Brake mean effective pressure (BMEP)

Brake mean effective pressure is the constant pressure that, acting on the piston through one power stroke, would produce the measured brake power: $BMEP = P_b / (V_d \cdot n \cdot k)$, with swept volume $V_d$, speed $n$, and a cycle factor $k$ (1 for two-stroke, 1/2 for four-stroke per revolution). In bar, it is a load and rating yardstick independent of engine size; modern turbocharged two-strokes run around 20 bar and high-output four-strokes above 25 bar.