ELECTRIC TORQUE VECTORING SETS AUDI SPORTBACK APART
NEUBURG, GERMANY Torque is the power of twist: the spinning motion that moves a vehicle forward. But it can also be used to control what it does in the turns, and Audi is taking advantage of that with its upcoming all-electric e-tron S. I drove it as the Sportback S, a sloped-butt sibling to the e-tron SUV that’s now on sale.
Torque vectoring — applying more or less power to specific wheels as needed — is nothing new, but on a vehicle with a gasoline engine, it’s a mechanical process. Here it’s done with electric motors that independently drive each rear wheel, linked only by software that determines how much work each motor should do.
Audi says the e-tron S is the first mass-produced electric car with three motors. It borrows the bigger motor that powers the regular e-tron’s rear wheels, and puts that at the front. It then adds the two smaller ones at the rear.
The timeline for Canada hasn’t been determined yet, but expect to see the Sportback at dealers later this year, and the Sportback S to arrive after that. Pricing is still in the future as well, but as a general guide, the current e-tron starts at $90,000.
I took the Sportback S for a few laps at Audi’s test centre.
I’ve driven most of the electric cars out there, but it’s still always a bit odd to put my foot down hard, get pushed back in the seat, and hear almost nothing.
And it’s equally unusual for what’s essentially a crossover to feel like a sports car.
With all that battery and those motors, the e-tron is a heavy unit, and you can definitely feel its heft. But at the same time, the power adjustment at the wheels tucks it into the corners and then pulls it back out to give it the handling of something with much less mass. It’s also aided by progressive steering, which reduces the steering wheel input needed to get around a tight curve.
Power is what it’s all about. Under moderate driving, the three motors combine to create 429 horsepower and 596 poundfeet of torque.
But when you punch it hard, you get a boost to 496 hp and 717 lb-ft, enough to get you from zero to 100 km/h in 4.5 seconds. That power boost lasts up to eight seconds, thanks to a robust cooling system for the motors.
The e-tron S is all-wheel drive, but most of the motivation comes from the rear.
The front motor shuts off when it’s not needed, such as when highway cruising, to conserve power. The two rear motors always run, but the amount of torque they send to their respective wheels varies, and that’s the point behind torque vectoring.
Marc Bauer, Audi’s project manager for electric torque vectoring, uses the example of a boat. “For cornering and turning, if you want the boat to turn to the right, you use the oar on the left,” he said.
“But for stability, if it goes too far, then you use the other oar to bring it back.”
That’s what happens here. As I turned the wheel to the right in a corner, the left-side rear motor applied more power, tucking the car’s nose into the turn.
If necessary, the system will also apply a light brake tap to the inside front wheel to gather the front end in even tighter. When I unwound the wheel on exit, the right-side motor kicked in a little extra juice to help straighten me out. The system can send up to 162 lb-ft more torque to one rear wheel over the other.
In addition to cornering, it also reacts to traction differences, such as when one wheel loses its grip on slippery pavement, or if anyone actually takes one of these off the asphalt (and there’s an off-road mode that raises the air suspension for extra ground clearance).
The two rear motors sit in a single housing and share a cooling system, but they’re not connected, and each is responsible for its wheel only. The battery covers most of the floor, lowering the centre of gravity.
All three motors use regenerative braking to capture energy and store it in the battery, and the intensity can be increased to the point of “one-pedal driving,” where the car slows down enough to come to a complete stop, without using the brake pedal.
During hard braking, an electric motor rapidly pressurizes the fluid to shorten the stopping distance.
Electric cars are exciting for the potential they have for innovation when engineers are freed from the confines of mechanical connections. Torque vectoring is fun on a track, but it’s just as useful for improved stability in everyday driving. And if you can do it faster and with more power, well, that’s even better.