How is horsepower actually measured for both wheel horsepower and brake horsepower? And are there limits to the technology that measures them?

Question

How is horsepower actually measured for both wheel horsepower and brake horsepower? And are there limits to the technology that measures them?

In: Engineering

Answer 1

Torque, the twisting force the engine can make, is measured, either by hooking the engine itself up to a measurement device (brake), or running the car on rollers (wheel). Wheel will always be less because there is loss through the drive train between the engine and the wheels.

Horsepower is calculated from torque and rpm: Horsepower = Torque x RPM / 5252.