Rev report what does this tell you

Desert Dragon · 8 Jun 2017

I'd pass. RR 1-4 are fine.

5 and above are mishifts on a stock 997 turbo. If its been remapped it may perhaps be hitting RR 4 and 5 all the time as the rev limiter set higher on many remaps. If you register a RR 6 the engine is likely to let go at some stage even the mighty mezger. RR 5 is a pretty bad buzz for any engine though.

drabux · 10 Jun 2017

marconorth said:
If it was a normal C2/2S 4/4S etc engine then yes I would see it as an issue but this is a Mezger that has run for 1500 hours since the bad over rev events. It would not put me off!

What concerns me more is how many cars there are out there showing a perfect over rev DME read out but have been repeatedly caned before the engine reaches optimum temp?? Massive strain on the power plant, but there is no data that will show that!!

Nicely put. There needs to be some perspective here. The serious over revs were a long time ago and brief. Over 50k nearly all manuals will show 4 and 5s. A missed shift just happens eventually. The engine is robust and can take 1,2,3s in its stride. Relative to many other cars of about this mileage I've seen, this looks fine. If you took the advice about 'walking away' seriously then I suspect you'd do a lot of walking before you found a car of this mileage without seeing a few anomalous over-revs.

drabux · 10 Jun 2017

Demort said:
If its been remapped and that looks like it has then you wont get a Porsche warrenty unless you put a new dme on it.

Everything else though i agree with whats already been said .. range 5 is pretty bad but it was a long time ago and if there was any engine damage then it would have shown up well before now .

Sorry to say, you don't need a new DME to erase these data. £30 of hardware will do it!

deMort · 10 Jun 2017

drabux said:
Demort said:

If its been remapped and that looks like it has then you wont get a Porsche warrenty unless you put a new dme on it.

Everything else though i agree with whats already been said .. range 5 is pretty bad but it was a long time ago and if there was any engine damage then it would have shown up well before now .

Click to expand...

Sorry to say, you don't need a new DME to erase these data. £30 of hardware will do it!

Yup .. but on the 111 check it will be noted and Porsche will insist on a new dme im afraid , done prior to porsche knowing and its fine .. unless its had a val report in the past as Porsche will already be aware its been mapped .

neil_911 · 11 Jun 2017

Excuse me for asking a slightly off topic question,

I'm getting my head around an over-rev situation. I can only see this happening if you shifted down a gear too early, correct?

Or because the rev's climb so fast, is it possible the engine can't retard the spark to action the limiter at the correct RPM? causing the engine rpm to temporarily exceed the limit?

Surely an over-rev on a PDK isn't possible at all right? Even when it can hit the limiter in TIP mode?

I'd be with the guy who mentions the race bred history of the mezger engines on this one. 997.1 turbo engines appear to be pretty damn bullet proof. The history of the remap would be the only thing to put me off.

seeforez · 11 Jun 2017

over revs are caused by a change at too high a speed or more likely a missed gear (e.g 2nd instead of 4th) and cannot be caused by the limiter failing to kick in - unless the limiter is faulty.

Over rev is nearly impossible in a pdk unless some strange scenario where you are rolling down a steep hill as the box changes down a gear and your car speeds up......very unlikely

peterg1955 · 12 Jun 2017

neil_911 said:
Excuse me for asking a slightly off topic question,
Surely an over-rev on a PDK isn't possible at all right? Even when it can hit the limiter in TIP mode?

From here http://www.911virgin.com/porsche/rev-range-information/
"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."

tims1959 · 12 Jun 2017

For what it's worth -

The Bosch ME 7.8 DME's rev limiter works by cutting the fuel, not changing the ignition timing. To cut the fuel it stops opening the injectors.

As soon as the fuel's cut the engine speed immediately starts falling back - unless you're going down a bloody steep hill.

But the DME can only only cut the fuel after it's detected that the engine speed's been exceeded. This takes a finite time, it's not a perfect instantaneous or predictive process.

For cars with sport chrono when you turn on sport mode it sets the rev limiter to a hard rather than a gradual cutoff, so there's no safety net built in.

It seems that under full throttle the rev limiter process can react too slowly to cut the fuel in time to stop overrevs getting recorded. The process that records overrevs works independently of the rev limiter so it records all the overrevs that happened in the time the rev limiter process was being invoked but the engine was still on full throttle.

With a manual 997.1 Carrera and sport mode on it's dead easy to record overrevs in ranges 1-3 by accidentally slamming into the rev limiter while accelerating up through the gears (ie: not changing up in time as opposed to mis-shifting into the wrong gear).

Same thing can be 'achieved' by just sitting in the car in neutral with the engine running and flooring the throttle - which might also affect tip and PDK cars and might account for some overrevs on these cars.

neil_911 · 12 Jun 2017

tims1959 said:
For what it's worth -

The Bosch ME 7.8 DME's rev limiter works by cutting the fuel, not changing the ignition timing. To cut the fuel it stops opening the injectors.

As soon as the fuel's cut the engine speed immediately starts falling back - unless you're going down a bloody steep hill.

But the DME can only only cut the fuel after it's detected that the engine speed's been exceeded. This takes a finite time, it's not a perfect instantaneous or predictive process.

For cars with sport chrono when you turn on sport mode it sets the rev limiter to a hard rather than a gradual cutoff, so there's no safety net built in.

