Engine map showing the operating regions of the ICE. The x-axis is Engine RPMs. The y-axis is absolute load, the percentage of maximum air flow into the engine which is linearly correlated with brake torque. The solid black line estimates the maximum load at a given RPM.
Engine map showing the operating regions of the ICE. The x-axis is Engine RPMs. The y-axis is absolute load, or volumetric efficiency, i.e. the percentage of maximum air flow into the engine.