OK, so we do this mathematically right?

HP: 240 @ 8,300 rpm
Torque: 153 @ 7,500 rpm
Final Drive Ratio: 4.1:1
1st gear: 3.13
2nd gear: 2.05
3rd gear: 1.48
4th gear: 1.16
5th gear: 0.97
6th gear: 0.81

Now, I'm aware that on a car like the S2K, the cd would become a factor at higher speeds, but lets talk

 

I assume you would just shift at redline for going straight =P

 

unless the car has a real strange torque curve and they really messed up on choosing the gear ratios, always shift at redline.

you are usually putting more torque down to the ground in the lower gears than the higher gears

 

So it's that simple, just shift the thing at redline? Hmmm, weird. So, the redline on my Conquest TSi is 6,000, but peak HP is at 5,000, and peak torque is at 3,700, the thing totally sounds like it's running out of breath at 6K. Why wouldn't I shift at the HP peak?

 

I don't shift my s2k at redline, I shift at about 8600.

Not all cars should be shifted at redline for most power, the 3SGTE MR2 is the same way.

 

Every time you shift into the next gear you lose torque multiplication due to the lower overall gear ratio. Thus, as was said above, unless you have a very odd torque curve that falls off very sharply, you should shift as late as possible which would be at red line. On almost any car and certainly on the S2000, you will be slower if you shift before redline.

JeffA

 

Trust that Honda did the math for you and that they seem to be very good with their ratios. I could keep my 00 Civic Si in VTEC all day by taking it to redline. Shift early and I would be out of VTEC, I believe the S2000 is set up the exact same way, so winding it out and staying in VTEC would make the most sense to me. IMHO

 

in something like a 5.0 Mustang, you shift before redline as they lose torque fast. An S2K should be shifted at redline as it makes torque up high.

What you want to do is have the highest CUMULATIVE horsepower. What you want to do is have a dyno plot and figure the shift points that will send the highest AVERAGE HP to the ground. The best thing to do is shift AFTER the peak HP so you land just below it in the next gear. Ideally, the power peak should be in the middle, so you take advantage of the high HP areas both before and after the peak.

If you shift at the peak, that means that you land in a LOWER HP point than if you did it the way above. Average HP would be less as you go through the gears.

You can't calculate it based on peak HP and gear ratios. The SHAPE of the power curve is the important consideration. When you know the shape of the curve, then you can apply gear ratios and then do reverse integrals to figure the area under the power curve (you want to maximize it).

 

OK, that sounds reasonable, but doesn't the relationship between HP and torque figure in there somewhere? I mean, the curves are different, they don't follow each other, so do you just abandon the torque figure?

I'm not actually talking about one specific car here, I'm just wondering if there is a system or formula that one can use to get the most out of any car.

 

In a general hand-wavy formula:

power = torque * RPM * (the adjusting constant for measuring units)

steven975's method is one correct way (and totally mathematically correct) of figuring it out. What's nice about using HP is that it is "transmission independent". So, it is easier to figure out without doing a lot of car specific calculations.

What's important is the WHEEL torque over all the speeds of the drag race. But to do this properly you have to have the torque curve, and all the transmission ratios to calculate the wheel torque. You then can overlay all the wheel torque curves of each gear ratio on a wheel torque vs. car speed graph. It will then become obvious where there is more wheel torque and where the shift points is.

OR you can just look at the power curve. If the next gear puts puts you on a higher part of the power curve, then shift. This works unless there is a really oddball power curve.