Air fuel ratio in automobile engines

The air-fuel ratio is the ratio of weight of air to that of gasoline mixed by the carburettor for ideal combustion by the engine. This ratio of paramount importance because there are limits to how rich (with more fuel) or how lean (with less fuel) it may become, and still stay fully combustible for an efficient firing and better engine performance.

The engine can operate with an air fuel ratio that ranges from 8:1 to 18.5:1 i.e. from 8 kg of air/kg of fuel to 18.5 kg of air/kg of fuel.

Stoichiometric Air-Fuel Ratio

It is the ideal ratio at which all of the fuels blend with all available oxygen in the air and be completely burned. An air fuel ratio of about 14.7:1 i.e. 14.7 kg of air/kg of gasoline produce this ratio, but the exact ratio can vary somewhat.