Almost misshifted today.....
#31
Originally Posted by trey.hutcheson
And I would like to reiterate: overrevving a car is still possible when one mistakenly downshifts at high rpms. That action is is a mechanical condition which the ecu cannot correct.
#32
Originally Posted by trey.hutcheson
Just for clarification, the revlimit functions by way of a fuel cut. They are not the same thing, but when the revlimit threshold is met, the ecu issues a fuel cut. The revlimit is a condition, and the fuel cut is an action.
From page EC-25 of the FSM:
Fuel to each cylinder is cut off during deceleration, operation of the engine at excessively high speeds or operation
of the vehicle at excessively high speeds.
So - that means that the fuel cut function in the case of rev limiter and the speed governor.
And I would like to reiterate: overrevving a car is still possible when one mistakenly downshifts at high rpms. That action is is a mechanical condition which the ecu cannot correct.
From page EC-25 of the FSM:
Fuel to each cylinder is cut off during deceleration, operation of the engine at excessively high speeds or operation
of the vehicle at excessively high speeds.
So - that means that the fuel cut function in the case of rev limiter and the speed governor.
And I would like to reiterate: overrevving a car is still possible when one mistakenly downshifts at high rpms. That action is is a mechanical condition which the ecu cannot correct.
also - your excerpt from EC25 : states either excessive engine speed OR vehicle speed...fuel cut is more apparent in vehicle speed..since youve misgeared ( aned so have i ) did the car shut off when you bounced off revlimit? or did it just buck hard ( not due to engine speed, but because tranny revolutions didnt permit you to? )i'll bet money the car didnt die for a short period - it just bucked.
your re-itteration regarding overrevving - youre right, this is more of a mechanical condition - but if you geared down from 5th to 3rd gear..you would gain considerable RPM's but are you able to still REV past your redline?
or did you stay in gear only for a short period of time- either because you ran out of gearing - or, because you hit the rev limiter?
for those who have raced ( street and/or track ) when you brought the engine speed ( rpms ) up to redline..did your car turn off? or did that needle just bounce/ping off revlimiter? once again - i'll put money up that cars did not " turn off" due to no fuel, instead, the latter happened.
lol- i'm not trying to argue w/ anyone - nor am i trying to call anyone out - once again - the thread was started because another member had mis-shifted..all i ways pointing out was luckily - he had a stock ecu which would not allow him to rev to 10k's when th emotor is not prepped for it.
#33
#34
Originally Posted by j-champaco
d efinately wrong.
reread you prior post -
1. rev limit doesnt cut the fuel, it DOES keep the motor from over revving, but this is via ECU.
2. fuel cut and speed governor work almost hand in hand ( more so in this case than w/ rev limit ) once youve hit max speed - your car will shut off ( for a quick second - then regain rpm's and continue to work )
youre right though - fuel cut is more of an ECU issue - but so is the speed gov.
* anyways, the point of the thread was that he almost mis-shifted, i was pointing out the fact that he was better off having a stock ecu than a reprogrammed ecu - he may have floated a valve and either damaged the head or the block *
reread you prior post -
1. rev limit doesnt cut the fuel, it DOES keep the motor from over revving, but this is via ECU.
2. fuel cut and speed governor work almost hand in hand ( more so in this case than w/ rev limit ) once youve hit max speed - your car will shut off ( for a quick second - then regain rpm's and continue to work )
youre right though - fuel cut is more of an ECU issue - but so is the speed gov.
* anyways, the point of the thread was that he almost mis-shifted, i was pointing out the fact that he was better off having a stock ecu than a reprogrammed ecu - he may have floated a valve and either damaged the head or the block *
Both Trey and Trey's wife are correct, which is exactly what I stated.
True, this is swaying off topic, but im sure it could help anyone understand how it works. Besides, when you mis-shift, its good to know how it works.
James, having conversations like this, as long as it doesnt go completely wrong, is always a good thing. The more we learn, the better.
.
#35
Originally Posted by skaterbasist
You're confusing yourself. ECU and Rev-Limiter are directly related.
Both Trey and Trey's wife are correct, which is exactly what I stated.
True, this is swaying off topic, but im sure it could help anyone understand how it works. Besides, when you mis-shift, its good to know how it works.
James, having conversations like this, as long as it doesnt go completely wrong, is always a good thing. The more we learn, the better.
.
Both Trey and Trey's wife are correct, which is exactly what I stated.
True, this is swaying off topic, but im sure it could help anyone understand how it works. Besides, when you mis-shift, its good to know how it works.
James, having conversations like this, as long as it doesnt go completely wrong, is always a good thing. The more we learn, the better.
.
#36
Originally Posted by j-champaco
in your prior post - you stated rev limit cuts fuel..what i was trying to point out was that rev limit DOES NOT cut fuel - it limits your rpm's! anyways - i think i know what you meant - im sure you knew what i meant as well...also - im sure WE both knew what Trey and his wife meant..they probably knew what WE meant..now the world knows what we ALL meant! kapeesh~~!! anyways - it was all good, all good point like you said -
I understand how it works, but we might end up confusing ourselves since we're just using different ways to show our understanding.
.
#37
#38
Originally Posted by j-champaco
also - please don't think im calling you and/or your wife out on this - it's just a thread - no harm / malice intended. and also to skterbassist ( i may have spelled your name wrong )
- james.
- james.
Back to the topic, the rev limit functions because of the fuel cut. However, just because the ecu cuts fuel does not mean that the engine is off. It's still revolving, and the ecu is still monitoring all of the sensors.
