TURLUTTE

Hi everyone, this is the reading of the 997 C2 i'm looking at :
Range 1: 8274 1455.2
Range 2: 2307 1455.2
Range 3: 667 1379.6
Range 4: 266 1346.4
Range 5: 0
Range 6: 0

Total hours: 2060.5 (mileage: 55k)

What do you guys think ? Thanks.

Domer911

I'm going to ask the stupid question....Since the rev limiter limits revs, How does the rest happen?

simsgw

As everyone else said: run.

That isn't 'maybe' it's been abused. It has been. Period. You cannot rev a Carrera into any of those ranges. The rev-limiter logic simply cuts fuel to the injectors and the engine stops going faster. It isn't magic. You don't 'coast' from 80 to 100 mph on level ground and an engine doesn't 'coast' from 7500 to 8000 rpm, so when the fuel is cut only one thing is left to make the engine turn over faster: kinetic energy of the car. Someone has downshifted at ridiculous speeds to create those numbers. In particular, notice that someone created those big R1 to R3 numbers only an hour ago.

Run.

Gary

Edgy01

UP shifts don't lead to those numbers (due to the revlimiter), only downshifts with a missed shift (selecting 2nd instead of 4th, for example) will give you those numbers.

While I personally drive fairly hard, I have no numbers in the upper ranges like 4, 5, 6 at all because I have never missed a shift.

The OP DME scan is REALLY excessive.

Macster

Well, I used to be on the side of the 'run away' posters, but after this overrev question came up on another forum I talked to a senior Porsche tech about this.

Now the car in question was a 996 Turbo with just range 1 and range 2 overrevs.

I do not recall the range 1 number but it was not high. IIRC the range 2 number was 147.

The time at which the overrevs occured was some time prior to when the overrev counts were read.

Paraphrasing the tech he said the overrev counts don't matter unless the car is in for an engine problem and then the overrev counts are used to catch some kind of fraud in that the owner overreved the engine (missed a shift is the usual scenario) and the engine blows up or at least gets very obviously sick.

The tech says as long as the engine is run a reasonable amount of time *after* the overrevs occured and the engine is without any signs of distress, that a test drive doesn't have the check engine light come on, the engine is fine.

You must be sure the CEL bulb is present and comes up when you turn on the key.

You must be sure when the engine fires the light goes out.

You must use the car long enough in a variety of conditions to give the DME every chance to flag any problems and turn on the CEL.

The DME checks for 'weak' (or strong) cylinders all the time. That is what the misfire monitoriing is for. As soon as the DME detects an out of spec cylinder it will turn on the CEL (maybe even flash it) and log one or more error codes.

The DME also checks/tests various other sensors and systems like the secondary air injection system, the converters, the O2 sensors, and so on.

The DME checks a whole slew of these and if it finds no problems sets the continuous readiness monitors to complete. You must use a code reader that not only reads codes, pending codes, but also reads/reports what continuous ready monitors are supported and if they are complete.

Now the presence of range 1 and higher overrevs does suggest the engine has been overreved some. Even if the engine exhibits no symptoms from this you may not want the car simply because it has been subjected to harsher usage than other candidate cars.

Sincerely,

Macster.

AYHSMB

The rev limitter is not a hard limit, it just cuts gas, but the engine still has some momentum; when you bounce off the rev limiter, you will get some R1 over-revs.

If you see only R1 and R2 over-revs there was probably no bad shift.

The high ones R3+ are generally due to a missed downshift. The typical ones are someone going for 5th and getting 3rd or going for 4th and getting 2nd.

Even if you immediately notice the bad shift and get out of it, it will be quite a lot of over-revs because they are counting ignitions, not seconds.

