Catalytic converter (Mercedes-Benz S-Class W220)

The catalytic converter has a central ceramic part of a honeycomb structure "3" covered with a carrier layer. On the carrier layer are salts of noble metals acting as converters. The catalytic converter is fixed in the housing "1" by means of an insulating support layer "2" that simultaneously compensates for the thermal expansion of the catalytic converter.





(Article obtained from this portal: www.MercedesMan.ru)

Petrol engines

In order to reduce harmful emissions with the help of a catalytic converter, the injection system must precisely dose the amount of injected fuel required for combustion. The oxygen sensor is located in the intake pipe before the catalytic converter and is washed by the flow of exhaust gases. The oxygen sensor is an electronic sensor that measures the oxygen content in the exhaust gases and represents it in the form of voltage fluctuations. Information from the oxygen sensor is transmitted to the injection system control unit. The resulting value allows you to adjust the composition of the air-fuel mixture. On the one hand, this is necessary, since operating conditions are constantly changing (idle, full throttle), on the other hand, since optimal afterburning of fuel in the catalytic converter occurs only in this case if the exhaust gases contain a sufficient amount of fuel.



In order for the fuel to be burned in the catalyst, a temperature of 300 - 800°C is required. This requires a higher fuel content in the mixture than for pure combustion.

The catalytic converters used in gasoline engines are so-called three-functional devices. In the controlled conversion process, carbon monoxide (CO) and hydrocarbon (HC) are oxidized, and the concentration of nitrogen oxides (NOx) is reduced.

Safety precautions to avoid damage to the catalytic converter

To avoid damage to the oxygen sensor and catalytic converter, the following requirements must be met:

• Be sure to use only unleaded gasoline.
• Starting a warmed-up petrol engine by pushing or towing is permitted only in one attempt and at a distance of no more than 50 m. It is better to use a jumper cable for this purpose. Unburned fuel during ignition can lead to overheating of the catalytic converter and its destruction.

Note: Starting cars with automatic transmission is not possible for technical reasons.

• If you have difficulty starting the engine, do not engage the starter for too long. This will cause continuous fuel injection. It is necessary to identify and eliminate the cause of the malfunction.
• If there are problems with the ignition system, when determining their nature, it is necessary to exclude fuel injection when the starter is turned on. To do this, disconnect the fuel pump relay.
• Never empty the fuel tank completely.
• If misfiring occurs, do not increase engine speed and correct the problem immediately.
• Use only recommended spark plugs.
• Do not perform spark testing with the spark plug connector disconnected.
• It is not allowed to test the operation of the cylinder by disconnecting the spark plug wire from its spark plug. This will cause unburned fuel to enter the catalytic converter.
• Do not park the vehicle over dry leaves or grass. The exhaust system in the area of the catalytic converter is very hot and radiates heat even after the engine has stopped.
• Do not apply underbody protection products to exhaust system components.
• It is not permitted to change the design of heat shields.
• When filling the engine with oil, pay special attention to the fact that under no circumstances should the level indicated on the indicator be exceeded as Max. Excess oil due to incomplete combustion enters the catalytic converter and can damage its alloy metal coating or completely destroy the catalytic converter.