The catalyst consists of a honeycomb ceramic monolith coated with a protective layer. The protective layer contains noble metal salts, which ensure the exhaust gas cleaning process.
The catalytic converter housing contains a support insulator that simultaneously compensates for thermal expansion.
Gasoline engines
Thanks to the electronic control of the fuel injection system, in combination with information from the lambda probe, fuel is injected into the combustion chambers in a dosed manner so that the catalyst can reduce the level of harmful substances in the exhaust gas.
The lambda probe is installed in the exhaust pipe and is washed by the exhaust gases there. The lambda probe is an electrical sensor that reacts to the content of oxygen residues in the exhaust gases by fluctuations in electrical voltage, which ultimately allows the control unit to evaluate the composition of the air-fuel mixture.
The injection system control unit, based on information from the lambda probe, can change the ratio of fuel and air in a split second. On the one hand, this is necessary because operating conditions are constantly changing («full throttle», idling), and on the other hand, because afterburning in the catalyst occurs only when the exhaust gases contain a sufficient proportion of gasoline.
In order for afterburning processes to take place in the catalyst at temperatures from +300°C to +800°C, the air-fuel mixture must have a larger proportion of fuel than is necessary for simple combustion.
The installed catalyst is a so-called three-channel catalyst. This means that in such a catalyst, as a result of regulation by the lambda probe, carbon monoxide is simultaneously oxidized (SO) and hydrocarbons (NS), as well as a decrease in nitrogen oxides (NOx)
To reduce the level of harmful substances in the exhaust gas even before they enter the catalyst, a system for using secondary air and an exhaust gas recirculation system is used.
Catalyst on vehicles with a diesel engine
Diesel vehicles also have catalytic converters as standard. However, only unregulated catalysts are used here. Such a catalyst reduces the emission of environmentally harmful carbon monoxide and hydrocarbons to a level that is significantly less than that of a regulated catalyst in gasoline engines. In addition, the catalyst in diesel engines neutralizes the smell of burnt fuel characteristic of a diesel engine. The higher level of nitrogen oxides in the exhaust gas, typical of diesel engines, is reduced by exhaust gas recirculation.
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