Mercedes M-Class W163

since 1997 of release

Repair and car operation

Power supply system of diesel engines

General information

At operation of the diesel engine in its cylinders external air which is compressed to a high pressure is soaked up. Thus air temperature as a result of adiabatichesky heating rises to value 700-900°C, ignition of diesel fuel exceeding temperature. Fuel is injected into the cylinder with some advancing and ignites. Thus, spark plugs for ignition of fuel are not used.

For reduction of the maintenance of toxic components in the fulfilled gases diesel models are equipped with the special oxidizing catalytic converter. At the same time the system of a retsirkulyatsiya (EGR), at the expense of the dosed-out podmeshivaniye to air of a small amount of the fulfilled gases soaked up in the engine and, - as a result, - decrease in concentration in gas mixture of oxygen, provides essential decrease in contents in products of combustion of oxides _{of nitrogen (NOX)}. At the expense of functioning of EGR system leads to reduction of a delay of ignition and decrease in temperature of combustion that as a result conducts to reduction of formation _{of NOX}. An indispensable condition at the organization of a retsirkulyatsiya is accuracy of a dosage of a podmeshivaniye, the content in the fulfilled gases of firm particles of carbon (soot) otherwise increases. The amount of air soaked up in the engine is defined by the special measuring instrument, given out which information allows the electronic module of management to carry out control of retsirkulyatsiya process.

Injection of fuel is carried out directly in chambers of combustion of cylinders.

Functioning of the engine the electronic system, on structure and a functioning principle similar to the control system of the engine applied on petrol models by petrol engines operates. In a basis developed by the module of management of teams the data arriving from the whole set of information sensors, continuously tracing operational parameters lay down.

Information on position of the crankshaft and speed of rotation of the engine arrives in the control unit from the sensor of position of the crankshaft (CKP). The inductive head of the sensor is located opposite to a flywheel and constantly scans the special basic labels put on a surface of the last. When passing label by a sensitive element of a measuring head the sensor develops the alarm impulse which is given out on the module of management. Labels are evenly put on a flywheel surface, except for the unique admission corresponding to situation 90 ° before VMT of the piston of the first cylinder. At the moment of passing by a flywheel of this point the alarm impulse does not stand out on the management module that allows the last to define VMT moment. On length of pause/porosity of impulses the module receives information on frequency of rotation of a cranked shaft.

Information on quantity and temperature of air arriving in the engine arrives from sensors of absolute pressure in the inlet pipeline (MAP) and temperatures of soaked-up air (IAT). The MAP sensor is connected by a vacuum hose to the inlet pipeline and measures depth of depression in the last. For control of temperature of soaked-up air two IAT sensors one of which is established ahead of a turbokompressor, another - behind the Intermediate cooler (interkuler) are used. Instruments read by sensors are used by the management module at calculation of exact amount of fuel which should be injected into chambers of combustion of the engine.

The traditional sensor of temperature of cooling liquid is replaced with the sensor of temperature of a head of the block, supplying module of management with information which is using at corrections of quality of an air and fuel mix and calculation of the moments of injection. Besides, data taken off by the sensor are used at management of functioning of system of preliminary warming up of the cold engine.

The sensor switch of stoplights/provision of a brake pedal informs the control unit on the current provision of a pedal of a foot brake. When receiving signals from these sensors the control system instantly transfers the engine to a mode of idling and supports it to the moment of receipt of a signal from the sensor of provision of a pedal of gas.

The system of supply of fuel is organized according to the scheme of direct injection. In the bottoms of pistons the vortical chambers providing a twisting of combustion injected into chambers of cylinders of fuel are provided. Opening of nozzles is made for optimization of process of combustion of fuel in two steps (for this purpose in each nozzle it is placed on two springs). When opening the working valve of a nozzle the small part of fuel gets on internal components of the last, providing their greasing, then comes back to a fuel tank.

Control of preliminary warming up also is carried out by the module of engine management which at the cold engine provides a certain shift of the moment of injection. Besides, the module of management supervises process of functioning of candles of an incandescence. Glow plugs are screwed in each cylinder, are activated before start of the engine and remain in a hot condition during the whole time of a provorachivaniye of a cranked shaft a starter, and also some time after engine start. Application of candles of an incandescence allows to facilitate considerably engine start in cold weather. About activation of candles of the driver the control lamp (warns special, built in in a combination of devices see. Head Governing bodies and receptions of safe operation), - as soon as a lamp will go out, it is possible to start engine start. In especially cold weather, candles continue to function still some time after start, supporting stability of turns of the engine and providing decrease in toxic components in combustion products.

The design of modern diesel engines differs the increased efficiency of start therefore need for application of candles of an incandescence arises only at air temperatures below - 10°С.

Fuel pumped up by the preliminary fuel pump is passed via the fuel filter where its cleaning of impurity of moisture and other pollution is made, try to treat honestly performance of procedures of maintenance, in due time making replacement of a filtering element.