Page 356 - Mechanic Diesel - TT

MECHANIC DIESEL - CITS

hydraulic energy instead of mechanical energy to operate fuel injectors. Working along with the engine’s ECM
(Electronic Control Module), the HEUI system provides extremely accurate control of fuel metering and timing, so
that it ensures unmatched engine performance and economy.
Unmatched engine performance and economy.
In the traditional common rail fuel system, the entire fuel line is under high pressure. With the HEUI system, fuel
remains at low pressure until it is injected into the cylinder. Fuel pressure is created hydraulically in response to
a signal from the Electronic Control Module (ECM).
The HEUI fuel system consists of four basic components
HEUI (Fig 1) Injector Uses hydraulic energy (as opposed to mechanical energy from the engine camshaft) from
pressurized engine lube oil for injection. The pressure of the incoming oil (800 to 3300 psi) controls the rate of
injection, while the amount of fuel injected is determined by the ECM.
Electronic Control Module (ECM) This sophisticated on-board computer precisely manages fuel injection and
other engine systems. The HEUI injector solenoid is energized by an electronic signal generated in the ECM.
Using input from multiple sensors, the ECM’s dual microprocessors use proprietary software and customer
supplied performance parameters to produce maximum engine performance under any conditions.
High Pressure Oil Pump The variable displacement axial pump features a built-in reservoir to immediately supply
oil at cold starts.

Injector Actuation Pressure Control Valve. This electronically operated valve controls oil pump output and injection
pressure.
Working principle
HEUI is divided in two sections. One is low pressure fuel chamber. Another one is high pressure oil chamber, fuel
is supplied at low pressure and oil is supplied at high pressure to the respective chamber.
At the time of injections allows the high pressure oil in to the injection body and actuates the intensifier. The
intensifier in turn pressurizes the diesel on the other side of it. So that the intensifier pressurizes seven times of
the oil pressure and increases the pressure of the diesel. After then the injector lifts the spindle and injects the
diesel through the holes of an injector.

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CITS : Automotive - Mechanic Diesel - Lesson 114 - 117