Like the title says. A lot of folks have been asking about this. So I'm attempting to clarify some stuff about it. This will be a comprehensive, although somewhat not as in-depth as I woud like, write-up.


General Info:

There is a lot of misconception about where to shift for maximum acceleration. Some people say shift so that you put the motor in max torque, or max power, in the next gear. Some say shift at redline. Some say shift at a hair below the fuel cut-off.

Which one is right? Well, technically they all could be right, but it really depends on the motor and the gearbox setup. Sometimes you shift at redline, sometimes below that, and even sometimes above that!

So if you're serious about driving your car, read on to find out what's really going on.

For this write-up, I'm using a stock Evo as the baseline. When you start modifying your motor or your gearbox, the shift point will change.

Okay, here we go.

 

Step 1: Dyno Run

You'll need a dyno readout of your car. It doesn't really matter which type of dyno you use, so long as you can get an accurate shape of your torque curve. So the dyno can read a little high or a little low, it doesn't matter. What you're more interested in is the shape of the torque curve.

This is my dyno run on the stock Evo motor.

 

Step 2: Analysing the Dyno Readout

So now that you have the dyno results, we need to analyse it. I won't get too in-depth here, just enough to figure out what you need.

It's best to plot your run against RPM as the scale on the bottom. This will make youre life easier. Sometimes they plot it against MPH. You can convert it to RPM, but it will take a little more time and a little math.

They generally plot 2 curves: power and torque. You can ask the dyno operator to plot only the torque curve. That will make life easier.

On my readout, they plot both power and torque. The scale for power is on the left. The scale for torque in on the right. RPM is on the bottom.

The torque curve is the higher curve going left to right. At 5250 RPM, the torque curve dips down and becomes the lower of the two. Pretty easy to figure out.

Here it is outlined in red:

 

Step 4: Extracting Data From Torque Curve

You'll need to figure out how much torque you make at each RPM. This can get a little tedious if you do it for every RPM. For precision's sake, I'm going to do it for every 100 RPM. The stock tachometer is likely not to be much more accurate than this, so as long as you're in the ballpark you'll be good to go.

I have blown up the dyno readout here so it will be easier to see.

 

Hold on. Working on it, ie. kitchen fire.

 

pre dynoflash, i hit 263 lbs of torque peaked at 4k RPMS....post dynoflash, i hit 279 lbs of torque peaked at 4.3k RPM, so thats when i **** for daily drive

 

Bear with me, folks. A lot of numbers to chug through

 

Very nice and helpful. Too many people I have talked to think that you shift at the redline, then when I say that's probably wrong, they're like well what is it? My only logical response is to ask where their peak torque and hp is on a dyno, then they look at me like wtf?

Anyway, this is useful to me, it comes at a time that I am almost at the adhesion limits of my car at Buttonwillow Raceway, so the next step in getting a second or 2 off the lap times will be to work on shift points and, entry/exit speeds. Thanks!

 

On our car, wouldn't redline be best? The dyno showed that I was still gaining at redline.

 

remember at redline, you have very low torque... theres always a saying.. hp wins dyno contest but torque wins races on a track....

 

Yes, but he's referring to my dyno after the reflash, and my torque drops no less than 10 ft/lb between 3500 and 5800 rpm. But technically, my redline is now 6900 and that would be too high to shift. The torque really starts to drop off around 6000 and the hp is dropping by 6300

 

Ah. *smacks forehead*

 

??? I was defending your statement. In a way, you're both right. Although it all depends. Car's with huge exhaust and no intakes have their torque drop off way early yet the hp usually doesn't even reach its max by redline... main reason for upgrading intake parts before exhaust. And my car just has a good fuel map that lets the torque stay strong for a lot longer. I have the luxury of having a dyno curve that will allow me to shift within a wide range or RPMs and not affect acceleration much. That is useful in road racing, when you can't always shift at max torque or whatever you determine is the optimal point. But I'm still new at this, I might change my conclusion.

 

This might be rather simplistic, but it prolly works as well as most methods. I'd set my shift light (or the CEL with the AEM EMS) to blink at the rpm point where the torque and hp curves intersect. At any rate, I'd not shift anywhere after the hp curve peaks.

 

Definitely agreed. That would be way too late.