of all Super Duty trucks are diesel-powered, the new oil-burner is the
more interesting of the engines. There is also considerable interest because
of the durability problems with the outgoing 6.0-liter PowerStroke engine.
Those problems were attributable to the fuel injection system’s
need for calibration that was tolerant of various levels of fuel quality,
according to chief engineer Pete Reyes. By the 2007 model year, reliability
scores for the 6.0 PowerStroke topped those of the tried-and-true 7.3-liter,
Ford says the 6.4-liter PowerStroke is all-new, and that is mostly true.
The engine is based on the same basic architecture as the 6.0-liter engine,
but the parts are upgraded. Only the crankshaft is carried over from the
old engine, with everything else replaced.
The significant change is the replacement of the old hydraulic fuel injection
system with a modern common rail system featuring piezoelectric injectors.
This high-tech system is key to the new PowerStroke’s ability to
meet the tough gas engine-equivalent emissions rules.
critical part of the new induction system is the sequential turbocharger
assembly. The combination of a quick-reacting variable-geometry small
turbo with a high-volume large unit gives the PowerStroke the quick reflexes
and maximum power that customers demand. Ford says that tests indicate
the new engine powers the Super Duty to 60 MPH a second faster than the
old 6.0-liter did. The injection system also contributes to a promised
cold start capability down to minus 20 degrees F.
The large catalyst and particulate trap permit the truck to earn the
clean bill of health from the EPA, but they do cost a bit of power because
of the increased back pressure. Further, the system for cleaning the particulate
trap involves sending extra fuel through the engine to help burn off the
gunk in the trap, and that periodic fuel use puts a small dent in the
truck’s fuel efficiency.
The engineering team balanced emissions, power and efficiency, but because
of the new government regulations for diesel emissions, that factor had
to take priority. Ford insists that unlike the 6.0-liter’s trouble-plagued
launch, the new 6.4-engine is thoroughly tested, with more than ten million
equivalent miles of testing in both trucks and on engine dynos.
have no truck with diesels can still choose the 6.8-liter Triton V10 gas
engine. Transmission choices are a six-speed manual or a five-speed automatic.
I drove only the automatic, which is well-calibrated, with smooth shifts
in casual around-town driving, while also delivering smart gearchanges
in harness. Climbing hills, pulling trailers and hauling a load, the transmission
makes good decisions about downshifts, when to hold a gear for a while,
and when to upshift.
While Ford doesn’t have a name-brand transmission like GM’s
Allison gearbox, the company has experienced good reliability with its
much less-expensive in-house transmission, Reyes said.