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Hi, looking at buying a 2016 981 GT4. I have the below overrev report, can someone tell me if it looks good? The car has a Cobb dundon tune, unsure if that affects anything. Thanks.
No it doesn't look good. You have over revs in range 4 and 5. Porsche wont CPO a car in those ranges for a reason. For range 5 for example, the car has 55 ignitions when the engine had a total of 488 operating hours on it. The engine only has 50 operating hours on it since the over rev. Mechanical over revs can bend valve stems which reduces power and efficiency and later may lead to catastrophic failure. The damage can take up to 200 engine operating hours to reveal itself. I wouldn't risk buying this car.
My understanding is that for turbos, the tune does impact and skew the over rev report. I don't quite understand it but there is a video explaining it somewhere. It may be the same with NA engines.
No it doesn't look good. You have over revs in range 4 and 5. Porsche wont CPO a car in those ranges for a reason. For range 5 for example, the car has 55 ignitions when the engine had a total of 488 operating hours on it. The engine only has 50 operating hours on it since the over rev. Mechanical over revs can bend valve stems which reduces power and efficiency and later may lead to catastrophic failure. The damage can take up to 200 engine operating hours to reveal itself. I wouldn't risk buying this car.
My understanding is that for turbos, the tune does impact and skew the over rev report. I don't quite understand it but there is a video explaining it somewhere. It may be the same with NA engines.
There’s something off with the DME report as there are more range 4 ignitions than ranges 2 or 3 which is impossible. The tune may explain it.
Not necessarily. Given that the range 2 - 5 events happened at the same time, it was probably part of the same downshift event. Clutch engaged below range 4, then revved to range 5, then engine wound back down through lower ranges. But to put in context, if there are (3) ignitions per revolution, and (130) revolutions (390 ignitions) per second at 7,800 RPM, the engine spent ~0.4 seconds in range 4 and 5 (158 ignitions). But there was probably a missed shift into range 2 prior.
Not necessarily. Given that the range 2 - 5 events happened at the same time, it was probably part of the same downshift event. Clutch engaged below range 4, then revved to range 5, then engine wound back down through lower ranges. But to put in context, if there are (3) ignitions per revolution, and (130) revolutions (390 ignitions) per second at 7,800 RPM, the engine spent ~0.4 seconds in range 4 and 5 (158 ignitions). But there was probably a missed shift into range 2 prior.
thank you for the input. Is 0.4s something that should really deter me from the car if everything else checks out? Just trying to gauge how “severe” the overrev report is. Car only has 17k miles if that matters
No it doesn't look good. You have over revs in range 4 and 5. Porsche wont CPO a car in those ranges for a reason. For range 5 for example, the car has 55 ignitions when the engine had a total of 488 operating hours on it. The engine only has 50 operating hours on it since the over rev. Mechanical over revs can bend valve stems which reduces power and efficiency and later may lead to catastrophic failure. The damage can take up to 200 engine operating hours to reveal itself. I wouldn't risk buying this car.
My understanding is that for turbos, the tune does impact and skew the over rev report. I don't quite understand it but there is a video explaining it somewhere. It may be the same with NA engines.
thanks for the explanation, are you saying that the tune could have potentially made the overrev report look worse? And in your mind how bad is this report? Absolutely stay away?
It may be fine or not. It may take up to 200 hrs to show issue. I would feel comfortable once it gets past 100 hrs after the event personally. It’s a personal question on comfort, what is your ability to pay out of pocket if it need to be rebuilt? That should be factored in to a offer, is it a dealer or private party?
Agreed with others - the report isn't great but is worse because of the short time since the range 4/5 events. My car, for example, has range 5 and 6 events, but that was over 800 hours before I bought it, which is why it was deemed a non-issue.
I might suggest having the seller provide a "short" warranty for that, if you can negotiate yourself there... basically to buy yourself some covered "hours" on the engine. It may be a tough sell to win that argument, but it's worth a shot.
Agreed with others - the report isn't great but is worse because of the short time since the range 4/5 events. My car, for example, has range 5 and 6 events, but that was over 800 hours before I bought it, which is why it was deemed a non-issue.
I might suggest having the seller provide a "short" warranty for that, if you can negotiate yourself there... basically to buy yourself some covered "hours" on the engine. It may be a tough sell to win that argument, but it's worth a shot.
Hmm thank you for the idea, might consider that since I really like everything else about the car
thank you for the input. Is 0.4s something that should really deter me from the car if everything else checks out? Just trying to gauge how “severe” the overrev report is. Car only has 17k miles if that matters
Like anything, the length of time in use shouldn't be the indicator...its how something was used, when it was used. Did the operator let the car warm up properly before getting up in the rev range? Were they generally mechanically sympathetic during their ownership? Etc., etc. I remember coming home late one night, cold enough for parked cars to have frost on the windows. I passed a local pub, and a new, at the time, E46 M3 was pulling out of the pub. Rear window was fully frosted, and driver sped out of parking lot, at or near red line, right after entering car and starting it up. This when the M3 was having all the crank shaft failures. Its memories like those that always make me hesitate to buy used performance cars.
I'd be more concerned with the Range 1, (90) minutes before the report was run. "To me", someone was trying to "get it in, before they got rid of it". That said, if you can fund a new motor, or motor rebuild shortly after purchase, it shouldn't be a concern. Realistically, its probably "one bad shift". That said, again, what were the conditions when it happened? However if your bank accounts work like mine, I'd keep looking, or at least find one with CPO left.
thanks for the explanation, are you saying that the tune could have potentially made the overrev report look worse? And in your mind how bad is this report? Absolutely stay away?
I'm not saying stay away. Porsche over designs these engines and in all probability, its going to be ok......but maybe not. Who knows. What's your risk tolerance and financial situation? (rhetorical question). Check out this video. It's excellent.
04-16-2023, 12:38 AM
Help with 981 GT4 Overrev report
