The purpose of a catalytic converter is to reduce harmful emissions from the exhaust of a "Properly Tuned" combustion engine. It accomplishes this through heat and a precious metal catalyst that causes the harmful emissions to either oxidize or reduce to safe elements in the exhaust flow. If the engine is out-of-tune and not calibrated to OEM specs, the catalytic converter's efficiency is greatly diminished and could lead to a converter failure.

The precious metal catalyst is bound to an extruded ceramic honeycomb substrate. The ceramic has hundreds of flow channels that allow the exhaust gasses to come in contact with a maximum amount of surface area where the catalyst reaction takes place. The catalyst must come in direct contact with the exhaust gasses for the reaction to take place.

If the ceramic inside your converter becomes clogged or coated with carbon, lead, oil, antifreeze, or silicone, then the converters efficiency is greatly reduced.

There are three basic types of automotive catalytic converters; Two-Way, Three-Way and Three-Way + Air. Each type uses a slightly different method and chemistry to reduce the harmful elements in exhaust emissions. Early model converters used a pelletized catalyst, but most modern converters are now designed with a free-flowing honeycomb ceramic catalyst. The type of converter required on a particular vehicle varies with model year, engine size and vehicle weight. Some vehicles even make use of more than one type of converter or a pre-converter to meet emission reduction standards.

Two-Way Oxidation Converter A Two-Way converter, used on cars between 1975 - 1980 oxidizes unburned harmful hydrocarbons and carbon monoxide along with secondary oxygen into water and carbon dioxide.	HC, CO OXIDIZES TO H20 and CO2
Three-Way Reduction/Oxidation Converter A Three-Way converter is a triple purpose converter. It reduces nitrous oxides into nitrogen and, like the two-way converter, it oxidizes unburned harmful hydrocarbons and carbon monoxide into water and carbon dioxide.	NO2 REDUCES TO N2 HC, CO OXIDIZES TO H20 and CO2
Three-Way + Air Reduction/Oxidation Converter A Three-Way + Air converter performs the same functions as the Three-Way converter. It oxidizes and reduces. The difference is the addition of secondary air between the two internal catalyst substrates that improves the oxidation capabilities of the converter. The secondary air is pumped into the middle of the converter between two separate catalyst coated ceramic substrates. The front ceramic performs the reduction and the back ceramic performs the oxidation. It’s like having two converters in one.	NO2 REDUCES TO N2 HC, CO OXIDIZES TO H20 and CO2