Over Revved The Bimmer

[bkcraun]

My son missed a shift. I can't hear anything wrong and the car (1992 325i M50)still runs great. I'm still going to take the car in for a leakdown test to see if any damage was done. If the results show that valve work is needed, what else can I get done while they are in there to increase performance?

[CiscoKid]

might as well replace the head gasket and cams wile you are at it

[catalyst.]

If he did bend some valves, the only way to know that the pistons werent damaged too is to strip down the motor and inspect the pistons, there is no point in spending money on new valves if you dont know whether or not the pistons were damaged. Alot of times its more cost effective to just replace the entire motor.

[kyle_baker]

It depends on how bad he over revved the engine. How high did the tac rev to and how long. If it wasn't much and not very low then in most cases this is nothing to worry about (unless of course this happens often).

If this does happen often, or the over rev was tremendouslly over then i would have it check out, other wise i think it should be fine. Just keep an eye on it for a week or two for anything unusual. Keep in mind that if there are any major problems and you wait to see what happens and later find the problems you will probably spend the same amount to have it fixed (with the motor swap being sometimes cheaper than repairs), also if you find no problems you still have a running car and saved money on the checkup and what not.

Could you be more specific on the severity of the over rev and for how long?

[catalyst.]

Is it a vanos m50?

[dutchbmw]

There's a rev limiter on every BMW. Over about 6500 the fuel injection stops.

[kyle_baker]

I thought vanos were after 92 models?

[NeverLeaned]

How bad did he hit it? If he overrev'd to 8 you'll probably be ok

I Missed a shift on my CBR once and watched the Tack needle go over the gauge (it rev's to 15K.) I thought it was a goner but it still serves me happily through the twisties!

[jrhaile]

93+ are vanos

[kyle_baker]

Originally posted by NeverLeaned@Mar 14 2005, 11:08 AM
How bad did he hit it? If he overrev'd to 8 you'll probably be ok

I Missed a shift on my CBR once and watched the Tack needle go over the gauge (it rev's to 15K.) I thought it was a goner but it still serves me happily through the twisties!

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if you over rev a 325 to 8 then you better have it checked out, they only register 7 on the tac and redline at around 6.25

[catalyst.]

Originally posted by jrhaile@Mar 14 2005, 11:08 AM
93+ are vanos

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aight.. thats what i thought.

ive heard of people getting non vanos m50's up to 8k without doing damage..

[jrhaile]

ummm no very wrong lol.. my buddy Adam has gone through 2 non-vanos engines because of over revving lol

[CiscoKid]

there is a differnce between mechanical overrevving and just bounceing it off of th rev limiter. If you just rev it up, it will stop at the rev limiter. But if you downshift it, there is a physical connection between the wheels and the engine, and there is no way the computer will be able to slow it down

[bkcraun]

Interesting information here. To answer some of your questions. It is a non-vanos M50 engine. I was in the car and the mis-shift was corrected very quickly, a second maybe. My son says he saw the tack go into the red and the rear tires squealed, again for just a second. Son says he never even fully engaged the clutch before pushing it back to floor. Again, I don't see or hear any problems, but I think leakdown test would help me know for sure if anything happened.

[bkcraun]

Originally posted by jrhaile@Mar 14 2005, 01:22 PM
ummm no very wrong lol.. my buddy Adam has gone through 2 non-vanos engines because of over revving lol

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Did your friend know right away that his motor was toasted?