Catalytic Converter: Description and Operation

The catalytic converter is designed convert harmful pollutants in the exhaust gasses into inert gasses and water. The flow of hot exhaust gases activates the catalyst, causing it to promote oxidation of the unburned pollutants. In addition, on some models fresh air is directed into the converter under certain conditions to continue combustion of the exhaust gasses in order to maintain the proper temperature for efficient conversion.
A three-way catalytic converter is used on all models with feedback carburetor controls and fuel injection, including Accord, Prelude Civic 1500, CRX Std., CRX Si and 1986-87 federal and high altitude CRX HF. This type of converter converts hydrocarbons (HC), carbon monoxide (CO) and oxides of nitrogen (NOx)into carbon dioxide (CO2), dinitrogen (N2) and water vapor. The precise fuel mixture control provided by the feedback control or fuel injection system is necessary for the proper operation of this type of catalyst. Use of this type of converter allows engine calibrations to be tailored for increased performance.
A two-way catalytic converter is used on Civic 1300, 1985 CRX HF and 1986-87 CRX HF California models. This type of converter converts hydrocarbons (HC) and carbon monoxide (CO) into carbon dioxide (CO2) and water vapor. Precise calibration of spark advance and the use of auxiliary air devices in the fuel system are necessary to provide proper emission control with this type of converter.