Almost misshifted today.....
#46
04-20-2007, 11:34 PM
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Originally Posted by DaveB
I might be reading your post wrong, but no matter what type of over-rev device is hooked up, it will not stop the engine from over-reving if the wrong gear is choosen at the wrong time. If someone was to shift into 2nd at 100mph, the mechanical connection between the engine and tranny will raise the rpms well above 8000rpms. A mechanical over-rev situation cannot be stopped. It's not the fuel, ignition, etc that kills the engine in the over-rev, it's simply the momentum. The end result is a shattered clutch, flywheel, floated valves, spun bearing, snapped rod, etc.
When this occurs, ( 100 mph - drop into 2nd gear ) your are correct - mechanical connection and tranny gear/speed are way off ( engine speed exceeds tranny gearing ) this will cause the car to " buck" ( i stated this in earlier posts ) but what would cause a shattered clutch, floated valve,crank walk... would be the fact that the motor would be "bouncing" off the revlimit ( if you dont engage the clutch ) causing an incredible LOAD on the valvetrain / rotating mass. ie- springs / retainers / valves being dropped / piston - valve contact / crank walk and so forth )
The point ( this is where the difference of opinion came in ) was that FUEL would shut the car off. i stated before fuel would be shut off - the rev limiter would engage. in the end, we both were on the same page ( myself / skater / trey and his wife ) just " worded" differently ( in fact, from the start - we were all headed in the right direction, just took some clarification on all parties involved )
---> in this specific instance ( accordhrbyd ) misshifted and was wondering if any harm would come of this - i replied stating he was lucky to have a stock ecu, and not a reprogrammed one ( i'm sure in the end - you too would agree )
#47
04-21-2007, 02:32 AM
OK, I want to clarify that at least in my case, we are NOT on the same page. I don't know if the terms we are using are confusing one another or not but I do NOT agree with you on this.
The rev-limiter on these cars is an ECU imposed "limit" to prevent the car from going past the engine redline. When you hit the rev-limiter there IS a momentary fuel cut. Anyone who has bounced off the rev-limiter in a G should be able to tell this. The rev-limiter does not prevent the engine from being able to be mechanically over revved. If you are traveling at 80 down the interstate and you downshift to 2nd instead of 4th then the engine WILL overrev and the conditions previously stated would most likely then occur. Even if the fuel were cut to the engine the mechanical conditions that turn the engine would not be stopped if the vehicle was still in motion.
His having a stock ECU rather than a reflashed ECU has nothing to do with this. His having NOT come out of the clutch saved him from having an issue but had he in fact come off of his clutch, he would have quite a large possible problem.
The rev-limiter on these cars is an ECU imposed "limit" to prevent the car from going past the engine redline. When you hit the rev-limiter there IS a momentary fuel cut. Anyone who has bounced off the rev-limiter in a G should be able to tell this. The rev-limiter does not prevent the engine from being able to be mechanically over revved. If you are traveling at 80 down the interstate and you downshift to 2nd instead of 4th then the engine WILL overrev and the conditions previously stated would most likely then occur. Even if the fuel were cut to the engine the mechanical conditions that turn the engine would not be stopped if the vehicle was still in motion.
His having a stock ECU rather than a reflashed ECU has nothing to do with this. His having NOT come out of the clutch saved him from having an issue but had he in fact come off of his clutch, he would have quite a large possible problem.
#48
04-21-2007, 12:08 PM
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Originally Posted by trey's wife
OK, I want to clarify that at least in my case, we are NOT on the same page. I don't know if the terms we are using are confusing one another or not but I do NOT agree with you on this.
The rev-limiter on these cars is an ECU imposed "limit" to prevent the car from going past the engine redline. When you hit the rev-limiter there IS a momentary fuel cut. Anyone who has bounced off the rev-limiter in a G should be able to tell this. The rev-limiter does not prevent the engine from being able to be mechanically over revved. If you are traveling at 80 down the interstate and you downshift to 2nd instead of 4th then the engine WILL overrev and the conditions previously stated would most likely then occur. Even if the fuel were cut to the engine the mechanical conditions that turn the engine would not be stopped if the vehicle was still in motion.
