One horsepower is 550 foot pounds per second.
You can double the horsepower by either spinning the engine twice as fast at the same torque output, or you can double the torque at the same speed.
Indy cars zinging along 10,000 rpm make very little torque, but it's made a high speed so it can be multiplied in the gear box. There is no substistute for cubic inches. Correct, but a 1 liter engine spinning at 10,000 rpm is pumping just as much air, theoretically, as a 2 liter engine at 5,000 rpm. The problem is getting a wide, usable, powerband with the smaller engines.
In the 1960's Honda made some very impressive racing motorcycles, spinning them upwards of 20,000 rpm or more. The power band got so narrow they had to have a crap load of gears, as the powerband, aka, usable rpm range where torque was made, got very narrow.
Most of the time when I see someone refering to torque, what they are actually refering to is power available over a wide range of rpm.
Horsepower is nothing but a number derived from torque times RPM.
Dale
