Audi A4, S4

since 2000 of release

Repair and car operation

System of injection of fuel of the diesel engine

General information

The fuel system of the diesel engine copes an electronic control system of the engine. It has the following advantages:

Self-diagnostics of a control system by the engine allows to make fast troubleshooting. Exact dispensing of amount of injected fuel provides reduction of the content of harmful substances in the fulfilled gases and low fuel consumption. Regulation of turns of idling and restriction of turns is made automatically.

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°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.

Air in the engine is sucked in or arrives from a turbokompressor and passes through the air filter. Turbokompressor compresses air which then arrives in an interkuler where it is cooled after heating as a result of compression in a turbokompressor. Cooling promotes the best filling of cylinders with forced air that in turn raises a torque and engine capacity.

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 of 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 cylinders of the engine. 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, the maintenance of a soot otherwise increases in the fulfilled gases. For this purpose the amount of sucked-in air is defined by a measuring instrument that allows the electronic block to operate retsirkulyatsiya process.

Injection of fuel is carried out directly in the combustion chamber.

In the bottoms of pistons there are the vortical chambers providing a turbulence of combustion arriving in chambers of fuel.

Management of warming up of the cold engine is carried out by the control unit the engine. At the cold engine the moment of injection is displaced by the control unit. The control unit the engine, in turn, operates work of candles of an incandescence. Glow plugs are established in each cylinder and join before engine start, work during an engine provorachivaniye with a starter and some time after engine start. Candles considerably facilitate start of the cold engine. After ignition inclusion on a control panel the lamp (address to Head Governing bodies and receptions of safe operation), signaling about inclusion of candles of an incandescence lights up. As soon as the lamp will go out, you can start the engine. If air temperature very low, candles continue to work still some time after engine start. It reaches stable operation of the engine and decrease in harmful impurity in the fulfilled gases.

Owing to high starting qualities of the engine with direct injection in a cold condition preliminary heat is required only at temperature below - 10°С.

Fuel passes through the fuel filter. In the filter fuel separates from water and pollution. Therefore it is important to delete water from fuel and to make timely replacement of a filtering element.

The engine of 2.5 l with direct injection

Fuel is soaked up by distributive TNVD from a fuel tank.

TNVD creates pressure about 900 atm. also injects fuel through multijet nozzles in two steps, according to ignition order. At first preliminary injection of small volume of fuel that creates necessary conditions for the subsequent injection of the main volume of fuel is made. Such process provides softer and less noisy combustion of fuel just as it occurs at vikhrekamerny injection.

TNVD does not demand service. All mobile parts of the pump are greased with diesel fuel. The drive of TNVD is carried out from a cranked shaft of the engine by a gear belt.

The engine of 1.9 l with direct injection

Arrangement of elements of system of injection in a compartment of the diesel engine of 1.9 l

1 — the Mechanical valve of a retsirkulyatsiya of the fulfilled gases with a zaslonka of the inlet pipeline 2 — the Sensor of temperature of cooling liquid 3 — the block Socket the pump nozzle 4 — the Sensor of temperature of fuel 5 — the Sensor of pressure of absorption with the sensor of temperature of soaked-up air 6 — the Socket of the sensor of number of turns of the engine 7 — the Socket of the sensor of the Hall of provision of a camshaft 8 — electronics Box in a water modular compartment. The control unit of system of direct injection with the height sensor

9 — the Sensor of number of turns of the engine 10 — the Sensor of the Hall of provision of a camshaft 11 — the Electromagnetic valve of restriction of pressure of pressurization 12 — the Vacuum drive of pressure of restriction of pressure of pressurization 13 — the Valve of switching of a zaslonka of the inlet pipeline 14 — the Valve of 1 system of a retsirkulyatsiya of the fulfilled gases 15 — the Measuring instrument of weight of air

Here injection occurs by means of nasos-forsunka system (an illustration lower). Unlike the previous system of injection where fuel is compressed by one TNVD for all nozzles, the nasos-forsunka system has own TNVD for each cylinder.

Thus, TNVD, the operating valve and a nozzle are incorporated in one block.

Block pump nozzle

1 — the Nozzle 2 — the pressure Pump 3 — the Control unit (the electromagnetic valve) 4 — the Roller lever 5 — an injection Cam 6 — the Cavity of a high pressure	7 — a piston Spring 8 — the pump Piston 9 — fuel Return 10 — Supply of fuel 11 — the Glow plug 12 — a nozzle Needle

Supply of diesel fuel is carried out by the electric fuel pump located in a tank, and also the mechanical fuel pump submitting fuel to the block the pump nozzle. Mechanical fuel насосвместе with the vacuum pump it is fixed on a head of cylinders and it is actuated directly from a camshaft. Four fuel pumps of the block the pump nozzle are actuated by the additional cam, located on distributive to a shaft, via the roller lever. The volume of injected fuel is regulated by the engine control unit via electromagnetic valves.

Owing to a high pressure of compression in the block the pump nozzle fuel strongly heats up that negatively affects operation of the sensor of a stock of fuel in a tank. For fuel cooling in the returnable pipeline there is a special refrigerator.

Before fuel hit in the fuel pump it passes through the fuel filter. There from fuel water and pollution separate. It is necessary to pay attention to importance of service of the fuel filter.

At work with fuel system it is necessary to observe security measures and special purity, address to the Section General information and security measures.