Page 243 - 05. Subyek Teknik Mesin - Automobile Mechanical and Electrical Systems Automotive Technology Vehicle Maintenance and Repair (Vehicle Maintenance Repr Nv2) by Tom Denton

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Engine systems 227

Figure 2.298 Common rail system. (Source: Bosch Media)

Figure 2.299 Four-cylinder system. (Source: Bosch Media)

The Bosch VR electronic diesel control system uses a number of sensors and
control actuators. This allows it to achieve optimum performance. However, even
this sophisticated system has virtually been superseded, so read on to discover
more about the common rail system!

2.5.3.2 Common rail system
The development of diesel fuel systems is continuing, with many new electronic
changes to the control and injection processes. One of the latest developments
is the common rail (CR) system, which operates at very high injection pressures
( Fig. 2.298 ). It also has piloted and phased injection to reduce noise and
vibration.

The common rail system has made it easier for small high-speed diesel
Key fact
engines to have all the advantages of direct injection ( Fig. 2.299 ). These
developments have resulted in signifi cant improvements in fuel consumption The combustion process, with
common rail injection, is improved
and performance.
by a pilot injection of a very small
The combustion process, with common rail injection, is improved by a pilot quantity of fuel, at between 40° and
injection of a very small quantity of fuel, at between 40° and 90° before top 90° BTDC.
dead centre (BTDC). This pilot fuel ignites in the compressing air charge so that
the cylinder temperature and pressure are higher than in a conventional diesel