Catalytic Converter: Description and Operation

Fig. 7 Three Way Catalytic Converter:

PURPOSE AND OPERATION
Catalytic converters which form part of the engine emission control system, are designed to clean the exhaust gases, by closely controlling the fuel air ratio delivered to the engine and converting the residual exhaust compounds into products more acceptable to the environment.


The front section of the exhaust system to each cylinder bank contain the ceramic elements of the catalytic converters. The heated oxygen sensors which transmit information to the electronic control unit ECU for control of the mixture, are located in the exhaust down pipes.


The Hydrocarbons (HC), Nitrogen oxides (NOx) and Carbon monoxide (CO) emitted by the engine react with the catalytic element and exhaust temperature to convert the toxic gas, into Nitrogen (N), Carbon dioxide (CO2) and water vapor.

Should the engine be supplied with a rich mixture causing high CO in the exhaust gas, the ceramic element will become coated and the useful life of the catalyst reduced. If the mixture is too weak, excess oxygen in the exhaust gas will cause the catalysts to burn out.