EPA07 Aftertreatment System
(ATS)
On-road diesel engines built after December 31,
2006 are required to meet EPA07 guidelines for re-
duced exhaust emissions of particulate matter and
nitrogen oxides (NOx). NOx is limited to just over 1
gram per brake horsepower hour (g/bhp-hr), and par-
ticulate matter cannot exceed 0.01 g/bhp-hr.
EPA07-compliant engines require ultralow-sulfur die-
sel (ULSD) fuel, and they should never be run on
fuel with sulfur content higher than 15 ppm. In addi-
tion, they require low-ash engine oil. The following
guidelines must be followed, or the warranty may be
compromised.
•
Use ultralow-sulfur diesel (ULSD) with 15 ppm
sulfur content or less, based on ASTM D2622
test procedure.
•
Do not use fuel blended with used engine lube
oil.
•
Engine lube oil must have a sulfated ash level
less than 1.0 wt %, meeting the API CJ-4 index
specifications.
IMPORTANT: Using non-specification fuels or
oils can lead to shortened diesel particulate filter
(DPF) cleaning or exchange intervals. For ex-
ample, using CI-4+ oil with 1.3% sulfated ash
(30% more ash content) may result in the need
for DPF cleaning or exchange 20 to 30% sooner
than would normally be required.
The "exhaust system" in EPA07-compliant vehicles is
called the aftertreatment system (ATS). The ATS var-
ies according to engine manufacturer and vehicle
configuration, but instead of a muffler, an aftertreat-
ment system has a device that outwardly resembles
a muffler, called the aftertreatment device (ATD).
IMPORTANT: See your engine operation manual
for complete details and operation of the after-
treatment system.
Inside the ATD on Mercedes-Benz, Detroit Diesel,
and Cummins engines, the exhaust first passes over
the diesel oxidation catalyst (DOC), then it passes
through the diesel particulate filter (DPF), which traps
soot particles. If exhaust temperature is high enough,
the trapped soot is reduced to ash, in a process
called passive regeneration (regen). Passive regen-
eration occurs as the vehicle is driven normally
under load; the driver is not even aware that it is
happening. The harder an EPA07 engine works, the
better it disposes of soot, as the exhaust heat alone
is enough to burn the soot to ash. Over the course of
a workday, however, passive regeneration cannot
always keep the ATD filter clean, so the filter must
undergo active regeneration. In active regeneration,
extra fuel is injected into the exhaust stream to su-
perheat the soot trapped in the DPF and turn it to
ash. Active regeneration happens only when the ve-
hicle is moving above a certain speed, determined by
the engine manufacturer. Consult manufacturers’
documentation for details.
Both active and passive regeneration happen auto-
matically, without driver input.
NOTE: Caterpillar engines do not use a DOC;
CAT engines burn diesel fuel at the regeneration
head to superheat the exhaust and burn the
trapped soot to ash. Engine software monitors
and controls this process.
Only when operating conditions do not allow for ATD
filter cleaning by at-speed active or passive regen-
eration, the vehicle may require a driver-activated
parked regeneration. The vehicle must be standing
still, and the driver must initiate a parked regen.
Completing a parked regen takes 20 minutes to an
hour, depending on ambient conditions.
DANGER
During parked regeneration, exhaust tempera-
tures are very high, and could cause a fire, heat
damage to objects or materials, or personal in-
jury to persons near the exhaust outlet.
Before initiating a parked regeneration, make cer-
tain the exhaust outlets are directed away from
structures, trees, vegetation, flammable materi-
als, and anything else that may be damaged or
injured by prolonged exposure to high heat.
The warning lamps in the driver message center alert
the driver of a regen in progress, high exhaust tem-
peratures, the need to perform a parked regen either
soon or immediately, and of an engine fault that af-
fects the emissions.
A slow (10-second) flashing of the high exhaust sys-
tem temperature (HEST) lamp indicates that a
parked regeneration is in progress, and the engine’s
Engines and Clutches
7.1
To Next Page
Loading...
