How to Calculate Horsepower by ET
It can be an expensive endeavor to measure your car's horsepower after every modification. But why spend money on expensive dynanometer runs? Since the ultimate goal is to increase the performance of the car, and the performance is directly related to the car's horsepower, you can calculate it straight from the performance figures. All you need need is the vehicle weight and quarter-mile time (ET) to calculate an estimate of the horsepower of your car.
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Instructions
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Measure the time it takes for your car to travel a quarter of a mile, starting from a stand-still. You should try to achieve your fastest time with the car's quickest acceleration. You should perform the test several times and select the best ET, measured in seconds.
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Measure the weight of your car, in pounds, as it was when performing the quarter-mile tests, which means the driver should be included in the measurement. If you do not have access to a vehicle weight scale, you can reference the vehicle weight from the manufacturer's specifications and add your own weight. The specifications should be in the manual or printed on a sticker on the inside door panel.
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Use the formula:
Horsepower = Weight / (ET / 5.825)^3
(The notation "^3" means to cube the figure in the preceding parenthesis.)
As an example, suppose you had a 3,800 pound vehicle that ran a quarter-mile in 11.5 seconds:
Horsepower = 3800 / (11.5 / 5.825)^3
Horsepower = 3800 / (1.97)^3
Horsepower = 3800 / 7.65
Horsepower = 497 hp
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References
- Photo Credit Out of Rubber image by JDsheely from Fotolia.com
