Rated displacement is measured at standard conditions, but real output changes with operating conditions and machine condition.
Rotor Speed
Displacement scales with air end speed. Belt slip or a slow motor reduces actual output below rating.
Intake Conditions
Hot, high-altitude or restricted intake air is less dense, lowering free air delivery.
Pressure Ratio
Higher discharge pressure reduces volumetric efficiency and delivered airflow.
Wear and Clearances
Internal wear opens clearances and lets air leak back, cutting output over time.
Summary
Keep intake clean and cool, hold pressure at the minimum needed, and service the air end to stay near rated output.