Auto Manual of VW Passat B5

4.6.2. The general information

THE GENERAL DATA

Arrangement of elements of management of the diesel engine in a motor compartment

1 – gauges of pressure and temperature of air arriving in the engine. On the cars made to VIII.1997 of year, the gauge of pressure of air arriving in the engine is established in a control mean of system of direct injection of diesel fuel; 2 – an electric socket of the gauge of number of turns of a cranked shaft of the engine; 3 – an electric socket of the gauge  of moving of a needle; 4 – the valve of system of repeated giving of exhaust gases; 5 – the gauge of temperature of a cooling liquid; 6 – an electric socket of the fuel pump of a high pressure. The ten-contact socket is intended for the gauge of temperature of fuel, a regulator of volume and the gauge of moving of a zolotnik, and also for the valve отсечки fuel and the valve of the moment of injection;

7 – the gauge of turns; 8 – a control mean. The management gauge establishes ся only on diesel engines with direct injection of fuel; 11 – an electric socket. A seven-contact electric socket for the valve отсечки fuel and the valve of the moment of injection of fuel; 12 – a place of measurement of volumes of the fuel pump of a high pressure ; 13 – a fuel atomizer with the gauge of moving of a needle; 14 – the magnetic valve. The magnetic valve is intended for restriction of pressure of a turbo-supercharging; 15 – the valve of repeated giving of exhaust gases; 16 – a measuring instrument of a stream of air

Arrangement of vacuum hoses in a control system of the diesel engine

1 – a connecting air line. The heat exchanger of air forced турбонагнетателем; 2 – vacuum connection. For adjustment of pressure of pressurisation of air created турбонагнетателем on engines AFN; 3 – connection for the vacuum amplifier of brakes; 4 – vacuum connection. For adjustment of pressurisation of air created турбонагнетателем on engines AFN;

5 – the vacuum pump; 6 – a ventilation hose. For adjustment of pressurisation of air created турбонагнетателем on engines AFN; 7 – a ventilation hose on the air filter; 8 – the valve of repeated giving of exhaust gases; 9 – the modulating valve of repeated giving of exhaust gases

This type of the engine has received the name by name the German engineer Rudolf Dizelja who has constructed in 1897 the first engine with spontaneous ignition of fuel. Structurally diesel engine is similar to the petrol engine: the same cylinders, pistons, a camshaft, valves. But there is also a number of differences from which the main thing, it is possible even to tell basic, consists that fuel ignition in the diesel engine is made not by a spark from a spark plug, and at the expense of a heat which reaches air as a result of compression by its piston in the cylinder.

The second important point – a way of giving of fuel. In the petrol engine a working body is the mix of gasoline with air. The mix prepares in advance (in the carburettor) or is direct at the moment of its giving in cylinders (in injection systems) – the main thing that fuel moves together with air, and is set fire and the stuffy mix burns down rather homogeneous топливовоз.

In the diesel engine fuel and air giving occurs separately. In the beginning in the cylinder air is soaked up, then it is compressed, and only after that fuel is injected, therefore to tell about homogeneous топливовоздушной mixes it is not necessary. Injection is made in the end of a compression step, fuel and air actually do not mix up with each other, burning occurs at the front a stream of fuel injected into compressed air.

Fuel spontaneous ignition is accompanied by sharp, spasmodic increase of pressure in the cylinder – it usually noisy, rigid work of the diesel engine speaks. In низкооборотных diesel engines with the big working volume which are used by trucks, this lack is shown to a lesser degree, and with it are reconciled. In diesel engines of cars of it try to get rid application of the vortical chamber, or the prechamber, – a small compartment of the chamber of combustion into which fuel is injected. There it ignites, partially mixes up with air then the burning mix extends on the basic volume of the cylinder. This way reduces rigidity of work of the engine a little, but reduces its thermal efficiency and fuel profitability. For smoother ignition of fuel two-level injection and the difficult electronic scheme of management are used.

Prominent feature of diesel engines is presence of firm particles in the fulfilled gases. Because of heterogeneity of process of burning on поверхнос ти separate particles of fuel some lack of oxygen therefore instead of their oxidation there is a partial thermal decomposition to formation of firm products – soot is always observed. For good burning of diesel fuel the superfluous quantity of air is required considerable, even.

