Ars talks about the future of electric powertrains with Audi

The Audi e-tron quattro concept paves the way for a forthcoming battery electric vehicle from the German marque. Jonathan Gitlin

It's rumored that Audi will use next month's Detroit auto show to unveil a sister car to the e-tron quattro that we saw up close in Los Angeles last month. Dubbed the Q6 h-tron by Autocar, the new alternative fuel SUV will use a hydrogen fuel cell. Audi has registered h-tron as a trademark and some journalists have sampled an A7 h-tron. Whether or not the fuel cell rumors pan out for Detroit remains to be seen. But what is certain is that electrification is going to be a significant theme for Audi in the coming years, as we found out recently when we sat down with Filip Brabec, director of product management for Audi of America, and Siegfried Pint, head of Audi's electric vehicle powertrain development.

Although it's tempting to see Audi's push towards electrification as a response to the diesel emissions scandal plaguing it and Volkswagen Group stablemates, it's actually been in the works for quite a long time, Brabec told Ars. And it goes beyond just developing EVs—it requires an investment in infrastructure, something that Tesla and its network of superchargers has made quite evident. Brabec was bullish about the his company's progress here: "fewer than 10 [Audi] dealers across the United States have signed up to the E-ready program" of installing EV chargers, he said.

The next step will be to offer customers a compelling product, Brabec said. "We wanted to go into a volume segment, and develop a car with mainstream appeal. An SUV is the right place, and the C-segment [for mid-size SUVs] is the right place. We're not looking to sell five cars in an obscure state. What we want is a car that's marketable, that's desirable, that people want to buy," he told us. What's more, don't expect radically styled EVs that look nothing like conventional cars. "Developing an EV isn't the easiest or cheapest, so you want mainstream appeal," he said, possibly signaling an end to the "Prius effect."

"As the technology becomes more mainstream it will be less about differentiation and more about "is it a cool car", he added.

Further Reading CGI gives us the first glimpse inside Porsche's electric Mission E

Mackevision builds virtual cars for commercials and configurators.

As we've previously reported, Other VW Group brands are also moving full steam [full charge?] ahead with electrification. Porsche's Mission E sedan has been greenlit for production before the end of the decade, as has VW's electric Phaeton. How much technology sharing was going on behind the scenes between the brands, we asked? Quite a lot, according to Pint. Cell technology and battery technology is shared across VW Group, which has two German laboratories working on EV technology, one near Wolfsburg (VW's home) and a second near Audi HQ in Ingolstadt. "We share the science, software, and battery management systems," he said.

Talk turned to the benefits of EV performance cars, (as it often does when I'm in the room and asking the questions). Here, Pint saw the advantage primarily being on of CO2 emissions reduction, something that warmed the cockles of my heart. "Looking to the future you may find the case where you can cut down the internal combustion engine and avoid a V12 or V10 and use a V8 plus electrification—that might be the direction we're thinking," Pint said.

EV batteries are getting cheaper every year, but every 3kW (4hp) of battery power adds another kg (2.2lbs) of weight to a car, but the weight penalty is even greater than that. "You add another kg to raise 3kW of power, but you also need an electric motor, power electronics, connectors, cooling," he said. On the other hand, boosting conventional power comes with much less weight penalty. "If you want to raise the power of an internal combustion engine you just blow up [boost] the turbocharger. Just using more expensive materials you get 50, 60, 70kW out of it easily." For purely performance applications, "I don't know if electrification is the right measure. But for other parameters—CO2 reduction, you can save building big engines, that might be a positive result," he told us.

Further Reading Sports car with a social conscience: Ars reviews the BMW i8

It's an extremely accomplished vehicle... as long as you're an extrovert.

"One of the unique selling points of electric mobility is that seamless acceleration. From my point of view, driving pleasure comes from acceleration. Instantaneous pedal response, the combination of longitudinal and lateral dynamics," Pint said, making him a man after my own heart. (Interestingly, before joining Audi, Pint was responsible for BMW's i3 and i8 powertrains, a pair of cars we adore here at Ars).

Right now, he's particularly excited about the dynamic possibilities offered by EVs compared to even just a few years ago. "There's a reason why we're going with a three-motor system," he said, referring to the e-tron quattro's powertrain layout of a single motor-generator unit for the front wheels and a pair at the rear, one for each wheel.

"Previously [in his career working in motorsports and earlier EV powertrains] I was only there to determine longitudinal dynamics. Only acceleration. Now I have a great effect on lateral dynamics—cornering ability. One motor up front, to have quattro and to have efficiency and regeneration. And now we have the possibility to implement a yaw momentum from the back," he said. Powering each rear wheel does away with the need for a differential, which helps with cost.

"Now if [the car] detects a steering angle and acceleration, I can implement a yaw momentum that gives the driver the feeling that the car behaves like a much lighter car. And that's something that I think is very important. It's something every driver can experience, you don't have to be a journalist or race car driver to judge that, you can feel it instantaneously," he said.

Implementing this will require much faster computers controlling the suspension. "We need 1kHz," he said, referring to the speed at which the powertrain and suspension control units work. "In the past it was 10ms, 100ms." But that increased sampling and reaction rate would derive handling benefits. "At corner entry you have the differential torque at the rear that helps overcome the polar moment of inertia, and then comes the power phase. And we want to keep that in neutral or oversteer. That's pretty new—we can have safe oversteer," he told us.

Still, getting EV torque vectoring systems working properly is no mean feat. Pint told us that, compared to a mechanical diff that can handle a 200Nm differential across the axle, "theoretically we could implement a 2000Nm differential in torque. In combination with an antiroll bar, you have the impression of driving a gokart." The hardware is the easy bit, as you just need a motor, gearbox, and driveshaft.

"From a software point of view it's tough," he said. "The regulations say if I can implement 2000Nm differential in torque I have to detect any mistake, otherwise the car turns uncontrollably. The requirement we have is even higher than power steering or brake failure. You have to make sure the vehicle goes straight if it's supposed to."

Source: Ars talks about the future of electric powertrains with Audi