As engine demands and loads change, the fuel must maintain a proper air-fuel ratio. It is the proportion of air and fuel, by weight supplied by the engines cylinders for combustion. Fifteen pounds of air to one pound of fuel is an example of the ratio of air to fuel by weight. This is written as 15:1.
The ideal air-fuel ratio is the stoichiometric ratio of 14:7:1. The stoichiometric ratio provides the most efficient combustion, giving the chemically correct mixture of air and fuel.
Automotive fuel is a mixture of many different hydrocarbons. When the hydrocarbons burn in the combustion chamber of an engine, energy is released. The energy moves the piston to create mechanical energy. To move a hydrocarbon, oxtgen atoms are added in the combustion chamber. A spark then ignites the mixture.
A good-quality gasoline should have: Proper volatility which determines how easily the gasoline vaporizes; The correct octane rating, which minimizes detonation; antioxidants which are the chemical compounds which prevent formation of varnish in the fuel systems. Anti-icers added seasonally that minimizes icing in the throttle body or fuel line. Detergents which keep the fuel injectors clean and deposit control agents which prevent or removefuel system deposits.
In a 100 % efficient gasoline engine, all hydrocarbons would burn. Only CO2. H2O and nitrogen would be left to come out of the chamber. Automotive engines are not 100 % efficient. Unburned fuels such as Carbon monoxide and nitrogen oxides are also produced.
Increasing the amount of oxygen in the combustion chamber will burn more of the fuel. Less CO and unburned fuel will go out of the tailpipe. More energy will be released.