[aerohead]

If you want to work with dinosaur units as I do,for the drag force calculation you can use: 0.00237 slugs,for "rho" ( air density ), S becomes A (frontal area ),measured in square feet,V is your velocity,measured in feet-per-second [( MPH multiplied by 5,280 ( feet per mile ) divided by 3,600 ( seconds per hour )].------------------ Once you obtain F,your drag force ( pounds resistance ),if you want to know the horsepower necessary to overcome that force at that speed,take F,and multiply it by ( V divided by 550 ( foot-pounds-per-second ).That's the amount of power that must be delivered to the drive wheel(s) to overcome aerodynamic drag at that speed.------------------Engine power will be higher do to driveline losses.I'll get to metric one day,just not there yet.Sorry!