The concept behind the Audi R18 e-tron quattro is unprecedented in LMP sport, and its realization a pioneering achievement. In the first development step, the engineers from Audi Sport and their partners investigated a wide variety of solutions. These included a parallel hybrid, where both drive systems propel the rear wheels. After weighing up considerations such as traction, handling characteristics, packaging and weight distribution, they ultimately decided to separate the drive systems by axle – the combustion engine drives the rear wheels permanently, and the electric drive propels the front wheels on demand.
On the R18 e-tron quattro, part of the braking energy benefits the motor generator unit (MGU) that is located at the front axle. Their two permanently excited synchronous machines convert the recovered energy into direct current through power electronics. This current drives a flywheel energy storage system positioned on the left inside the cockpit.
When the speed exceeds 120 km/h, the energy is called up from the storage system again. Converted back into alternating current by the power electronics, it then supplies the MGU’s two electric motors. These jointly feed more than 160 kW to the front wheels via single-stage planetary gears; the central control unit keeps the revs and torque in line with the conditions prevailing at the rear wheels. The racing car temporarily becomes a quattro with four driven wheels.