» Design changes, along with the need to
meet strict federal emission standards,
have led to technological innovation
that is creating even cleaner and more
efficient heavy duty diesel engines.
Photo courtesy PACCAR
uch has changed since the diesel engine was developed
by German engineer Rudolf Diesel in 1896 —
M
in an attempt to improve upon the ineffi cient steam
engines common in his day — especially over the
past decade or so. Today’s heavy duty diesel engines
have evolved to provide greater effi ciency and
produce less carbon (greenhouse gas) emissions.
Th is has been brought about by engine design
changes which “gradually transitioned the image
of diesel — rooted in vehicle technologies dating
back to the 1970s — as a “slow, smoky, dirty, noisy,
heavy and smelly engine” to a responsive, more
effi cient and much cleaner engine, observes
DieselNet (https://dieselnet.com), an online
information service exclusively devoted to diesel
engines and emissions.
Making Modifications
Changes made to diesel engine over the years have
included:
Optimizing the combustion chamber design.
Increasing the injection pressure in the fuel
injection system to help with engine performance,
emissions and noise.
Th e use of charge air systems to supply additional
combustion air during engine acceleration.
Advanced fuel injection (common rail systems
and electronic unit injectors) to manage fuel
injection electronically for more precise control
of the combustion process.
Turbocharging, which uses what would have
been wasted energy in exhaust gases to power
turbines that pressurize air in the engine’s cylinder,
allowing the engine to produce more power.
“Diesels initially enjoyed modest emission regulations,”
according to DieselNet.
Th at changed in the 1990s when diesel emission
standards — enacted to reduce emissions of
nitrogen oxides (NOx) and particulate matter (PM)
— became increasingly diffi cult to meet.
Strict Emissions Regulations
In December 2000, the U.S. EPA adopted a
rulemaking entity to establish stringent federal
emissions standards for model year 2007
and later heavy duty highway engines. Th e U.S.
EPA Emissions Standards for Heavy Duty Diesel
Engines were intended to reduce emissions from
on-road heavy duty trucks and buses by up to 95
percent, plus cut the allowable levels of sulfur in
diesel fuel by 97 percent.
Th ese standards included new rigorous limits
for PM and NOx. Th e PM emission standard took
full eff ect in 2007. Th e NOx standard was phasedin
between 2007 and 2010.
AUGUST 2017 | VehicleServicePros.com 17
Advancements
In Heavy Duty
Diesel Engines
By David A. Kolman, Editor
How technological
breakthroughs have
helped develop cleaner
and more effi cient diesels
Page 18
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