Audi A3

since 1997 of release

Repair and car operation

Audi A3
+ Maintenance instruction
+ Current leaving and service
+ Engine
+ Systems of cooling, heating
- Power supply system and production of the fulfilled gases
   + Power supply system
   + System of injection of fuel
   - System of injection of the diesel engine
      Direct injection
      Removal and installation of nozzles
      Check and adjustment of the beginning of injection of TNVD
   + System of production of the fulfilled gases
+ engine Electric equipment
+ Manual box of gear shifting
+ Automatic transmission and models with a full drive
+ Coupling and power shafts
+ Brake system
+ Suspension bracket and steering
+ Body
+ Onboard electric equipment
+ Elektroskhema

System of injection of the diesel engine

GENERAL INFORMATION

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

Fuel is sucked in by the fuel pump of a high pressure (TNVD) directly from a tank. In TNVD fuel is compressed to pressure necessary for injection. Injection is carried out as it should be, similar to an ignition order in the petrol engine.
For reduction of a share of harmful substances in the fulfilled gases diesel engines have the diesel oxidizing catalytic converter. At the same time the system of a retsirkulyatsiya provides essential decrease in the fulfilled gases the content of oxides of nitrogen. It is reached thanks to supply of the fulfilled gases to air soaked up by the engine that provides decrease in concentration of oxygen in the air, arriving in engine cylinders. It leads to a delay of ignition and to lower temperature of combustion that as a result reduces formation of NOx. Process of a retsirkulyatsiya of the fulfilled gases should be dosed out precisely however, deposit issue otherwise increases. For this purpose the amount of sucked-in air is defined by a measuring instrument that allows the electronic device to operate retsirkulyatsiya process.

At the cold engine the temperature of compression of air appears insufficient for fuel ignition. In this case preliminary heat is required. For this purpose in each cylinder of the engine the electric glow plug is established.
Duration of heat depends on temperature of external air and is regulated by the special relay.

Fuel injection in cylinders can be carried out in three ways: via the prechamber, the vortical chamber or it is direct in the combustion chamber.

At prechamber injection diesel fuel is injected into the prechamber of the corresponding cylinder. The hot fuel mix ignites at once. However the volume of the oxygen containing in the prechamber, is sufficient for burning only parts of the injected fuel. The remained not burned down part of fuel under the influence of pressure of combustion is thrown in the main chamber of combustion where there is a complete combustion of fuel.

At vikhrekamerny injection fuel is injected into the chamber separated from the main chamber of combustion. Difference from prechamber injection is other performance of the connecting channel between vortical and main chambers. Here at compression in the vortical chamber there is a strong air turbulence that promotes good mixing of air with injected fuel.