The Trick to Mastering the Perfect Upshift
If you want to ring the best 0-60 and quarter mile times out of your car, first you've got to find the perfect shift point. Here's how.
Figure out Maximum Wheel Torque
Looking at the example used by Engineering Explained, finding the perfect shift point for a stock 2002 S2000 is pretty simple because your best bet is to shift at the redline in every gear. The explanation is that there is only a torque variance of 18% throughout the power band, and 18% is less of a torque disadvantage than changing gears at any point. With most cars, this is true at least in the first 2-3 gears, as the ratio spread is so large. So if you needed another reason to rev your Honda to the redline, here you go!
Calculate Wheel Torque for Each Gear Ratio
Next, you'll need to look at the gear ratios for each transmission gear and calculate the differences between gear ratios. To confuse things, the S2000 transmission has a primary reduction gear of 1:1.160 in the AP1, and 1:1.208 in the AP2, but that doesn't really change this calculation much. In both cars, the 1st gear ratio is 3.133 and 2nd gear is 2.045, this means in an AP1 you've got 53.2% more wheel torque in first gear than second gear (53.0% in the AP2) at any engine rpm. In layman's terms, this means the torque from the engine has to drop more than 50% in order to maximize acceleration, which, spoiler alert, means that you'll want to run to the redline in first gear before shifting.
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Analyze Dyno Sheet
To figure out the perfect time to shift each gear, you'll want to take a look at your dyno sheet. Ideally, you'll want to dyno your own specific vehicle to get the most accurate numbers, but in this case, we will use the stock S2000 dyno sheet as an example. With the stock 2002 S2000, the torque curve stays relatively flat until VTEC kicks in, yo, and the engine hits max torque, then tapers off as it passes 8,000 rpm. So when should you shift?
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Finding the Perfect Shift
What about the 3rd to 4th shift? Is shifting at 8,800 rpm the best decision? The gear ratio in 3rd is 1.481. To figure out what rpm we'll achieve if we shift to 4th gear, we simply multiply our 4th gear ratio, 1.161, by 8,800 and divide it by 1.481. That leaves us at roughly 6,900 rpm. Next, we want to find the wheel torque in each of these gears. To do that, multiply the gear ratio by the torque the engine is making at that point in the power band, which in this case is 110 lb-ft in 3rd gear at 8,800 rpm. In 4th gear at 6,900 rpm, torque stands at 130 lb-ft. With our example, we'd be making more torque in 3rd gear (163 lb-ft) than 4th (151 lb-ft) because of the gear reduction. Thus, shifting at the redline between 3rd and 4th is again the best choice.
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Putting it all Together
Looking at the example used by Engineering Explained, finding the perfect shift point for a stock 2002 S2000 is pretty simple because your best bet is to shift at the redline in every gear. The explanation is that there is only a torque variance of 18% throughout the power band, and 18% is less of a torque disadvantage than changing gears at any point. With most cars, this is true at least in the first 2-3 gears, as the ratio spread is so large. So if you needed another reason to rev your Honda to the redline, here you go!
>>Join the conversation about getting upshifts just right, right here in the Honda-Tech Forum!
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