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ENGINE
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2.1.7 FUEL SYSTEM
2.1.7.1 INTRODUCTION TO VARICOR SYSTEM
1. This engine uses DELPHI high-pressure pump
and a common rail for supplying all the cylinders
with high-pressure diesel through the electronical-
ly-controlled fuel injectors. High pressure results
in better atomization which leads to complete
combustion.
2. Common-rail is a key to better diesel engine per-
formance, since more accurate high pressure
injection results in more efficient fuel combustion.
It also injects the fuel only when it is required
thereby increasing fuel efficiency. It helps the en-
gine to create a perfect blend of power and fuel
economy.
3. The brain of the VARICOR engine is the ECU
(Electronic Control Unit) which keeps the
VARICOR engine functioning at its optimal ca-
pacity. It continuously receives signal from
various sensors to calculate the timing and quan-
tity of fuel required by the engine with complete
flexibility. Besides the ECU also controls Engine
cooling electric fans, A/C, EGR, VNT and diagno-
sis etc.
4. In addition to the other sensors, the ECU also
receives continuous inputs from the rail pressure
sensor which monitors fuel pressure. The ECU
can thus keep the system pressure at an optimal
value as per the engine speed, load and various
operating conditions. For example, if the pedal is
pressed, depending on the amount of pedal de-
pression, the accelerator pedal sensor
immediately sends a signal to the ECU. The
VARICOR System has “Drive by wire” technology
where in Driver demand translation is done
through ECU.
5. The ECU determines the load required by the
engine to meet the driver demand. It then sends a
signal to the high pressure pump through the IMV
(Inlet Metering Valve)
to send the exact amount
of fuel to common rail to meet the requirement.
The Inlet Metering Valve determines the quantity
of fuel required to be pumped to the rail depend-
ing on the engine speed & load and pressurizes
the same thus avoiding wastage of fuel. This
helps in improving the fuel consumption.
6. The ECU also tells the injectors exactly when and
how much to inject, to produce the amount of
power actually needed.
7.
The high pressure pump has an internal lift pump
to draw the fuel from the fuel tank.
(In case, the
pedal is released abruptly the excess fuel is recy-
cled back into the fuel tank via the injectors,
through the venturi and fuel return lines).
8. The desired amount of fuel is pumped into the
common rail after taking into account the current
fuel pressure
(as detected by the rail pressure
sensor and sent to the ECU).
9. The fuel gets distributed through the rail to the
individual electronically controlled injectors into
the cylinders.
10.The fuel is injected into the combustion chamber
at the specified time and pressure. As a result it
increases the power output and vastly enhances
the fuel efficiency.
11.In addition the ECU commands the injectors to
inject a small amount of fuel in to the cylinder be-
fore the main injection happens. This pilot
injection helps to reduce the instantaneous com-
bustion which causes the traditional Diesel
‘Knock’. As a consequence there is far less noise,
vibration and harshness that is conventionally as-
sociated with DI diesel engines.
12.This entire process happens in tiny fractions of a
second.
13.Finally to control the emission, the EGR
(Exhaust
Gas Recirculation)
valve along with EGR cooler
does its bit to reduce nitrogen oxides and particu-
late matter content in the emissions by effectively
managing exhaust gas and unburned fuel by re-
turning it to the combustion chamber for further
combustion events.
14.The VARICOR System is equipped with Fuel filter
& fuel prefilter cum s
edimentor
designed to filter
out external particles & separate water from Die-
sel. The water sensor in Sedimentor gives an
alarm to the Driver through a Dashboard indicator
when the water level increases which indicates
presence of water in fuel.