Content .. 381 382 383 384 ..

Frelander 2. Manual - part 383

Item

Part Number

Description

Temperature sensor

HO2S

Differential pressure sensor

High pressure sensor pipe

Low pressure sensor pipe

Diesel particulate filter

Temperature sensor

The particulate emissions are the black fumes emitted from the diesel engine under certain load conditions. The emissions
are a complex mixture of solid and liquid components with the majority of the particulates being carbon microspheres on
which hydrocarbons from the engine's fuel and lubricant condense.

The DPF system comprises the following components:

Diesel particulate filter
DPF control software incorporated into the Engine Control Module (ECM)
Differential pressure sensor.

Diesel Particulate Filter

The DPF is located in the exhaust system, downstream of the catalytic converter. A major feature of the DPF is its ability
for regeneration. Regeneration is the burning of particulates trapped by the filter to prevent obstruction to the free flow of
exhaust gasses. The regeneration process takes place at calculated intervals and is not noticeable by the driver of the
vehicle.

Regeneration is most important, since an overfilled filter can damage the engine through excessive exhaust back pressure
and can itself be damaged or destroyed. The material trapped in the filter is in the most part carbon particles with some

absorbed hydrocarbons.

Item

Part Number

Description

Front face showing alternate closed cells

Side view showing exhaust gas flow through the filter and particulate build up

Rear face showing alternate closed cells

The DPF uses a filter technology based on a filter with a catalytic coating. The DPF is made from silicon carbide housed in
a steel container and has excellent thermal shock resistance and thermal conductivity properties. The DPF is designed for
the engine's operating requirements to maintain the optimum back pressure requirements.

The porous surface of the filter consists of thousands of small parallel channels positioned in the longitudinal direction of
the exhaust system. Adjacent channels in the filter are alternately plugged at the end. This design forces the exhaust
gasses to flow through the porous filter walls, which act as the filter medium. Particulate matter which are too big to pass
through the porous surface are collected and stored in the channels.

The collected particulate matter, if not removed, can create an obstruction to exhaust gas flow. The particles are removed
by a regeneration process which incinerates the particles.

The regeneration process uses NO

to remove the particles from the DPF. The NO

is generated by the catalytic converter

upstream of the DPF. The catalytic converter produces temperatures in excess of 250°C (482°F) at which point the
regeneration process is started.

DPF regeneration is controlled by the temperature of the exhaust gasses and the DPF. The DPF includes a wash coat to the
filter surface which comprises platinum and other active components and is similar to the catalytic converter. At certain
exhaust gas and DPF temperatures the wash coat promotes combustion and incineration of the particles in addition to
oxidizing carbon monoxide and hydrocarbon emissions.

The exhaust gas and DPF temperatures are controlled by the DPF software located in the ECM. The DPF software monitors
the load status of the DPF based on driving style, distance traveled and signals from the differential pressure sensor and
temperature sensors. W hen the particulate loading of the DPF reaches predetermined levels, the DPF is actively
regenerated by adjusting, in conjunction with the ECM, various engine control functions such as:

fuel injection
intake air throttle
exhaust gas recirculation
turbocharger boost pressure control.

The regeneration process is possible because of the flexibility of the common-rail fuel injection engine which provides
precise control of fuel flow, fuel pressure and injection timing which are essential requirements to promote the efficient
regeneration process.

Two processes are used to regenerate the DPF; passive and active.

Passive Regeneration

Passive regeneration requires no special engine management intervention and occurs during normal engine operation. The
passive regeneration involves a slow conversion of the particulate matter deposited in the DPF into carbon dioxide. This
process is active when the DPF temperature reaches 250°C (482°F) and is a continuous process when the vehicle is being
driven at higher engine loads and speeds.

During passive regeneration, only a portion of the particulate matter is converted into carbon dioxide. This is due to the
chemical reaction process which is only effective within the normal operating temperature range of 250°C to 500°C (482°F
to 932°F).

