Refers to a condition in an
internal combustion engine when the ratio of
fuel to
air in the intake charge is too high. A very rich mixture will usually not
combust very well and over time can lead to fouled
spark plugs (coated with
soot) and
engine head and
piston crown carbonization. Excessive carbon buildup in the combustion chamber can lead to excessive
detonation (knock).
One must pay close attention to the air/fuel stoichiometry in tuning modern engines for performance, as a rich condition can easily turn into a lean condition, and vice versa.