How does RPM affect horsepower?

[richd]

Horsepower is the rate that the torque is being applied. Think of it this way:

Each cylinder produces a certain amount of force during the power stroke, let's call it X. For simplicity we'll assume that force is equal for any rpm. In an 8 cylinder engine there are 4 power strokes per revolution.

So at 1000 rpm the force being applied to the crank = X * 4 * 1000 = X * 4000 units of force per minute.

Move up to 5000 rpm and we see that the rate force is being applied to the crank = X * 4 * 5000 = X * 20000 units of force per minute.

The actual equation to relate torque to horsepower at a given rpm is

hp = torque * RPM / 5252


Not a very technical explanation, but I hope it helps.

Rich D.