The catalytic converter found in the exhaust system of the Volkswagen is an emission-reducing device that subjects harmful exhaust gases into an aftertreatment before they are emitted out of the vehicle. Traces of unburned elements called hydrocarbons, if allowed to exit the exhaust untreated, pose harmful effects on the environment. To counter this threat, the VW catalytic converter exposes the exhaust gases to a chemical reaction. It burns toxic pollutants, molecule by molecule, and converts them into less toxic gases. There are three main regulated emissions that the VW catalytic converter helps reduce: carbon monoxide (CO), volatile organic compounds (VOCs) and nitrogen oxides (NO and NO2). To do this, the converter uses two different types of catalysts, a reduction catalyst and an oxidation catalyst.
The VW catalytic converter typically consists of a core, wash coat, and catalyst. The catalysts fitted on every Volkswagen exhaust system are the chief failsafe of the car against harmful exhaust. They work two ways: reducing the nitrogen oxides into nitrogen and oxygen, and oxidizing the carbon monoxides into carbon dioxide. Palladium, platinum and rhodium are precious metals used as catalysts, with rhodium generally used as a reduction catalyst, palladium as an oxidization catalyst, and platinum used in both reduction and oxidation. Cerium, iron, manganese and nickel are also used, although each has its own limitations. Because the catalysts are ordinarily made of precious metals, the VW catalytic converter works on a structure that exposes the maximum surface area of catalyst to the exhaust stream, while also minimizing the amount of catalyst required.
Volkswagen models use different kinds of VW catalytic converters, depending on the type of the car's engine. For diesel engines, which uses compression ignition, the diesel oxidation catalyst is used. Compared to a VW catalytic converter on an internal combustion engine, the diesel catalyst uses the excess oxygen in the exhaust gas stream to oxidize carbon monoxide to carbon dioxide, and hydrocarbons to water and carbon dioxide, but is incapable of reducing nitrous oxides.
On the flip side of their limitations in exhaust reductions, the catalysts are reinforced by ceramic honeycomb cores, often called catalyst support. These converters often reach 90 percent effectiveness and are designed to snuff out additional exhaust contaminants like diesel odor and soot. Installing a VW catalytic converter has to correspond with the engine type, as the different catalysts are very much sensitive to gasoline types. Iron and rhodium catalysts, for example, are ineffective in the face of lead and prolonged exposure to leaded gasoline emission may poison the VW catalytic converter and render the exhaust system unguarded.
In addition to catalyst poisoning, the catalyst is likewise vulnerable to the same hazards as many of the other parts found in the car's exhaust system. Road debris, road splash containing dissolved salt, driving mishaps and other environmental conditions greatly affect the performance and reliability of the . Additionally, engine misfires can overheat and destroy the converter, especially when excessive amounts of unburned fuel are broken down within the catalyst.