Q: How Does a Catalytic Converter Work?

A catalytic converter is a device used to reduce the emissions of an automotive engine. Not enough oxygen is available to oxidize the carbon fuel in these engines completely into carbon dioxide and water; thus toxic by-products are produced. Catalytic converters are used in exhaust systems to provide a site for the chemical reaction of oxidation and the reduction of toxic by-products.

A catalytic converter uses basic chemical reactions to reduce the pollutants a car makes. It converts around 98% of the harmful fumes produced by a car engine into less harmful gases. It is composed of a metal housing with a ceramic honeycomb-like interior with insulating layers. This honeycomb interior has thin wall channels that are coated with a layer of aluminum oxide. This coating is porous and increases the surface area, allowing more reactions to take place and containing precious metals such as platinum, rhodium, and palladium. The construction requiring these precious metals is the cause of the consistent reports of recent catalytic converter thefts.

The fuel-injection system introduces the sensors needed to maintain the control of the exhaust environment within the converter required for a proper chemical reaction. This control system comprises oxygen sensors that monitor how much oxygen is in the exhaust stream, and in turn tells the engine computer to adjust the air-to-fuel ratio, keeping the catalytic converter running at the stoichiometric point (14:1 air-to-fuel) required and near 100% efficiency.