Formulas

Formulas

Approximate 1/4 mile equations:

Trap Speed: TS = 235([hp/weight]^[1/3])

Trap Speed, TS, equals 235 times the quantity: horsepower, hp, divided by weight of your vehicle, quantity: raised to the 1/3 power (cubed root).

1/4 mile time: ET = 5.5([weight/hp])^[1/3])

1/4 mile elapsed time, ET, is equal to 5.5 times the quantity: weight of your vehicle divided by horsepower, hp, quantity raised to the 1/3 power (cubed root). Please note, in my Data Tables section I use this equation for a dada table but I used 6.357 instead of the 5.5 as the weighted constant because I felt it reflects a more conservative scale for weight loss and 1/4 mile times.

Horsepower from time: hp = 200weight/(ET^3)

Horsepower, hp, is equal to 200 times weight of your vehicle divided by your 1/4 mile elapsed time, ET, to the third power.

Horsepower from Trap Speed: hp = weight ([TS/234]^3)

Horsepower, hp, is equal to the weight of your vehicle times the quantity: Trap Speed, TS, divided by 234, quantity raised to the third power.

Dynamic equations (equations that do not involve mass):

hp = vam

Horsepower, hp, equals velocity, v, times acceleration, a, times mass, m.

hp = (rpm*torque)/5252

Horsepower, hp, equals engine rpm, times torque divided by 5252 (that's why horsepower and torque always equal at 5252).

Kinematic equations (equations that do not involve mass):

d = vt

d, distance equals a constant velocity, v, times time, t. This equation does not really show us anything neat about our vehicles, but it is the definition of velocity, which gives us our next equation.

d = 0.5at^2

d, distance equals 0.5 times acceleration, a, times time, t, squared. We can adapt this to measure acceleration in Gs. One G is 32.1 fps^2.

d = 16.05at^2

Distance, d, is in feet, a is acceleration in Gs and t is time in seconds. A stock sports car can accelerate off the line at about 0.5 Gs. In 10 seconds that sports car can travel 802.5 feet (d = 16.05*0.5G*10s^2). We can then manipulate this formula to give us acceleration in Gs if we know the amount of time it takes to travel a fixed distance: a = d / (16.05t^2)

s = (rpm*td) / (wr*gr*336.13524)

Your speed in MPH, s, is equal to the quantity: engine rpm times tire diameter, td, in inches, divided by the quantity: wheel ratio (rear end ratio or axle ratio), wr, times the transmission gear ratio, gr, you are in, times 336.1354 (to convert inches to miles and minutes to hours).

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