SsangYong Rodius (2013 year). 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.