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Exhaust Gas Treatment


The exhaust gas treatment is supposed to regulate the air-fuel mixture in the Otto-cycle engine in such a way that the catalyst is able to convert a maximum of pollutants into harmless exhaust gases. Harmless exhaust gases are CO2 (carbon dioxide) and H2O (water), where water leaves the exhaust system as 'white smoke' with less than 70°C.

For humans ...
... harmlessNitrogen (N)
Carbon dioxide (CO2)
... absolutely deadlyCarbon monoxide(CO)
... respiratory irritationNitrogen oxides (NOX
Hydrocarbons (CH)


While the engine is running, the lambda probe delivers signals to the control unit regarding the air-fuel mixture.For most ranges it uses the data to regulate the ideal mixture of 14.8 kg air with 1 kg fuel (lambda = 1).In this case the ratio of pollutants (CO,CH and NOX) is such that with simultaneous oxidation and reduction they can be offset against each other. NOX carries too much oxygen, which is compensated by the need for oxygen of CO and CH. Just in the ranges of cold starting, accelerating, and (for most cars) full load, relatively more fuel is used for the mixture. 08/11

Carbon dioxide (CO2) causes the greenhouse effect.