your pickup truck to watch television, microwave popcorn and light up
your house at the same time? Well, if you live in California these days
you probably wish you could and you will be able to by 2004 when GMC starts
shipping Sierras with its new Parallel Hybrid Powertrain, aka Flex-Power.
GMC has taken
a different approach to the hybrid vehicle philosophy and designed the
electric drivetrain components as supplements to the normal displacement
motor, not replacements for some portion of the gas generated power.
to the hybrid powertrains found in Toyota's Prius and Honda's Insight,
the electric motor in the Sierra doesn't power the vehicle at low speeds
but is used to restart the gasoline engine, which shuts off at stoplights
instead of idling. This means no compromise in power or towing, clear
advantages in emissions and a claimed 15% bump in gas mileage. Plus the
ability to use the truck as a generator and source of stored power.
the Displacement on Demand truck, the PHT Sierra shows no exterior
differences from a regular Sierra.
have inserted a 42-volt motor into the 285 horsepower Vortec 5300 engine,
between the crankshaft and transmission, eliminating the need for a starter
and alternator. The benefit of this motor is its ability to also power
household and work-related appliances.
vehicles use 12-volt power systems, so more volts means redesigning everything
from light bulbs to major systems. The power steering motor, for instance,
in the Flex-Power concept we drove, used a 42-volt replacement part, smaller
than the original equipment, and capable of operating with the engine
off. But most truck components won't be redesigned to take advantage of
the 42-volt capabilities until well after 2004, likely requiring production
PHT Sierras to come equipped with dual voltage systems to power both 42-volt
and traditional 12-volt components.
As far as
driving the PHT Sierra, well, it takes a little getting used to. It's
kind of like driving using a manual transmission and forgetting to put
the vehicle in neutral or releasing the clutch while still in gear at
a stoplight. The engine just 'stalls' but in the PHT Sierra you still
have full air conditioning, full steering abilities and radio. It's only
when we lifted our foot off the brake that the engine seamlessly restarted
to move us on our way.
motor includes a brain that determines loads, and when to engage the gas
motor for drive and for recharging. If there is too much load on the truck,
say when the AC is blowing full tilt, the gasoline engine may not shut
off when stopped. The electric motor is also purposed with torque smoothing
for shifts and engine engagement, but with the test mules we had, the
shift points and torque smoothing was clearly something GMC was still
working to perfect.
42-volt electric motor replaces both the starter and alternator and
stores power in lead acid batteries under the rear passenger seats.
Electric outlets are accessible within the cab and bed.
At the halfway
point in our test drive we were given a convincing demonstration of the
PHT's power generating capabilities. We pulled the Sierra up to a tent
and plugged the truck in to watch television, turn on a set of reading
lights and microwave some popcorn. GMC claims that the Flex-Power truck
provides 4.8 kW of electricity. That's enough to keep a small house running.
lead-acid batteries are positioned under the rear seat to store power,
mostly occupying space that wasn't very usable to begin with anyway. An
outlet is also provided under the seat so that a laptop computer or other
device can be powered inside the car using the electric assist.
The PHT Sierra
also uses regenerative braking to capture energy and recharge the battery
packs while slowing the truck.
on Demand uses the oil pump system for hydraulic pressure to activate
the system. Four control valve solenoids then act together to achieve
seamless transition between four and eight cylinder operation.
question asked by all the journalists was about the convergence of DOD
with Flex-Power, and wouldn't that make the right mixture of fuel saving
technologies for a top-selling vehicle with substantial influence on the
company's CAFÉ metrics. Low-end power needs would be met by the
electric-gasoline hybrid engine during stop and go traffic and high-end
power needs would be met by the DOD engine during light-duty driving.
The engineers and others present seemed to agree that this would be the
right blend of features for some of the thirstiest vehicles on the road.
the new trucks were clearly a highlight of the event, the overall impression
of "Professional Grade" came, first and foremost, from the GMC
engineering team, and their complete involvement with, and obvious passion
for, the development of first-rate products. Talking to Gene Rodden about
Quadrasteer and suspension engineering to account for towing requirements
was a real plus. Chris Meagher, the Yukon Denali racer in GMC's commercials,
was consistently available for questions and very solicitous of detailed
responses from the journalists. Mark Cieslak, also star of GMC stage and
screen, was a great listener and constantly took notes on ideas offered
by drivers and reviewers of the vehicles. We came away as impressed with
the people behind the trucks as the trucks themselves.
enjoyed and think highly of the concept vehicle-type technology we had
a chance to drive. With 2004 rapidly approaching, a new Sierra with all-wheel
drive, Quadrasteer, Flex power, and DOD would be the real benchmark in
the industry for fuel efficient light trucks.