Fleet Maintenance - 14

Heavy duty engine

Reducing emissions and improving efficiency
have been at the forefront of truck engine
and aftertreatment system design.
By Erica Schueller

all three aftertreatment systems - the DOC, DPF,
and SCR.
Active thermal management refers to improvements to the actual process of emissions reduction
while the vehicle is in operation. Some examples
of active thermal management include engine
throttling, heated aftertreatment systems, and
flow bypass filters.
A variety of technologies are currently in developmental or testing phases to determine their
viability on the next generation of heavy duty
diesel trucks.

Variable valve actuation


rompted by federal regulations, engine
manufacturers have created systems and
methods to reduce emissions in four primary
categories: particulate matter, hydrocarbons,
carbon monoxide, and nitrogen oxide (NOx).
While the exact numbers of emissions reductions
don't matter to the fleet operations, fleets must
be aware of the different technologies and how
design and functionality may change.
A number of new engine and emissions system
technologies are on the horizon to help further
improve vehicle efficiency while continuing to
enhance powertrain performance.
The aftertreatment system in particular is an
integral part of the powertrain, designed especially to help reduce greenhouse gas (GHG) emissions. The aftertreatment system is made up by
a number of segments, including an exhaust gas
recirculation (EGR) system to reduce emissions
through the collection of particulate matter and
soot - most often collected via the diesel particulate filter (DPF); a diesel oxidation catalyst (DOC)
to reduce hydrocarbons and carbon monoxide
output; and the select catalytic reduction (SCR)
system to reduce NOx. The SCR catalyst uses diesel
exhaust fluid (DEF) in order to operate effectively.

14 Fleet Maintenance | February 2020

»»A number of new engine and emissions
system technologies are on the horizon
to help improve vehicle efficiency and
enhance powertrain performance.
Photo courtesy of Volvo Trucks North America

The aftertreatment system is often subject to
additional challenges for fleets running at lower
speeds or in urban environments. This is because
the numerous systems work together most effectively at hot operating temperatures that are hard
to reach in certain duty cycles.
Thermal management engine technologies in
development today may help to optimize engine
combustion, improve air handling, reduce friction,
improve catalytic aftertreatment technologies,
and waste heat recovery - even for low-speed or
low-load applications.
Passive thermal management designs aim to
address changes to the aftertreatment system
through using lighter weight materials, insulation techniques, restructuring system designs
to place components working in unison closer
in proximity to one another (moving the turbocharger closer to the SCR inlet, for instance), and
considerations using the same substrate across

Variable valve actuation (VVA) is a modular
design approach integrated into the valvetrain.
VVA works by adjusting the timing on one or more
of the engine intake valves or exhaust valves.
The VVA capsule is controlled through oil pressure, according to Dr. Mihai Dorobantu, director of
technology planning and government affairs for
vehicle power management provider Eaton Corp.
"It's one technology that - depending on how
it's integrated into the valvetrain - allows you
to modify the timing, or the lift, of the [intake
or exhaust] valves, or to deactivate the valves
completely," Dr. Dorobantu explains. "It's an
oil-controlled capsule that modifies the amount
of movement being transmitted from the camshaft
to the valve itself. It modifies the way the valve
[operates] with respect to the camshaft."
Because these valves are oil-controlled, it is
imperative for engine oil checks and proper oil
change intervals to be completed, along with using
the appropriately specified engine oil weight and
viscosity for these next generation engines.
Modified timing of the valves means they could
be opened earlier or later - this refers to an early
intake valve closing (EIVC) and late intake valve
closing (LIVC) respectively. The third modification, cylinder deactivation (CDA), means the
valves would close off the cylinder completely.
In other words, these valves assist to limit the
number of cylinders operating at a given time.
This method can help to periodically restrict
airflow to the engine, raising the temperature in
the still-operating cylinders. This process can be
particularly beneficial at low speeds and/or low
loads. This allows the SCR catalyst to reach a high
enough operating temperature more quickly, initiating the aftertreatment process sooner.
"The goal of this is primarily to reduce the
sub-volume of the engine - so you have a 6-cylin-


