Enter the engine efficiency (VE), the CID, RPM, and speed into the calculator to determine the engine air intake diameter.

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## Engine Intake Diameter Formula

The following equation is used to calculate the Engine Intake Diameter.

D1 = SQRT ( VE * CID * RPM * 144 * 4 / (S * 88 * 3456*pi))

- Where D1 is the engine intake diameter
- VE is the engine efficiency
- CID is the engine size
- RPM is the rotations per minute
- S is the speed (miles/hr)

## What is an Engine Intake Diameter?

Definition:

The engine intake diameter, also known as the inlet diameter or bore is the diameter of a cylinder at the point where the piston travels through the cylinder head into the combustion chamber.