The catalytic converter consists of a ceramic honeycomb body -3- coated with a carrier layer. On the carrier layer there are salts of noble metals, which cancel the influence on the conversion processes. An elastic and heat-resistant wire mesh -2- is used to fasten the shock-sensitive ceramic housing to the outer housing -1-, which also compensates for thermal expansion.
Gasoline engines
The combination of an electronic injection system and an oxygen sensor allows precise dosing of the amount of fuel for combustion so that the catalytic converter can reduce the output of harmful substances. The oxygen sensor is located in the exhaust pipe before the catalytic converter and is bathed in the exhaust gas flow. The oxygen sensor is an electrical sensor that indicates the residual oxygen content in the exhaust gases through fluctuations in electrical voltage and allows you to draw conclusions about the composition of the air-fuel mixture. In a fraction of a second, the oxygen sensor can transmit the appropriate signal to the injection system control unit and thereby constantly change the quality of the mixture. Firstly, this is necessary because operating conditions are constantly changing (idle, full load), secondly, optimal afterburning in the catalytic converter occurs only when there is still a sufficient proportion of gasoline in the exhaust gases.
So, in order for afterburning to occur in a catalytic converter at temperatures from +300°C to +800°C, the air-fuel mixture must contain more fuel than is necessary for its complete combustion in the engine cylinder.
The catalytic converter in question is a three-way one.
This means that in this catalytic converter, thanks to the regulation of the excess air ratio, the oxidation of carbon monoxide is simultaneously carried out (SO) and hydrocarbons (CH), as well as a decrease in nitrogen oxides (NOx),
Diesel engines
On vehicles with diesel engines, a catalytic converter is also fitted as standard. First of all, no adjustment of the composition of the mixture is possible here, as is the case in a gasoline engine. However, the catalytic converter reduces the emission of environmentally harmful carbon monoxide and hydrocarbons to a level that is significantly lower than gasoline engines with variable catalytic converters. In addition, the opacity of the exhaust gases typical of a diesel engine is reduced. The higher content of nitrogen oxides in the exhaust gases of conventional diesel engines is kept low by installing an exhaust gas recirculation system.