A couple of weeks ago Ted Schumacher posted a note to the FOT list with a
formula for estimating horsepower based on quarter-mile speeds.
Since I couldn't seem to get the right results from the formula, Ted has
clarified it an asked me to post the revised version to the list:
To estimate your car's horsepower (accurate within 5%) based on a
quarter-mile dragstrip time, use the following formula -
HP = ((MPH/234)^3)*(CarWeight)
Where:
HP is horsepower at the rear wheels
MPH is the car's speed at the end of the quarter mile
"^3" means that you cube the results of dividing MPH by 234
As an example, if your car weighs 2000 pounds and turns the quarter at
100mph, the calculation would be:
> HP = (100/234)^3 * (2000)
> HP = (0.42735)^3 * 2000
> HP = ((0.42735) * (0.42735) * (0.42735)) * 2000
> HP = 0.0780 * 2000
> HP = 156
(Use your favorite formula for converting rear-wheel horsepower to hp at the
flywheel.)
Of course if you're only interested in knowing whether a particular
modification has affected horsepower, you can also use the "Max Balchowski"
method - From a standing start on Mulholland Drive . . . well, you know the
rest.
Jim Hill
Madison WI
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