Catalytic Converter: Description and Operation

A three-way catalytic converter is used downstream of the exhaust manifold to reduce Oxides of Nitrogen (NOx) and to oxidize Hydrocarbons (HC), and carbon monoxide (CO). The converter contains the elements Platinum, Rhodium, and Palladium, which, at high temperatures, act as catalysts to promote the oxidation and reduction reactions. Pollutants are converted into Carbon Dioxide (CO2), water vapor, and free Nitrogen. An oxidizing catalyst, mounted directly in the exhaust manifold, is also used on some models, to oxidize the excessive Hydrocarbons that occur in the exhaust when the engine is cold.