three-way catalyst - catalyst used in a catalytic converter for purifying car exhaust emissions. The catalyst is only active at temperatures above 300°C, which is some time after start up, and is poisoned and deactivated by lead compounds.
Specific conditions concerning exhaust emissions.
2.1. Motor vehicles equipped with positive-ignition (petrol) engines
(a) Where the exhaust emissions are not controlled by an advanced emission control system such as a three-way catalytic converter which is lambda-probe controlled ...
Most cars currently sold in Canada are equipped with oxidation or two-way catalytic converters that reduce the amount of HC and CO emissions only. A catalytic converter which can do the job of burning off hydrocarbons and carbon monoxide while reducing nitrogen oxide is called a three-way catalyst.
The dual-bed or three-way catalyst, consisting of two chambers, reduces hydrocarbons (HC), carbon monoxide (CO) and nitrogen oxides (NOx) by converting them to water vapor (H2O), carbon dioxide (CO2) and nitrogen (N2).
