i might have over revved my engine in an accidental downshift from 3rd to 2nd. i'm not sure to what extent or if it even happened at all. i've been driving the car for weeks after the incident and haven't noticed anything out of the ordinary. no power loss, no unusual sounds, etc. could i have done any major damage to the engine (ie. bent exhaust valves) if i did indeed slightly over rev it? should i have it checked out and if so, what should i have tested?
thx,
AaRoN


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If you did anything to the engine, that check engine light would've turned on. I don't know how far you revved in but I wouldnt be too worried unless that light comes on.

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wow, that was fast.

nope, no check engine light, nothing out of the ordinary. i did some research on the subject and found a bmw m3 forum with numerous users who messed up their engines due to an over rev. apparenty their engines had a problem with the cylinder hitting the exhaust valve when the engine was over revved.


2004 Twilight Blue G35 Coupe 6MT, Stillen Intake + Z-Tube.

 

I had a friend who got a 325 in stick. We were racing it and he shifted from 3 to 2... The car wouldnt start after that. I believe he bent all the valves on the car, cost something like 3g's to repair.

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Correct me if i'm wrong, but isn't that what the "rev-limiter" is for? It stops the engine from exceeding an over-rev, say up shifting and including downshifting? I'm not entirely sure, since i have a 5AT, but does that sound right?

 

nope. the rev-limiter limits the amount of fuel delivered to the engine in order to prevent an over-rev while accelerating. if you downshift into the wrong gear while going too fast for that particular gear, your engine is mechanically connected to the rear wheels and the rpm's can go off the scale as there is nothing the rev-limiter can do about it. the automatics prevent this situation from ever occuring as they won't let you downshift into the wrong gear in the first place.


2004 Twilight Blue G35 Coupe 6MT, Stillen Intake + Z-Tube.

 

It all depends on the minumum valve to piston clearance is on our engines. Depending on timing, the valve can be closest to the piston at 7-15 deg off TDC. Another issue would be valve float in that, the cam is moving so fast that the valve spring cant return the valve fast enough, causing contact with the piston. My father recently raced a porsche gt3rs in the le mans series and when he was still in the learning stages of getting to know the car, he overevved to about 13k probably 20 times and the piston never made contact with any valves. God bless those genius porsche engineers.

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