His having a stock ECU rather than a reflashed ECU has nothing to do with this. His having NOT come out of the clutch saved him from having an issue but had he in fact come off of his clutch, he would have quite a large possible problem.
The rev-limiter on these cars is an ECU imposed "limit" to prevent the car from going past the engine redline. When you hit the rev-limiter there IS a momentary fuel cut. Anyone who has bounced off the rev-limiter in a G should be able to tell this. The rev-limiter does not prevent the engine from being able to be mechanically over revved. If you are traveling at 80 down the interstate and you downshift to 2nd instead of 4th then the engine WILL overrev and the conditions previously stated would most likely then occur. Even if the fuel were cut to the engine the mechanical conditions that turn the engine would not be stopped if the vehicle was still in motion.
His having a stock ECU rather than a reflashed ECU has nothing to do with this. His having NOT come out of the clutch saved him from having an issue but had he in fact come off of his clutch, he would have quite a large possible problem.
* even if the fuel were cut, the mechanical conditions that turn the engine would not be stopped ( this is your last sentence in mid. paragraph )
-->while moving ( given that timing hasnt been AFFECTED / motor is not ceased) youre somewhat wrong. The motor will no longer be on / runing - THE MOTOR WOULD STOP. you would coast to a standstill, the engine would not be running, but the car would continue to move ( due to momentum ) AND ONLY MOMENTUM. --> once again, a motor needs 3 things to run ( air / fuel / spark )
* if you travel @ 80 and shift into 2nd gear - the engine will not REV TO 10K - instead ( like stated in earlier posts, not just by me ) the motor will bounce of the revlimit - it's the LOAD on the valvetrain/rotating mass that would harm the motor ( not the occasional redline - but the fact that in a matter of seconds, the components that hold the motor together can't handle that pressure / LOAD )
* him ( accordhybrd ) coming out of the clutch saved him - yes. i think we've all agreed to this - what i stated was that if he had a reproggramed ECU and had not upgraded his valvetrain / motor and was able to REV as high as he wanted to - he wouldve been in a world of hurt.
* in fact - just park your car and let it idle...rev it and have it hit revlimit - your car will not die, it would feel like you've lost ignition / have timing problems..it would sputter for that quick instance. ----> i think theres a misunderstaing, im under the impression that you think that if the ecu cuts the fuel - a acar would keep running because theirs fuel in the lines?.... this ( and i may be wrong regarding my assumption ) is not true - once the ecu cuts fuel - the INJECTORS STOP PULSING. this is why the motor would die almost instantly. ( i believe you and your husband have lened towards this - if i'm wrong, i apologize now ) anyways, ( not to sidetrack anyone ) but it's saturday!!!
#49
04-21-2007, 12:13 PM
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04-21-2007, 02:42 PM
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#51
04-21-2007, 04:55 PM
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#52
04-22-2007, 09:51 PM
Originally Posted by j-champaco
* the ECU does not work alone. This is also triggered by ignition timing - this signal / sensors send this info to th ecu. the ECU is actually a secondary / action reacting to a mechanical and or sensor reaction. re-read earlier posts ( not just one point - and also, please be opened minded when re-reading ) you'll see where the miscommunication happened.
* even if the fuel were cut, the mechanical conditions that turn the engine would not be stopped ( this is your last sentence in mid. paragraph )
-->while moving ( given that timing hasnt been AFFECTED / motor is not ceased) youre somewhat wrong. The motor will no longer be on / runing - THE MOTOR WOULD STOP. you would coast to a standstill, the engine would not be running, but the car would continue to move ( due to momentum ) AND ONLY MOMENTUM. --> once again, a motor needs 3 things to run ( air / fuel / spark )
* if you travel @ 80 and shift into 2nd gear - the engine will not REV TO 10K - instead ( like stated in earlier posts, not just by me ) the motor will bounce of the revlimit - it's the LOAD on the valvetrain/rotating mass that would harm the motor ( not the occasional redline - but the fact that in a matter of seconds, the components that hold the motor together can't handle that pressure / LOAD )
* him ( accordhybrd ) coming out of the clutch saved him - yes. i think we've all agreed to this - what i stated was that if he had a reproggramed ECU and had not upgraded his valvetrain / motor and was able to REV as high as he wanted to - he wouldve been in a world of hurt.
