Audi R18
Audi's first closed-cockpit diesel hybrid Le Mans prototype.
The Audi R18 is a family of closed-cockpit Le Mans Prototype race cars built by Audi AG. It replaced the R15 TDI and marked the first time since the 1999 R8C that Audi used a closed cockpit for a Le Mans car, as well as the company’s first racer with hybrid power. Under the hood sits a 3.7-liter V6 TDI turbocharged diesel engine, smaller than the R15’s powerplant.
Audi Sport boss Wolfgang Ullrich suggested that the R18 name could serve as a lasting designation for the brand’s endurance racers, rather than giving each new model a distinct number. Five further evolutions of the R18 followed before Audi left the FIA World Endurance Championship in 2016.
The 2011 R18 TDI (RP1) debuted at the 1000 km of Spa. New regulations that year cut diesel engine displacement, reducing power and torque, so Audi adopted a closed cockpit to lower drag and maintain top speed. Despite the heavier design, weight-saving efforts made the R18 lighter than the R15 at 850 kg (before adding 50 kg of ballast to meet the 900 kg minimum). The single-piece monocoque reportedly weighed as little as 70 kg. A shorter wheelbase than the R15—by 64 mm—accommodated the smaller V6, and the car used double-wishbone suspension with pushrod torsion bars and dampers at both ends. Michelin developed wider front tires, similar in width to the rears, specifically for the R18.
Audi tested the car in a climatic wind tunnel in addition to Sauber’s facility in Hinwil, Switzerland, to study rain effects, visibility, and wiper performance. This also optimized driver cooling airflow, allowing removal of the air conditioning unit to save weight and improve efficiency. A heated windscreen, first developed for Audi’s A4 DTM program, was fitted.
The 3.7-liter V6 engine, developed from 2009, used an aluminum alloy block with a 120-degree bank angle to lower the center of gravity, enable a hot-vee turbo layout, and leave space for a hybrid system. A diesel particulate filter gave the car a quiet exhaust note and little soot. The engine weighed 25% less than the R15’s 5.5-liter V10 and was similar in weight to the R8’s 3.6-liter petrol V8, producing over 540 hp and 900 Nm of torque. A single Garrett TR30R VGT turbocharger sat in the hot valley, unlike the twin TR30R setup on the Peugeot 908 HDi FAP and the previous R15 TDI.
- Engine
- 3.7L V6 TDI turbocharged diesel
- Power
- Over 540 hp (hybrid system total over 700 hp)
- Torque
- 900 Nm
- Weight
- 850 kg (plus 50 kg ballast to meet 900 kg minimum)
- Transmission
- 6-speed sequential electrically activated gearbox by Xtrac
- Hybrid system
- 150 kW front MGU-K with Williams flywheel accumulator (max 45,000 RPM)
- First race
- 2011 1000 km of Spa
Lore & Background
The R18 was introduced for the 2011 season under new regulations that reduced diesel engine displacement, prompting Audi to adopt a closed cockpit to reduce drag and maintain top speed. Despite the heavier concept, weight reduction efforts made the R18 lighter than its predecessor, with a single-piece monocoque rumored to weigh as little as 70 kg. The car featured a 64 mm shorter wheelbase than the R15, double-wishbone suspension, and wider front tires developed by Michelin. The 3.7L V6 engine, developed from 2009, used a 120-degree bank angle for a lower center of gravity and a hot-vee turbocharger layout, and included a diesel particulate filter that resulted in a quiet engine note and reduced exhaust soot.
For 2012, Audi introduced two versions: the R18 ultra (non-hybrid) and the R18 e-tron quattro (hybrid), sharing the same RP2 chassis. The e-tron quattro's hybrid system used a 150 kW electric motor on the front axle and a Williams-supplied electromagnetic flywheel stored in the passenger seat area, capable of deploying energy above 120 km/h. The 2013 RP3 evolution retained the flywheel system but replaced the single MGU-K with two Bosch Motor Generator Units, providing four-wheel drive. Significant aerodynamic changes included rear wing extensions and a blown diffuser system that used exhaust gases to improve rear diffuser performance, though off-throttle blowing increased fuel consumption.
Reader's Guide
The Audi R18 series marked a significant shift in Audi's endurance racing strategy, combining diesel efficiency with hybrid technology for the first time. The closed-cockpit design, driven by regulatory changes, set a new aerodynamic direction for the manufacturer. The R18's development emphasized weight reduction and innovative solutions such as a heated windscreen from Audi's DTM program and climatic wind tunnel testing for rain visibility and driver cooling. The hybrid system, supplied by Williams F1, allowed Audi to compete with four-wheel drive capability under specific speed thresholds. The R18 designation was suggested by Audi Sport head Wolfgang Ullrich to be used for the foreseeable future, and five further evolutions of the R18 were produced until Audi exited the FIA World Endurance Championship in 2016. The car's 2012 and 2013 Le Mans victories demonstrated the effectiveness of its hybrid powertrain and aerodynamic refinements.
Did You Know?
- The R18 was Audi's first Le Mans prototype to feature a closed cockpit since the 1999 R8C.
- The hybrid system's flywheel unit was supplied by the Williams F1 team and could spin up to 45,000 RPM.
- The 2013 R18 e-tron quattro consumed 21% more fuel to cover only 1.5% more distance than the previous year at Silverstone due to off-throttle exhaust blowing.
- The R18's engine weighed 25% less than the R15's V10 and was similar in weight to the R8's petrol V8.
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