What does it mean when engine power is calculated instead of tested?

When engine power is calculated, it typically refers to the measurement known as indicated power. This measurement derives from the thermodynamic conditions within the engine's cylinders, based on factors such as cylinder pressure and engine displacement. It quantifies the total power developed by combustion in the engine, before losses such as friction and mechanical inefficiencies occur.

Indicated power takes into account the work done during the combustion cycle without the influence of the actual mechanics that would reduce this power to what is available at the crankshaft. This contrasts with brake power, which is the actual usable power that can be measured at the engine's output (after accounting for losses), and mean effective pressure, which is a theoretical concept used to compare engine performance under different operating conditions.

Understanding that indicated power is a calculated value helps clarify its role in engine performance assessment, focusing on internal engine efficiencies rather than real-world output. By utilizing this calculation, technicians can analyze engine performance and efficiency, identify potential improvements, and make adjustments before conducting physical tests, which might reveal different results due to external factors.