Fleet Maintenance

Table of Contents for the Digital Edition of Fleet Maintenance

Vehicles: What's Next in Federal Vehicle Emissions Standards?
In the Bay: Technician Tool Support
Shop Operations: State of the Industry
Taking the Extra Step to Prevent Wheel-offs
Planning Ahead for Vehicle Cybersecurity Threats
Management: How Do You Know When to Replace a Vehicle?
Economic Outlook: Won't Get Fooled Again
Letter from the Editor: Real-world Views on Parts, Service, and Operations
Tools & Equipment
Guest Editorial: Moisture in Trailer Brakes is Not Just a Nuisance
Hand & Specialty Tools Supplement
Specialty Hand Tools: The Problem Solvers
Time to Multitask
Get a Hold on Hand Tool Safety
Electric Vehicle Tool Set
Tool Review
Fleet Maintenance - 1
Fleet Maintenance - 2
Fleet Maintenance - 3
Fleet Maintenance - 4
Fleet Maintenance - 5
Fleet Maintenance - 6
Fleet Maintenance - 7
Fleet Maintenance - 8
Fleet Maintenance - 9
Fleet Maintenance - Vehicles: What's Next in Federal Vehicle Emissions Standards?
Fleet Maintenance - 11
Fleet Maintenance - 12
Fleet Maintenance - 13
Fleet Maintenance - 14
Fleet Maintenance - 15
Fleet Maintenance - 16
Fleet Maintenance - 17
Fleet Maintenance - 18
Fleet Maintenance - 19
Fleet Maintenance - 20
Fleet Maintenance - 21
Fleet Maintenance - 22
Fleet Maintenance - 23
Fleet Maintenance - 24
Fleet Maintenance - 25
Fleet Maintenance - In the Bay: Technician Tool Support
Fleet Maintenance - 27
Fleet Maintenance - 28
Fleet Maintenance - 29
Fleet Maintenance - Shop Operations: State of the Industry
Fleet Maintenance - 31
Fleet Maintenance - 32
Fleet Maintenance - 33
Fleet Maintenance - 34
Fleet Maintenance - 35
Fleet Maintenance - 36
Fleet Maintenance - 37
Fleet Maintenance - Taking the Extra Step to Prevent Wheel-offs
Fleet Maintenance - 39
Fleet Maintenance - Planning Ahead for Vehicle Cybersecurity Threats
Fleet Maintenance - 41
Fleet Maintenance - 42
Fleet Maintenance - 43
Fleet Maintenance - Management: How Do You Know When to Replace a Vehicle?
Fleet Maintenance - 45
Fleet Maintenance - Economic Outlook: Won't Get Fooled Again
Fleet Maintenance - 47
Fleet Maintenance - Letter from the Editor: Real-world Views on Parts, Service, and Operations
Fleet Maintenance - 49
Fleet Maintenance - 50
Fleet Maintenance - Tools & Equipment
Fleet Maintenance - 52
Fleet Maintenance - Classifieds
Fleet Maintenance - Guest Editorial: Moisture in Trailer Brakes is Not Just a Nuisance
Fleet Maintenance - 55
Fleet Maintenance - 56
Fleet Maintenance - Hand & Specialty Tools Supplement
Fleet Maintenance - A2
Fleet Maintenance - Specialty Hand Tools: The Problem Solvers
Fleet Maintenance - A4
Fleet Maintenance - Time to Multitask
Fleet Maintenance - A6
Fleet Maintenance - Get a Hold on Hand Tool Safety
Fleet Maintenance - A8
Fleet Maintenance - Electric Vehicle Tool Set
Fleet Maintenance - Tool Review
Fleet Maintenance - A11
Fleet Maintenance - A12
Fleet Maintenance - Products
Fleet Maintenance - A14
Fleet Maintenance - A15
Fleet Maintenance - A16