DEARBORN, Mich., Sept. 23, 2009 ““ People who know diesel engines are
familiar with, and expect, the noisy clatter generally associated with
diesels. That is, until now. When Ford’s new 6.7-liter Power Stroke®
diesel engine debuts in the 2011 Super Duty lineup, it’s expected to be
the quietest, smoothest diesel on the market, outperforming its closest
competitors by several decibels.
Engineering and design improvements to the all-new Ford-engineered,
Ford-tested and Ford-built 6.7-liter Power Stroke® turbocharged diesel
engine ““ debuting in the 2011 F-Series Super Duty ““ eliminate the harsh
sounds of the typical diesel to make it one of the quietest and
smoothest diesels on the market. Significantly quieter than its
toughest competitor, the 6.7-liter diesel challenges traditional views
about how diesels should sound.
"Historically, consumer perception has been that diesels should
sound rough and tough, but from a sound quality perspective they were
actually loud and unrefined," said Scott DeRaad, engine NVH (noise,
vibration and harshness) engineer. "At Ford, we approached the new
diesel development as though it was more than a work truck and
something that people wanted to drive, making “˜quieter’ a reason to
Most of the improvement in NVH comes from changes made to the
combustion system and the structural integrity of the compacted
graphite iron block, as well as from mounting one turbocharger on the
engine block instead of two.
Specific design upgrades were made to both the piston and the piston
bowl to optimize the combustion process, which features a two-stage
combustion event instead of a single-injection event, causing harsh,
sudden and loud combustion. Instead, a starter or pilot injection of
fuel begins the compression process before the main injection.
The result is a smoother combustion and a more refined sound for the
customer. When at idle, two pilot injection events are used to make the
firing process even smoother and aid in quietness. The "ticking" of the
high-speed injectors also is masked by specially designed covers on the
Mounting the turbocharger from the center housing directly to the
block provided several advantages as well in terms of NVH performance.
"When turbochargers vibrate, it can lead to other parts of the
vehicle vibrating," said DeRaad. "The exhaust system, for example, is
directly attached to the turbocharger. So when the turbocharger
vibrates a lot, the exhaust system vibrates too and that’s disturbing
to the customer. Bolting the turbocharger directly to the block
eliminates that concern."
Using one turbocharger, instead of two operating in series or sequentially, helped solve some NVH challenges as well.
"Having one turbocharger eliminates the air-handling noises ““ the
whooshes ““ as the engine switches from one turbo to the next turbo,"
DeRaad said. "Our turbocharger also has ball bearings that pilot the
shaft in the turbo, which helps eliminate the potential for the shaft
of the turbocharger to gyrate in its housing, which can create noise."
Other improvements include the addition of two resonators in the
intake system as well as a third resonator near the air cleaner.
"We’ve been able to tune the diesel intake system to give us the
sound we wanted," DeRaad said. "It’s now a nice complement to the
The new diesel will also deliver other significant improvements
including better torque and horsepower, class-leading fuel economy and
best-in-class towing and payload for unparalleled performance.