Lightweight powertrain tech for Audi e-tron FE07 race car

Pre-season testing for Formula E commences this weekend at Valencia in Spain – providing our first look at the new Audi e-tron FE07 ahead of the opening round at Santiago, Chile, on January 16.

“The coming seventh Formula E season will be the first to be held as an official FIA World Championship,” says Stefan Aicher, Head of Development e-Drive at Audi Sport.

“However, at Audi Sport, we’re celebrating a premiere all of our own: The Audi e-tron FE07 has an all-new electric powertrain that was developed in-house for the first time.

“We went to the limits in all areas of this project.”

The Audi Sport ABT Schaeffler team will run two cars, each piloted by Lucas di Grassi and René Rast.

A highlight of the new car is its motor/generator unit, which Audi labels ‘MGU05’. According to the boffins who have developed this system, it weighs less than 35kg, including the weight of the inverter.

Despite its ‘97-pound’ status though, this motor is no weakling. At 95 per cent efficiency, as claimed by Audi, the motor can propel the 903kg car to 100km/h in 2.8 seconds and on to a top speed of 240km/h. In practice sessions the motor car generate as much as 250kW, but in race trim it’s rated at 200kW, although in ‘attack mode’ during a race it can peak at 235kW.

All the power for this motor is stored in a 52kWh lithium-ion battery that sits between the driver and the motor-generator unit, and weighs 385kg. That’s 43 per cent of the car’s weight, which includes 80kg for the driver. McLaren supplies this ‘spec’ battery to all Formula E teams.

While the 52kWh battery is less than the battery capacity of a road-going Hyundai Kona Electric, it holds enough charge to run the FE07 at race pace for the 45-minute (and one extra lap) duration of Formula E races. Key to that range is a brake-energy recovery system driven by the rear wheels. Other technical highlights include a high-efficiency cooling system and extensive use of carbon-fibre throughout the car, including the driveshafts to the rear wheels.

Formula E is a category that doesn’t match F1 for outright speed and acceleration, but it is a showcase for efficiency as much as performance, a point made by Audi’s Project leader Formula e Sport, Tristan Summerscale. And it’s how that efficiency is exploited that wins races.

“Efficiency in Formula E is absolute key to a successful race, and we try to reduce energy losses to an absolute minimum,” Summerscale told international journalists during an online presentation this week.

“The complete efficiency of this powertrain is over 95 per cent – so quite a remarkable number – and again, comparing to an internal-combustion engine powertrain, that's more than double the efficiency.”