Audi A4, S4

since 2000 release

Repair and operation of the car

Catalytic converter

The catalytic converter has the central ceramic part of a cellular design-3-covered with a carrier layer. On a layer of the carrier there are salts of precious metals operating as converters. The catalytic converter is fixed in the case-1-by means of the insulating basic layer-2-compensating at the same time thermal expansions of the catalytic converter (address to the illustration Arrangement of Elements of System of Injection in a compartment of the diesel engine of 2.5 l).

Petrol engines

To reduce harmful emissions by means of the catalytic converter, systems of injection has to dose precisely amount of the injectable fuel necessary for combustion. The lambda probe is in a reception pipe in front of the catalytic converter and is washed by a stream of the fulfilled gases. The lambda probe represents the electronic sensor measuring the content of oxygen in final gases and representing its type of fluctuations of tension. Information from a lambda probe is transferred to the control unit of system of injection. The received value allows to regulate composition of air-petrol mix. On the one hand it is necessary as service conditions (idling, full gas), on the other hand, constantly change as optimum reburning of fuel in the catalytic converter happens only in this case if final gases contain enough fuel.

That in the catalytic converter there was a fuel reburning, it is necessary to have temperature of 300 - 800 °C. For this purpose the bigger content of fuel in mix, than is necessary for pure burning.

The catalytic converter of the petrol engine represents the so-called three-functional device. In adjustable process of transformation oxidation of carbon monoxide (WITH) and hydrocarbon (NANOSECOND), and also reduction of concentration _{of nitrogen oxides (NOx)} is carried out.

Security measures for an exception of damages of the catalytic converter

For an exception of damages a lambda probe and the catalytic converter it is necessary to fulfill the following requirements:

Petrol engines

• Surely apply only unleaded gasoline.
• Start of the heated-up petrol engine pushing or towage is allowed to carry out only in one attempt and at distance no more than 50 m. Better for this purpose to apply a starting cable. Not burned down fuel at ignition can lead to an overheat of the catalytic converter and its destruction.

• At difficulties with start of the engine it is not necessary to include a starter too long. Thus continuous injection of fuel is made. It is necessary to reveal and eliminate a cause of defect.
• If there are malfunctions with system of ignition, at determination of their character it is necessary to exclude injection of fuel at inclusion of a starter. For this purpose switch-off the relay of the fuel pump.
• Never spend fuel in a gasoline tank completely.
• At emergence of interruptions in ignition do not raise number of turns of the engine and immediately eliminate malfunction.
• Apply only the recommended spark plugs.
• Do not carry out an inspection of a spark with the disconnected shtekerny connection of a spark plug.
• Carrying out check of operation of the cylinder by disconnection of a wire of ignition from its candle is not allowed. Thus not burned down fuel gets to the catalytic converter.

Petrol and diesel engines

• Do not stop the car over dry foliage or a grass. The system of production of the fulfilled gases around the catalytic converter very hot also radiates heat even after an engine stop.
• Do not apply on elements of system of release of means for protection of the bottom of the car.
• It is not allowed to change a design of heat-shielding screens.
• When filling the engine with oil especially pay attention to not to exceed the level designated on the index as Max at all. Excess of oil owing to incomplete combustion comes to the catalytic converter and can damage its covering from the alloyed metal or completely destroy the catalytic converter.