Truck & Off-Highway Engineering - February 2022 - 9

TECHNICAL INNOVATIONS
brake setting. ThermoCoasting also reportedly
improves aftertreatment system
performance. The Gen 5 DD15 features
additional thermal management
upgrades such as improved cooling circuitry
and greater temperature distribution
across the cylinder head.
Roughly 50% of the components for
the Gen 5 DD15 were new or redesigned.
These include a proprietary asymmetric
ball bearing turbocharger that improves
performance via reduced internal friction
and enables peak power and torque to
be achieved at lower engine speeds.
According to Detroit, peak horsepower of
the Gen 5 DD15 is achieved at 1,500 rpm,
compared to the prior generation's 1,625
rpm. Peak torque is realized at 900 rpm
versus a previous rating of 1,075 rpm.
A new piston bowl shape was designed
to promote a swirling effect in
the combustion chamber. Detroit claims
this effect creates a fuel spray pattern
that promotes improved fuel mixture
atomization. The engine's inlet ports
were also modified. This modification
combined with the new piston design
and the DD15's 21:1 compression ratio
netted a three percent improvement in
fuel efficiency over the previous-generation
engine as well as reduced carbon
dioxide emissions. These improvements
for the Gen 5 DD15 also resulted in increased
downspeeding.
The Gen 5 DD15 displaces 14.8 liters
and the High Power engine has a peak
output of 505 hp (377 kW) at 1,625 rpm
and 1,850 lb-ft (2,508 Nm) torque at
975 rpm. Its GCW rating stands at
80,000 lb (36,300 kg) and it can be
mated to several variations of the DT12
transmission depending on the application.
The engine was first available in
January 2021 truck builds and is currently
an option for Freightliner
Cascadia and Western Star 49X trucks.
" The award-winning DD15 Gen 5 engine
is a key part of our ability to provide
highly reliable service to our customers, "
said Max Fuller, executive chairman and
former CEO of U.S. Xpress. " The DD15
platform has been a go-to for our operations
for years now and the new platform
has exceeded our expectations of uptime,
DPF health and overall running costs. "
TRUCK & OFF-HIGHWAY ENGINEERING
Rob Reich, chief administration officer
for Schneider National, echoed
Fuller's praise of the updated DD15 engine.
" Our commitment to the global
community to be a green transportation
solution provider is closely aligned with
the efficiency gains of the DD15 Gen 5
engine, " he said. " The highly efficient
new engine means less hydrocarbons
consumed, and an overall smaller carbon
footprint for our operations. "
Matt Wolfe
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Truck & Off-Highway Engineering - February 2022

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