To reduce the content of toxic components in exhaust gases, diesel models are equipped with a special oxidizing catalytic converter. At the same time, the recirculation system (EGR), due to the metered mixing of a small amount of exhaust gases into the air sucked into the engine and, as a result, a decrease in the concentration of oxygen in the combustible mixture, provides a significant decrease in the content of nitrogen oxides (NOX) in the combustion products. Due to the operation of the EGR system, it leads to a reduction in ignition delay and a decrease in combustion temperature, which ultimately leads to a decrease in the formation of NOX. An indispensable condition for organizing recirculation is the accuracy of the mixing dosage, since otherwise the content of solid carbon particles (soot) in the exhaust gases increases. The amount of air sucked into the engine is determined by a special meter, the information from which allows the electronic control module to monitor the recirculation process.
Fuel is injected directly into the combustion chambers of the cylinders.
The engine operation is controlled by an electronic system, similar in structure and operating principle to the engine management system used in petrol models with petrol engines. The commands generated by the control module are based on data received from a whole set of information sensors that continuously monitor operating parameters.
Information about the crankshaft position and engine speed is sent to the control unit by the crankshaft position sensor (CKP). The inductive head of the sensor is located opposite the flywheel and constantly scans special reference marks applied to the surface of the latter. When a mark passes the sensitive element of the measuring head, the sensor generates a signal pulse sent to the control module. The marks are uniformly applied to the flywheel surface, with the exception of a single gap corresponding to the position 90° before the TDC of the piston of the first cylinder. When the flywheel passes this point, the signal pulse is not sent to the control module, which allows the latter to determine the TDC moment. Based on the length of the pause/pulse duty cycle, the module receives information about the crankshaft speed.
Information about the amount and temperature of air entering the engine comes from the manifold absolute pressure (MAP) and intake air temperature (IAT) sensors. The MAP sensor is connected to the intake manifold by a vacuum hose and measures the depth of vacuum inside the latter. Two IAT sensors are used to monitor the intake air temperature, one of which is installed in front of the turbocharger, the other - behind the intercooler (intercooler). The readings taken by the sensors are used by the control module to calculate the exact amount of fuel that should be injected into the engine's combustion chambers.
The traditional coolant temperature sensor has been replaced by a cylinder head temperature sensor, which supplies the control module with information used to adjust the quality of the air-fuel mixture and calculate injection timing. In addition, the data collected by the sensor is used to control the operation of the cold engine preheating system.
The brake light/pedal position sensor-switch informs the control unit of the current position of the foot brake pedal. Upon receiving signals from these sensors, the control system immediately switches the engine to idle mode and maintains it until a signal is received from the gas pedal position sensor.
The fuel supply system is organized according to the direct injection scheme. The piston bottoms are provided with swirl chambers that ensure the swirl of the fuel injected into the combustion chambers of the cylinders. To optimize the fuel combustion process, the injectors are opened in two stages (for this purpose, two springs are placed inside each nozzle). When the injector's working valve opens, a small amount of fuel gets onto the injector's internal components, providing lubrication, and then returns to the fuel tank.
Preheating is also controlled by the engine control module, which provides a certain offset of the injection timing when the engine is cold. In addition, the control module monitors the functioning of the glow plugs. The glow plugs are screwed into each cylinder, are activated before the engine is started and remain hot during the entire time the crankshaft is turned by the starter, as well as for some time after the engine has started. The use of glow plugs makes it much easier to start the engine in cold weather. A special indicator lamp mounted in the instrument cluster warns the driver about the activation of the glow plugs (see Chapter Controls and safe operating techniques), - as soon as the lamp goes out, you can start the engine. In particularly cold weather, the spark plugs continue to function for some time after starting, maintaining the stability of engine speed and ensuring a reduction in toxic components in combustion products.
Note: The design of modern diesel engines is characterized by increased starting efficiency, as a result of which the need to use glow plugs arises only at air temperatures below -10°C.
The fuel pumped by the preliminary fuel pump passes through the fuel filter, where it is cleaned of moisture and other contaminants. Try to conscientiously perform maintenance procedures, replacing the filter element in a timely manner.