[Tommy]

It's not possible to accurately calculate a car's rate of acceleration from its weight and a single horsepower number for several reasons. For one, the engine does not run only at the RPM at which the horsepower was measured. It may have much less torque and horsepower at RPM's above and below that cited. And as was mentioned earlier, friction and aerodynamic drag can also differ significantly from car to car. The bottom line is that you can't declare winners and losers from looking at a limited set of data. You've got to run them side by side to see who's fastest.