Audi Formula E Drivetrain Is 95% Efficient

Formula E is heading into its 7th season. The all electric racing series was the brainchild of Alejandro Agag, a former racing driver who had the idea for a series featuring battery operated race cars back about the time the first Tesla Model S was rolling off the assembly line in Fremont. Agag had been promoting his idea for several years, pitching it to anyone who would listen but finding few who were seriously interested. Then FIA president Jean Todt got on board and everything changed.

Agag was a proponent of the KISS method — Keep It Simple Stupid. He knew that one of  the problems with traditional racing series was the amount of money needed to keep pace with technical developments. There are rumors that Mercedes, whose Formula One team has dominated the sport for the past 6 years, spent over $400 million to compete in the 2019 season. It’s no wonder the smaller teams, who often have budgets under $100 million, can’t compete.

The genius of Agag’s vision was to make every car exactly alike, at least to begin with. The same batteries, motors, brakes, tires, transmissions, battery management systems — everything except what brand of shoe the drivers should wear — was frozen. Buy a car, stick a driver behind the wheel, and go racing. The mission was to spread the gospel of electric cars, not see who could spend the most money to win a championship. To bring the electric car message home to ordinary people, the races would be on city streets in the heart of downtown areas where they could be easily viewed. No need to schlep 6 hours to upstate New York to Watkins Glen or journey to the Ardennes Forest. Just take the bus or metro downtown, watch the race, and be home in time for dinner.

A Formula E race is about 50 minutes long. At first, the batteries could not last long enough to complete an entire race and so the drivers had to pit during the race and switch to a second car. But today’s spec 52 kWh battery, supplied by McLaren, can power a car for an entire race. Each team must use the same battery but is free to develop its own motor and transmission packages. That places a premium on drivetrain efficiency.

Audi Formula E car
Credit: Audi

Ahead of the start of the next Formula E season in Santiago, Chile next January, Audi has announced that its all new MGU05 motor/transmission package, developed by Audi Sport and Schaeffler, converts 95% of the energy stored in the battery into forward motion. “The Audi e-tron FE07 has an all-new electric powertrain that was developed in-house for the first time,” says Stefan Aicher, the head of e-Drive development at Audi Sport in a press release. The new power unit started with a clean sheet design and “We went to the limits in all areas of this project,” Aicher adds.

The Audi MGU05 is an electric one-speed drivetrain with an internal rotor concept, external magnets, a highly efficient cooling system, and six electrical phases. During development, the emphasis was on the use of lightweight materials and intelligent integration of the drive unit into the race car. “We were able to directly reinvest these savings in the new MGU for the benefit of enhanced efficiency. This was an exceptional achievement by the whole team,” says Aicher.

Efficiency is the key factor of success in Formula E. “That is why we are leaving no stone unturned to reduce the energy loss within the system to an absolute minimum,” says Tristan Summerscale, Formula E project leader at Audi Sport. In numerous extremely rigorous testing cycles, the entire powertrain was stressed to its limits in order to raise the entire high-voltage system to a maximum performance level. “We have achieved an overall efficiency of more than 95 percent for our powertrain. The new MGU inverter unit has an efficiency of even more than 97 percent in all relevant driving conditions.”

Credit: Audi

The compact size combined with high performance is particularly impressive. “If you compare our MGU with an internal combustion engine delivering a comparable power output of 250 kW, our efficiency is not only twice as high, but our weight of less than 35 kilograms is also much lighter,” says Summerscale. “This clearly shows what an efficient solution an electric powertrain is.” The electric powertrain for the Formula E car is twice as efficient as the hybrid powertrain currently in use by Formula One, according to Engadget.

The MGU05 produces 335 horsepower under normal racing conditions but that can be boosted to 382 horsepower during the limited time the drivers are allowed to utilize “attack mode” during a race. The cars have a top speed of 149 miles per hour and can accelerate from a standing stop to 62 mph in 2.88 seconds.

Typically, racing improves the breed. Technologies like overhead camshafts, turbochargers, and disc brakes that are common on street cars today trickled down from Formula One racing over the years. But in this instance, Aicher says weight reduction techniques pioneered by Audi engineers for production cars found their way into the new power unit. Many people expected Formula E to fade away after a season or two but it is gaining in popularity. In fact, some observers expect it will be Formula One that fades away as the EV revolution picks up speed.

Steve Hanley

Steve writes about the interface between technology and sustainability from his home in Florida or anywhere else The Force may lead him. He is proud to be "woke" and doesn't really give a damn why the glass broke. He believes passionately in what Socrates said 3000 years ago: "The secret to change is to focus all of your energy not on fighting the old but on building the new."

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