SsangYong Rodius (2013 year). Service manual — part 81

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4. POST-INJECTION AND AIR MASS CONTROL

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
sensor. If the temperature is less than 600℃, the amount of post-injection is increased to

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.

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Rear temperature sensor

Measure the outlet

temperature of DOC.

This sensor is located at the
rear side of DOC and
monitors the overheating of
CDPF and post injection
volume.

Differential pressure sensor

Measures the difference between

inlet and outlet pressures of CDPF.

If the difference is higher than the
specified value when collecting the
PM, this makes the post injection
for forced recycling of PM.

Front temperature sensor

Measures the temperature of

exhaust gas.

This sensor is located at the rear
side of exhaust manifold and
monitors the temperature of
combusted gas to prevent the
exhaust system from overheating.
When the temperature gets higher,
this sensor cuts off the fuel delivery
and controls the EGR to lower the
temperature.

Engine ECU (D20DTR)

T-MAP sensor

Intake air

mass

Measures

the

excessive

amount of

PM.

Injector (C31)

Controls the post injection.

Electric throttle body

Controls the intake air mass.

HFM sensor

Wide band

oxygen

sensor

Boost

pressure/

temperature

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Collecting PM

→ Regeneration

The engine ECU detects the
amount of PM collected by the
information from the
temperature sensors and
differential pressure sensor.
When the soot is accumulated,
the engine ECU performs post-
injection to increase the
exhaust gas temperature and
burns the collected PM at
approx. 600°C.

Oxidation (DOC)

When the exhaust gas enters
into the CDPF assembly, its
CO, HC and PM are reduced
by the redox reaction of the
DOC. The remaining PM is
filtered and collected in CDPF,
and the temperature of the
exhaust gas is increased to
between 450 and 500°C.

5. OPERATING PROCESS

[Configuration and principle of operation]

The exhaust gas

passed through the

exhaust manifold

enters into the CDPF

assembly (at approx
250℃).

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1) Oxidation of DOC

The DOC oxidizes HC and CO of the exhaust gas in the two-way catalytic converter at 180℃ or
more, and performs best at the temperature between 400 and 500℃. The front EGT sensor

detects whether the DOC can burn (oxidize) the post-injected fuel or not, and sends the signal to the
ECU to maintain the DOC operating temperature between 300 and 500℃. The DOC reduces

CO and HC of the exhaust gas by redox reaction and also reduces small amount of PM.

Oxygen adheres to the catalyst materials: Less than 180℃

1.

CO and HC are oxidized by the catalyst materials: More than 180℃

2.