Contents: Petrol engines ↡ Diesel engines ↡
The catalyst is designed to reduce the level of harmful substances in exhaust gases.
It consists of a honeycomb ceramic monolith 2 covered with a protective layer (see illustration 2.0). The protective layer contains salts of noble metals, which ensure the exhaust gas cleaning process.
In the body 1 of the catalyst there is a support insulator 3, which simultaneously compensates for thermal expansion.
Petrol 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 metered manner so that the catalyst can reduce the level of harmful substances in the exhaust gases.
The lambda probe is an electrical sensor that reacts to the content of residual oxygen in the exhaust gases by fluctuating electrical voltage, which ultimately allows the control unit to evaluate the composition of the fuel-air mixture.
The injection system control unit can change the fuel-air ratio in a fraction of a second.
On the one hand, this is necessary because the operating conditions are constantly changing ("full throttle", idle), and on the other hand, because afterburning in the catalytic converter occurs only when the exhaust gases contain a sufficient proportion of gasoline.
(Material taken from a web resource: «Mercedesman.ru»)
Diesel engines
Unlike catalytic converters installed on gasoline engines, diesel vehicles are equipped with 2 non-adjustable catalytic converters, since the diesel engine is supplied with more air than is necessary for combustion.
This catalyst converts carbon monoxide and hydrocarbon compounds contained in the exhaust gases into carbon dioxide CO and water (H 2 O). In addition, it neutralizes the characteristic smell of burnt fuel in a diesel engine (see illustration 2.1).
High levels of nitrogen oxides (NOx) in the exhaust gases is reduced as a result of the operation of the exhaust gas recirculation system.
The EGR valve is located on the intake manifold and is actuated by low pressure.
The valve ensures that part of the exhaust gases are diverted back into the combustion chambers in order to reduce the ignition temperature of the fuel-air mixture and thereby reduce the content of harmful substances in the exhaust gases.