An interesting all-wheel-drive advancement is called torque vectoring, something that can really improve how well a vehicle handles. It’s a complicated sounding name for something that’s fairly straightforward.
Both Audi and Acura employ torque vectoring, the former with its optional rear sports differential and the latter courtesy of something known as Super Handling All-Wheel Drive.
Taking a peek at Acura’s SH-AWD technology on the TL luxury sedan, it keeps up to 90 percent of the engine’s torque at the front wheels during regular driving. This helps minimize friction to maximize fuel economy. During hard acceleration 45 percent of the power can be sent to the rear axle for better traction. Pretty standard stuff, but SH-AWD really comes into its own on twisting roads.
During hard cornering and acceleration, up to 70 percent of the available torque can be directed to the rear, but all of that can be funneled to just the outside wheel if necessary. This helps the car rotate as it turns, minimizing understeer and keeping it headed where the driver intends.
Automakers are doing everything they can to improve the efficiency of their vehicles. The move to part-time all-wheel drive instead of full-time setups is a small step to higher fuel economy. The next tread on the MPG staircase is disconnecting the system altogether when it’s not needed.
If a large part of an all-wheel-drive assembly can be completely shut down when extra traction is not required, parasitic losses can be minimized. AAM’s upcoming EcoTrac™ technology does just that. It stops the PTU, prop shaft and part of the rear drive module (RDM) from spinning unnecessarily. Altogether it’s a patented design.
“We’re going to be the first in the industry to launch this EcoTrac™ disconnecting all-wheel-drive system in the second quarter of 2013” Barrett said. What he did not say is which automaker will be using the system, only hinting that it’s a major global OEM whose products are sold in North America, Europe and Asia.
A disconnecting all-wheel-drive system is not without its challenges. Barrett said “[there’s] a lot of energy to control.” Imagine all those heavy, robust drivetrain components are stationary, when the vehicle needs some extra traction they have to spin up to highway speed in just milliseconds, and they have to do it absolutely transparently, without the driver ever knowing. Not an easy task. “How you make all that work together is very important,” and AAM has it figured out he said.
ALL-WHEEL-DRIVE BY WIRE
Like hybrids supplanting traditional internal-combustion engines, electricity will probably bring about the final development of all-wheel drive. It seems inevitable that motors, wires and battery packs will replace the heavy and complicated series of shafts, clutches and differentials that make the technology possible today.
In fact, this is already being done. In Europe French automaker Peugeot sells an electrified version of its 3008 crossover called the HYbrid4. Its front wheels are powered by an efficient diesel engine but the rears are driven purely by electricity – no mechanical links connect the front and rear axles.
Acura is also implementing a similar system. Its 2014 RLX flagship sedan is expected to debut with a new Sport Hybrid Super Handling All-Wheel Drive system. Similar to what Peugeot is doing, Honda’s luxury division is amping up the car’s rear end. It will feature two electric motors, one driving each wheel – no mechanical bits will connect the front and back of the car. Acura’s Sport Hybrid SH-AWD technology should hit the market in late 2013.
Not to be left out of the party, AAM is also developing a similar system called eAWD. Barrett said it’s the “next evolution of all-wheel drive.” It’s modular and easily scalable, meaning “it could be made to work on any vehicle platform,” he said.
Hybrids would be the perfect application for eAWD because they already have a battery pack onboard. If the system were adapted to other vehicles they would need a battery or a generator to power the electric motor.
Packaging is a major advantage of these electric all-wheel-drive systems. Without clutches and prop shafts and differentials (oh my) they’re very compact and much easier to fit underneath a vehicle.
All-wheel drive is like an ice-cream sundae for motorists. Improved traction is the creamy foundation, greater safety the delicious hot fudge, and peace of mind the cherry on top. It’s a tasty treat more and more drivers are opting for.
“The percentage of usage of all-wheel-drive systems is going up,” Barrett said. Anywhere from 5 to about 25 percent of new-vehicle buyers opt for the technology, figures dependent on model, platform and manufacturer, of course. Based on current trends, AAM sees the take rate increasing to between 25 and 50 percent, or more, over the next five years. Pickup trucks are already leading the charge. Right now about 50 percent of them are purchased with some sort of four-wheel drive.
At the end of the day the right system for you depends on your vehicular needs. If you’re looking for a spacious and efficient crossover that can handle snowy roads, part-time is just about your only choice. Pickups and truck-based SUVs usually offer proper four-wheel-drive systems for serious off-roading. But if performance is your thing, driver-focused vehicles tend to offer less-efficient but sportier full-time all-wheel drive.