The Audi R18 e-tron quattro only starts its second race season in 2013 – but it is already a legend: exactly like the Audi R10 TDI, the first hybrid racecar to win the 24 Hours of Le Mans was voted by an Automobile Club de l’Ouest (ACO) jury to be one of the most important Le Mans racecars of all time.
Technical milestones at the 24 Hours of Le Mans are nothing unusual for Audi: the brand with the four rings has always consistently used the endurance classic to race new technologies – TFSI, TDI, VTG, ultra lightweight design or now e-tron quattro are good examples of the brand’s pioneering spirit in motorsport.
Through the intelligent combination of a conventionally powered rear axle with an electrically powered front axle the Audi R18 is transformed into an e-tron quattro – the first Audi racecar which is not powered exclusively by a combustion engine. The system located in the front of the car comprises of two driveshafts and a Motor Generator Unit (MGU) together with planetary gearbox, which retrieves its own energy from the electric flywheel accumulator mounted alongside the driver in the cockpit.
The energy is recuperated and stored during braking. In the process, the front wheels drive the Motor Generator Unit. This accelerates electrically a carbon-fiber flywheel, which runs in a high vacuum. Once the corner is taken and the driver accelerates again, the system delivers the energy to the front axle – but as the regulations state, however, only above a speed of 120 km/h. “As a result, the advantage that we could theoretically have with the electric quattro drive is obviously severely limited,” explains Head of Audi Motorsport Dr. Wolfgang Ullrich. The regulations also limit the maximum amount of energy that can be transmitted to the front wheels between two braking phases.
The hybrid system and quattro driver are, however, not the only peculiarities of the Audi R18 e-tron quattro. Only with the help of consistent and logical ultra lightweight design was it possible to realize the minimum weight permitted by the regulations – and this without compromising the aspects of safety and reliability.
To achieve this Audi Sport explored every possibility in all the decisive areas: with the chassis in the same way as the engine and drivetrain. The R18 grabbed attention in 2011 with a one-piece carbon-fiber monocoque – a first among Le Mans Prototypes. Consequently, the safety cell is particularly light, yet extremely stable and safe at the same time. An innovation in the transmission area followed in 2012: a new gearbox with carbon-fiber composite casing was developed for the R18 – another premiere for endurance racing. In the suspension area, new materials and manufacturing processes to reduce mass are also used.
Thanks to its innovative architecture, the particularly compact 3.7-liter V6 TDI engine with mono turbocharger plays a significant role in compensating for the additional weight of the hybrid system. Despite the frequent new restrictions imposed by the regulations, Audi Sport still extracts over 360 kW (490 hp) and a maximum torque of more than 850 Nm from the power plant thanks to the efficiency of the overall concept.
Numerous other technical innovations such as the electromechanical steering, digital rear view mirror, which shows the events unfolding behind on an AMOLED display in the cockpit, or the extremely bright full LED headlights make the R18 e-tron quattro a unique technology demonstrator.
Although the R18 successor for the new LMP1 regulations, which come into force in 2014, has long since taken shape, many details of the Audi R18 e-tron quattro were reworked for the 2013 season. The flywheel accumulator is even more efficient. The MGU now produces over 2 x 80 kW instead of the previous 2 x 75 kW. The aerodynamic efficiency was further optimized, the ultra lightweight concept systematically continued, and the digital rear view mirror used for the first time last year was complemented by an additional two forward-facing cameras that give the drivers the maximum field of front-vision.
The 2013 model Audi R18 e-tron quattro celebrates its race debut on March 16 in the 12-hour race at Sebring (Florida).
Technical data Audi R18 e-tron quattro
Vehicle type: Le Mans Prototype (LMP1)
Monocoque: Carbon-fiber composite with aluminum honeycomb, tested according to the strict FIA crash and safety standards
Battery: Lithium ion batteries
Engine: Turbocharged 120° V6, 4 valves per cylinder, DOHC, 1 Garrett turbocharger, mandatory intake air restrictor of 1 x 45.1 mm diameter and turbo boost pressure limited to 2.8 bar absolute, diesel direct injection TDI, fully stressed aluminum cylinder block
Engine management: Bosch MS24
Engine lubrication: Dry sump, Castrol
Displacement: 3,700 cc
Power: Over 360 kW / 490 hp
Torque: Over 850 Nm
Hybrid system: Electric flywheel accumulator, max 500 KJ, WHP
Motor Generator Unit (MGU): MGU on the front axle, water cooled with integrated power electronics, 2 x 80 kW
Drive / transmission: Rear wheel drive, traction control (ASR), four-wheel drive e-tron quattro from 120 km/h
Clutch: Carbon clutch
Gearbox: Sequential, electrically activated 6-speed racing gearbox
Differential: Limited-slip rear differential
Gearbox housing: Carbon-fiber composite with titanium inserts
Driveshafts: Constant velocity sliding tripod universal joints
Steering: Electrical assisted rack and pinion steering
Suspension: Front and rear double wishbone independent suspension, front pushrod system and rear pull rod system with adjustable dampers
Brakes: Hydraulic dual circuit brake system, monobloc light alloy brake calipers, ventilated carbon disc brakes front and rear, infinitely manually adjustable front and rear brake balance
Wheels: O.Z. magnesium forged wheels
Tires: Michelin Radial, Front: 360/710-18, rear: 370/710-18
Length: 4,650 mm
Width: 2,000 mm
Height: 1,030 mm
Minimum weight: 915 kg
Fuel tank capacity: 58 liters