Volumetric Efficiency and Airflow
Theoretical and actual induction CFM and volumetric efficiency from displacement, RPM, and cycle.
Example
You enter
- Displacement (ci) 350
- RPM 5500
- Cycle four
You get
- Theoretical CFM 557
Checked against published worked examples from: Classical four-stroke airflow derivation + SAE.
Details, formula, and sources
ScopeWith VE above 100% allowed for forced induction.
Formula or table4-stroke theoretical CFM = displacement(ci) * RPM / 3456 (3456 = 1728 * 2 revs per intake cycle); 2-stroke uses /1728. VE% = actual / theoretical * 100.
Source and editionClassical four-stroke airflow derivation; SAE engine-test conventions, by name.
Free accessThe 3456/1728 constants are pure unit derivations, public.
What governsEstimate. AHJ and licensed professional govern.
API field namesdisplacement_ci, rpm, cycle, theoretical_cfm
- Cycle constant 4-stroke fires every 2 revolutions (3456 = 1728 in3/ft3 * 2)engine-builder reference