Who says
you can't drive concept vehicles? Well, you still might not find GMC's
Terradyne parked in your driveway anytime soon but in the near future
three cutting-edge, concept-worthy technologies will change the way you
drive and use your pickup.
We spent
two days with GMC in La Jolla, California getting familiar with four-wheel
steering and two new powertrains featuring automatic cylinder shutoff
and hybrid gasoline-electric propulsion.
Quadrasteer
Back in 1988
Honda became the first auto maker to introduce four-wheel steering, in
its compact Prelude sedan. About the same time GM was showcasing a much
more advanced version of four wheel steering in its Blazer XT-1 concept
vehicle. For whatever reason the feature never took off, probably because
the Prelude's purely mechanical setup didn't provide much benefit in the
already nimble car and the XT-1's system was as complex and expensive
as a NASA X-plane.
Enter the
2002 GMC Sierra Denali, the successor to the 2001
Sierra C3. The Sierra Denali makes an already outstanding truck even
better with the addition of Quadrasteer four-wheel steering, aka QS4.
Quadrasteer
electronically controls the rear wheels at different speeds and under
various load bearing conditions to create an amazing amount of agility
and maneuverability - especially when towing or parking. The rear
wheels turn in proportion to the front up to a maximum 12-degree angle
depending on vehicle speed and driving
mode. 12-degrees may not seem like a lot but consider the following:
at 37.4 feet the Sierra Denali's turning radius in four-wheel steer
mode is only three inches greater than that of a three door Saturn
coupe! That's almost 10 feet smaller than the 2001 Sierra C3 was capable
of performing! Quadrasteer on the 2002 Sierra Denali is a game-changer.
The
2002 Sierra Denali's turning radius is almost 10 feet smaller than
the 2001 Sierra C3.
Quadrasteer
steer-by-wire rear axle is controlled by two sophisticated microprocessors.
At low speeds the rear wheels turn in the opposite, or negative, direction
of the front wheels up to a transition zone of around 40 to 45 mph where
the rear wheels track neutrally. At speeds over 45 mph the rear wheels
turn in concert, or positively, with the front. If at any time the two
microprocessors 'disagree' over the steering information they have received
QS4 automatically shuts down and reverts back to traditional two-wheel
steering.
Located on
the dash of the Sierra Denali is a push button Quadrasteer control panel
similar to the four-wheel drive control panel found in many trucks today.
The driver pushes the button to change steering modes from two-wheel steer
(2WS) to four-wheel steer (4WS) to four-wheel steer tow (4WS TOW). In
4WS mode the rear wheels turn up to the maximum allowable amount below
40-45 mph. The wheels transition and turn in the same direction as the
front above this speed. When towing, Denali drivers can select 4WS TOW.
4WS TOW reduces the amount of rear wheel steer at slower speeds, when
the wheels are turning in opposite directions, but increases it at higher
speeds when the wheels turn in the same direction.
With
Quadrasteer, drivers can select 2 Wheel Steer, 4 Wheel Steer or 4
Wheel Steer Tow Modes using a push button control panel on the dashboard.
Created in
an exclusive partnership with Tier 1 supplier Delphi automotive, GMC won't
comment on how long this arrangement will last. Dana Corporation provides
the Sierra Denali's axle and Delphi completes the final assembly, adding
the electronics and delivering the final unit to GM's Oshwa, Ontario plant
where the Denali is produced.
The Quadrasteer
system adds a weight penalty of about 285 pounds to the truck but gives
back this amount and more in additional towing and hauling capabilities
over the C3. The rear axle's weight rating increases by 250 pounds to
4000 pounds and maximum GCWR (gross combined weight rating) climbs from
14000 to 16000 pounds. Trailering capacity has increased from 8700 pounds
to 10000 pounds. The wider rear axle also provides more stability when
towing.
Sam Mancuso,
the Sierra Brand Manager, proudly proclaims, "The Sierra Denali is
the most capable ½-ton pickup truck available in its class. There
is nothing else like it from Ford, Dodge or Toyota."
