01-23
ENGINE GENERAL
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1) CLEANNESS OF DI ENGINE FUEL SYSTEM AND SERVICE
PROCEDURES
10. CLEANNESS
The fuel system for DI engine consists of transfer (low pressure) line and high pressure line. Its
highest pressure reaches over 1600 bar. Some components in injector and HP pump are
machined at the micrometer 100 μm of preciseness. The pressure regulation and injector
operation are done by electric source from engine ECU. Accordingly, if the internal valve is
stucked due to foreign materials, injector remains open. Even in this case, the HP pump still
operates to supply high pressurized fuel. This increases the pressure to combustion chambe
(over 250 bar) and may cause fatal damage to engine.
You can compare the thickness of injector nozzle hole and hair as shown in below figure (left
side). The right side figure shows the clearance between internal operating elements.
The core elements of fuel system has very high preciseness that is easily affected by dust o
very small foreign material. Therefore, make sure to keep the preliminary works and
ob
procedures in next pages. If not, lots of system problems and claims may arise.
Hair
Valve actuator lift: 0.028 mm
Operating
clearance:
0.002 mm
Diameter:
2.0 mm
Diameter: 0.40 mm
Nozzle hole
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