Will Torque Vectoring Be The End Of Mechanical All Wheel Drive Systems?


Yesterday, Audi announced a new all wheel drive system it says is more efficient than its traditional Quattro system. Quattro has been available on Audis in one form or another for 40 years. The Audi Quattro Ultra system is said to improve efficiency by 5% in normal driving and more in steady state highway driving. It works by adding clutch packs just after the transmission and before the rear differential that decouple the rear driveshaft from the rear differential. Audi Quattro Ultra all wheel drive

The system needs about a quarter of a second to react and couple everything back together when the computer senses a need for all wheel drive such as wheel spin at the front of the car or a demand for full acceleration from the driver. It says upcoming autonomous features will give the system better predictive powers to ensure all wheel drive is available when needed.

Car and Driver recently got to test drive a car equipped with Quattro Ultra in the mountains of Austria. It says it was impossible to detect when the system coupled and uncoupled while driving aggressively. The system was developed by automotive supplier Magna. It took five years to get everything to work the way Audi thought it should. It will be offered on all Audis with 4 cylinder engines and some with lower power V-6 units. It cannot currently handle the torque generated by the engines in Audi’s performance models.

While a 5% gain in efficiency is laudable, it begs the question: Isn’t there a better way than with a mechanical system that is so costly and complex? The folks at GKN, another automotive supply house, think the answer is yes. It is showcasing its new electric eTwinster axle for automakers this week at its Wintertest proving ground in Arjeplog, located in Northern Sweden.

GKN eTwister electric all wheel drive

The eTwinster is a plug-in hybrid module that makes it simpler for vehicle platforms to offer electric all-wheel drive and torque vectoring. The driveline combines eAxle technologies proven in the Volvo XC90 T8 Twin Engine, Porsche 918 Spyder, and BMW i8 plug-in hybrids and the twin-clutch torque vectoring technology that features in the Ford Focus RS and Range Rover Evoque, according to a company press release.

The GKN system features a 60 kW electric motor with 177 lb-ft of torque through a 1:10 reduction gear. A system of clutches distributes the power to each wheel according to how much grip it has on the road surface, a process known as “torque vectoring.”GKN head of technology Peter Moelgg says, “We believe our prototype torque-vectoring eAxle system represents the next step forward for the industry: a production-ready way to create higher performance hybrids that are more rewarding to drive.”

Moelgg adds, “GKN is focused on developing technologies that can achieve this crucial tipping point for electric drives in mass production. More powerful, dynamic electric drives from GKN will help put batteries in the driving seat and create new electric driving experiences for customers. The success of our eAxle systems in cars for Porsche, BMW and Volvo demonstrated how the right kind of hybridization creates new value propositions for the driver. Torque vectoring is the next step and we are excited to be demonstrating this technology during Wintertest.”

By 2025, GKN forecasts that 40-50% of vehicles will have some level of electrification, with a greater proportion hybrids’ power delivered from the electric motor. The eTwinster could be programmed and integrated into a vehicle platform for production within the next three years.

All wheel drive used to be a rare and expensive option. Within a few years it may be as common as cell phones. Audi’s Quattro Ultra may be nothing more than a stop gap measure on the highway to vehicle electrification.


About the Author

I have been a car nut since the days when Rob Walker and Henry N. Manney, III graced the pages of Road & Track. Today, I use my trusty Miata for TSD rallies and occasional track days at Lime Rock and Watkins Glen. If it moves on wheels, I’m interested in it. Please follow me on Google + and Twitter.

  • James Rowland

    That’s nice, Audi. Now dump the front-to-rear driveshaft. 🙂

    The similar system on the new Focus RS apparently has some “durability issues”; you get a dashboard light that tells you it’s time to change the oil for the clutch packs.

    eTwinster looks better, but again I don’t see a great future in clutches of any kind, let alone ones that routinely slip under roadwheel torque levels. The Right Way to do this is with independent motors.

    • Steve Hanley

      I agree. I think in wheel motors will prevail eventually. Yes, the have high unsprung weight, but if Elon Musk can make a car that can drive itself across the entire continent, someone should be able to create an active suspension that offsets 95% of the disadvantages of in-wheel motors.

      • James Rowland

        Independent motors and driveshafts aren’t mutually exclusive. 🙂

        • Steve Hanley

          Really? Tell us more, sir!

          • James Rowland

            Motors inboard, wheels in the usual places, the two connected by driveshafts and reduction gears. Rimac were using this approach, if I recall correctly.

            Might need some clever packaging to do this at a reasonable cost and size, but my gut tells me this will be more easily attainable than hub motors of reasonable mass and with reliable power, cooling and control interconnects.

            Mind you, my gut also told me that chocolate bar was a good idea…

          • super390

            The one catch with your idea is that these same driveshafts have to handle the torque of regenerative braking, so they’ll have to be overbuilt for non-braking loads. Unless that’s what you’re using the reduction gear for. But gears are expensive too.

            The power to weight ratio of electric motors is improving almost as fast as batteries. This is why we’re seeing manned aircraft with electric motors now. The last barrier to using them in wheels is replacing the conventional brakes already sitting there. That’s hard because in emergencies brakes have to shed far more torque than motors can regenerate. If, however, you could integrate a motor with a cheap emergency brake that will rarely have to be used, the unsprung weight and cost might work.

          • James Rowland

            Regenerative braking is typically at a lower torque than is already used to accelerate, so no.

          • Steve Hanley

            “they didn’t become popular for other reasons – one being accessibility for servicing.”

            Ahhh…..that brings back memories of trying to bleed the rear brakes on my XK-E!

          • James Rowland

            Didn’t you have to drop the diff to change disks on that?

          • Steve Hanley

            I had the official shop manual for the car, which had about 17 sections to it. Every one began with the words “Remove engine from car……” Want to change a tail light lens? “Remove engine from car……” Fix a flat tire? “Remove engine from car…..”

            The XK-E was a gorgeous automobile. It was, however, a lousy daily driver. ; – )

  • You’d have issues on slippery rocks, etc. during serious off-roading with the electric hub motors. They have peak TQ at 0 RPM, so would likely have traction issues where a mechanical system with a crawl gear could modulate TQ. Not that an EV is a bad option, just that there are advantages to other systems.