Calculate HP For Speed

Back HomeWallace Racing     Back to Calculators ProgramsBACK to Calculators        





For all you Bonneville Salt Flat people or wannabes
This equation will show you how much Horsepower it
would take to run those high speeds.           


This is just an approximation.
Uses Cd (coefficient of Drag) and Square Foot Area of your vehicle to calc
how much HP would be needed to run a certain speed.
This is just the HP necessary to sustain that speed, not what your engine total HP is.
I.E. It takes almost 197 HP to be able to run to 150 MPH.
So, if your car only makes 180 HP, you won't be able to get to 150 MPH.



Air Drag Coefficients and Frontal Area Calculation

Coefficient of Drag

The aerodynamic "features" of a vehicle in motion are reflected in its drag coeficient values. Low coefficients indicate low air resistance. The following chart list some ranges for various vehicles, which will suffice when actual measured values are not available: 

     Vehicle             Drag Coefficient
     Description       Low     Medium   High
     ----------------------------------------
     Experimental      0.17    0.21     0.23
     Sports            0.27    0.31     0.38
     Performance       0.32    0.34     0.38
     60's Muscle       0.38    0.44     0.50
     Sedan             0.34    0.39     0.50
     Motorcycle        0.50    0.90     1.00
     Truck             0.60    0.90     1.00
     Tractor-Trailer   0.60    0.77     1.20

Calculation of Frontal Area

Frontal area represents the front projection area of the vehicle. If one takes a picture of a vehicle, it is the area included in the outline. Use the following to calculate:

1. Calculate the area of a rectangle which would encompass the front of the vehicle (multiply width by the height). For motorcycles, use the handlebar width (to a maximum width of 30 inches) and a height consisting of seat height plus an estimated "seat to helmet" height.

2. Adjust the figure obtained above for areas not included, such as top rounded corners, etc. Typical adjusting values are 85 percent for cars, 70 percent for motorcycles, and 100 percent for trucks.



Calculate HP For A Given Speed
Coefficient of Drag
Frontal Area of Car   Sq/Ft
Weight of Car   Lbs  
Velocity of Car   MPH