This calculates the cubic feet per minute (cfm) of air that an engine will consume at its maximum rpm. This is a great tool for estimating carburetor or throttle body sizing to avoid going either too small or too big (which is a common mistake).

variabledescription
cubic inchesthe total displacement of the engine in cubic inches (see our cid calculator)
max rpmthe engines maximum rpm limit
volumetric efficiencythe volumetric efficiency is a measure of the efficiency of the engine moving the intake charge into the chamber and the exhaust out. Typical values are as follows:

2 valve head – 80%

4 valve head – 88%

it is not unusual however to have VE’s of 95% or more in correctly built race engines
cubic feet per minutethe total cubic feet per minute of air that the engine will consume
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