How Audi Is Adapting Old-School Quattro AWD Tricks for the Electric Age03/17/2022
On the ice, driving at 55 mph feels like 155 mph on asphalt. It’s not quite the speed that creates this impression; it’s the feeling deep in your gut that even the most negligible misstep will send you and your car kart-wheeling into a nearby tree. The 1970s saw the birth of Audi’s Quattro all-wheel-drive system in these glacial conditions, and it’s here that the company continues to fine-tune its electric cars.
I trekked out to a frozen lake near Arvidsjaur, a small Swedish town located about two hours south of the Arctic Circle, to get a better idea of how Audi configures its all-wheel-drive systems, what electrification means for the future of Quattro, and which features engineers are toying around with on the ice. It’s not all about safety and ice-proof traction: Dialing in a certain level of fun is part of the process as well.
“All of our models must be easy and effortless to drive, and they must always be controllable,” Carsten Jablonowski, the head of Audi’s driving characteristics development team, explained as we watched an RS E-Tron GT gallop sideways across a frozen lake. This holds true whether a car runs on electricity or gasoline. And while building capable electric cars opened several doors for members of Audi’s engineering team, it also created new challenges for them to overcome.
Through-the-Road All-Wheel Drive
In a gasoline-powered all-wheel-drive car like the Audi RS3, a driveshaft connects the front and rear axles. Power travels through what’s essentially a tube, or a series of tubes depending on the configuration. Sending 60 percent of the engine’s torque to the back wheels means that the front wheels can’t receive more than the remaining 40 percent; the axles are dependent on each other.
In contrast, most all-wheel-drive systems fitted to electric cars use what’s called through-the-road all-wheel drive. It assigns each set of wheels its own motor, so the axles are independent. Through-the-road all-wheel-drive isn’t a new idea: If you fish in the well of automotive history for long enough, you’ll pull up a number of obscure prototypes with an engine at each end. Citroën adopted this solution in the 1950s, Mini tried and gave up in the 1960s, and Lancia attempted to take a Trevi with two engines racing in the 1980s. All came to the same conclusion: It’s a concept that’s not terribly practical or cost-efficient to put into production. Full electrification makes it viable, however.
Determining the precise amount of torque that each set of wheels receives is relatively easy because it’s software-based, according to Jablonowski, but it requires careful planning in the development phase.
“You have more options with an electric car than with one powered by a combustion engine,” he said. “It depends on the size of the motors, though. You have to think about that during the design process and figure out how big each motor needs to be.”
In turn, this balance directly influences a car’s handling and how it puts down its available power.
Just Add Ice
Various (and numerous!) electronic driving aids enter this equation as well, which brings us back to the ice: Unlike a gasoline-burning engine, an electric motor delivers instant torque and this response time needs to be kept in check during slippery conditions. But that on-demand torque also gives Audi more freedom to make a car fun in the right conditions.
One of the cars I drove in Sweden was an E-Tron GT-based prototype fitted with an experimental electronic stability control (ESC) mode that filled the gap between ESC Sport—which is already available—and ESC off. The system’s intervention was delayed to allow for more wheel spin. It’s a trick that customers asked for, Jablonowski told me.
Darting around (and occasionally knocking over) cones, the difference between ESC Sport and this as-of-yet unnamed mode was perceptible. It made the E-Tron GT more eager to wag its tail, yet it’ll also catch you if you overshoot it—a courtesy you evidently can’t expect with ESC off. Jablonowski added that the effect is more noticeable on ice, where traction is a luxury even in a car wearing studded snow tires, but that it’s something enthusiasts will also feel on pavement… assuming it eventually reaches production. It’s still at the prototype stage, and his team hasn’t decided whether to let it loose on public roads.
ESC’s basic functions are the same regardless of where the system is installed. Whether in an RS Q8 or an E-Tron, its aim is to keep the shiny side up and crease-free—but the system’s layout is powertrain-specific. “In the E-Tron, we moved some parts of the ESC system directly to the rear-mounted motor to decrease the response time and improve stability,” Audi engineer Achim Gulde pointed out. “This is a big advantage.”
The Power of Torque Vectoring
He’s right, but who gets thrilled about ESC? It’s kind of like a life jacket on a kayak: you’re relieved to have one while simultaneously hoping that you don’t wrangle your way into a situation where you have to rely on it to save your ass. What truly got Gulde, Jablonowski, and the other engineers I spoke to excited is torque vectoring; in their cosmos, it’s revered as the holy grail of handling, both on and off the ice.
Torque vectoring is not EV-specific and there are several high-octane cars (like the RS3) equipped with it, but going electric simplifies the process: instead of a trick differential, engineers can add a second motor to the rear axle and use software to teach the rear wheels to balance themselves out as-needed. That the extra motor adds horsepower just sweetens the deal. Audi’s E-Tron S uses this technology, for example. Its powertrain consists of one front-mounted electric motor and a pair of rear-mounted motors, making for three in total.
If two is good and three is better, then four must be best, right? Nope; electrification doesn’t work that way. “The problem [with four motors] is weight,” Jablonowski said. “Adding a fourth motor makes the drivetrain much heavier, it’s more expensive, and it’s ultimately not worth it. Of course, you can ask yourself if it makes sense to use three motors, because the cost is critical. I think that there won’t be very many cars with three or four motors in the future; two is a good number.”
In short, his answer makes the three-motor layout sound like the V12 of the electric car world: it’s special, and it’s not for everyone.
One of the most interesting takeaways from my time shadowing members of Audi’s engineering team is that, at the end of the day, tuning an electric car is not that different from tuning one with, say, a V6. Sure, you’ve got different parts to play with and more leeway when it comes to software, but the goal is the same: the car needs to be easy to control, easy to drive, sure-footed, quick, and safe. “Tuning new models revolves around [this] philosophy,” Gulde stressed. It also revolves around a big, empty patch of snow.
Drifting in a circle might sound like an adult version of a merry-go-round, but there’s a real engineering benefit to it: “To adjust a system [like the steering], we want to drive on a continuous curve. On a handling track, or on a public road, you’re going to have to turn around and go back. When you have a continuous curve, like a circle, you can keep going and it’s easier to tune the systems,” Jablonowski said.
Fittingly, this idea brings Audi’s Quattro system full circle. “When the topic of all-wheel drive comes up,” Jablonowski observed, an oversteer-induced grin lighting his face from observing a sliding E-Tron S, “the first thing you think about is traction. Driving like this really came about in the 1980s, with the original Quattro.”
Quattro was born during a winter testing session in the late 1970s when engineers looked on puzzlingly as a four-wheel-drive Volkswagen Iltis (a bare-bones, Jeep CJ-like off-roader) easily outperformed more powerful, front-wheel-drive Audi models through deep snow. What was envisioned as little more than a niche brought the brand unexpected success in rallying and in showrooms. Democratizing all-wheel drive also played a significant role in building Audi’s image: Quattro remains an important component in the constitution of an Audi’s character, and unscrambling this egg would be easier said than done.
Even as driving aids and powertrains evolve, the concept of spinning a car’s four wheels in order to effectively put power down has not. Safely charging through a blizzard will never go out of style—and neither should having fun in a car!
An American automotive journalist and historian, Ronan Glon is based in France. His work has appeared in Autoblog and Digital Trends.
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