Is it possible the rev limiter could have malfunctioned at any point?

Is everyone in agreeance that there is no way the car could have malfunctioned in any way allowing either the RPMs to reach those levels without downshifting or the car reporting wrong RPM levels? I'm not trying to argue or anything, I'm just trying to understand everything. As I said, I don't downshift and I would remember hitting 9,500 RPMS. In fact, if that happened during a downshift I'm surprised the engine didn't shoot out of the back of the car when that happened, and am dumbfounded I wouldn't be able to remember it.

I rarely drove the car and each time I did it was special, so it's not like I drove it everyday and driving trips would blur together. On average I drove the car 1,500 miles each year and most of those miles came from me driving 100+ miles at a time on nice days.

 

Unless you removed the mass of the flywheel, you could not achieve those engine speeds by even revving quickly and repeatedly in neutral. Someone did briefly over rev by a missed shift. Does anyone else on the household drive the car occasionally? How about valet parking?

 

That is exactly what I was thinking.

To the OP. You may have not downshifted, but did you shift to a lower gear (when you meant to go to a higher gear) by accident at anytime? You may have 'downshifted' on accident.

What does the DME show for average MPH? Perhaps somebody local can connect a dura metric or the likes and retrieve the DME for you? Not that I doubt the records were mucked with, rather just so you have them.

 

Thanks SirClip for the clarification and adding some needed facts. It looks just like I suspected.

It's hard to tell from the pics, but if the pulley is aluminum I bet the crank is fine. It looks like most of the material on the crank is from the pulley. The crank is very hard steel, so most of the damage should be on the pulley.

If it were my car and I was positive I did not money shift. I would have them do just as SirClip recommended. Drop the engine, fix the pin and put a new pulley on it. Certainly cheaper than a new engine if it works.

Now if you did over rev to 9k then who knows what else could be wrong. But it looks like the car drove fine after the over revs so one could hope that it would be fine once the pulley was fixed.

Last question would be, where does the computer sense rpms? Is it off a hall sensor directly mounted to the crank? If so then you or someone else money shifted. If it's off something else on the belt then it would make sense that belt slipping would give bad rpm data... but I bet rpms are sensed off the crank so forget I even mentioned that.

 

OP,
What you say dont make sense to most of us as you see from the replies. You say that you know how to drive a manual shift car but you dont know how to downshift. That is..well an oxymoron.

If you can not downshift to decelerate using engine breaking or to get out of a corner, clearly you are driving the wrong car with wrong transmission, your WRX exoerience notwithstanding. Also, part of the reason why you post of forums such as these is to get different opinions from birds of the same feather. Now, everyone here is pretty much saying the same thing...so time take stock and dont get offended or defensive.

Get the car fixed and then go to PDS in Alabama. Drive the car as if you stole it thereafter. It will be worth your 20k. There is nothing like the scream of the flat six in your ears when you downshift into a corner, and then floor the gas pedal, drive off, watch revs go to 7000 and hear that wail!!!

 

I"m afraid the answer is 'no' to both those questions. Certainly the first one, because there is no rev-limiter, as I already explained. The role of limiting engine speed belongs to the computer. Without getting all technical, an older pure analog engine will accelerate until something breaks if the throttle is open. Rev-limiters interposed themselves to prevent that. A modern engine like ours is controlled by the computer. The computer can't decide how much fuel to provide or when to fire the plugs without reading the crankshaft rotation sensors. When it does that, the first question the code asks is whether the limit of crankshaft speed has been reached. When it is reached, the computer simply doesn't go any further. No fuel and no plug firing means the engine cannot go faster of its own accord. The rev's are limited, but not by a rev-limiter. And if the computer failed, the engine wouldn't run period. So the answer to your first question is no.

The engine can go faster if the kinetic energy of the car spins it up without fuel. That's why we say it's a blown shift. I haven't suggested it had anything to do with a downshift and frankly I doubt that possibility. So we're not all in agreement with that idea. Blowing an UPshift is how these serious over-revs happen. Not a downshift. When you go up through the gears, you don't shift up a gear until the car is in the upper half of the rev range. (Well... some people may at some times, but nobody uses the lower half all the time.) So when we shift upward, we're aiming for a gear that will reduce the engine speed. If we miss and catch the gear right next to it, the engine speed rises instead, and because we're suddenly wrong by two gears it rises sharply. Disastrously.

Everybody gets lost in the shift gates occasionally. Part of race training is to keep the clutch disengaged (the pedal down) and head for a safe haven on the right side of the box: a very high gear, which is always safe. Either fifth or sixth in our cars. If you don't notice it's the wrong gear from the feel in your hand, then the shock load has to cause you to disengage the clutch immediately. Again, in race training (and PCA DE days I suspect) the lesson is "both feet in" whenever something untoward happens. That means clutch pedal and brake pedal both down. It gets us out of bad situations with the least damage. Or death. That's good too.

All it takes is two incidents to create that DME record. An upshift from second to third at the quite moderate 4400 rpm will create that second incident that blew the engine. All it takes is to hit first gear when you intended to hit third. At that point, the engine speed increases to range four within a second or two.

