Enter the volumetric efficiency for your engine as a percentage. If you do not know your engine efficiency, you can calculate it using the Efficiency calculation, or you can estimate using this guide:
Older passenger car - 80-90%
Modern passenger car - 90-95%
Racing car - 95-105%
Efficiency is considered at atmospheric pressure. Do not compensate for turbocharging or supercharging using both the efficiency and boost inputs.