S-class W202 Mercedes

1993-2000 of release

Repair and car operation

W202 Mercedes
+ 1.2. General information
+ 2. Maintenance
+ 3. Engines
+ 4. Greasing system
+ 5. Cooling system
+ 6. Heating, ventilation
+ 7. Ignition system
- 8. Fuel system
   + 8.1.1. Introduction
   + 8.2. System of injection of petrol engines
   + 8.3. System of injection and food of diesel engines
   - 8.4. System of production of exhaust gases
      8.4.2. Main and average exhaust silencers
      8.4.3. Cars with the catalyst
      8.4.4. Device of neutralization of exhaust gases of the diesel car
      8.4.5. Rub in one – or how to save the catalyst
+ 9. Transmission
+ 10. Running gear
+ 11. Steering
+ 12. Brake system
+ 13. Body
+ 14. Electric equipment
+ 14.2. Electroschemes

b47c026d b47c026d

8.4.3. Cars with the catalyst


Engines which are established on the S-class are serially equipped with the adjustable catalyst. This catalyst demands, that the petrol engine was essentially maintained on unleaded fuel. Besides, cars with the adjustable catalyst should have an adjustable carburetor.

The adjustable carburetor is understood as the carburetor or system of injection of fuel at which the relation of fuel to air can constantly change depending on modes of movement and from the content of oxygen in exhaust gases. It cannot be carried out when using the traditional carburetor as it is not equipped with the corresponding control unit. For this reason come back or to the carburetor regulated by means of electronics, or to system of injection of fuel.

The carburetor receives commands of management from the oxygen sensor which is established in the final pipeline in front of the catalyst or in a final collector and here is washed by a stream of final gases. The oxygen sensor is a sensitive element and signals about the residual content of oxygen in exhaust gases by means of fluctuation of tension and promotes issue of the conclusion about structure of a toplivovozdushny mix. In fractions of a second the oxygen sensor can transmit the corresponding electric signals on the control unit of the carburetor and, thanks to it, the ratio fuel-air constantly changes. It, on the one hand, is required, as in any case service conditions (the idling, complete opening of a butterfly valve), and, on the other hand, as well constantly change because only in this case on the catalyst there is a reburning as in the fulfilled gases of the engine still there is a sufficient share of gasoline.

Therefore, in order that at temperature from 300 to 800 ° With on the catalyst in general there could be a reburning, gas mixture should have bigger percent of fuel, than its would be required for pure combustion. Thus, at use of the catalyst it is necessary to reckon with the increased fuel consumption reaching from one five percent.

The catalyst is established under the basis of a body of the car instead of the additional exhaust silencer. The catalyst consists of the porous ceramic monolith covered with a layer of platinum or rhodium. For installation of a ceramic body sensitive to pushes the elastic and heat resisting metal fabric is used.

In this case it is a question of the so-called three-functional catalyst. It means that on this catalyst, on the basis of the data received from the oxygen sensor, oxidation of an oxide of carbon (WITH) and hydrocarbons (NANOSECOND) to CO2 and H2O, and also simultaneous restoration of oxides of nitrogen (NOH) to nitrogen is carried out.

Care of the cars equipped with the catalyst

To avoid damage of the oxygen sensor and the catalyst, surely follow the following instructions:

 – Essentially fill the car with only unleaded gasoline. If you by mistake refueled etilirovanny gasoline, it is necessary to replace an exhaust pipe in front of the catalyst, and also the catalyst. Before installation of new details of the catalyst it is necessary выездить not less than two fuel tanks filled with unleaded gasoline. Engine start by means of pushing or towage can be made only in that case when the engine is started at once. Not burned down fuel at ignition can lead to a catalyst overheat and by that to its destruction. Use starter start from the auxiliary storage battery.

 – It is necessary to avoid frequent start-up of the cold engine following one after another. In this case on the catalyst not burned down fuel which at the subsequent heating suddenly ignites gathers, and thus to the catalyst is harmed.

 – At emergence of difficulties at start of the engine it is not necessary to press a long time a starter. During start fuel is continuously injected. Define and eliminate a cause of defect.

 – Apply only the spark plugs of Mercedes firm resolved to operation.

 – Do not inspect existence of the spark category on tips of wires to spark plugs.

 – If iskroobrazovaniye interruptions are observed, avoid high frequency of rotation of a shaft of the engine and urgently eliminate defect.

 – Do not stop the car over the dried foliage or a grass. The system of production of exhaust gases becomes very hot catalyst in a zone and radiates residual heat even after an engine stop.

 – During the filling or a dolivka of engine oil especially pay attention to that the maximum mark in the index of level of oil was not exceeded at all. Otherwise superfluous oil because of incomplete combustion gets on the catalyst and can damage precious metal or completely destroy the catalyst.