Page 55 - E BOOK ENGINE MECHANICAL M2

3. FUEL SYSTEM

1. GENERAL
A common rail fuel injection system is developed in order to comply with current increasingly-strict
exhaust gas regulations, and it is completely different from the fuel system equipped with a conven-
tional injection pump. A common rail fuel injection system is composed of parts including a supply
pump, common rail, injectors, sensors which convert the engine operating conditions to electrical
signals, and an Engine-ECU which controls these components.
The followings are the components related to the common rail fuel supply system:
◆ Fuel injector assembly (to be explained in the section: Common rail fuel system)
◆ Supply pump assembly
◆ Common rail assembly
◆ Fuel tank assembly
◆ Fuel filter assembly

The common rail fuel injection system has the following
characteristics that a conventional diesel fuel injection
system does not have.
◆ The injection of fuel can be delivered at extremely
high & variable pressures to reduce the particular
matter (PM) emissions.
◆ Because of the electronic control, there is a wide
operational range to deliver the injection quantity,
injection timing, and injection pattern. This
achieves the optimal injection for every condition,
while it reduces NOx and PM emissions.
◆ An air flow sensor and the electronic controlled
throttle valve are used like in a gasoline engine with
MPI system, but in common rail diesel the air flow
sensor is used to calculate the EGR ratio, and the
Fig. 3-1 throttle vale to suffocate the engine.

<Why common rail fuel injection system is required?>
Common rail fuel injection system has the following features compared to the ordinary diesel en-
gine with the mechanical fuel injection pump. The advantages of the common rail can be achieved
by higher injection pressure, improved atomization, multiple injection, etc.

Fig. 3-2

3 - 1 Pub. No. PTAE1228