Regeneration; Passive Regeneration; Active Regeneration - Mercedes-Benz OM 471 Introduction Into Service Manual

Function
The exhaust, which has been pre>cleaned by the diesel oxidation
catalytic converter (DOC) (4), flows through the filter element in
the diesel particulate filter (DPF) (5). The soot particles are
retained in its porous honeycomb structure.
The effectiveness of the diesel particulate filter (DPF) (5) is so high
that about 90 % of the particulate mass and approx. 95 % of the
number of particles can be retained.
The exhaust aftertreatment control unit (ACM) (A60) can calculate
the current load condition of the diesel particulate filter (DPF) (5)
via the signal evaluations of the pressure and temperature sensors
attached to the inlet and the outlet of the exhaust aftertreatment
unit, and initiate regeneration measures via the engine
management control unit (MCM (A4).
In spite of passive and active regeneration, the diesel particulate
filter (DPF) (5) does not have an unlimited service life and
therefore requires regular maintenance.
>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>

Active regeneration

For active regeneration, diesel fuel is added to the exhaust flow
via the diesel fuel metering device. Extremely high temperatures
occur in the exhaust aftertreatment unit during the ensuing
reaction.The deposited soot is burned and turns into ash.
Whereas passive regeneration takes place unnoticed in the
background, when active regeneration occurs an indication is
given, and in some cases the driver is requested to initiate active
regeneration at the next opportunity. Regeneration can be
interrupted, but this must be avoided if possible.
i Introduction of engine OM 471 and exhaust aftertreatment > 09/2011 >
– This printout will not be recorded by the update service. Status: 09 / 2011 –
System components

Regeneration

The diesel particulate filter (DPF) (5) regenerates itself more or less
independently. This is achieved using a passive self>cleaning
mechanism. This passive regeneration is based on CRT technology
(Continuously Regenerating Trap).
If a certain condition is reached in which passive regeneration is
not longer sufficient, active regeneration is initiated.

Passive regeneration

Passive regeneration takes place imperceptibly to the driver while
the vehicle is being driven. Because of the diesel oxidation
catalytic converter (DOC) (4) upstream of the diesel particulate
filter (DPF) (5) the exhaust contains carbon dioxide (CO
of carbon monoxide (CO). This reacts with the soot particles on
the oxidization layer of the filter element. This exothermic
reaction releases heat, meaning that some of the deposited soot
particles combust when a temperature of approx. 250 ∞C is
reached.
>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>
Basically, the regeneration duration is variable and is calculated
on the basis of sensor signals, recorded values, the distance driven
since the previous regeneration and the different operating
ranges of the engine.
When the diesel particulate filter (DPF) (5) has reached its filling
limit and active regeneration is no longer possible, it must be
cleaned or replaced by a specialist workshop.
) instead
2
219