|Photo: Kevin Corrigan|
The Haldex System
This Haldex XWD system is similar to that found in the Cadillac SRX, the European Opel Insignia, and that used in the last of the Saab 9-3 models. In fact, the system debuted on the Saab 9-3 Turbo-X performance sedan back in 2008.
Like most all-wheel drive systems, it has a clutch that dictates the levels of torque going through it at any given time. To decide these levels, the system analyses signals from the vehicle’s onboard sensors. Those signals include: engine torque, individual wheel speed, throttle position, yaw, latitude and longitude sensors, and more. The system then decides how much torque is to be sent back to the rear wheels.
During acceleration, the clutch demands a high torque level. It then looks for wheel slip and backs off if slip is not detected. For a normal, everyday launch (say, from a stoplight), the torque split between the front and rear is roughly equal. After the initial acceleration, the system backs off and returns to a more traditional front-wheel drive configuration. This obviously greatly assists fuel economy, but also makes for excellent traction when you need it most.
On the highway while cruising, the system drops to near zero and all but a small amount of torque, for clutch preload, is sent to the rear wheels. However, the system is continuously variable and will react depending on the sensor inputs. Again, fuel economy comes to the forefront as you’re basically now driving a FWD vehicle.
The system also features a proper electronic limited-slip differential, not one of those erratic brake-operated traction-control systems which try to mimic an LSD. The eLSD enables side-to-side adjustment to the torque split between the rear wheels to optimize vehicle stability and cornering capabilities.
The Interactive Drive Control system
Available on the 2014 Buick Regal GS is an Interactive Drive Control system which allows the driver to select various drive modes (Touring/Sport/GS). In GS mode, the setting increases steering efforts for more direct feedback to the driver. It also increases damping levels and alters the shift points of the 6-speed automatic transmission.
Put to the test
We recently had the opportunity to test drive the new all-wheel-drive 2014 Buick Regal GS. Take it from me, the addition of AWD turns this sedan into a truly fun-to-drive Buick, especially in GS mode. The car feels properly confident going into the turns (those Brembo brakes certainly help), and there’s grip galore on exiting those corners. We also managed to locate an ice bridge in Quebec on which to drive. There, on sheet ice, the advantages of AWD were obvious and the benefits of the eLSD came at us like a slap in the face. This system works, and it does so extremely well.
This all-wheel-drive system literally transforms the Buick sedan, and it’s going to be interesting to see just how many other GM products feature this system in the future.
|Photo: Kevin Corrigan|