Seems to me the fastest 1/4mi times on this forum have been from people shifting at 6200rpm. It apprently keeps you in the powerband the longest. Try it out, it seems to be faster to me on the street, although I havent been to the strip yet.

 

You would have to have a really crappy motor for that to be the case (i.e. a diesel). Basically because of the gearing difference between the gears the engine would have to make a *LOT* more torque at 4000 rpm than at redline. For example first and second gear ratios are 3.79:1 and 2.32:1 respectively in the 6MT - this is a difference of 63%. If you assume that you generate about 250 lb-ft at redline, you would need to generate 407 lb-ft of torque at 4000 rpm for it to make sense to shift earlier. This is because the torque that you generate at the crank gets multiplied by the gear ratio to get to torque at the wheel (which is related linearly to acceleration). Now, 1st to 2nd is the most obvious example because the gears are the two with the widest numerical spacing, but this will still happen in every gear. Specifically, 2nd gear gives you 43% more wheel torque than 3rd, 3rd in turn gives you 28% more wheel torque than 4th, 4th gives 27% more wheel torque than 5th and 5th gives 27% more wheel torque than 6th. Because the torque curve is relatively flat, there is no point where it makes sense to be in the next higher gear before reaching redline if you are trying to maximize acceleration.

Hope that's clear.

 

I hold what I believe to be the quickest stock 350z 1/4 mile E.T. out there...and I ALWAYS shift at redline. If you shift at 6200 it drops you BELOW the torque peak for the next gear.

The ideal shift point is 300-400rpms AFTER the peak hp....my car peaks between 6200 and 6300rpms....so shifting at redline is perfect.

 

Fuel cut-off is just a fancy term for rev-limiter. Your engine computer won't let your motor rev any higher by cutting fuel to the cylinders..it's a safe way to keep people from overrevving motors.

If you have your shift light set @ 6,600rpms then it will start to blink @ 6,100rpms (500rpms before your set "shift point")...and then go solid @ 6,600rpms. If you are shifting when the light comes on...then you are shifting @ 6,100rpms...which is MUCH to early. Shift @ redline for maximum acceleration.

 

Originally posted by mplc
I know this will obviously be a stupid question to most......but, am I to understand that my fuel will cut off at 6,600 rpm's????
I have my rev light set to 6,600 and shift when it lights. What happens when the feul is cut off?


then wouldnt it be logical to set the rev light to about 7000 so when it comes on it is actually 6,800 the "ideal rpm to shift at?????????? did that make sense ??????

 

Hmmm, I shift at redline all the time and dont hit the REV limiter, I got a 2004 Roadster 6MT.

 

get the Technosquare ECU.
i got one on my G and i can shift way past redline now. its a much better feeling. much better times for sure.

 

yeah, I was goign to suggest to people that have this problem. I am probably goign to do technosquare myself. It lets you rev to 7,100 revs.

 

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I just put my shift light to 7100 so it lights at 6600, so when i see the light its already in the next gear b4 i can think

 

Really mine seems to cut in early like around 15.2-15.3k, what year is yours? Mine is an '04.

 

Honestly, in my 04.5 my rev-limiter is pretty soft, i shift around 6700 without issue.

 

Understand that accelerating and hitting the redline or rev limiter is an electronic fuel cut-off for engine protection. BUT downshifting is a direct mechanical connection and CAN over rev the engine. A fuel cut-off cannot protect this.

 

what he said. this is worse with a manual since there is no soft connection like the automatic has between the engine and the wheels.