* in fact - just park your car and let it idle...rev it and have it hit revlimit - your car will not die, it would feel like you've lost ignition / have timing problems..it would sputter for that quick instance. ----> i think theres a misunderstaing, im under the impression that you think that if the ecu cuts the fuel - a acar would keep running because theirs fuel in the lines?.... this ( and i may be wrong regarding my assumption ) is not true - once the ecu cuts fuel - the INJECTORS STOP PULSING. this is why the motor would die almost instantly. ( i believe you and your husband have lened towards this - if i'm wrong, i apologize now ) anyways, ( not to sidetrack anyone ) but it's saturday!!!
* even if the fuel were cut, the mechanical conditions that turn the engine would not be stopped ( this is your last sentence in mid. paragraph )
-->while moving ( given that timing hasnt been AFFECTED / motor is not ceased) youre somewhat wrong. The motor will no longer be on / runing - THE MOTOR WOULD STOP. you would coast to a standstill, the engine would not be running, but the car would continue to move ( due to momentum ) AND ONLY MOMENTUM. --> once again, a motor needs 3 things to run ( air / fuel / spark )
* if you travel @ 80 and shift into 2nd gear - the engine will not REV TO 10K - instead ( like stated in earlier posts, not just by me ) the motor will bounce of the revlimit - it's the LOAD on the valvetrain/rotating mass that would harm the motor ( not the occasional redline - but the fact that in a matter of seconds, the components that hold the motor together can't handle that pressure / LOAD )
* him ( accordhybrd ) coming out of the clutch saved him - yes. i think we've all agreed to this - what i stated was that if he had a reproggramed ECU and had not upgraded his valvetrain / motor and was able to REV as high as he wanted to - he wouldve been in a world of hurt.
* in fact - just park your car and let it idle...rev it and have it hit revlimit - your car will not die, it would feel like you've lost ignition / have timing problems..it would sputter for that quick instance. ----> i think theres a misunderstaing, im under the impression that you think that if the ecu cuts the fuel - a acar would keep running because theirs fuel in the lines?.... this ( and i may be wrong regarding my assumption ) is not true - once the ecu cuts fuel - the INJECTORS STOP PULSING. this is why the motor would die almost instantly. ( i believe you and your husband have lened towards this - if i'm wrong, i apologize now ) anyways, ( not to sidetrack anyone ) but it's saturday!!!
#53
04-23-2007, 01:05 AM
#54
04-23-2007, 01:08 PM
Not sure what to make of all this but anyhoo. There seems to be some confusion of mechanial rpm on an engine.
If you over rev an engine due to a down shift. ie.. 2nd from a 5th gear at some high speed. ie.. 100mph or so, MECHANICALLY, the engine rpm WILL exceed the motor's safe rotating speed.
While the engine might not be actually running, it's still rotating at that high rate. It's the mechanical high speed rotating that will damage the engine. It doesn't matter if the engine is running or not. Now yes, the car will coast to a stop. But it takes mere seconds to do the damage. It would be too late. Even pushing in the clutch might not be fast enough.
If you over rev an engine due to a down shift. ie.. 2nd from a 5th gear at some high speed. ie.. 100mph or so, MECHANICALLY, the engine rpm WILL exceed the motor's safe rotating speed.
While the engine might not be actually running, it's still rotating at that high rate. It's the mechanical high speed rotating that will damage the engine. It doesn't matter if the engine is running or not. Now yes, the car will coast to a stop. But it takes mere seconds to do the damage. It would be too late. Even pushing in the clutch might not be fast enough.
