Was just thinking of this today and wanted to get some feedback....

I have been used to modded imports like civics, integras, and RX7s, where you have to rev the crap out of them to get into their peak torque range so it made sense to take the car up to redline before shifting. With the G, its highest torque output is between appx. 3800 and 5500 rpms, generally speaking from looking at various torque curves from dynos. Since it is torque that provides the acceleration, why would I want to rev it up to 6600 rpms and when shift have the rpms fall back to the high 5000's, which is still out of its peak torque range. Wouldn't it make more sense for me to rev up to about between 5300 and 5600 (or even lower) and then shift so I can keep getting the car back to close to its peak torque point of 4250. Wouldn't this ultimately lead to faster acceleration and quicker track times? By reducing my shift point to fall more within the higher torque range, I can easliy get my tires (still fairly new) to chirp a good ways when shifting into 3rd, which I couldn't do before (unless I am just wearing them out from all the hard accelerations). Please post comments. This might be obvious to some people, but I just want to get some feedback before I head to the track.

Also, what about skipping a gear? May sound stupid, but I was trying different shift points and I found that if I rev up to the high 5000's in 2nd and I shift to directly to fourth, it puts my car in the high 3000's/low 4000's, just about where its peak torque is. This would also mean than I have one less shift in the run as well. If I am a sloppy shifter and have to shift only 3 times instead of 4 down the track, this also should theorhetically improve my time. Comments would be appreciated.


2003.5 Sedan 6MT

 

The way I do it on my 5AT is like this. Shift to second just past the torque peek (4-5k rpm) to get the car moving, then from second on at 6200rpm which is the hp peek, you definatelly want to get the most out of second, at least on the 5AT second gear is just sick, I feel the hardest acceleration from it. From what I understand while the car is allready in motion you want to shift at hp peak so then at thext gear you end up at the point were hp curve goes up again. I can definatelly feel a strong pull all the way up to 6200rpm.

 

Good question, but the other part you need to consider is torque multiplication from gearing. Lower gears in effect multiply your torque at the wheels, and so by staying in the gear longer before upshifting, you retain that advantage. Hypothetical - say at around 6000rpm the engine only makes 225 ft-lbs of torque, but at around 4500rpm it makes 300 ft-lb. Let's say 2nd gear is a 3:1 ratio and 3rd is 2:1. Does it accelerate faster in 2nd gear@6000rpm or 3rd gear@4500rpm?

2nd gear torque@wheels = 225 ft-lbs x 3 = 675 ft-lbs
3rd gear torque@wheels = 300 ft-lbs x 2 = 600 ft-lbs

Thus it accelerates faster at 6000rpm in 2nd, and you would be much better off staying in 2nd gear well past the engine torque peak before shifting. These #'s are of course completely hypothetical but hopefully it demonstrates the concept.

2004 Black 6MT

 

Thanks. I took a sample SAE-corrected torque curve I found for the 6MT as well as the gear ratios to figure out FT-LBS per gear, per RPM. See below.

It looks like it is still the best to take it up to as close to redline as possible because the actual FT-LBS at redline is still going to be higher than where you'll be at after you shift. (assuming this logic of multiplying the torque by the gear ratio for a given RPM level is correct).





105951-tqchart.GIF

 

Don't forget that the torque you have there is multipliied further by 3.54 in the differential before it gets to the wheels so approximately (ALOT) of torque at the wheels in the end result.

Better Life thru Chemistry

 

for my car, the best shift point is at 6900 rpm. but thas with an ECU. hahahahaha suckas. oh yea, btw, my redline is at 7100.

G35S 6MT
K&N Typhoon intake
Technosquare ECU
350Z Springs & Struts (soon)
6-wire ground kit