The power output of an engine can be ***bench-measured*** to give a brake horse-power figure which can be related to engine speed. This however may bear little relationship to the power of the engine in actual driving conditions and is in any event not useful for monitoring engine performance under actual driving conditions when performance-related parameters may change, such for example as ambient temperature, fuel mixture, spark-plug timing (in petrol engines) and so on.

Спасибо.