The operating principle of diesel engine fuel injection systems (Opel Vectra C)

When a diesel engine is running, clean air is sucked into its cylinders and compressed to high pressure. The air temperature rises to 600'C, which exceeds the ignition temperature of diesel fuel. Fuel is injected into the cylinder a little ahead of time and ignites. Thus, spark plugs are not used to ignite the fuel. When operating the vehicle in conditions of low outside air temperatures, the air temperature inside the cylinders after compression may be insufficient for the fuel to ignite spontaneously. In this case, it is necessary to preheat the incoming air flow. For this purpose, glow plugs are installed in the combustion chambers, heating them to the required temperature. The duration of preheating depends on the outside air temperature and is regulated by the engine management system via a preheating relay. When the glow plugs are activated, the corresponding indicator lamp lights up on the instrument panel.

5. There are three fuel injection methods for diesel engines: swirl injection, pre-chamber injection and direct injection.

6. In the swirl-chamber and pre-chamber methods, fuel is injected into the pre-chamber (fort chamber) the corresponding cylinder where it mixes with air and creates a ready working mixture, while part of the fuel immediately ignites and burns. Due to the swirls of the air flow and heating during combustion of part of the fuel, the working mixture becomes more homogeneous and heated. This ensures complete combustion of the fuel when it enters the cylinder and "softer" engine operation. The main disadvantage of these injection methods is the complication of the engine design. Direct injection continues to be the most common and most economical.



7. With direct injection, fuel enters directly into the combustion chamber through the nozzle atomizer. Each atomizer usually has 4-6 very fine holes drilled at different angles, through which fuel is sprayed in specially specified directions. Usually, there is a swirl chamber in the piston crown. Swirl chambers can have different shapes, which correspond to the directions of fuel spraying, promote better mixture formation and more efficient combustion of the working mixture. This method is used on all diesel engines discussed in this Manual.

8. On Y20DTH/Y22DTR engines, fuel is sucked from the fuel tank by a high-pressure fuel pump (HPFP). The HPFP creates the high pressure required for injection (about 900 bar) pressure and supplies fuel through the injectors to the engine cylinders in the order of cylinder operation. First, a preliminary injection of a small amount of fuel is performed, which, burning, prepares the conditions for the injection of the main portion of fuel. Due to this, a "softer" and more uniform combustion of fuel occurs, as in engines with a swirl-chamber injection method.

9. On Z19DT(H) engines, fuel is sucked from the fuel tank by an electric fuel pump and supplied to the high-pressure fuel pump (HPFP). For direct injection, these models use the "Common Rail" - common fuel distribution line for all cylinders (see accompanying illustration). This system frees the injection pump from the function of fuel distribution, which allows the pump to create a higher (approximately 1600 bar) pressure, - this promotes very fine atomization of fuel, due to which the process of mixture formation in the cylinders improves and the efficiency of combustion of the working mixture increases. Fuel distribution line (Common Rail) it is designed as a manifold, from which fuel is supplied to individual injectors.





10. On the 6-cylinder Y30DT engine, direct injection is also carried out through the Common-Rail system, but the fuel from the fuel tank is sucked in by the high-pressure fuel pump. The fuel injection pump of this engine is driven by the crankshaft via a gear mechanism.

11. On all engines, before the fuel enters the high-pressure fuel pump, it is cleaned in the fuel filter from dirt and water. The engine is equipped with injectors with electromagnetic control elements that receive signals from the engine management system, which regulates the amount of fuel supplied to the cylinder.

12. The high-pressure fuel pump does not require any special maintenance work. All moving elements of the fuel system are lubricated with diesel fuel.