I let my buddy try out my '03 Z06 with the usual admonishments - he's used to some fairly high-HP cars so I figured he'd be fine. He came back after 20 minutes or so with "that look", noting that he had "missed a shift". On further discussion, he was cruising at about 70 MPH and downshifted...and hit the rev limiter, twice. He honestly couldn't say from what gear to what gear. He did say the car still pulled, even on the limiter, so I have to think he didn't do anything incredibly stupid like first gear.

So, no codes at the time and nothing historical. I'm trying to determine if there is slightly more valvetrain noise now - although there's always been just a bit and I'm not sure if I'm just being paranoid. The car runs, drives and shifts fine.

How worried should I be, and is there anything I should do?

And no...this is not me blaming this on a friend

 

Did he hit the rev limiter or blow right past it? Hitting the limiter is nothing, blowing past it is another. They are completely different animals.

 

He hit the rev limiter on a downshift?

 

You don't hit the rev limiter on a downshift fast enough to save the engine if your more than a gear down. This is how many people bend pushrods/valves and break spings.

 

I wasn't in the car, so I can't speak to what happened. What would it sound like to "blow past" the limiter? Since he said it hit it, I assume it was cutting out the way it usually would...

 

Um - yes.

 

I guess I'm not understanding. How did he know that he hit the rev limiter? Did he do it two seperate times? Why didn't you ride with him?

 

Yeah, that's what I'm afraid of. I'm wondering if he was in 5th or 6th (maybe going faster than 70, do ya think? ) and got 3rd...anyone have the math to work out what that would be for RPM or a table of max speeds in gears?

 

He knows what a rev limiter sounds like. He said he let the clutch out, hit the limiter, looked to see he was in the right gear and then let it out again...then put it in neutral to sort things out.

I've already given myself a <fail> on the stupid test for letting him take it on his own.

 

Ok, typically when damage is done, it's on a downshift because you don't hit the rev limiter like on an upshift. I'm not sure what he heard, but I doubt it was the rev limiter. I guess you will just have to see how the car is running, and listen for abnormal noise.

 

I hope your car is alright and it sounds like you learned your lesson:

No one else drives your baby

 

I have to agree with Lucky...I can only suggest that what your friend (if he is still that lol) thought was the rev limiter was in fact the rev-over-rev he was hearing...it is quite a bit different. If he was +7000 RPM's the engine whines like out of control and pops quite a bit out of the exhaust (depending on your cat back system), the tires may squeal for losing traction, the car may go into various different modes (traction on, off, abs may engage...I have even read that on one occasion the motor went into a temporary "reduced power mode") all by itself as well. This is all done simultaneously mind you and can be perceived to the non-regular corvette C5 driver as hitting a rev limiter.

As far as I know there is no protection or "rev limiter engagement" at all upon an accidental downshift... now you might be asking...hmmmm how do you know? I missed one from 3rd to 2nd. Though nowhere near anything bad like others have posted, it does result in the same way...no over-rev protection...no rev limiter....just a bunch of other things that happen that I listed above.

Good luck and you might have been one of the lucky guys that has a strong motor and took the beating! There are a few of em out there...but then again...go and do a search and you'll find out there are also some not so fortunate guys as well.

 

I have almost done it a few times but I wasn't speed shifting. If you aren't going super fast there is usually a tell tale grinding noise when trying to get it into the new gear.

I don't think it makes a big difference in sound once engaged except for the fact that you will be much higher in the RPM band. If you are mechanically inclined to do so, pull out the push rods and roll them on a piece of glass to see if roll smoothly. They are the first weak point.

 

The limiter certainly can't stop the mechanical overdriving of engine speed, but I would expect that if the engine was forced to (say) 7500 RPM the limiter would be engaged and trying to cut the ignition...although it would have no effect.

 

well sounds great in theory unfortunately I have not read anyone yet on here that has said that they have heard actually the fuel being cut off/ignition being cut, for a mis-shift and over rev. I know mine definitely never kicked in. I stopped my problem very quickly knowing exactly what I had done. It only took a split second blowing the 3rd to 4th shift and hitting 2nd instead at 60mph to have my tach almost instantly read 6100rpms which is where I caught it and got the clutch back down to throw it into the correct gear. During that split second everything I mentioned above had happened. I have read many posts on here from guys saying that they too have blown the 3rd to 4th shift while way up in the RPM band (doing greater then 60mph). When they missed there shifts some reported as high as over 8000 and still having the motor take it and suffering no consequences. Unfortunately others did not fare that well and needed replacing push rods and in worst cases pistons & rebuilding was necessary. Again...no one has ever posted hearing the definitely blip, blip, blip you would hear from the fuel cutoff of the rev limiter when running out of gear and just leaving the car floored.

Let us know if you end up just riding this out or investigate it to set your mind at ease. I would almost bet that if you drive it around for a week or so and don't see or hear anything...that chances are your fine and are one of the lucky ones. The fact that your "buddy" did this twice!!! would really have me wondering what exactly kind of "buddy" this is.

 

I'd expect at this point I'm going to ride it until October 1st unless something shows up, and then replace the pushrods and possibly have the rockers rebuilt at the same time when it's down for the winter. Unfortunately I'm autocrossing so I don't have the option to use aftermarket

As for the many comments about my buddy - stuff happens. Let he who has never accidently screwed up something you've borrrowed throw the first stone He's offered to make it right up to and including a new crate LS6...so we don't have to beat on him too much. I should mention in passing that I stuffed a friends BRAND NEW 1976 Corvette backwards into the median ditch in my youth...so maybe it's just karma

 

Thats what I would do