What is meant by the stoichiometric ratio in relation to gasoline engines?

M

mathiusdragoon

New member
As far as I know, gasoline consists of a blend of several different hydrocarbons which are extracted from raw petroleum. In chemistry the stoichiometric ratio would refer to the the number of mols of each reactant required to make the reaction a balanced equation (or else it would violate the law of conservation of matter) That being said different hydrocarbons would have different stochiometric ratios with the atmospheric oxygen when they combust. So my question is this: How can their be a single value which is considered 'stoichiometric' for gasoline?
 
L

LeAnne

Member
You're splitting hairs. The equations to balance the most often used 14.7:1 ratio simply satisfy the chemical equation.

In modern vehicles, the air/fuel ratio is electronically controlled by feedback from the amount of oxygen in the exhaust gasses. The exhaust gas oxygen sensor is also called the lambda sensor, since it can be used to maintain the air-fuel ratio at lambda equal to 1, within very close limits.

This amount is obviously varied somewhat by different atmospheric conditions, variations in fuel and so fourth - but that doesn't change the fact that this input is in direct relation to the combustion in the cylinders regardless of varying other factors.
 
Top