+1...I've done it on a rev-limited car... though not in the G, thankfully...

 

revlimit functions by way of fuel cut - this is incorrect. the rev limit functions by way of ignition / timing - youre right, fuel cut may happen for a brief moment - but revlimit is not dependant ( entirely ) from fuel.( you state this in your first paragraph ) im not talking about being able to set your own " shift point" im talking rev-limit. ( ie - a cars redline ( any car - not just the g ) may be at 8k...you may be able to rev to 8300 - but w/ out a reprogrammed ecu - you will not rev to 10k )

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.

 

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.

 

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.

.

 

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 -

 

Well, what I meant is, the ECU cuts the fuel, which consequently limits your RPM's. (Therefore, directly related).

I understand how it works, but we might end up confusing ourselves since we're just using different ways to show our understanding.

.

 

after re-reading your posts, i know thats what you meant! in fact - after re-reading all of OUR posts - i came to that conclusion as well. maybe we should get into more " arguments"@@@!!! bring this board to life!!! lmao - j/k,
pm also sent
james.

 

No harm man. I don't mind arguing. I don't mind being wrong. And you're not attacking anybody, so it's cool.

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.

 

I'm so glad to see someone finally using G35 for what it was intended........
that's right to gain knowledge.....and get the correct answers! It gets old
seeing members being childish because the don't get immediate responses
to their questions........waaaa

 

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.

 

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.

 

throwing piston out of block

floating a valve

crank walk

too much friction w/in the cylinder wall

running way too lean

list goes on..

 

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.

 

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!

 

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.