# Volumetric Efficiency

on . Posted in Fluid Dynamics

Volumetric efficiency, abbreviated as $$\eta_v$$ (Greek symbol eta), a dimensionless number, is the calculation for an internal combustion engine.  This is the calculation for the volumetric efficiency for an internal combustion engine.  For a thermal engine, the combustion process depends on the air-fuel ratio inside the cylinder.  The more air inside the combustion chamber, the more fuel that can be burned and the higher the output engine torque and power.

## Volumetric Efficiency Formula

$$\large{ \eta_v = \frac{3456 \; CFM}{CID \; RPM} }$$
Symbol English Metric
$$\large{ \eta_v }$$  (Greek symbol eta) = volumetric efficiency $$\large{dimensionless}$$
$$\large{ CFM }$$ = air flow in cubic feet per minute $$\large{\frac{ft^3}{min}}$$ $$\large{\frac{m^3}{min}}$$
$$\large{ CID }$$ = cubic inch displacement $$\large{in^3}$$ $$\large{mm^3}$$
$$\large{ RPM }$$ = pump revolution per minute $$\large{\frac{r}{min}}$$ $$\large{\frac{r}{min}}$$

## Motor Volumetric Efficiency Formula

$$\large{ \eta_v = \frac{ s \; 100 }{ TS } }$$
Symbol English Metric
$$\large{ \eta_v }$$  (Greek symbol eta) = volumetric efficiency $$\large{dimensionless}$$
$$\large{ s }$$ = speed $$\large{\frac{ft}{sec}}$$   $$\large{\frac{m}{s}}$$
$$\large{ TS }$$ = theoretical speed $$\large{\frac{ft}{sec}}$$   $$\large{\frac{m}{s}}$$

## Punp Volumetric Efficiency Formula

$$\large{ \eta_v = \frac{ GPM \; 100 }{ TF } }$$
Symbol English Metric
$$\large{ \eta_v }$$  (Greek symbol eta) = volumetric efficiency $$\large{dimensionless}$$
$$\large{ GPM }$$ = flow in gallon per minute $$\large{\frac{gal}{min}}$$ $$\large{\frac{l}{min}}$$
$$\large{ TF }$$ = theoretical flow $$\large{\frac{ft}{sec}}$$   $$\large{\frac{m}{s}}$$