MICHAELWWW

Thanks!

swajames

Macster, just a short note of appreciation for your excellent replies and contribution to the forum. I always look out for your posts, and I learn a lot from them.

simsgw

Sorry, but momentum doesn't work that way. It does not create acceleration. Ever. An engine turning over at 7600 rpm has more kinetic energy than an engine turning 7500 rpm. Something has to put that energy into the rotating masses within the engine. If no fuel is being put into the cylinders then it isn't combustion converting chemical energy into kinetic energy. The only other source is the kinetic energy of the car itself. You can stuff a load of that into the engine by letting out the clutch in any gear, but of course it won't overspeed the engine unless it's a gear too low for the current road speed. (That is, an engine at idle can be bumped up to perhaps 3000 rpm if you pop the clutch in fifth gear while coasting along the freeway at 75 mph, but you can't get it over the redline. Not using fifth gear, but if you shift into second and then pop the clutch, you will indeed hit range one at least.)

I've heard two different descriptions of R1 and can't speak to that, but R2 is definitely above the rev-limited rpm, so if you see ignitions reported in R2 the car has been subjected to a bad shift. Either the driver wanted second (or on track, third gear) and just downshifted a little too soon while braking, or the intended shift was upward from third to fourth and he caught second instead.

A very large passenger let his knee slide over my shift pattern while we were coming onto a freeway. When I grabbed third to move briskly into traffic, his knee and my hand negotiated a compromise and the car ended up in first. At 70 mph. Quite dramatic noise, but I was preoccupied finding a working gear to stay out from under the cement truck coming up in the slow lane. Downhill.

It's true the engine can be spared when that happens if the driver is bloody fast getting out of that wrong gear, unless the cement truck interrupts the recovery, but such incidents are not to be ignored. In that case, the car needed a new transmission.

Notice that all the discussion of "watch the engine for awhile" is irrelevant to the OP. The most recent incident on that engine was only one hour ago. Not nearly long enough to reveal all the potential kinds of damage whatever that mechanic may think, Macster.

Gary

No HTwo O

Everyone always forgets the scenario when the rev-limiter does not protect, when the engine is spun backwards. This is also how you get over-revs exceeding range #2 and not just missed shifts.

utkinpol

we think same you do think - this engine with R5 overrevs will never be covered by warranty. find another one.

in theory if car runs for 50+ hours after msot recent R4+ overrev it should not result in PCNA deny of your engine work claim but in reality people do get rejected based on DME readings, so, why to bother?

ps. what macster said above is all true, but if you want to buy a new hassle-free car then i see no reason to bother with all those issues. find a car that did not have any missed shifts and range 4+ overrevs. 'good' looking range 3 should have 100-400 number top.

Vancouver-BC

Run don't walk, lots of great well cars out there without potentially problematic DME readings.

Macster

If one hour is not long enough then how long is long enough?

Damage from overreving occurs instantly and often that an overrev has occured is obvious from the horrible noises coming from the engine compartment area and a trail of vital fluids behind the car.

Even if the engine stays together, say a valve just got bent rather than losing its head (with fatal to the engine results), the engine will misifre.

The DME constantly checks for misfires and if it finds any it signals this with the CEL, sometimes flashing this light if the misfires pose a risk of damage to the converters.

As long as the engine is run long enough, used in ways that ensure the DME has time to complete a thorough checkout of the various systems/sensors -- and this includes misfire monitoring -- and the check engine light is off (and it has been *confirmed* the light does some on and go off when the engine starts) -- and a readout of the readiness monitors shows all have been complete (the tech tells me at least in the case of the 996 Turbo these are checked twice to be marked complete) the engine is ok.

As I said before, it is only when the car is brought in with a sick engine the DME overrev counts matter.

Now I agree what the presence of range 2 and higher overrev counts suggests the car has been used in a way that if I had a choice I would prefer a car that didn't exhibit having been used this way.

But the presence of overrevs with an engine that after a thorough test ride/drive and with the checks/tests I mentioned above is nothing from which to run screaming.

Added: My post was initially not to the OP (his post from Feb of this year) but to another more recent post in which the engine had run 500 or more hours after the overrev most recent event.

But in the case of the OP I note the engine did run one hour and as I asked above, if one hour is not enough time how much time is enough time? What I posted in response to the more recent question on this overrev business applies to the OP as well.

Sincerely,

Macster.