It is when the "correct" air to fuel ratio is used to completely burn the fuel in question in an internal combustion engine.
If exactly the correct amount of air is used this is called the stoichiometric mix.
The ratio is about 15:1 fuel to air.
The air fuel ratio of the petrol engine is controlled by Carburetor
Air/Fuel Ratio
Air to fuel ratio is the ratio between the weight of air to the weight of fuel, for example: 14.7 pounds of air to 1 pound of fuel would be a air:fuel ratio of 14.7:1 This particular example is called the stoichiometric ratio for gasoline...it's ideal ratio in order to efficiently use all the fuel. This ratio varies for different fuels....for example, ethanol fuels have a stoichiometric air:fuel ratio of 13.85:1. In actuality, a gasoline car gets it's best fuel mileage when the fuel is reduced slightly and produces it's best power when the ratio is a little heavier on the fuel side.
A FUEL SYSTEM stores, and supplies fuel to the cylinder chamber where it can be mixed with air (air & fuel ratio) to transmit power
the ratio of the amount (mass) of air to fuel. Ideal is 14.7 lbs of air to 1 lb of fuel to completely burn air the fuel. A slightly rich raitio of about 12.5:1 car produce more power at the expense of emissions.
25.0
Control of the ratio gas fuel/air in the burner.
Ideally it is 14.7 air to 1 fuel in an internal combustion engine.
Air is used in combination with gasoline at a ratio of 14.7 (air) to 1 (fuel) for an ideal combustion mix.
Mixes fuel and air at the desired ratio for burning.
11:3