# Air–fuel Ratio

Written by Jerry Ratzlaff on . Posted in Fluid Dynamics

Air–fuel ratio, abbreviated as AFR, is the mass ratio of air to fuel mixture present in an internal combustion engines. Because it is a ratio, it is unitless.

 $$\large{ AFR = \frac {m_a} {m_f} }$$ Where: $$\large{ AFR }$$ = air–fuel ratio $$\large{ m_a }$$ = air mixture $$\large{ m_f }$$ = fuel mixture