What is the term for usable power at the flywheel of an engine?

The term for usable power at the flywheel of an engine is referred to as brake power. This is the amount of power delivered by the engine at the output shaft, reflecting the engine's performance in producing usable work. Brake power is measured after accounting for losses due to friction and other factors within the engine, making it a true representation of the engine's capability to perform work.

This term is crucial in assessing engine efficiency and comparing the performance of different engines. It is derived from the power measured at the engine’s output under load conditions, typically using a dynamometer.

In contrast, the other terms listed serve different purposes in the context of engine performance. Brake-specific fuel consumption (BSFC) measures the fuel efficiency of an engine, indicated power refers to the total power produced in the combustion chamber before losses, and torque measures the rotational force produced by the engine but does not directly reflect usable power output.