#55
04-23-2007, 01:15 PM
Originally Posted by Jeff92se
Not sure what to make of all this but anyhoo. There seems to be some confusion of mechanial rpm on an engine.
If you over rev an engine due to a down shift. ie.. 2nd from a 5th gear at some high speed. ie.. 100mph or so, MECHANICALLY, the engine rpm WILL exceed the motor's safe rotating speed.
While the engine might not be actually running, it's still rotating at that high rate. It's the mechanical high speed rotating that will damage the engine. It doesn't matter if the engine is running or not. Now yes, the car will coast to a stop. But it takes mere seconds to do the damage. It would be too late. Even pushing in the clutch might not be fast enough.
If you over rev an engine due to a down shift. ie.. 2nd from a 5th gear at some high speed. ie.. 100mph or so, MECHANICALLY, the engine rpm WILL exceed the motor's safe rotating speed.
While the engine might not be actually running, it's still rotating at that high rate. It's the mechanical high speed rotating that will damage the engine. It doesn't matter if the engine is running or not. Now yes, the car will coast to a stop. But it takes mere seconds to do the damage. It would be too late. Even pushing in the clutch might not be fast enough.
#56
04-23-2007, 08:32 PM
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Originally Posted by Jeff92se
Not sure what to make of all this but anyhoo. There seems to be some confusion of mechanial rpm on an engine.
If you over rev an engine due to a down shift. ie.. 2nd from a 5th gear at some high speed. ie.. 100mph or so, MECHANICALLY, the engine rpm WILL exceed the motor's safe rotating speed.
While the engine might not be actually running, it's still rotating at that high rate. It's the mechanical high speed rotating that will damage the engine. It doesn't matter if the engine is running or not. Now yes, the car will coast to a stop. But it takes mere seconds to do the damage. It would be too late. Even pushing in the clutch might not be fast enough.
If you over rev an engine due to a down shift. ie.. 2nd from a 5th gear at some high speed. ie.. 100mph or so, MECHANICALLY, the engine rpm WILL exceed the motor's safe rotating speed.
While the engine might not be actually running, it's still rotating at that high rate. It's the mechanical high speed rotating that will damage the engine. It doesn't matter if the engine is running or not. Now yes, the car will coast to a stop. But it takes mere seconds to do the damage. It would be too late. Even pushing in the clutch might not be fast enough.
* once the engine STOPS RUNNING - it stops. kapoot. no mas. ( your first sentence on the last paragraph - you state " while the engine might not be actually running, it's still rotating at that high rate )even if your timing is off or you spun rod ( bearing ) the motor will not keep revving past redline. you've now lost timing / compression - say bye bye to your motor ( for the time being) it will barely idle - OR run like crap!
* the motor will BOUNCE off the revlimiter ( once again, it may exceed the redline by a hundred or so RPM'S - but it will not SHOOT TO 10K) - here's where your partly right / wrong - it's not the high speed rotating mass ( cars rev to 9k - 10k ALL DAY LONG - if prepped, it's the LOAD on the components that cause the failure )
it DOES matter if the engine is running ( it needs to be running - once something happens - timing will be OFF - this will either SHUT THE CAR OFF OR MAKE IT RUN LIKE CRAP)
* and i agree w/ you whole heartidly - it takes a mere FRACTION of a second, once damaged, it doesnt matter if the clutch is engaged or not.
once again - PLEASE, reread all of the posts ( not just the last page ) there was a confusion regarding not only mechanical rpms / load - but revlimit / fuel cut off - i'm not trying to call everyone out, i just speak from experience ( yes - w/ other makes of cars - but n/a internal combustion motors all work almost identical )in fact, i'll go as far as saying internal combustion motors all work on the same principle ( suck / squish / BOOM! )
- james.
#57
04-23-2007, 08:38 PM
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* raises the white flag *
#58
04-24-2007, 02:37 AM
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