Also, degree of compression at the diesel engine in 2 times above, than at the petrol engine. High, not less than 14 (reaches 25), compression degree is necessary that air temperature in the cylinder has risen to size, sufficient for fuel ignition. Usually in diesel engines compression degree makes 21–22 and is limited only прочностными to engine characteristics.

For fuel giving in diesel engines it is much more difficult than the device, than in petrol. Their complexity defines ся first of all that it is necessary to inject very small, all some milligramme, portions of fuel on Wednesday with a high pressure. These portions should be very precisely measured – quantity of submitted fuel work of the diesel engine copes. Are for this purpose necessary быстродействую щие and exact atomizers. High degree of compression demands application соответству ющих fuel pumps – pressure in an atomizer nozzle should reach several hundreds bar. It complicates all and is notable удорожает system of giving of fuel and, accordingly, the diesel engine.

Fuel from a fuel tank gets the fuel pump of a high pressure, and then under a high pressure moves to fuel atomizers.

For reduction of quantity of the harmful substances containing in exhaust gases on cars with diesel engines the oxidising catalyst is established. Also the system подмешивания exhaust gases to the fresh air arriving in the engine therefore percentage of oxygen in air which will be burnt in engine cylinders decreases is used. As a result of it the temperature of combustion of a fuel mix therefore the quantity of the formed oxides of nitrogen decreases decreases.

Three ways of injection of diesel fuel in engine cylinders are known. Through форкамеру, through the vortical chamber and direct injection.

At injection of diesel fuel through форкамеру fuel is sprayed on форкамере and instantly ignites. In connection with insignificant quantity of oxygen in форкамере burns down only a fuel part, and other fuel is superseded from форкамеры in the engine cylinder where burns down completely.

At fuel injection through the vortical chamber process of combustion of fuel is made in the same way, as well as at fuel injection through форкамеру. Difference consists in the form and the sizes of the channel connecting the vortical chamber with the chamber of combustion. At fuel injection in the vortical chamber there is considerably best hashing of fuel to air, and combustion process is carried out more smoothly.

Direct injection of fuel

At direct injection of fuel fuel moves directly in the combustion chamber. The fuel pump submits fuel under pressure nearby 900 bar, and fuel injection is made in two stages.

Use of two-channel fuel atomizers gives the chance to make initial injection незначитель ache fuel parts therefore process of combustion of fuel improves, and process of combustion proceeds more smoothly. The quantity of injected fuel is regulated by an electronic control system of the engine. The quantity of injected fuel is regulated by a control system on the basis of the information from following gauges:

 – The gauge of position of a pedal of an accelerator hands over the information to a control mean the engine about position of a pedal of an accelerator at the moment time;
 – The gauge of turns of a cranked shaft of the engine;
 – The gauge of moving of a needle of a fuel atomizer. On the basis of the information from this gauge the moment of injection of fuel is defined and adjustment of process of injection depending on operational modes and turns of a cranked shaft of the engine is made;
 – The gauge of pressure of air arriving in the engine (the pressurisation gauge);
 – The gauge of temperature of air arriving in the engine;
 – The gauge of temperature of a cooling liquid;
 – The gauge of temperature of diesel fuel;
 – A potentiometer of position of a zolotnik. On the basis of the information from this gauge the actual quantity of injected fuel is defined.

Air arriving in the engine in inlet channels, twists on a spiral therefore combustion process in engine cylinders improves. Also start of the cold engine is thus facilitated, and the preliminary heating of the engine is necessary for making at air temperatures more low–10 .

Before fuel receipt in the fuel pump of a high pressure fuel passes through the fuel filter in which from it water which is necessary for merging periodically also separates.

The drive of the fuel pump is carried out from a cranked shaft of the engine through a gear belt. Internal mobile details of the fuel pump are greased with diesel fuel.

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The prevention

Do not suppose hit of diesel fuel on hoses of system of cooling. Hoses which long time influenced diesel fuel, it is necessary to replace.

The fuel system of the diesel engine is especially sensitive to pollution, therefore at work on fuel system observe the maximum cleanliness. Before рассоединением топливопроводов carefully clear them of a dirt.

Do not use compressed air for clearing of elements of the fuel system established on the engine.

At check of work of fuel atomizers never substitute hands or any part of a body under the stream of fuel leaving an atomizer. Fuel leaves an atomizer under a high pressure and can get into a body through a skin.

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