The processing power is incredible. Every second, Mazda’s i-ACTIV all-wheel-drive (AWD) system monitors a network of inputs and sensors, two hundred times. That’s a full check of individual wheel speeds, brake and throttle pressure, steering angle, inclination, outside temperature, and even whether the wipers are activated.
Two hundred times, every single second.
It’s all part of the design of an AWD system intended to extend the brand’s promise of above-average driving pleasure into more conditions, including snow and ice.
But for Mazda engineer David Coleman and his team, enabling a high volume of data analysis by an AWD system was only a starting point.
“We’re using data that’s already available, in new ways,” says Coleman. “But having the data is only part of the equation. We need our AWD system to act on it, as quickly as it comes in.”
That’s the job of the lowly power coupler, a small cylinder full of clutches and electromagnets, stacked one over the next, about the size of a coffee can. The coupler mechanically joins the front drive axle to the rear, to varying degrees, depending on the state of the clutches inside. Just 3 amps applied to the coupler’s electromagnets locks the clutches, and both drive axles, together. Less amperage means less bite from the clutches, and less power to the rear wheels. With no current applied, the coupler is open, and the vehicle is front-wheel drive.
For absolute AWD precision, an electromagnetic coupler is ideal, because it can vary the level of torque sent to each axle as quickly as a computer can vary the level of current flowing to its electromagnets, which is to say, instantly. Individual power coupler units are even run through a barrage of tests at the plant, where minuscule variances in response characteristics are recorded, and programmed into the computer for full optimization. This contributes to a coupler that can respond to an enormous stream of data, at the speed of electricity.
This isn’t new technology, but the major advance flaunted by Mazda’s i-ACTIV AWD system is in the programming, which responds to a much wider range of data than typical of other systems. For instance, by considering wiper activation and outside temperature, i-ACTIV AWD can accurately guess whether there’s snow underfoot, and dial in a more even front-to-rear power split, for better off-the-line traction.
In a demonstration, drivers stopped at the apex of a slippery hill, and turned the steering wheel one rotation, before setting off once more. When steering angle is detected while the vehicle is stationary, many AWD systems disengage their power coupler, preventing a common binding sensation in the driveline, but effectively leaving the rear wheels out of the equation, for a moment.
In this specific test, a CX-5 regained forward motion over the hill instantly, with all four wheels visibly participating, from the first inch of movement. A Honda CR-V and Subaru Forester, in the same test and on the same (winter) tires, were left with front wheels spinning and rear ones dragging behind, unpowered. The latter two machines took far longer to crest the peak, if at all.
Why? The CX-5’s sensor network knew it was stopped on a slippery hill, having considered temperature, incline, traction levels as it began its climb, and wiper activation. Once stopped, the collected data led the computer to energize the power coupler, clamping the clutches (and front and rear axles) together for a quick getaway. The Subaru and Honda systems, having only considered steering angle, did the opposite.
The new i-ACTIV AWD system isn’t just about traction, either. Numerous incremental optimizations reduce power losses and system weight, right down to small ribs in the system’s gear case, which strategically trap oil in key areas, so less oil is needed. Less oil means less power loss, and lighter system weight. A multitude of incremental improvements like this add up to make the i-ACTIV AWD system easier on fuel, and up to 100 pounds lighter than older AWD systems, depending on the model.
And from the driver’s seat? It’s perhaps what you don’t feel, more than what you do, that’s most impressive. Pushed vigorously in a variety of challenging winter conditions, i-ACTIV AWD stands among the best when it comes to seamlessly and invisibly extracting maximum traction from the surface beneath. There’s no digging or torque-steer, no lurching through the driveline as power is shuffled fore and aft, and no sense of any wheel wastefully spinning away.
Drive spiritedly, and the system enables a lively, playful and predictable dynamic. Drive with absolute care and caution, and your inputs are confidently and precisely transmitted to the road, with no fuss, and no second guessing. Whatever the driving style, i-ACTIV AWD users can expect to feel well supported, even in very inclement conditions.
Mazda’s intelligent AWD system debuted in the CX-5 in 2013, with the CX-3 following last year. The new CX-9 will also offer i-ACTIV AWD when it arrives later in 2016.
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Courtesy: The Globe And Mail