Three-Way Catalytic Converter

The three-way catalytic converter is used in conjunction with the conventional oxidation catalytic converter. All models use this type of converter on vehicles with the Oxygen Sensor/Feedback Carburetor emission system. American Motors and Chrysler Corp. uses two separate converters while Ford Motor Co. and General Motors use a single converter.

The first converter in the exhaust system (three-way) reduces hydrocarbons (HC) and carbon monoxide (CO), but mainly oxides of nitrogen (NOx). The second converter (oxidation) reduces, with the extra air provided by the air pump, hydrocarbons (HC) and carbon monoxide (CO) only.

Fig 1: Dual Catalytic Converter, Three-Way Catalyst in Front, Oxidation Catalyst in Back (Ford Motor Co. Shown, Other Manufacturers Use Two Separate Converters)

Courtesy of GENERAL MOTORS COMPANY