Camry Wagon V6-180.5 2959cc 3.0L DOHC (3VZ-FE) (1993)
Three Way Catalytic Converter: Description and Operation
PURPOSE
The three way catalytic converter simultaneously removes up to 90% of all three major pollutants, (HC, CO, and oxides of nitrogen). A complete
catalytic reaction depends on the fuel mixture staying within a very narrow range + 1% of 14.7:1 which can only be achieved with a properly
functioning oxygen sensor system.
OPERATION
As the exhaust gasses containing HC and CO pass through the converter in the presence of oxygen, the platinum catalyst starts the oxidation
(burning) process. The HC and CO then unite with oxygen to form water vapor and carbon dioxide. This oxidation process has no effect on the
NOx emissions.
To reduce the oxides of nitrogen (NOx), a separate reaction is necessary called "reduction." A reduction reaction is the removal of oxygen from a
material. In Three Way Catalyst type converters, rhodium is used as a catalyst to break down oxides of nitrogen into nitrogen and oxygen. The
effective conversion of pollutants begins at about 250°C (480°F).
CONSTRUCTION
The catalytic converter consists of a metal housing, a ceramic grid substrate, and a catalytic coating of platinum and rhodium. The active metal
content is about 2 grams of platinum/rhodium.