Above this temperature range the conversion efficiency of the particulates into carbon dioxide increases as the DPF
temperature is raised. These temperatures can only be achieved using the active regeneration process.

Active Regeneration

Active regeneration starts when the particulate loading of the DPF reaches a threshold as monitored or determined by the
DPF control software. The threshold calculation is based on driving style, distance traveled and back pressure signals from
the differential pressure sensor.

Active regeneration generally occurs every 450 miles (725 km) although this is dependant on how the vehicle is driven. For
example, if the vehicle is driven at low loads in urban traffic regularly, active regeneration will occur more often. This is
due to the rapid build-up of particulates in the DPF than if the vehicle is driven at high speeds when passive regeneration
will have occurred.

The DPF software incorporates a mileage trigger which is used as back-up for active regeneration. If active regeneration
has not been initiated by a back pressure signal from the differential pressure sensor, regeneration is requested based on
distance traveled.

Active regeneration of the DPF is commenced when the temperature of the DPF is increased to the combustion temperature
of the particles. The DPF temperature is raised by increasing the exhaust gas temperature. This is achieved by introducing
post-injection of fuel after the pilot and main fuel injections have occurred.

This is determined by the DPF software monitoring the signals from the two DPF temperature sensors to establish the
temperature of the DPF. Depending on the DPF temperature, the DPF software requests the ECM to perform either one or
two post-injections of fuel:

The first post-injection of fuel retards combustion inside the cylinder which increases the temperature of the
exhaust gas.
The second post-injection of fuel is injected late in the power stroke cycle. The fuel partly combusts in the cylinder,
but some unburnt fuel also passes into the exhaust where it creates an exothermic event within the catalytic
converter, further increasing the temperature of the DPF.

The active regeneration process takes approximately 20 minutes to complete. The first phase increases the DPF
temperature to 500°C (932°F). The second phase further increases the DPF temperature to 600°C (1112°F) which is the
optimum temperature for particle combustion. This temperature is then maintained for 15-20 minutes to ensure complete
incineration of the particles within the DPF. The incineration process converts the carbon particles to carbon dioxide and
water.

The active regeneration temperature of the DPF is closely monitored by the DPF software to maintain a target temperature
of 600°C (1112°F) at the DPF inlet. The temperature control ensures that the temperatures do not exceed the operational
limits of the turbocharger and the catalytic converter. The turbocharger inlet temperature must not exceed 830°C (1526°F)
and the catalytic converter brick temperature must not exceed 800°C (1472°F) and the exit temperature must remain
below 750°C (1382°F).

During the active regeneration process the following ECM controlled events occur:

The turbocharger is maintained in the fully open position. This minimizes heat transmission from the exhaust gas
to the turbocharger and reduces the rate of exhaust gas flow allowing optimum heating of the DPF. If the driver
demands an increase in engine torque, the turbocharger will respond by closing the vanes as necessary.
The throttle is closed as this assists in increasing the exhaust gas temperature and reduces the rate of exhaust
gas flow which has the effect of reducing the time for the DPF to reach the optimum temperature.
The Exhaust Gas Recirculation (EGR) valve is closed. The use of EGR decreases the exhaust gas temperature and
therefore prevents the optimum DPF temperature being achieved.

If, due to vehicle usage and/or driving style, the active regeneration process cannot take place or is unable to regenerate
the DPF, the dealer can force regenerate the DPF. This is achieved by either driving the vehicle until the engine is at its
normal operating temperature and then driving for a further 20 minutes at speeds of not less than 30 mph (48 km/h) or by
connecting a Land Rover approved diagnostic system to the vehicle which will guide the technician through a regeneration
procedure to clean the DPF.

Diesel Particulate Filter Control

The DPF requires constant monitoring to ensure that it is operating at its optimum efficiency and does not become
blocked. The ECM contains DPF software which controls the monitoring and operation of the DPF system and also monitors
other vehicle data to determine regeneration periods and service intervals.

The DPF software can be divided into three separate control software modules; a DPF supervisor module, a DPF fuel
management module and a DPF air management module.

