Exhaust Gases

Products of combustion which are discharged from the cylinder after doing work on the piston.

The exhaust from internal combustion engines contains CO2, CO, NOx, SO2 and unburnt hydrocarbons alongwith some soot. All these have bad effects. There is no way to avoid CO2 emissions but the other emissions can be reduced by various methods:

Carbon Dioxide

At stoichiometric Air/Fuel ratio CO2 is at a maximum of 13%. When the Air/Fuel ratio is high then CO2 is lowest at around 4%.

CO2 and CO in the exhaust gas vary opposite to each other.

Carbon Monoxide

At stoichiometric Air/Fuel ratio CO is low and around 2%. When the Air/Fuel ratio is high then CO can be as high as 16%.

In car engine CO is high during deceleration events.


NOx is high during acceleration and during cruising.

See also: Aftertreatment, Exhaust, Exhaust Catalyst, Exhaust Pipe, Exhaust System, Total Hydrocarbons.

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Subjects: Engines