Hyundai Elantra

since 2000-2004 of release

Repair and car operation

Characteristics of system of injection

Characteristics of usual system of injection

In usual systems of injection of fuel with the switching center and the pump of direct injection the system of injection includes only the main phase of injection – without control and late injection. On the distributive fuel pump with electromagnetic management of action occur to approach to a control phase of injection of fuel. In usual systems of operation of creation of pressure and adjustment of amount of injected fuel are connected with each other at the expense of interaction of a cam and a plunzher of the fuel pump. It makes the following impact on characteristics of injection of fuel:

– pressure of injection increases together with increase in speed and amount of air arriving in the engine;
– during the actual process of injection pressure of injection increases and then decreases to final pressure of injection.

As a result of it the following consequences take place:

– the smaller amount of fuel with lower pressure, than amount of air arriving in the engine is injected;
– peak pressure makes more than the doubled average value of pressure of injection;
– according to requirements for effective combustion the curve of speed of unloading actually is triangular.

Peak pressure is solving for mechanical loading of elements of the fuel pump and its drive. On usual systems of injection of fuel it is solving for quality of formation of a mix in the combustion chamber.

Characteristics of system of injection of "Common Rail" (storage fuel system)

In comparison with usual systems of injection for obtaining the ideal characteristic of injection it is necessary to fulfill the following requirements:

– for each operational mode of the engine division of the knot creating pressure, and knot of injection of fuel is necessary;
– during the initial moment of injection the amount of injected fuel should be low as far as it is possible (i.e. the lag effect between the initial moment of injection and the ignition beginning) should be considered.

These requirements are carried out by system of injection of "Common Rail" – storage fuel system – with its control and main phases of injection.

«Common Rail» represents block system and, in fact, the following knots are responsible for the characteristic of injection of fuel:

– nozzles with the electromagnetic management, screwed in a head of cylinders;
– accumulator of a high pressure (rail);
– fuel pump of a high pressure.

Also the following knots are necessary for functioning of system:

– electronic control ECU device;
– sensor of frequency of rotation of a cranked shaft;
– sensor of provision of a camshaft (phase sensor).

In cars for creation of pressure the radial piston pump of a high pressure, thus pressure is used created irrespective of process of injection of fuel. Productivity of the pump is directly proportional to frequency of rotation of a cranked shaft of the engine. In comparison with usual systems of injection the actual forcing of fuel is homogeneous, i.e. in Common Rail the fuel pump of a high pressure not only has the smaller sizes, but also its drive is to a lesser extent subject to peak loadings.

Fuel nozzles are connected to a lath short pipelines and, in essence, include sprays and the solenoidal valve operated by ECU. After tension interruption of supply on the solenoidal valve injection of fuel stops. Assuming constant pressure, amount of injected fuel in direct ratio to an interval of time during which the solenoidal valve is open. This process is completely independent of frequency of rotation of a cranked shaft of the engine and frequency of rotation of the pump (fuel injection depending on time).

High-speed switching of the solenoid is reached at the expense of use of a high voltage and a current. It means that it is necessary to use specially developed solenoidal valve providing a platform at the moment of opening. The moment of injection is defined by EDC control system (Electronic Diesel Control – Electronic control by the diesel engine) which uses the sensor of frequency of rotation of a cranked shaft and the sensor of provision of a camshaft for phase definition of a running cycle.