These three modules are controlled by a fourth software module known as the DPF co-ordinator module. The co-ordinator
module manages the operation of the other modules when an active regeneration is requested. The DPF supervisor module
is a sub-system of the DPF co-ordinator module.

DPF Fuel Management Module

The DPF fuel management module controls the following functions:

Timing and quantity of the four split injections per stroke (pilot, main and two post injections).
Injection pressure and the transition between the three different calibration levels of injection.

The above functions are dependant on the condition of the catalytic converter and the DPF.

The controlled injection determines the required injection level in addition to measuring the activity of the catalytic
converter and the DPF. The fuel management calculates the quantity and timing for the four split injections, for each of
the three calibration levels for injection pressure, and also manages the transition between the levels.

The two post injections are required to separate the functionality of increasing in-cylinder gas temperatures and the
production of hydrocarbons. The first post injection is used to generate the higher in-cylinder gas temperature while
simultaneously retaining the same engine torque output produced during normal (non-regeneration) engine operation. The
second post injection is used to generate hydrocarbons by allowing unburnt fuel into the catalytic converter without
producing increased engine torque.

DPF Air Management Module

The DPF air management module controls the following functions:

EGR control
Turbocharger boost pressure control
Intake air temperature and pressure control.

During active regeneration, the EGR operation is disabled and the closed-loop activation of the turbocharger boost
controller is calculated. The air management module controls the air in the intake manifold to a predetermined level of
pressure and temperature. This control is required to achieve the correct in-cylinder conditions for stable and robust
combustion of the post injected fuel.

The module controls the intake air temperature by actuating the EGR throttle and by adjustment of the turbocharger boost
pressure control.

DPF Co-ordinator Module

The DPF co-ordinator module reacts to a regeneration request from the supervisor module by initiating and co-ordinating
the following DPF regeneration requests:

EGR cut-off
Turbocharger boost pressure control
Engine load increase
Control of air pressure and temperature in the intake manifold
Fuel injection control.

When the supervisor module issues a regeneration request, the co-ordinator module requests EGR cut-off and a
regeneration specific turbocharger boost pressure control. It then waits for a feedback signal from the EGR system
confirming that the EGR valve is closed.

When the EGR valve is closed, the co-ordinator module initiates requests to increase engine load by controlling the intake
air temperature and pressure.

Once confirmation is received that intake conditions are controlled or a calibration time has expired, the co-ordinator
module then changes to a state awaiting an accelerator pedal release manoeuver from the driver. If this occurs or a
calibration time has expired, the co-ordinator module generates a request to control fuel injections to increase exhaust
gas temperature.

Differential Pressure Sensor

Item

Part Number

Description

High pressure connection

Low pressure connection

Electrical connector

The differential pressure sensor is located in the engine compartment, on the lower RH side of the bulkhead. The sensor is
located on two studs and secured with nuts.

The differential pressure sensor is used by the DPF software to monitor the condition of the DPF. Two pipe connections on
the sensor are connected by pipes to the inlet and outlet ends of the DPF. The pipes allow the sensor to measure the inlet
and outlet pressures of the DPF.

As the amount of particulates trapped by the DPF increases, the pressure at the inlet side of the DPF increases in
comparison to the DPF outlet. The DPF software uses this comparison, in conduction with other data, to calculate the
accumulated amount of trapped particulates.

By measuring the pressure difference between the DPF inlet and outlet and the DPF temperature, the DPF software can
determine if the DPF is becoming blocked and requires regeneration.

Differential Particulate Filter Temperature Sensors

Two temperature sensors are used in the DPF system. One is located in the turbocharger outlet elbow, adjacent to the
HO2S and the second sensor is located in the DPF inlet.

The sensors measure the temperature of exhaust gas exiting the turbocharger and before it passes through the DPF and
provides the information needed to calculate the DPF temperature.

The information is used, in conjunction with other data, to estimate the amount of accumulated particulates and to control

Content .. 381 382 383 384 ..