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      12-22-2011, 07:32 PM   #1
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Fuel cut-off

If the engine is revved beyond the max allowed RPM, you get a fuel cut-off, right? Then what happens next? When does it get the power back?
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      12-22-2011, 08:00 PM   #2
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      12-22-2011, 08:01 PM   #3
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Once you hit fuel cut (assuming you didn't money shift) the car will bog down and power will return somewhere around 7000-7500rpm. Not sure exactly where since I've only let it happen twice.

Also, if you are in gear and ride it out to redline the car won't actually over-rev..that's what fuel cut is there for
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      12-22-2011, 08:09 PM   #4
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Engine redline is 8400 rpm. When this is exceeded, fuel is cut off. When this is not exceeded, fuel flows. There is a relatively sharp cut off. You will reflexively pull your foot off the gas. This engine starts to loose power after 8500 rpm (Dinan software upgrade will increase redline to 8600rpm), so ideally you want to start your upshift to time the next gear just before redline.
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      12-22-2011, 09:23 PM   #5
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Quote:
Originally Posted by PGabriel View Post
If the engine is revved beyond the max allowed RPM, you get a fuel cut-off, right? Then what happens next? When does it get the power back?
Have you never heard of "bouncing on the limiter", watch any 5th gear or Top Gear video on youtube and you will hear it.
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      12-22-2011, 10:13 PM   #6
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Quote:
Originally Posted by Aussie335iM View Post
Have you never heard of "bouncing on the limiter", watch any 5th gear or Top Gear video on youtube and you will hear it.
This car will only bounce off the limiter in neutral or when your rear wheels don't have traction. Otherwise, you hit fuel cut.
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      12-22-2011, 10:23 PM   #7
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Quote:
Originally Posted by Krozi View Post
This car will only bounce off the limiter in neutral or when your rear wheels don't have traction. Otherwise, you hit fuel cut.
The fuel cut is the limiter. If you are "bouncing off the limiter" engine rpm's are reduced by cutting the fuel injector pulse. The ignition system is NOT used as a rev limiter because of emissions and damage to the catalytic converters. Fuel cut is also used on coast down under the right conditions.
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      12-22-2011, 10:35 PM   #8
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Quote:
Originally Posted by kenwelch View Post
The fuel cut is the limiter. If you are "bouncing off the limiter" engine rpm's are reduced by cutting the fuel injector pulse. The ignition system is NOT used as a rev limiter because of emissions and damage to the catalytic converters. Fuel cut is also used on coast down under the right conditions.
Wrong. (The first part)
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      12-22-2011, 11:19 PM   #9
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In my experience on track I was bouncing off the limiter quite a bit. In fact in certain spots it seemed like I could just keep the RPMs at the limit for a sec instead of having to shift for that split second. Power does stop for a second which I assume is fuel cutoff but can power through that and pretty much sit at redline if wanted IME. I do have ESS software with an increased redline, but don't think that would make a difference, but then again I could just be insane
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      12-23-2011, 06:11 AM   #10
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Originally Posted by Krozi View Post
Wrong. (The first part)
Really? Rather than just fling this sort of pithy reply, why don't you explain the correct answer?
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      12-23-2011, 06:33 AM   #11
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Originally Posted by GIdriver View Post
I'm so glad you got popcorn.

I really wanted to reply before you, and I spent all this time thinking about how can I reply and be helpful, inspiring, or even make a comment that might in some weird sort of way push someone in the right direction, or even if its wrong ... that my comment might make a difference in someone's life.

But I guess popcorn is the answer.

GJ.
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      12-23-2011, 06:57 AM   #12
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Originally Posted by Superfly_M3 View Post
I'm so glad you got popcorn.

I really wanted to reply before you, and I spent all this time thinking about how can I reply and be helpful, inspiring, or even make a comment that might in some weird sort of way push someone in the right direction, or even if its wrong ... that my comment might make a difference in someone's life.

But I guess popcorn is the answer.

GJ.
Thanks! I had to do it.
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      12-23-2011, 09:49 AM   #13
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Quote:
Originally Posted by DivideBYZero View Post
Really? Rather than just fling this sort of pithy reply, why don't you explain the correct answer?
Pretty sure I did. Read the thread genius.
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      12-23-2011, 09:52 AM   #14
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You guys are funny, especially since I'm drinking.
OP, so what happens next? Why not just try it? You'll see what happens first hand.
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      12-23-2011, 11:35 AM   #15
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Originally Posted by Krozi View Post
Pretty sure I did. Read the thread genius.
Nah, you didn't. You're posting that there is a difference between fuel cut and the limiter. If you're so sure of yourself, explain the technical detail that defines each and the conditions under which each activates.
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      12-23-2011, 02:50 PM   #16
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I thought I read something about a "soft cut" limiter. It does seem to be pretty "soft" compared to the 350Z I previously had. If you hit the limiter with it, you had to stop yourself from hitting your face on the steering wheel.
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      12-23-2011, 05:16 PM   #17
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Quote:
Originally Posted by luis_m3 View Post
You guys are funny, especially since I'm drinking.
OP, so what happens next? Why not just try it? You'll see what happens first hand.
I like this cats style-drinking alone and reading the boards! Love it (most probably think I am smashed when I post-actually don't drink these days but back in the day was good fun!)

In regards to the thread. I seem to hit fuel cutoff once every couple days. Apparently I suck ass at shifting at 8400. Its a game and fun to me to see if I can nail the shift right at the limit but often fuel cutoff totally rains on my parade, stutters and I keep it pinned anyway and in a second you are on your way when you shift!
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      12-23-2011, 05:28 PM   #18
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Quote:
Originally Posted by DivideBYZero View Post
Nah, you didn't. You're posting that there is a difference between fuel cut and the limiter. If you're so sure of yourself, explain the technical detail that defines each and the conditions under which each activates.
Urrrrrrrrrrrr r huuuuuuuuuuuuuurrrrrrrrrrrrr durrrrrrrrrrrrrrrrrrr


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Last edited by Krozi; 12-23-2011 at 05:38 PM.
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      12-25-2011, 03:52 AM   #19
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The purpose of the "rev-limit", is to cut fuel and or modulate the throttles to ensure that RPM does not exceed the maximum permissible range. There are soft and hard rev limits. You'll notice the M3 doesn't "bounce" of the rev limiter, it pretty much sits right there at that RPM. You will feel individual fuel cuts before hitting the hard revlimter. That's the feeling that you get at high RPM where the car strains (for lack of a better term), right at the top of what the RPM limit is set at. At this point the injection is modulated - the system can even alternate cuts to different cylinders.

Injectors go off and the car goes full lean when decelerating. That's not really a "fuel-cut" per se, more of a function of reducing emissions and for drivability.

My redline is 8,650 - shes a screamer.
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Last edited by Mike Benvo; 12-25-2011 at 03:59 AM.
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      12-26-2011, 03:34 PM   #20
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Originally Posted by Krozi View Post
Urrrrrrrrrrrr r huuuuuuuuuuuuuurrrrrrrrrrrrr durrrrrrrrrrrrrrrrrrr


That's what I thought.
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      12-26-2011, 03:40 PM   #21
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Quote:
Originally Posted by DivideBYZero View Post
That's what I thought.
Duuuuuuuuhhhrrrrrrrr huuuuuuurrrrrrrrrrrrrrrrrrrrrr
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      12-26-2011, 05:39 PM   #22
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