Can someone out there explain to me the real calculations on how to get real numbers on horsepower at the motor (crank) based on rear wheel horsepower. For example, my Shelby GT500 is at 702 rwhp (730 torque if it matters) and I hear numbers from 810 to 825 for hp at the crank, what is the real number ? Seems you ask 10 people and you get 10 different answers. I was just using my car for an example, but if you were at 500 at the wheels or 576 at the wheels or whatever it might be, how is it calculated ?