The electric-hybrid Audi R18 E-Tron quattro is to compete in the Le Mans 24 Hours .
From 1981 to 1997, Audi won four titles in the World Rally Championship, clinched three victories at Pikes Peak, a championship win in the TRANS-AM, two DTM titles and eleven national Super Touring Car Championships plus a Touring Car World Cup with quattro models.
For the first time since the 1998 ban, an all-wheel drive model is now allowed to compete in the FIA’s circuit racing programme. Yet what sounds like a simple return has been one of the biggest tasks ever tackled by Audi Sport to date, to package an additional front-wheel drive and a hybrid system into a sports car.
The Audi R18 E-Tron Quattro has a hybrid front-wheel drive system. Audi claims that the small and lightweight hybrid technology recovers more energy than any other system.
Audi has achieved a particularly compact MGU (motor generator unit) on the front axle. During energy recuperation, which is fully electronically controlled, drive shafts transmit the power to the inside of the MGU where the kinetic energy is converted into electric power during braking periods. The principle is similar to that of the commonly known dyno – albeit with extremely high energy flows.
Converters integrated into the housing transform this energy from alternating into direct current which in turn drives a rotating mass storage device located alongside the driver. The energy is stored by the current, accelerating this carbon fibre flywheel which runs in a high-vacuum to as much as 45,000 revolutions per minute. After cornering, this energy is available again to power the electric motors of the MGU unit which in turn drive the front wheels. Up to 150 kW of short-term power (204 HP) can be supplied to the front axle.
Audi has split the electric drive and the combustion drive between two axles, so achieving a positive weight distribution in the vehicle while making use of at least some of the advantages of a quattro drive system.
After presenting the concept to the ACO and the FIA for the first time Audi received a relatively quick response. The FIA wanted the focus to be on hybridisation, not the return of all-wheel drive. Therefore, a clause in the regulations was agreed that limits the advantage of a standard quattro drive when accelerating out of tight corners. The electrified axle may only be additionally used for acceleration above a speed of 120 km/h.
At the same time, the number of braking zones is specified by the FIA for each track. The prescribed 58-litre fuel tank capacity of the hybrid vehicle is two litres less than that of the conventional car. Also the amount of energy that may be recuperated between two braking zones is limited to 500 kJ.
So Audi is bringing back a form of quattro into motorsport even though the company is only allowed to compete with ‘part-time’ quattro at the moment.