I'm certainly in sympathy with your plight. As I said, it happened to me as well and I had to have a new transmission after less than half a second in the wrong gear. This engine was in the wrong gear for many many seconds. If it's any consolation, the latest event happened while your buddy was driving. And if you think back to 400 miles ago, he might have been behind the wheel that time as well.

Bottom line: it happens to all of us once in a while. 20,000 miles of careful driving can indeed be overcome by 20 seconds in the wrong gear. Or even two seconds honestly. The trick is to develop reflexes for dealing with a missed shift before the damage gets this expensive. As someone else said, I learned the hard way, but on cheap cars, like a '49 Ford coupe and a '53 VW. Both of them died teaching me, so my beloved MG got the best of the deal. That was forty years ago, but it still happened to me only a few years ago.

Learning on a Porsche is painful I know.

Gary

 

Again, I really appreciate everyone's help. Here's my stance right now:

From what I've read it seems as if it's unanimous among the forum members that the car did reach these RPMs. So I will assume that the car did get to those RPMs (whether by accidental downshifting, the RPM limiter malfunctioning, or by act of a deity). I personally don't remember the RPMs getting that high, but there's no way I can prove that unless I take a polygraph test.

The records show that the car hit 9,500 RPM over a year ago (i don't drive the car much so 10 hours is probably more like 16 months ago of engine run time). On 06/30/2011 I had the car's 20,000 scheduled maintenance service done at the Porsche dealership (the car probably had 200-300 miles less than it has on it right now and it cost me $840, so I strongly think it was that service). At the time of the service, everything was ok. So with that being said the 9,500 RPM did not damage the engine, because I would think they would have noticed that.

So it looks like the damage came from the recent spike in RPMs. So do you think that the recent RPM spike would have damaged the entire engine or just a portion of the engine?

With that being said, which option would you take if a) you were going to keep the car b) you were going to sell the car and didn't want to be a dirt bag

Would you:

Replace the pully, replace the crank, or replace the engine?

Personally, I think the wheel took the brunt of the damage, but I don't know.

BTW I'm not planning on selling this car because I tore it up and it has lost its value. Rather I would sell this car because I didn't get a chance to enjoy the Porsche experience that everyone in this forum knows. I've only driven the car 11,000 miles and in my mind it is still brand new to me, yet the engine is destroyed. So everyone please just let me know the best action to take now so the next owner will be able to enjoy the Porsche or if you would want to enjoy the Porsche yourself.

By the way, if I do keep the Porsche, I'm going to enroll in the Porsche driving school. Because if I can manage to get the car's RPM to 9500 for half a second without remembering, then I clearly need to see a doctor for my memory issues and have a professional teach me how to drive the car. I feel like I need to go and shake the hand of the guy who built my Subaru's engine, because I drive it the same way I drive the Porsche and the man must have forged the engine from a meteorite or something.

 

I read the whole thread patiently. I suggest the thread should be locked. Those who understand manual transmission cars know what I mean. It does not deserve arguing about the obvious and supporting a thread that should never have seen the light of the day.

 

Ok Wait... If the Car is Say Chipped (ECU Program like EVOMSit) Would'nt Hitting the Rev Limiter (Fuel Cut Off Before Up Shift) count as a Type 5 or 6 Over Rev?

 

No.

Gary

 

If I blew a shift that badly in a race car, we'd have the engine pulled and replaced without question. But we expect racing to be expensive and the question is always "How fast can you afford?"

With a road car, you seriously need to consider the advice of a dealer, and from what others have said, that dealer SirClip represents is a good one. First, have them review the diagnostic data with you. Decide how much chance there is that the external visible damage is all that's wrong. If the odds are reasonable, then I'd roll the dice on the simplest fix that amounted to just a thousand or so: try to replace that pulley and they can get a better look at the crank condition while they're at it.

As for the middle option, you really have to rely on the dealer. As I said once before, I wouldn't think you could damage the crank in a modern Porsche without doing so much other damage you'd end up with a complete rebuild. That's my intuition, but I'm just a hobbyist, a retired NASA engineer, whose last engine rebuild was thirty years ago. Trust your dealer on this one. Seriously. It takes someone with hands-on experience working on damaged Porsche cranks and particularly with his hands on this engine.

Again, as I said before, if the repair estimate for that second option climbs above six or seven thousand, I personally wouldn't consider a rebuild. For me, that's the time to install a factory reman engine so you have one you can trust.

Gary

 

I don't think I could let my friend off the hook so easily.

 

Thanks Gary, your advice has been extremely helpful and is why I came to the forums.

The prices I was quoted are the following:

- Replace the pully - $1,300
- Replace the crank - $13,000
- Replace the engine - $20,000

 

All of this is one reason that I am happy to be back in a PDK. When you think about how easy it is to miss a shift it is amazing that we don't hear about these on a daily basis. The lateral distance between a 5-4 and a 5-3 downshift is maybe equal to about twice the thickness of a wallet, both stuffed with $100 bills.

 

I've learned that sometimes the cheapest fix in the long run costs the most up front money.