It seems that under full throttle the rev limiter process can react too slowly to cut the fuel in time to stop overrevs getting recorded. The process that records overrevs works independently of the rev limiter so it records all the overrevs that happened in the time the rev limiter process was being invoked but the engine was still on full throttle.

With a manual 997.1 Carrera and sport mode on it's dead easy to record overrevs in ranges 1-3 by accidentally slamming into the rev limiter while accelerating up through the gears (ie: not changing up in time as opposed to mis-shifting into the wrong gear).

Same thing can be 'achieved' by just sitting in the car in neutral with the engine running and flooring the throttle - which might also affect tip and PDK cars and might account for some overrevs on these cars.

That's kind of what i wanted to know. The PDK Sports chrono shift is pretty savage, and there's not much you can do about it when in D mode. Unless you were hanging the arse end out in first gear, I doubt you'd ever fool it fast enough to bounce the limiter. The only way you could hit the limiter in a PDK car is driving in M, which is the softer limiter anyway. OR like you say sat in N and revving it - who even does that?!

I read that 911virgin page, which basically said "it shouldn't but it might". That guy should work as a politician :lol:

tims1959 · 12 Jun 2017

...sat in N and revving it - who even does that?!

Agreed, you'd have thought only a complete lunatic would do that , same with flooring it down a one-in-six hill.

There are probably a few other mad edge cases, but the DME's system isn't infallible so overrevs can be recorded and put down to weird ***** happenz.

It seems Bosch's best engine management engineers had to prioritise spoofing diesel emissions figures for VW group over foolproof rev limiters.

OP, if you haven't already decided - if it was my money and the car was otherwise perfect for you I'd push for some discount on the sale price given the overrevs. But, the range 4 and 5 overrevs were a very long time ago, and as marconorth said the Mezger engine is much stronger than an M96 or M97. So should be fine unless you wanted to sell it on any time soon and worried about what the next buyer might think.

seeforez · 12 Jun 2017

Not sure i get this - RR1-3 yes can be caused by hitting the limiter, but they aren't technically over revs. You state that can you get into RR5 (>8400) by hitting the limiter in a stock car in sports mode - where did you get this info from ???

tims1959 · 13 Jun 2017

seeforez said:
Not sure i get this - RR1-3 yes can be caused by hitting the limiter, but they aren't technically over revs. You state that can you get into RR5 (>8400) by hitting the limiter in a stock car in sports mode - where did you get this info from ???

If aimed at me I don't think I've said anywhere that you can get a range 5 overrev by hitting the limiter, apologies for any misunderstanding.

The multiple range 5 and 6 overrevs in the OP's report can only have been caused by buzzing the engine more than once.

For anyone who hasn't already got them, the rev limiter and overrev ranges for a 997 turbo are

Rev limiter 6800 RPM

Range 1: 6800-7000 RPM
Range 2: 7000-7200 RPM
Range 3: 7200-7400 RPM
Range 4: 7400-7900 RPM
Range 5: 7900-9000 RPM
Range 6: > 9000RPM

and for a 997 Carrera

Rev limiter 7300 RPM (7450 for X51)

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: > 9500RPM

seeforez · 13 Jun 2017

tims1959 said:
If aimed at me I don't think I've said anywhere that you can get a range 5 overrev by hitting the limiter, apologies for any misunderstanding.

Sorry yes you did say RR1-3 - must have been tired last night :thumb:

I have heard that remaps can affect the RR reports calibration itself somehow...and i don't just mean by allowing it to go past the limiter i think it can knock out the calibration slightly

drabux · 14 Jun 2017

Demort said:
drabux said:

Demort said:

If its been remapped and that looks like it has then you wont get a Porsche warrenty unless you put a new dme on it.

Everything else though i agree with whats already been said .. range 5 is pretty bad but it was a long time ago and if there was any engine damage then it would have shown up well before now .

Click to expand...

Sorry to say, you don't need a new DME to erase these data. £30 of hardware will do it!

Click to expand...

Yup .. but on the 111 check it will be noted and Porsche will insist on a new dme im afraid , done prior to porsche knowing and its fine .. unless its had a val report in the past as Porsche will already be aware its been mapped .

Er, that is incorrect. This is not mapping. The 'map', as you call it, goes into the Flash. The overrevs goes into the IMMO EEPROM - 95P08 chip - and changes cannot be detected.

Oh and just to add that records of maps in the flash can also changed, too! Ever heard of ABRITES?

deMort · 17 Jun 2017

Im sorry i didnt make myself clear enough , over revs are one thing and the usual Porsche checks apply there but if a car has been mapped then porsche used to insist on a new DME .. this is because even if the DME is remapped to original it will still show up on a test that it has been altered and this is how Porsche check this .

A new DME will be blank so wont show as being mapped if that makes sense . Over revs are a seperate thing but also stored in the DME .

My intention was to explain to the OP that getting a Porsche warrenty is going to be rather expensive in this case .

Not really interested in what ever software you can remap to be honest .. im just trying to answer the OP,s question .

Im afraid theres a reason why im just a mechanic .. my ability to expalin things is not brilliant .. but hopefully by know people here can make sense of what i write

Rev report what does this tell you

Desert Dragon

Montreal

drabux

Nurburgring

drabux

Nurburgring

deMort

Monaco

neil_911

Monza

seeforez

Barcelona

peterg1955

Monza

tims1959

Silverstone

neil_911

Monza

tims1959

Silverstone

seeforez

Barcelona

tims1959

Silverstone

seeforez

Barcelona

drabux

Nurburgring

deMort

Monaco

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