An internal combustion engine uses the energy
released by a chemical reaction (the burning of
gasoline and oxygen) to create rotation. To make
the most rotation i.e., torque and horsepower, all
of the fuel must be consumed. A full burn occurs
when there is a ratio of 14.7 parts air to 1 part
fuel in the mix (for 87 octane gasoline). A visual
of this ratio appears to the right.
I use the term air-because its most common in
the industry; air in this case implies oxygen. Air
(at sea level) includes only 21% oxygen, but the
ratio is the same.
Much of the modern automotive computers job is
to maintain this 14.7-1 ratio. Computers use
sensors to measure the air into the engine and
out in the exhaust gases. Specifically, the Mass
Air Flow Sensor measures the incoming air and
the Oxygen Sensor measures oxygen content in
the exhaust gases.
Air to fuel mix ratio