VOLKSWAGEN GOLF IV
since 1997 of release
Repair and car operation
Foltsvagen Golf 4
+ 1. Maintenance instruction
+ 2. Engine
+ 3. Cooling system
- 4. Fuel system
+ 4.1. Cars with petrol engines
- 4.2. Cars with diesel engines
4.2.1. Direct injection of fuel
4.2.2. Fuel tank
4.2.4. Check of system of preliminary heating of the diesel engine
4.2.5. Check of candles of an incandescence
4.2.6. Removal and installation of candles of an incandescence
4.2.7. System of heating of fuel
+ 4.2.8. Fuel nozzles
4.2.9. Moment of injection of the fuel pump of a high pressure
4.2.10. Main malfunctions of a control system of the engine
+ 5. Exhaust system
+ 6. Ventilation and heating system
+ 7. Coupling
+ 8. Transmission
+ 9. Suspension brackets and power shafts
+ 10. Steering
+ 11. Wheels and tires
+ 12. Brake system
+ 13. Body
+ 14. Electric equipment and electroschemes
This type of the engine received the name by name the German engineer Rudolf Dizelya who has constructed in 1897 the first engine with spontaneous ignition of fuel. Structurally diesel engine is similar to the petrol engine: same cylinders, pistons, camshaft, valves. But there is also a number of differences from which the main thing, it is possible even to tell basic, is that fuel ignition in the diesel engine is made not by a spark from a spark plug, and at the expense of high temperature of which air as a result of compression reaches it the piston in the cylinder.
The second important point – a way of supply of fuel. In the petrol engine a working body is the gasoline mix with air. The mix prepares in advance (in the carburetor) 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 rather homogeneous toplivovozdushny mix burns down.
In the diesel engine supply of fuel and air 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 speak about a homogeneous toplivovozdushny mix it is not necessary. Injection is made at 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.
Spontaneous ignition of fuel is accompanied by sharp, spasmodic increase of pressure in the cylinder – it usually noisy, rigid operation of the diesel engine speaks. In low-turnaround diesel engines with large working volume which are used by trucks, this shortcoming is shown to a lesser extent, and with it are reconciled. In diesel engines of cars of it try to get rid use 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 main volume of the cylinder. This way reduces rigidity of operation 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.
Characteristic of diesel engines is existence of firm particles in the fulfilled gases. Because of heterogeneity of process of burning on a surface of 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. Good burning of diesel fuel needs considerable, even superfluous amount of air.
Also, extent of compression at the diesel engine in 2 times is higher, than at the petrol engine. High, not less than 14 (reaches 25), extent of compression is necessary in order that air temperature in the cylinder rose to size, sufficient for fuel ignition. Usually in diesel engines extent of compression makes 21–22 and is limited to only prochnostny characteristics of the engine.
In diesel engines it is much more difficult than the device for supply of fuel, than in petrol. Their complexity is defined first of all by that it is necessary to inject very small, only some milligram, portions of fuel on Wednesday with a high pressure. These portions should be very precisely measured – amount of submitted fuel operation of the diesel engine copes. High-speed and exact nozzles are for this purpose necessary. High extent of compression demands use of the corresponding fuel pumps – pressure in a snivel of a nozzle should reach several hundred bar. All this complicates and is notable удорожает system of supply of fuel and, respectively, 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 nozzles.
For reduction of quantity of the harmful substances containing in exhaust gases, on cars with diesel engines the oxidizing catalyst is established. Also the system of a podmeshivaniye of exhaust gases to the fresh air arriving in the engine therefore percentage of oxygen in air which will be burned in engine cylinders decreases is used. As a result of it the temperature of combustion of a fuel mix therefore the amount of the formed oxides of nitrogen decreases decreases.
Three ways of injection of diesel fuel in engine cylinders are known: through a forkamer, via the vortical chamber and direct injection.
At injection of diesel fuel through a forkamer fuel is sprayed after a forkamer and instantly ignites. Due to the insignificant amount of oxygen in a forkamer burns down only a part of fuel, and other fuel is forced out from forkamer in the engine cylinder where burns down completely.
At fuel injection via the vortical chamber process of combustion of fuel is made in the same way, as well as at fuel injection through a forkamer. Difference consists in a form and the sizes of the channel connecting the vortical chamber to the chamber of combustion. At fuel injection in the vortical chamber occurs the best hashing of fuel with air is considerable, and process of combustion is carried out more smoothly.