Turbo Airflow Calculator

When to use it

• Compare how a change in displacement affects compressor inlet flow before committing to parts, setup, or strategy changes.
• Check a workshop, dyno, simulator, or trackside spreadsheet result using a transparent formula: Four-stroke NA airflow × pressure ratio.
• Use the result to compare possible hardware and operating targets, then validate the setup with compressor maps, charge-temperature data, exhaust backpressure, fuel capacity, knock margin, and dyno testing.

How to use it

1. Enter displacement in L; the default value shown is 2 L.
2. Enter engine speed in rpm; the default value shown is 7,000 rpm.
3. Enter volumetric efficiency in %; the default value shown is 95 %.
4. Enter pressure ratio as a plain number; the default value shown is 2.36.

How to read the result

Compressor inlet flow is shown in CFM. Use the number as a calculated reference point, then compare it with measured data from the car, the part supplier, or the race environment. A mathematically clean answer can still be unsuitable if the inputs are estimated, rounded, measured under different conditions, or outside the normal range for the vehicle.

Assumptions and checks

• The calculator applies the displayed formula directly and assumes the entered displacement, engine speed, volumetric efficiency, and pressure ratio are valid for the vehicle and conditions being considered.
• Changing displacement and engine speed together can move the answer in ways that are easy to miss, so make related setup changes deliberately.
• Check whether each pressure input is gauge pressure or absolute pressure.
• Leave margin for heat, altitude, turbine restriction, pressure drop, and real compressor efficiency.
• Do not size boost hardware from a single formula without checking maps and temperature behaviour.