Catalytic Converter: Description and Operation

Catalytic Converter / Exhaust System:

PURPOSE
Three-way catalytic converters reduce emissions of CO (carbon monoxide), HC (hydrocarbons), and NOx (oxides of nitrogen). For efficient operation, the front converter is close to the exhaust manifold so it will heat up quickly. The front converter also protects the main converter from damage by acting as a phosphorus and lead filter.

LOCATION
Front converter is near exhaust manifold; rear converter is beneath vehicle.

OPERATION

Catalytic Converter System Operation:

Catalytic converters reduce CO and HC emissions through oxidation, and NOx emissions by chemical reaction. The RX-7 converter system operates in conjunction with the secondary air injection system:
^ At cold start, when CO and HC emissions are high, the main converter is supplied with port air and uses both front and main converters as the oxidation catalyst.
^ In normal driving, the main converter is supplied split air. The front converter is the ternary [1] catalyst and the main converter is the oxidation catalyst.
^ During high speed driving, additional air to the main converter is cut off. Both converters are used as the ternary catalysts.

[1] Three-way.