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DESCRIPTION AND OPERATION
MANUAL REGENERATION
A procedure called “Manual Regeneration” can
be used to regenerate the filters while they
remain in the vehicle. The VCADS service tool or
the Premium Tech Tool can be used to perform
this function.
The exhaust system reaches extremely high
temperatures. Ensure that the system
components are clear of all combustible
materials. Ensure that personnel are aware
that the surfaces are extremely hot. Failure to
heed this warning may result in severe
personal injury and property damage.
ULTRA LOW SULFUR DIESEL FUEL
A catalyst works better the higher the
temperature up to about 400°C (750°F). Above
this temperature, sulfur can become sulfuric acid.
These filtering systems are practical only on
vehicles that use ultra low sulfur fuels. It is
required that diesel engines operating in
conjunction with a DPF system use ultra low
sulfur fuel that contains 15 parts per million
(ppm), or less, of sulfur.
OPERATIONAL MODES
The exhaust aftertreatment system (EATS)
usually operates in one of five modes.
앫 Normal Mode
앫 Heat Mode
앫 Passive Regeneration Mode
앫 Active Regeneration Mode
앫 Service Mode
In the Normal Mode, the engine is controlled by
its regular calibration. However, the filters can be
self-cleaning through passive regeneration. Heat
Mode indicates that active regeneration is in
process. In Passive Regeneration Mode, the
engine creates sufficient exhaust temperature to
convert the gases and regenerate (clean) the
filters. In Active Regeneration Mode, exhaust
temperature is artificially raised for short periods
of time to convert the gases and clean the filters.
The applicable controller reacts to data from back
pressure sensors to start and stop the active
regeneration process. A system in Service Mode
is being inspected for accumulation of soot and
ash in the filters to determine whether they
should be manually regenerated or removed for
external regeneration.
DPF SYSTEM VEHICLE MOUNTING
The catalyzed DPF system (Figure 36) is either a
vertical back-of-cab (VBOC) DPF unit with muffler
or a space saver (MACK Cap) DPF unit with
muffler for the conventional chassis. The space
saver unit attaches to the outside of the right rail
under the cab. For the cabover and low cab
forward chassis, the non-catalyzed vertical
back-of-cab design (Figure 37) in which the
combustion chamber is in the structure
back-of-cab is used.
36
Figure 36 — Catalyzed DPF Units — Vertical
Back-of-Cab and Space Saver
1. Vertical Back-of-Cab Unit 2. Space Saver Unit
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