Air–fuel ratio

The air-fuel ratio (AFR) is a measure of the amount of air in relation to the amount of fuel in an internal combustion engine's combustion chamber. It is a critical parameter in engine performance, efficiency, and emissions. In general terms, the air-fuel ratio is expressed as a ratio of the mass of air to the mass of fuel. For example, an AFR of 14.7:1 means that there are 14.