ckworks

There are countless opinions around Overrev and what's acceptable range. I'm looking at a 911.2 at an official Porsche dealership with 84 ignitions of Range 5 overrev...likely due to money shifting...60 hours ago. The Porsche dealership says this happens often and these cars are so solidly built that it's not a worry. I drove the car and felt nothing funny.

I'm trying to figure out if the opinions of "run away fast" have merit...or just overly cautious opinions. Please respond ONLY if you've had to rebuild and / or had significant work to your motor / transmission due to a Range 4 or 5 Overrev. What range? And what was the work required?

Larson E. Rapp

If they're that confident, they won't mind providing a warranty at their cost. So there's no problem. Right?

Greyvdub

Imagine how often this happens with cars that don’t have logging capabilities - and it’s fine. It’s overblown - if a money shift Messed something up, you’d know by now

stout

^ Not necessarily.

One of North America's foremost 911 engine builders was called to testify about this during a lawsuit. His feedback: 1) An engine that's been over-revved can continue to run for a long time before it fails, 2) what matters if the engine doesn't let go immediately is how much the rod bolts were stretched, which dictates the loss of torque value on these critical fasteners. Lose enough torque, and it's only a matter of time. Trouble, for most of us, is it's a huge gamble unless you take the engine apart to check—at which point I'd be replacing the rod bolts and nuts as a precaution, along with all of the other "while you're in there" items. YMMV...

jakermc

Do we know what he meant by a "long time"? 50 hours? 100 hours? 500 hours?

And how does length of the over rev effect this? I'm not sure what the Range 5 RPM is, but if we use 84 ignitions and 8500 RPM for Range 5 for a mathematical example, then the event mentioned about this car lasted about 6/10ths of a second. Is that enough that we should live in perpetual fear of a failure? What is required to "loose enough torque"? Was there any data presented or was the testimony this vague? He may be an expert on building engines, but I suspect he is not an expert on fasteners. The cross examination here must have been fun!

Hoosier_Daddy

Agreed. What does Porsche A.G. say? If they won't certify it there must be a reason if falls in line with all other requirements for CPO.

jfischet

anyone out there who has range 5 (or more) overrevs without issue?

-if Y to above: how many hours on your engine since event?

jakermc

Never had a level 5. I bought a GT4 that had 62 ignitions at Level 4 which had occurred a little more than 50 hours before my purchase if I remember right. Looking back at my records, it occurred with 323 hours and I sold the car with 627 hours. No issues, obviously.

Somewhere, in the darkest corners of the engine building room. they are discussing a new slogan "IMS bearings, bore scoring, and over-rev reports ... scaring the internet since 1999!"

jfischet

exactly.

Jack F

Is this the purple unicorn build that is otherwise unattainable? Why risk it and own a very expensive problem car. Of course they are going to say it’s solid.

Greyvdub

context here is helpful - he's speaking to the potential of possibilities, as one would, to ensure you're not misrepresenting anything in a trial. I would say, more likely than not, your damage will occur within 20-30 miles of the "money shift"...havent you watched enough youtube?!?

stout

^ No. I recall that he was brought in to testify that a 911 engine over-revved in the past absolutely can suffer catastrophic failure later on—sometimes much later. His take: The time to failure depends on how much the rod bolts were stretched and how much of the torque value on the fasteners was lost.

YM(and what you choose to believe)MV, but I think it's telling that Porsche won't CPO a used car with ignitions into or beyond certain rev ranges. Rod bolts are the first (but not only) thing I'd be concerned about, and I suspect Porsche's engineers have specified a value past which they suggest it isn't a good idea to warranty the engine via CPO. Could everything be fine? For sure! But that's not what the OP was asking—and one could say the OP's question is somewhat problematic, because each case is going to be different—the story of one engine over-revved may not translate to another.

The real question might be something more like "Do you feel lucky?"

HardRider

Where is it in writing that a car will not be CPO based on DME report and over rev's. I have searched and searched and cannot find. As far as certified how sure are we they are even checking for over rev's, you think the dealer really wants to know which would "devalue" their asset???

ckworks

This dealer told me it was part of the 100+ point inspection for Porsche to CPO it. They have to turn in the results to HQ

Denny Swift

Gotta love the countless stories that begin with. "My brother's friend knows an expert mechanic, and he said..."