Mechanical Engineering - Automobile Engineering - Discussion

But maximum it depends up on air fuel mixture but not richer.

The air-fuel ratio is the most common reference term used for mixtures in internal combustion engines. The term is also used to define mixtures used for industrial furnace heated by combustion. The AFR in mass units is employed in fuel oil fired furnaces, while volume (or mole) units are used for natural gas fired furnaces.

AFR = \frac{m_{air}}{m_{fuel}}

It is the ratio between the mass of air and the mass of fuel in the fuel"air mix at any given moment. The mass used is the mass of all constituents that compose the fuel and air whether the constituents are combustible or not. For example, if calculating the mass of natural gas which often contains carbon dioxide (CO2) and nitrogen (N2) as well as various alkanes, the mass of the carbon dioxide and nitrogen are included in addition to all alkanes to determine the value of m_{fuel}.

For pure octane the stoichiometric mixture is approximately 14.7:1, or λ of 1.00 exactly.

In naturally aspirated engines powered by octane, maximum power is frequently reached at AFRs ranging from 12.5 to 13.3:1 or λ of 0.850 to 0.901.

Because less the air fuel ratio more richer will be the mixture.