redline anyone?
11-18-2007, 02:13 AM
#1
Sunlit Sand Beauty
Thread Starter
Join Date: Apr 2007
Posts: 148
redline anyone?
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"?
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"?
11-18-2007, 08:08 AM
#8
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"
11-18-2007, 04:58 PM
#11
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Posts: n/a
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
11-18-2007, 06:00 PM
#12
Supporting Maxima.org Member
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Join Date: Nov 2004
Location: Baton Rouge, LA
Posts: 5,432
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
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
11-18-2007, 06:29 PM
#13
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.
In the auto the only way you can downshift and overrev, AFAIK, is the shift_fast mod.
11-20-2007, 10:38 AM
#15
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...
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...
11-20-2007, 10:45 AM
#16
Guest
Posts: n/a
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...
11-20-2007, 12:11 PM
#19
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...
Let me find a stock 5th gen dyno curve...
11-20-2007, 12:12 PM
#20
11-20-2007, 12:15 PM
#21
11-20-2007, 12:19 PM
#25
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.
11-20-2007, 12:20 PM
#26
Oh lord. This is getting out of hand.
Here's a good read.
Here's a good read.
Originally Posted by FSM Freak
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).
11-20-2007, 12:21 PM
#27
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.
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.
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.
11-20-2007, 12:21 PM
#28
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...
11-20-2007, 12:24 PM
#30
11-20-2007, 12:25 PM
#31
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.
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.
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.
11-20-2007, 12:26 PM
#32
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.
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.
x2http://forums.maxima.org/showpost.ph...0&postcount=13
http://forums.maxima.org/showpost.ph...5&postcount=26
11-20-2007, 12:31 PM
#33
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!
11-20-2007, 12:34 PM
#34
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!
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!
11-20-2007, 12:39 PM
#35
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...
11-20-2007, 01:12 PM
#37
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...
HP = (TQ*RPM)/5252
For those who didn't know.
11-20-2007, 01:22 PM
#38
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.
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.
11-20-2007, 08:25 PM
#39
Originally Posted by Bborges
One way to measure this is with an accelerometer...
Originally Posted by Bborges
All you really have at that range is left over high RPM and dropping torque,
11-20-2007, 10:48 PM
#40