Turbo Airflow / HP Calculator
How much compressor airflow (lb/min & CFM) your HP target needs.
Spec your turbo build?
How it works
A turbo makes power by moving air. As a rule of thumb, an engine needs roughly 10 lb/min of airflow for every 100 crank horsepower (efficient setups get closer to 9.5, conservative ones 10.5). This calculator turns your HP target into the airflow a compressor must supply.
Once you have the lb/min figure, open the compressor map of any turbo you’re considering and check that your target airflow lands inside the efficiency islands at the boost (pressure ratio) you plan to run — not off the edge where it chokes or surges.
Airflow is only half the story: the right turbo also matches your displacement and RPM for spool. On a DMS turbo build we size the whole system — turbo, manifold, fuelling and calibration — to hit the number reliably, not just on paper.
These figures are engineering guidelines to help you plan. The reliable number always comes off the dyno — that's how every DMS build is proven.
FAQ
How accurate is 10 lb/min per 100hp?
It’s a solid planning rule for petrol engines. Very efficient combinations reach ~9.5; older or less efficient ones need ~10.5. Use it to shortlist turbos, then confirm against the actual compressor map.
lb/min or CFM — which do compressor maps use?
Most modern compressor maps use lb/min (mass flow), which is what you want since it’s independent of temperature. CFM (volume flow) is shown for reference and varies with air density.
Does this pick my exact turbo?
No — it gives the airflow target. Turbo choice also depends on displacement, target RPM and spool. Send us your build and we’ll match the turbo.