The factory service manual states that fuel cut is also invoked when decelerating above 1800rpms. So if you leave the car in gear, engine braking, and the revs are above 1800, the ecu will cut fuel. The ecu will start reuissing fuel commands at about 1500.
That last paragraph is not directly related to the discussion, but it does illustrate how the ecu will intervene in regards to fuel. The ecu performs the same operation when the revs exceed the rev limiter.
I will state this again. The rev limiter is not some mechanism that prevents revs from exceeding a predetermined value. The rev limiter is just a condition, a number. The ecu monitors the revs through its various sensors(crank position), and when the revs exceed this value(rev limiter), the ecu reacts by cutting fuel. I think you're confusing the action/reaction of revs/fuel cut.
By cutting fuel for a fraction of a moment, the revs will drop. That's why you can bounce off the limiter so to speak.
#39
Registered User
iTrader: (10)
#40
thanks trey - but, for sake of argument.. the rev limiter is not a condition, number. This is the point @ where it's unsafe for the engine ( rotating mass - crank walk..lean conditions, no lubrication and so forth) the reason you "bounce" off revlimit is because this has been a predetermined point - this is actually the ignition timing, ecu all working in conjunction w/ one another. turn you car on, let it idle..rev it up to the rev limit - you will only "bounce" off the limit, you car will not turn off...also, once fuel has been cut, injectors ( both styles - pulse / peak & hold ) will close. Once this is done - engine will turn off. it's a constant cycle air /fuel/spark - once one element is missing, this will cease.
* but back on topic - it's nice to know that there ARE people on here that acually know what theyre doing..im new on the site and all i thought was this was a " lowered on rims" community / exterior mods...like i told skater ( through PM ) it would be nice to actually meet each other and sit face to face and shoot the..well -shoot the breeze! i will leave this one alone - ACCORDHYBD - please -...for arguments sake - DON'T EVER START ANOTHER
MIS-SHIFT" THREAD AGAIN!!! LMAO~ james.
* but back on topic - it's nice to know that there ARE people on here that acually know what theyre doing..im new on the site and all i thought was this was a " lowered on rims" community / exterior mods...like i told skater ( through PM ) it would be nice to actually meet each other and sit face to face and shoot the..well -shoot the breeze! i will leave this one alone - ACCORDHYBD - please -...for arguments sake - DON'T EVER START ANOTHER
MIS-SHIFT" THREAD AGAIN!!! LMAO~ james.
#41
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Join Date: Sep 2005
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There should be a reverse "lock out" on most of the mt. to prevent you from shifting into rev. when you are on the highway and such but not all car have them. I would have to guess that g have one but would not try and find out.
Rev limiter is to stop the engine from throwing piston out of the block.
there are more than one way to do this.
The engine needs 3 thing to runs
-Fuel( controlled by injectors/fuel pump done by ecu )
-Spark(controlled by adjusting timing or no spark done by ecu )
-Air( drive by wire buterfly /cam shafts controlled by ecu on those have vvt. and such)
as new BMW they have electronic valves for almost everything from intake manifold to cams and exhaust valves
Take anyone of those away and the engine will slow down or stop.
Speed limiter is controll for all ya safety ( around 150 on most car ) by ecu.
That just the bacis. If you want to get into it technicaly then there are more lot more to it.
Rev limiter is to stop the engine from throwing piston out of the block.
there are more than one way to do this.
The engine needs 3 thing to runs
-Fuel( controlled by injectors/fuel pump done by ecu )
-Spark(controlled by adjusting timing or no spark done by ecu )
-Air( drive by wire buterfly /cam shafts controlled by ecu on those have vvt. and such)
as new BMW they have electronic valves for almost everything from intake manifold to cams and exhaust valves
Take anyone of those away and the engine will slow down or stop.
Speed limiter is controll for all ya safety ( around 150 on most car ) by ecu.
That just the bacis. If you want to get into it technicaly then there are more lot more to it.
#43
Red Card Crew
iTrader: (24)
Hmm... Fuel cuts vs ign cuts. I'm not too sure. On the maxima, I do believe there also hard and soft rev limit cut offs also. But not 100% sure on this.
As for the Rev limit, yes I suppose it's represents some "limit". But I don't believe it represents a "hard" or "definate" rev capabilities of the engine. But it's somewhere in the ballpark. I don't thin TS and others would be so willing to reflash the higher rev limits if the stock rev limiter was set THAT closely to the engine's capabilities.
As for the Rev limit, yes I suppose it's represents some "limit". But I don't believe it represents a "hard" or "definate" rev capabilities of the engine. But it's somewhere in the ballpark. I don't thin TS and others would be so willing to reflash the higher rev limits if the stock rev limiter was set THAT closely to the engine's capabilities.
#44
i agree, reflashing for a couple of HUNDRED rpm's on a stock motor..but nothing more than that ( once again, on a stock motor )powerband may not dictate a new rev limit, not to mention the design of th emotor - if the motor was not intended to rev high, then im sure it wasn't designed to.
couple of hundreds as in..no more than 500 rpms!
couple of hundreds as in..no more than 500 rpms!
#45
Originally Posted by j-champaco
lol- i'm not trying to argue w/ anyone - nor am i trying to call anyone out - once again - the thread was started because another member had mis-shifted..all i ways pointing out was luckily - he had a stock ecu which would not allow him to rev to 10k's when th emotor is not prepped for it.