Over Revved Engine

andrew15 · 08-03-2002, 06:17 PM

Due to a sticking throttle linkage, my 2.2 T engine briefly (less than 1.5 sec) revved to 7700 - 7800 (redline is 6800) before I turned off the ignition.
There was no load on the engine and it seems to have triggered the rev limiter on the distributor rotor (at higher rpms than I thought it would trigger)
I'm just wondering what I should be checking for before I start it up again. I'm kind of worried about re-starting and running the engine...

Regards,
Andrew M

Doug Zielke · 08-03-2002, 06:28 PM

Take the plugs out, and turn the motor over (slowly) by hand. If there is any binding, you have bent something.

Jim Sims · 08-03-2002, 07:10 PM

Check your distributor rotor; the rpm limit should be marked on it. One parts supplier sent us an S rotor for use in my son's T; fortunately we noticed the error before installing. Jim

RoninLB · 08-03-2002, 08:15 PM

not sure at what rpm that stock rod bolts stretch..a slight stretch would eventually destroy the bearings in a few thousand miles..definately not an expert on this/but am curious on the rpm?

Two Oh · 08-03-2002, 09:25 PM

I believe that the stretching of rod bolts was limited to modern 911 engines not the 2.0-2.7's.

On the modern engines an over the redline rev will stretch the rod bolt and will have to be replaced. The problem won't show up right away but it will eventually.

Do what Doug suggests to ease your mind.

I sometimes shift my 2.7 at 8100. Been doing this for the last 100,000 miles. No problems. Also while on the subject I do a lot of tire spinning, first and second gear with a 901. Never, never had a problem. Same 100,000 miles.

Early_S_Man · 08-03-2002, 09:36 PM

Andrew,

I don't think you have anything to worry about ... even if the rev-limiting rotor was for an 'S' ... you wouldn;t haave seen 7800 rpm ... that was most likely just the tach overshooting! The fact that this incident was not caused by a downshift makes me believe that the rev-limiter did its job!

If you want to be sure, pull the intake valve covers and look for evidence of broken rockers ... they shatter if an intake valve hits the piston! After confirming no rocker damage, do the slow rotation by hand, and after that ... do a compression test!

Wayne 962 · Wayne 962's Garage

I wouldn't worry about it - the rev-limiter is there for this reason. Even if it was the wrong one in there, then you shouldn't have done any damage. Warren's right - the tach probably overshot...

-Wayne

andrew15 · 08-04-2002, 10:01 AM

I'll check the car today, but I suspect that Warren and Wayne are correct in that the tach overshot. I have a spare tach that I played with last night and noticed that the needle can carry quite a bit of momentum. I suspect that as the rev limiter kicked in saving the engine, the tach needles momentum carried it a bit higher.

Today I'll check the rocker arms, check for binding, cross my fingers, and get back out there.

Regards,
Andrew M