Catalytic Converter: Description and Operation

Fig. 186 Three-Way Catalyst System:

The catalytic converter consists of an aluminum carrier coated with a catalyst (active material) such as platinum or palladium which is enclosed in a heat resistant steel shell. The catalyst material uses residual oxygen in the exhaust gasses to convert HC, CO and in some cases NOx, into less harmful substances. The three way catalyst (TWC) reduces oxides of nitrogen (NOx) as well as HC and CO, producing nitrogen, water and carbon dioxide.