Aerodynamic and Rolling Horsepower Calculations By Bowling

This web page calculates the aerodynamic horsepower loss in propelling a vehicle with given coefficient of drag (cd), frontal area (farea), and speed. Also calculated is the horsepower loss due to rolling friction from a given vehicle weight and speed. Click here for a chart of coefficients. As an added bonus, a calculation for the vehicle front-end lift force is performed, derived from the coefficient of lift input.

Program Inputs:

Coefficient of drag:

Frontal Area (Square Feet):

Test Temperature in Degrees F:

Test Barometric Pressure in Inches Hg:

Vehicle Miles Per Hour (MPH):

Vehicle Weight in Lbs:

Tire Inflation Pressure in psi:

Vehicle Coefficient of Frontal Lift:

Press this button to submit a computation: .

To reset the form input: .

Algorithm:

The following equations were used: 
AirDensity=0.0228645 * baro/(0.5555* (temp - 32) + 273.15)

AeroDragFactor = 1.07556 * AirDensity * cd * farea

RollingDragFactor = (C1 + C2 * mph2.5)

C1 = 0.034667 * (tpress - 35.000000)*(tpress - 45.000000) + 
    -0.063333 * (tpress - 20.000000)*(tpress - 45.000000) + 
    0.032000 * (tpress - 20.000000)*(tpress - 35.000000);

C2 = 7.704e-07 * (tpress - 35.000000)*(tpress - 45.000000) + 
    -8.33333e-07 * (tpress - 20.000000)*(tpress - 45.000000) + 
    3.148e-07 * (tpress - 20.000000)*(tpress - 35.000000);

AeroHP = (AeroDragFactor * mph3)/375.0

RollHP = RollingDragFactor * (weight/1000.) * (mph/375.0)

Lift = 0.00256 * farea * clift * mph2
Bruce Bowling
bbowling@earthlink.net
Bowling Superior