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3. INPUT/OUTPUT DEVICES
Front temperature sensor: This sensor is installed at the inlet of DOC and detects whether the DOC
can burn (oxidize) the post-injected fuel or not.
Rear temperature sensor: This sensor is installed at the inlet of DPF and monitors that the 1.
2.
post-injection is decreased.
amount of fuel post-injection is increased. -
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Differential pressure sensor: This sensor checks the amount of PM collected by calculating the
pressure difference between before and after the CDPF.
Electric throttle valve: This valve reduces the intake air flow to raise the temperature of the exhaust
gas when the CDPF is operating during idling. 3.
4.
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A DPS (Differential Pressure Sensor) measures the pressure difference between before and after the
CDPF and detects whether the soot is collected in the CDPF or not. If PM is collected in the CDPF (In
this case the pressure difference between before and after the CDPF exceeds the specified value.
Normally, the system sends the signal when the driving distance becomes approx. 600 to 1,200 km), the
temperature of exhaust gas is increased and the post-injection is started for regeneration. The amount of
fuel post-injection is controlled by the exhaust gas temperature measured by the rear temperature
increase the regeneration temperature. Otherwise, the fuel injection amount is decreased or the fuel is
not injected.
When the engine is running with low load, the intake air amount is also controlled as well as fuel injection
amount. This function is used to increaser the combustion temperature by increasing the amount of fuel
post-injection with the lowest air amount within the specified control logic.
4. POST-INJECTION AND AIR MASS CONTROL
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ECU (DCM 3.7)
T-MAP sensorIntake air
volume
Detecting
excess of PM
amount limit
Boos
t
pressure
/
temperature
Front EGT sensor
Measures the temperature of
DOC.
The DOC performs the redox
reaction at between 300 and
sensor monitors the
temperature of DOC.
Differential pressure sensor
Measures the pressure values
of before and after the CDPF.
The pressure difference
between before and after the
CDPF is measured by the
differential pressure sensor (If
PM is collected in the CDPF,
the pressure difference
between before and after the
CDPF exceeds the specified
value).
Rear EGT sensor
Measures the temperature of
DPF.
The DPF burns the soot with
hot exhaust gases
(regeneration) at around
sensor monitors the
temperature of DPF.
Injector (C3I)
Controls the post-injection.
Electric throttle body
Controls the intake air
volume.
HFM sensor
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1. ENGINE DATA LIST
Data Unit Value
Coolant temperature
Intake air temperature
temperature or engine mode)
Idle speed rpmA/T
M/T
Engine load % 18~25%
Mass air flow kg/h 16 to 25 kg/h
Throttle position angle
Engine torque Nm varies by engine conditions
Injection time ms 3 to 5ms
Battery voltage V 13.5 V to 14.1 V
Accelerator pedal position 1 V 04. to 4.8V
Accelerator pedal position 2 V 0.2 to 2.4 V
Throttle position 1 V 0.3 to 4.6 V
Throttle position 2 V 0.3 to 4.6 V
Oxygen sensor mV 0 to 5 V
A/C compressor switch 1=ON / 0=OFF -
Full load 1=ON / 0=OFF -
Gear selection (A/T) 1=ON / 0=OFF -
Knocking control 1=ON / 0=OFF -
Brake switch 1=ON / 0=OFF -
Cruise control 1=ON / 0=OFF -
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HFM
Accelerator pedalCoolant
temperature
(4) Swirl control
a. Overview
Variable swirl valve -
The strong swirl caused by intake air is important element for anti-locking function in diesel engine. The
swirl control valve partially closes the intake port to generate the swirl according to the engine conditions.
When the engine load is in low or medium range, the swirl could not be generated because the air flow
is slow. To generate strong swirl, there are two passages in intake manifold, and one of them has the
valve to open and close the passage. When the valve closes the passage, the air flow through the
another passage will be faster, and the strong swirl will be generated by the internal structure of the
passage. This swirl makes the better mixture of air and fuel, eventually the combustion efficiency in
combustion chamber could be improved. This provides the enhanced fuel consumption, power and
EGR ratio.
Components -
D20DTF ECU
Crankshaft
position sensor
Variable swirl
valve
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c. Types of swirl
Swirl: One cylinder has two intake air ports, one is set horizontally
and the other one is set vertically. Swirl is the horizontal air flows in
cylinder due to the horizontal intake air ports.
Tumble: Tumble is the vertical air flows in cylinder due to the vertical
intake air port
Squish: Squish is the air flows due to the piston head. Normally, this
is appears at the final process of compression. In CRDi engine, the
piston head creates the bowl type squish.
d. Swirl control
In DI type diesel engine, the liquefied fuel is injected into the cylinder directly. If the fuel is evenly
distributed in short period, the combustion efficiency could be improved. To get this, there should be
good air flow in cylinder. In general, there are two intake ports, swirl port and tangential port, in each
cylinder. The swirl port generates the horizontal flow and the tangential port generates the longitudinal
flow.
In low/mid load range, the tabgential port is closed to increase the horizontal flow. Fast flow decreases
the PM during combustion and increases the EGR ratio by better combustion efficiency.
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Load Engine speed Swirl
valveAmount of
swirlRemarks
Low speed,
Low loadbelow 3,000 rpm Closed HeavyIncreased EGR ratio, better air-fuel
mixture (reduce exhaust gas)
High speed,
High loadover 3,000 rpm Open LightIncrease charge efficiency, higher
engine power
The variable swirl valve actuator operates when
turning the ignition switch ON/OFF position to
open/close the swirl valve. In this period, the soot
will be removed and the learning for swirl valve
position is performed.
Swirl valve
Swirl: This is the twisted (radial) air flow along the cylinder wall during the intake stroke. This stabilizes
the combustion even in lean air-fuel mixture condition.
e. Features
Swirl and air intake efficiency
To generate the swirl, the intake port should be serpentine design. This makes the resistance in air
flow. The resistance in air flow in engine high speed decreases the intake efficiency. Eventually, the
engine power is also decreased, Thus, the swirl operation is deactivated in high speed range to
increase the intake efficiency.
Relationship between swirl and fuel injection pressure
The injector for DI engine uses the multi hole design. For this vehicle, there are 8 holes in injector. If
the swirl is too strong, the injection angles might be overlapped and may cause the increased PM and
insufficient engine power. Also, if the injection pressure is too high during strong swirl, the injection
angles might be overlapped. Therefore, the system may decreases the fuel injection pressure when
the swirl is too strong. -
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f. Relationship between swirl and fuel injection pressure
The injector for DI engine uses the multi hole design. For this vehicle, there are 8 holes in injector. If
the swirl is too strong, the injection angles might be overlapped and may cause the increased PM and
insufficient engine power. Also, if the injection pressure is too high during strong swirl, the injection
angles might be overlapped. Therefore, the system may decreases the fuel injection pressure when
the swirl is too strong. -
Anti-knock methods:
Shorten the ignition timing by pilot injection, lessen the fuel injection volume during ignition delay
period.
Increase engine speed.
Maintain intake sir temperature with intercooler or glow plug device.
Increase intake air pressure with turbocharger.
Warm up engine to keep the normal operating temperature.
Increase compression ratio.
Use the fuel with high cetane. *
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