 incidents. Range 4 is more of a grey area, and 5 (and particularly 6) are a significant a concern (and cannot be caused by missing an upshift, basically only by an incorrect downshift into the wrong gear).

In my case, with a low number of range 3 incidents, and just a single range 4 and range 5 incident, there should have been no problem with the warranty being granted (and after further investigation the warranty was indeed granted).

However, as it would be physically impossible for the engine to go from range 4 to range 5 with just one ignition cycle (0.07seconds apparently), then the only logical explanation is a computer error.

In my view, Porsche GB should have been able to work this out, and hence avoid me paying an extra £100 for an additional inspection which confirmed no engine damage. I've taken this up with Porsche GB.

Sidicks

 

[Rodney Naghar]

Is that what 'Pope' told you offline? (I understand if you can't confirm)

 

[sidicks]

No comment!

 

[sidicks]

Another update!!

Latest response from Porsche GB is that the computer does in fact log every intition in the specified ranges.

However (and this is something I'm really frustrated about) they categorically refuse to provide any information as to the frequency of the ignitions when the engine is operating at different rev ranges (in particular, in rev ranges 4 or 5). This suggests to me that they may have something to hide.

As you may recall, my case is that it is effectively impossible for the engine to go into rev range 4 with just one ignition incident recorded then into rev range 5 with just one ignition incident recorded and then (presumably) back to the lower ranges without further incidents being recorded in range 4 or 5 on the way back down

Can anyone help with the maths?

I'm assuming that it is simply 1 ignition per cylinder per revolution? Meaning that 8,200 rpm = 1 ignition every 0.0073 seconds.

So for this to be a genuine reading, the car must have have gone from 7,900 rpm (top of range 3) into range 4 and then into range 5 (8,400 rpm) within 2 x 0.0073 seconds = 0.015 seconds. And then dropped back to below 7,9000pm within a further 0.0073 seconds.

which seems unlikley...

The car is warrantied now, but it's more the principal that I've had to pay £100 for a diagnostic check that i feel is unnecessary.

Thanks

Sidicks

 

[Geoff_Fields]

Maybe Barry Hart (Hartech) will spot this thread and shed some light? Try PM to him with link to this thread.

 

[cdmci]

4 stroke engine - each cylinder will spark every 2 revolutions?
6 cylinders therefore 3 ignitions every revolution.... ?

 

[Nick_USA]

A word of caution, whilst it is not possible for a Porsche OPC to clear out the overrevs with his PIWIS to give a false indication that a car hasn't been abused, it is possible for a 'tuner' who has the right computer tools to do so.

I have seen it done in the US so I expect it is possible in the UK.

Just beware!

 

[sidicks]

ORIGINAL: Nick_USA

A word of caution, whilst it is not possible for a Porsche OPC to clear out the overrevs with his PIWIS to give a false indication that a car hasn't been abused, it is possible for a 'tuner' who has the right computer tools to do so.

I have seen it done in the US so I expect it is possible in the UK.

Just beware!

Thanks but I've owned this car from new, so nothing has been falsified!!

Sidicks

 

[Nick_USA]

ORIGINAL: sidicks

Thanks but I've owned this car from new, so nothing has been falsified!!

Sidicks

So can you remember the higher over-rev incident?

 

[sidicks]

ORIGINAL: Nick_USA

ORIGINAL: sidicks

Thanks but I've owned this car from new, so nothing has been falsified!!

Sidicks

So can you remember the higher over-rev incident?

No, I have not 'buzzed' the engine and believe that the single incident shown is purely a computer glitch.

Sidicks

 

[berty987]

Unless its rattling or making a noise and running lumpy , just put it down to blowing the cobwebs out. Far too many Porsches being driven like they are HGV's or some sort of 1910 classic. I agree Porsche need to accept the rev range data to allow a warranty , but beyond that I personaly wouldnt worry about it. Unless the car is regularly over revved , improperly warmed up or infrequently serviced its unlikely any harm has come to the engine. My understanding of the over revs is they indicate a risk to the valve train (cylinder head internals) in terms of broken valve springs or fractured valves / cracked seats etc , due to valve bounce at high rpms. I would suggest the rest of the engine internals are generally unaffected by infrequent or short periods of high revolutions , providing they are properly lubricated. Sustained or repeated periods of over revs is a different matter , but thats not the case here.

 

[sidicks]

ORIGINAL: berty987

Unless its rattling or making a noise and running lumpy , just put it down to blowing the cobwebs out. Far too many Porsches being driven like they are HGV's or some sort of 1910 classic. I agree Porsche need to accept the rev range data to allow a warranty , but beyond that I personaly wouldnt worry about it. Unless the car is regularly over revved , improperly warmed up or infrequently serviced its unlikely any harm has come to the engine. My understanding of the over revs is they indicate a risk to the valve train (cylinder head internals) in terms of broken valve springs or fractured valves / cracked seats etc , due to valve bounce at high rpms. I would suggest the rest of the engine internals are generally unaffected by infrequent or short periods of high revolutions , providing they are properly lubricated. Sustained or repeated periods of over revs is a different matter , but thats not the case here.

Thanks for your comments, but I think you are missing my key point here:

Because of a single rev range 4 and 5 incident, my car required additional investigative work that cost me £100 or so. In the scheme of things is not major (the total bill was £2.5k including 2 year warranty etc) and obviously the work showed nothing untoward so the warranty was granted.

However, my (limited) understanding is that it would be physically impossible for the engine to produce the single incidents shown, and hence I believe it must be a computer glitch (which they should have realised and hence I should not have had to pay that £100 !!).

Its now a matter of principle!

Sidicks