Over Reving
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From: Land Of Enchantment
Over Reving I read on another board of a guy who had a case of over reving with his Z06.
Needless to say he messed up some parts on the motor.
But my question is, lets say i was racing another car and in 3rd gear i go for forth and accidently grab 2nd. The car over revs right? Wont the rev limiter stop this? Or is there a case of mechanicl over reving where the rev limiter cant stop this. I was told by some one about this and the only reason im posting it is to have some one go in depth about it so dont be gettin hurt you know who.
Needless to say he messed up some parts on the motor.
But my question is, lets say i was racing another car and in 3rd gear i go for forth and accidently grab 2nd. The car over revs right? Wont the rev limiter stop this? Or is there a case of mechanicl over reving where the rev limiter cant stop this. I was told by some one about this and the only reason im posting it is to have some one go in depth about it so dont be gettin hurt you know who.
In that case the rev limiter can do nothing because the engine is not powering the drive train. The drive train is actually powering the engine. The engine will cease to get fuel once it reaches the rev limit, but this does no good if the cars speed and selected gear requires the engine to spin faster than that.
I figure if you were racing and reaching for 4th, that would put you north of 100mph. Selecting 2nd at that speed would most likely spin the engine past 9-10k if you didn't catch it and push the clutch back in.
Re'
I figure if you were racing and reaching for 4th, that would put you north of 100mph. Selecting 2nd at that speed would most likely spin the engine past 9-10k if you didn't catch it and push the clutch back in.
Re'
Staging Lane
Joined: Feb 2008
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From: Kentucky
In that case the rev limiter can do nothing because the engine is not powering the drive train. The drive train is actually powering the engine. The engine will cease to get fuel once it reaches the rev limit, but this does no good if the cars speed and selected gear requires the engine to spin faster than that.
I figure if you were racing and reaching for 4th, that would put you north of 100mph. Selecting 2nd at that speed would most likely spin the engine past 9-10k if you didn't catch it and push the clutch back in.
Re'
I figure if you were racing and reaching for 4th, that would put you north of 100mph. Selecting 2nd at that speed would most likely spin the engine past 9-10k if you didn't catch it and push the clutch back in.
Re'
The rev limiter is pure software in the PCM that only shuts of fuel and spark to the engine once the engine RPMs reaches a certain amount. There is no mechanical limiter. Most of the damage that is caused by doing what you did 3rd->2nd shift miss, is to the valve springs. A lot of time when single valve springs break at high RPMs, the valve is not raised up fully and will hit the piston as it comes up in the compression stroke. This usually causes damage to the valve and piston and sometimes even the head chamber and cylinder wall if the valve head breaks off. If you did not break a valve spring, you kind of lucked out. At this point I would still swap out the valve springs as over revving them is very hard on them and could cause them to fail later on prematurely.
Keith
Keith
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From: DFW
In that case the rev limiter can do nothing because the engine is not powering the drive train. The drive train is actually powering the engine. The engine will cease to get fuel once it reaches the rev limit, but this does no good if the cars speed and selected gear requires the engine to spin faster than that.
I figure if you were racing and reaching for 4th, that would put you north of 100mph. Selecting 2nd at that speed would most likely spin the engine past 9-10k if you didn't catch it and push the clutch back in.
Re'
I figure if you were racing and reaching for 4th, that would put you north of 100mph. Selecting 2nd at that speed would most likely spin the engine past 9-10k if you didn't catch it and push the clutch back in.
Re'
I did that twice in my LS6 CTSV. Everything was fine, rev limiter saved me! When I was putting the cam in I rolled the push rods on the ground to see if I had hurt them and they were fine. I guess it just depends on the case, I have heard of people bending rods and poping springs....
THe rev limited didn't save you. You got the clutch back in before the revs got to engine damaging levels. If you did any damage to the engine it was most likely to the valve springs if they went into floating. Though not impossible, it's unlikely to beld pushrods over reving the engine unless they were too weak for the application to begine with.
Re'
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p'v contact? what's that?
I've done that over revving thing quite a few times. If I can tell its trying to rev past 5500rpms on a up shift then I quickly catch it and hit the clutch and neutral it. Still runs like a dream
THANK GOD! Its scary when it happens but as long as you're quick to catch it you ought to be in the clear.
I've done that over revving thing quite a few times. If I can tell its trying to rev past 5500rpms on a up shift then I quickly catch it and hit the clutch and neutral it. Still runs like a dream
THANK GOD! Its scary when it happens but as long as you're quick to catch it you ought to be in the clear. 
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From: Dallas
You can't prevent mechanical overrev. One of these days ill make a poor mans sequential.
Anyways. Depending on the condition of your engine, you could have some problems. I've mech over-revved to over 10K on a handful of occaisions. My primary problems were valvetrain destruction; Springs were a little weak, lost 5hp. No piston to valve collisions however.
My possible biggest cautionary is your main bearings.
Anyways. Depending on the condition of your engine, you could have some problems. I've mech over-revved to over 10K on a handful of occaisions. My primary problems were valvetrain destruction; Springs were a little weak, lost 5hp. No piston to valve collisions however.
My possible biggest cautionary is your main bearings.
Moral of the story,...
..hit your gears boys. I must say, in all honestly, I have done the 3rd to 2nd gear swap, maybe twice(like 5 years ago),...however,...my brain is attached directly to my foot at that moment and the moment I feel any type of decel, the clutch goes back in, which saved me from a potentiol locking of the rear wheels, and or any engine damage,..
I have never broken any parts like that, however,...I do have some local buddie s here that have gone through more then one motor, doing this exact same thing.
If you cannot bang gears rapidly and accurately, shift slower, and work your way up.
..hit your gears boys. I must say, in all honestly, I have done the 3rd to 2nd gear swap, maybe twice(like 5 years ago),...however,...my brain is attached directly to my foot at that moment and the moment I feel any type of decel, the clutch goes back in, which saved me from a potentiol locking of the rear wheels, and or any engine damage,..
I have never broken any parts like that, however,...I do have some local buddie s here that have gone through more then one motor, doing this exact same thing.
If you cannot bang gears rapidly and accurately, shift slower, and work your way up.
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From: DFW
THe rev limited didn't save you. You got the clutch back in before the revs got to engine damaging levels. If you did any damage to the engine it was most likely to the valve springs if they went into floating. Though not impossible, it's unlikely to beld pushrods over reving the engine unless they were too weak for the application to begine with.
Re'
Re'
