Acura SH-AWD Test

I stepped out of a warm Acura RDX to feel the sting of below-freezing Canadian air hit my lungs. I was about 100 miles north of Quebec at a remote vehicle-testing facility known as Mecaglisse. The day's task was to try different all-wheel-drive systems on a variety of special test tracks laced with deep snow, hard-packed snow, and pure ice. On hand were various Acura vehicles shod with Super Handling All-Wheel-Drive (SH-AWD) along with a gathering of direct competitors fit with AWD as well, including a Lexus GS 350 AWD, Mercedes-Benz E350 4-Matic, Audi Q7 quattro, and BMW X3 X-Drive. Acura was convinced that back-to-back drives of different all-wheel-drive systems would show the superiority of its SH-AWD.

What is SH-AWD? First found on the 2005 Acura RL, Super Handling All-Wheel-Drive is an innovative, full-time all-wheel-drive system that actively distributes the optimum amount of torque not only between the front and rear axles but also between the left and right rear wheels. Such "Direct Yaw Control" improves cornering traction and steering precision. It's proven so effective that Audi has announced it'll incorporate similar yaw control with its next quattro all-wheel-drive system. While showing exceptional performance on dry pavement, the SH-AWD system provides significant performance gains in snow and ice as well as similar gains in off road performance. In fact, the SH-AWD system on an Acura MDX senses uphill motion and automatically shifts torque to the rear to improve launch traction-even before the vehicle starts to move.

SH-AWD greatly enhances stability on snow and ice, thanks to real-time interaction with Acura's Vehicle Stability Assist (VSA) system. During accelerating and cornering, SH-AWD first maximizes available traction by preemptively moving torque to the wheels with the maximum load. However, if the available traction limits are exceeded, the SH-AWD system can directly modify the drive torque distribution to stabilize acceleration and reduce the potential for vehicle oversteer.

With VSA, continually monitored is the vehicle's operating parameters, such as road speed, throttle position, steering wheel position, accelerating, braking, and cornering loads. While driving, VSA anticipates the vehicle approaching over- or understeer. To help correct either of these situations, VSA first acts to transfer torque bias to the axle with the most traction. This preventative measure significantly reduces the number of brake and throttle interventions. The response is so quick the instability may be corrected even before the driver knows it's occurring. Electronic traction control is integrated into the VSA system and helps SH-AWD-equipped Acuras accelerate smoothly on slippery surfaces. The VSA also can request the SH-AWD system to adjust its torque level, thus allowing the system's Direct Yaw Control to maximize stability under most driving conditions.

By overdriving the rear wheels 1.7 percent faster than the speed of the front axle, SH-AWD can provide an inward yaw moment while accelerating into and through cornering. This reduces unwanted understeer or "push" when the vehicle is aggressively driven in corners. Since Direct Yaw Control acts preemptively, VSA brake and throttle interventions are less intrusive than in many competitive all-wheel-drive systems. In changing road conditions, SH-AWD reacts to adjust drive torque more quickly than the VSA can apply stabilizing brake torque.