Saab Xwd "cross Wheel Drive" System

Saab, the Swedish automaker, has developed theas the clutch plates are forced together under
XWD "Cross Wheel Drive" system, with intention tohydraulic pressure. In effect, the RDM becomes
optimize vehicle handling and stability in all drivingengaged. In such process, detection of wheel slip
conditions. Currently, the system is being offered as anbefore the TTD activates is required, making it a
option in the 2008 Saab Turbo X and Aero versionssignificant improvement in the technology.
of the 9-3 Sport Sedan and SportCombi. It is beingIn open road cornering, Saab XWD offers enhanced
partnered with a 280 hp (206 kW), 2.8 V6 turbo engineand more finely balanced chassis dynamics. The data
that produces almost 15 percent more maximumfrom the vehicle's ABS/ESP sensors are being utilized.
torque of 400 Nm/295 lbs.-ft.), to enhance the availableAnd, the programming of the system permits the
traction.application of rear drive in balancing both oversteer
The all-wheel drive system will be available with eitherand understeer characteristics to optimize stability and
a six-speed manual or six-speed automaticroadholding.
transmission. It will provide to impressive features,For highway cruising, there is only about 5 to 10
namely: pre-emptive engagement of the rear wheelspercent of the engine torque is basically used in the
to optimize traction at take-off; and an active rearrear wheels to provide a measure of greater stability
limited-slip differential (eLSD) to allow variable torqueand enhancement of fuel consumption.
transfer between the rear wheels.The eLSD holds the most significant role in Saab
The Cross Wheel Drive is a fully automatic on-demandXWD. It is the first application of an
system. It could send up to 100 percent of engineelectronically-controlled, rear limited slip differential in the
torque towards the front or rear wheels whensegment. Along with RDM, the eLSD operates through
necessary. Its sophisticated operation adds furtherpressurized clutch plates under a principle same as
sporty dimension to the driving experience with thewith the larger TTD.
new Saab Turbo X and 9-3 Aero XWD. It producesThe eLSD also provides the driver better control on
fine balancing of the drive torque between the fronthard cornering and high speed maneuver. It happens
and rear axles that raises the threshold where ESPthrough the application of either more or less torque to
throttle and braking interventions are triggered; thus,the wheels, helping the rear follow the direction of the
provides more scope for intimate driver involvement.front wheels. Without requiring 'outside' intervention
The state-of-the art all-wheel drive system is beingfrom electronic stability aides and quality Saab struts,
dominated by its own electronic control unit that worksthe vehicle can be kept balanced and be tightly
with the engine, transmission and ABS/ESP controlcontrolled.
modules. In the front final-drive, the hardware comesFitment of a new rear sub-frame, in the process of
with a Power Take-off Unit (PTU), which transmitsinstalling the Saab XWD, is required to carry the RDM,
engine torque through a prop-shaft in the Rear Driverevised rear suspension geometry and new wheel
Module (RDM). It works with wet, multi-plate clutch unitshubs for the drive shafts. Wheelbase and rear track
from Haldex, namely a Torque Transfer Device (TTD)dimensions are kept unaltered.
and an electronically-controlled Limited Slip DifferentialCurrently, Saab, as a division of General Motors Corp.
(eLSD).Saab Automobile USA, is providing premium
In the process of take-off, the TTD is being activatedautomobiles for Saab Automobile AB, Sweden.