Optimal Shift Point Calculator

supraguru05

Offical Expert: Suspension & Vehicle Dynamics
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Dec 16, 2005
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louisville ky
This excel sheet was created by me and my friends to allow for the proper determination of shift points. I will be posting a report of how the calculations are made in the coming days. In order to use the sheet you must input your torque curve. You have 15 cells to use you can use some or all of them and change the RPMs as you see fit. You much also input tire diameter, tranmission ratios and final drive ratio. Simply click the large run button and the shift points will automatically update. Macros will need to be enabled.
 

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mad0314

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Apr 27, 2010
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That is a really neat tool but I think theres a flaw in it. I did some calculations by hand based on the numbers in your sheet when you first open it up. It tells you to do a 1-2 shift at 5490; at 5500 in 1st your car is making 225 at the ENGINE, which would end up at 3308 in 2nd making about 315, also at the engine. If we multiply those numbers by the gear ratio, ignoring diff/wheel size etc. since they are constant across all gears, I got 731.25 in 1st at 5500, 625.6 in 2nd at 3000 and 606.05 at 3500, which is between where it tells you to shift. Youre making more at the engine but less at the wheels.

It tells you to make the 3-4 shift at 4988 RPM, which at 5000 with a 1.31 ratio for 3th we're making 340.6tq, a number that is never reached in 4th at any RPM (max tq is 320 at 3000 since 4th is 1:1). Similarly the 4-5 shift is supposed to be made at 5070 and at 5000 RPM we're making 260 tq, which is never reached in 5th. Max for 5th with .735 ratio is 235.2 at 3000.

Someone double check my math.