When the engine is cold, compression alone does not reach the ignition temperature of the fuel. In this case, the engine must be preheated. To do this, each combustion chamber has a glow plug that heats up the combustion chamber. The warm-up time depends on the ambient temperature and is controlled by the engine control unit via the preheat relay.
Fuel injection into the cylinders of a diesel engine can be carried out in two ways: injection into a vortex or preliminary chamber and direct injection.
When fuel is injected into a swirl or pre-chamber, it is injected into the pre-combustion chamber of the corresponding cylinder. The hot mixture ignites immediately. However, the volume of oxygen in the pre-chamber is sufficient to burn only part of the injected fuel. The remaining, unburned part is blown into the combustion chamber by the overpressure that occurs during combustion. There, the fuel burns completely.
With direct injection, fuel is injected directly into the combustion chamber by means of a high-pressure fuel pump, namely into the combustion chute in the piston. At the same time, the injection pump generates a pressure of about 900 bar in order to inject fuel in two stages through a nozzle with a multi-jet atomizer. Initially, a small amount of fuel is injected, which improves the ignition conditions for the main portion of the fuel. This leads to a softer and at the same time quieter combustion, similar to what happens in a vortex chamber.
The injected portions are fully regulated by the electronic engine control unit. The advantages of this principle are lower fuel consumption and higher engine power.
The injection pump does not require maintenance. All moving parts of the pump are lubricated with diesel fuel. The pump is driven by the crankshaft via a toothed belt.
The principle of operation of the injection pump
The injection pump of a diesel engine creates high pressure, which ensures the supply of fuel to the high pressure fuel lines and to the injectors, and from them to the combustion chambers.
The air necessary for burning fuel is taken in by the engine through the air filter and forced by the compressor.
The engine control unit (microprocessor) receives and processes information from sensors and, based on this information, calculates the volume of injected fuel, as well as the moment of injection, and then issues the appropriate commands to the executive systems and mechanisms. In this case, actions are coordinated with the control units of other vehicle systems, for example, the control unit for the gearbox, air conditioning or anti-theft system.
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