so i inadvertently redlined my car last night, i had the shifter on second and forgot to change till i saw the needle approaching 7, already past redline


i was wondering,....what exactly happens when u redline a car...and i thought the ecu was supposed to change automatically, isnt there a rev limiter, or does it only work on "D"?

 

If its auto I don't think its possible to put it in the red unless you downshift. I've tried and the ECU seems to stop it at about 6,700 rpms, it won't even go into the red.

 

well i had it on 2nd (manual mode) and it went past 6500, half way to 7k

 

There is no "Manual mode" on 5th gen autotragics

 

ok let me rephrase, i had the shifter in the 2 position.

 

ok, thats better.

I had my 5-speed to ~8500 because of a mis-shift and nothing bad happened.

 

whar exactly happens when u redline though? i mean theres gotta b a reason why the engine speed is limited

 

So you don't bend valves.

My friend's E36 M3 was downshifted deep into the redline (i'd say like 9000rpm) He ended up bending valves and nothing else.

IIRC, Technosquare ECU allows AE to rev up to 7100rpm, so what you did is "acceptable"

 

TCM shouldn't allow you to take the revs that high...

 

Even if the manufacturer places its redline at X, the engineering safety limit, your VQ could probably tolerate a few dances at it without problem. Just don't make it a habit.

 

its time for some facts here:

1: you didnt even hit redline, the redline/rev cut is at 6650 and you would know if you hit it
2: the tach in 5ths gens is terribly calibrated thats why you think it was revving so high
3: you can hit redline all day and the vq doesnt care. i make it a habit and have for the past 3 years. they make the redline a good deal lower than it needs to be so that you can do that. the "engineering safety limt" was said by a nissan tech to be 7600 on a 3.5...and many people take 3.0s there often as well. your stock limiter is in a pretty safe zone

 

Thank you that's what I came to say. But 7600 is a little extreme for the VQ35 as the rod bolts are pretty weak. I'd say 7000-7200 is the safe zone.

 

http://www.youtube.com/watch?v=tD3pGEraVLAb That's twice now he's done that, and she still runs just fine...minus the ISB.

It's an ECM function, not a part of the TCM.

ECM cuts fuel when you hit...fuel cut. Not sure if it completely cuts fuel, or just takes IPWs down to near nothing, but either way you don't have the fuel to rev any higher. Downshifting into too low of a gear, though, will overrev your motor. Fuel cut can't help when the overrev is caused by a physical force (wheels turning, clutch engaged, trans in gear).

In the auto the only way you can downshift and overrev, AFAIK, is the shift_fast mod.

 

Didn't read he was in 2nd.

 

I never done it on the VQ, but my last two cars (both manual) the ECM would simply cut off fuel and the RPM wouldnt go any higher... you could easily feel/hear the engine "bugging" for gas...

I always thought any modern engine would have this built-in the ECM... but from some of the replies I guess the VQ does not have it... i'll try on my VQ one day to see how far it goes... or maybe not..


Also, for those that like to redline it, there is a lot of discussion not only on how healthy it is but also if there is any performance gain, since around redline you are already dropping on torque, past peak. All you really have at that range is left over high RPM and dropping torque, so depending on your torque curve, it doesnt help to go that far. One way to measure this is with an accelerometer...

 

it does, you dont need to test it. i already said this

you CERTAINLY want to redline your 2000, since the 00VI makes power well over 7k.

 

just don't hold it in the red.

 

Looks like all the fun has been had in here already.

 

I am still not clear, did you state it DOES CUT the fuel or it DOES GO PAST RED?




Weird, for if around 7K the engine was still torquing enough they shouldve get better valves and let it rev, getting even more PeakHP. I know the VQ has a very nice flat torque curve, Ive seen it before but never with what you said in mind...

Let me find a stock 5th gen dyno curve...

 

5th gens is flatter than a 5.5 gens

 

Only allows you to go past fuel cut from a downshift (i'm 5-speed)

I did this from 3rd to 2nd gear on accident.

 

My curve is pretty flat. i need my plx wired in mang.

 

And you even have your power rod removed.

 

exactly, no VI spike for easy tuning ftw!

 

That implies that the ECM does cut once it reaches certain RPM when acceleratinhg... thats exactly what happened to my other 5sp and I thought it happened in the Maximas..


But I thought DasYears was saying that the VQ ECM does NOT cut the fuel....


Now I am really confused... and no.. i am not talking about downshifting.

 

Oh lord. This is getting out of hand.

Here's a good read.

 

Here's how it works:

In my 2000 5-speed SE

if i take it up to "redline" from acceleration in say, 2nd gear, once it hits about 6600rpms, it cuts the fuel.

However when I downshift from say 5500rpm in 3rd gear back to 2nd gear, it will rev way past 6600, i'd say a good 7500rpm with the needle dug way into the tach.

 

Nice plot... and it does seem like a working 00VI get you another torque boost... SWEET! but still... I am sure if you plotted the torque curve after the 6.5K RPM you would see the torque really dropping dead...

 

Here's mine without VI:

 

Even if the tq falls @ that RPM, hp just flattens out/drops very little, you're still good, IMO.

 

Thank you! Thats EXACTLY what I said all the time and thats exactly how all manufacturers nowadays will program their ECM (read: warranty). I just got confused because I thought it was said that the maxima does not cut fuel past redline and since i've never tried it, i wanted to confirm if the info was good.


And regarding downshifting, thats mechanical inertia, the ECM has no way of controlling the RPM in a downshift, so obviously depending on the combo on the downshift, you will redline it.

 

x2
http://forums.maxima.org/showpost.ph...0&postcount=13
http://forums.maxima.org/showpost.ph...5&postcount=26

 

Nice output, 200HP flat at wheel...

the dyno i posted was not mine, and I am not sure what was done (if anything) to the car... but it is interesting to see how you guys are pulling the same torque 186 ft-lbs but because you have a much flatter torque, you have more HP...


SWEET!

 

Simple, when comparing 2 cars having the same peak torque, odds are that the car w/ higher hp is making more torque @ a higher RPM, whereas the car making less peak hp is probably making more hp @ a lower RPM.

 

http://forums.maxima.org/showpost.ph...2&postcount=33







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hmmm... makes me wonder if I could figure out how to relate torque and HP... maybe come up with a mathematical model and then a generic formula...


I wish they would teach these things in my engineering program...

 

i need tarbo!

200whp is nothing.

 

I hope all that was sarcasm

HP = (TQ*RPM)/5252

For those who didn't know.

 

All cars sold now have a fuel cut at a certain RPM to avoid an accidental over-rev. Virtually all cars do (I'm sure there were one or two older cars that didn't). We're no longer in the days of the carburetor, and over-revving just by flooring it.

 

How 'bout a dyno?
Depending on RPM, you could still be gaining in horsepower, EVEN if the torque is dropping. But you knew that.

 

I knew both of these thangs. Am I OG qualified?