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.

Located on either side of a hypoid gear that drives the rear axle, two identical Direct Electromagnetic Clutch systems control the amount of drive torque that reaches each rear wheel. These clutch systems can be controlled as a pair to alter the front/rear torque split-or be controlled independently to allow up to 100 percent of the total rear axle torque to go to one side of the vehicle. The fast-acting clutches coupled with smart control logic means traction is maximized in all conditions, without the need for driver intervention.

An electric coil controls the pressure in each clutch device. The amount of available rear axle torque transmitted to each rear wheel can vary continuously, between zero and 100 percent, depending on the conditions. Since the clutches are electromagnetically operated, the amount of drive torque delivered to each rear wheel can be controlled quickly and precisely, reducing wheelslip in low-traction conditions.

During acceleration and cornering on slippery surfaces, a conventional 4WD vehicle distributes torque evenly between the two rear wheels. This may lead to loss of traction of the inside rear wheel as load is transferred to the outside wheel due to load transfer during cornering. However, with SH-AWD, the side-to-side rear torque distribution varies according to the lateral g (and associated load transfer of the rear tires). For situations with low-traction roads, the side-to-side torque distribution is naturally aligned with the tire vertical loads. This enhances traction and allows maximum utilization of the available road surface grip during acceleration and cornering.

Enough techno talk, how'd the SH-AWD do? Quite well. Actually, every all-wheel-drive system tested did a good job on the traction-limited surfaces during slow and steady driving. However, when traction was pushed (such as in hard acceleration or during spirited cornering), the SH-AWD system was more predictable and recovered more quickly than the competitive AWD systems. With that said, the course was so slippery and treacherous that any major mishap would've been game over in any of the vehicles. When pushed, the SH-AWD did cover each of the traction-limited courses (a 2.1-kilometer icy road course, a 2.5-kilometer snow-packed road course, and a snow/ice 200-foot-diameter skidpad) in the shortest time with the fewest sweaty palms. Moreover, the SH-AWD system did its work with less intrusiveness, whereas many of the other systems delivered odd noises, suspension shuttering, and some kickback in the wheel. Again, all the competitive systems worked well, but proved more active whereas the SH-AWD was more seamless.

Regardless of all-wheel-drive system design, the best course of action on ice and snow is calculated and patient inputs matched with slower driving speeds. That, and having your passenger hold your snow cone while you drive.