Catalytic Converter: Description and Operation

Three-Way Catalytic Converter:

A three-way catalytic converter is used downstream of the exhaust manifold to reduce oxides of nitrogen (NOx) and oxidize hydrocarbons (HC) and carbon monoxide (CO). The converter contains the catalyst elements platinum, rhodium and palladium which promote oxidation and reduction reactions at high temperatures. Emissions are converted into carbon dioxide, water vapor and nitrogen. An oxidizing catalyst, mounted directly in the exhaust manifold, is also used on some models to oxidize excess hydrocarbons that occur in the exhaust when the engine is cold.