The four-wheel-drive technology fitted to the new Audi R18 E-tron quattro hybrid Le Mans racer will filter down to the Ingolstadt firm’s road car line-up in the future.
Yesterday Audi revealed the R18 E-tron quattro, a hybrid sportscar that has twin electric motors driving the front wheels in addition to the 3.7-litre V6 diesel engine powering the rear axle. Audi will enter two R18 E-tron quattros in the Le Mans 24 Hours in the summer, as well as a brace of conventionally powered R18 prototypes.
E-tron quattro will be offered as option on next-generation B9-series Audi A4, although unlike the racing car the system is likely to be on the rear axle due to the standard front-wheel drive layout of Audi’s road cars.
The E-tron system’s motors collect braking energy and send it to the rear of the car, where it powers another motor that spins up a flywheel, where the energy is ‘saved’.
The flywheel is then used to spin up the motor at the rear and send charge to front axle motors to assist the car’s acceleration out of corners for a limited period. The bursts of hybrid power are regulated and only kick in at speeds above 74mph. This cycle works around ten times per lap, and the R18 E-tron has a diesel fuel tank that is about two litres smaller than non-hybrid vehicles.
The flywheel system – sourced from Williams Hybrid Power, part of the same group of companies as the Williams F1 team – used to store the energy because it is lighter than a battery pack and able to cope with 3600 energy 'cycles' (charge/de-charge) per 24-hour race.
Le Mans organiser the Automobile Club de l’Ouest, together with the FIA, is encouraging hybrid technology at the famous endurance race. Audi will face stiff opposition from Toyota, which is returning to sportscar racing with a petrol-electric hybrid challenger. To be classed as a hybrid under Le Mans rules, a car must be able to exit the French circuit’s 400-metre, slightly uphill pitlane on electric power alone.