The Audi R18 is series of Le Mans Prototype (LMP) racing cars constructed by the German car manufacturer Audi AG. It is the successor to the Audi R15 TDI. Like its predecessor, the R18 uses a TDI turbocharged diesel engine but with a reduced capacity of 3.7 litres and in a V6 configuration. For the first time since the 1999 R8C, the Audi Le Mans prototype used a closed cockpit design. The R18 is also the first racing car from Audi to feature hybrid power.
Although Audi have previously given each new developed model of endurance racing car a distinct model number, the head of Audi Sport, Wolfgang Ullrich, suggested the R18 designation for Audi endurance racing cars could be used for the foreseeable future. There were five further evolutions of R18 until Audi exited the FIA World Endurance Championship in 2016.
2011: R18 TDI (RP1)
Due to the new regulations introduced in 2011 which significantly reduced diesel engine displacement and thus power and torque as a result, Audi moved to a closed-cockpit concept to reduce drag in order to increase efficiency and maintain top speed.
Despite the theoretically heavier closed-cockpit concept, a heavy focus on weight reduction resulted in the R18 being lighter than the previous R15 at (excluding of ballast to hit the minimum weight limit), with rumors that the single-piece monocoque weighed as little as . The R18 had a shorter wheelbase than the R15 due to its smaller V6 engine, and it used a double-wishbone suspension with pushrod torsion bars and dampers at both front and rear. The R18 uses wider front tires that are similar in width to the rear tires unlike previous cars, which were custom developed for the R18 by Michelin.
In addition to the Sauber wind tunnel located in Hinwil, Switzerland, Audi also tested the R18 in a climatic wind tunnel to test the effects of rain on the car, including visibility and windshield wiper performance. Additionally, it allowed for the optimization of driver cooling airflow within the cockpit, allowing for the removal of the driver air conditioning unit while staying under regulatory temperature limits, saving weight and gaining power and efficiency. Additionally, the R18 featured a heated windscreen first developed in Audi's A4 DTM program.
The R18's new 3.7L V6 which began development in 2009 uses an aluminium alloy block and 120 bank angle, chosen to reduce the center of gravity, allow for a hot-vee turbocharger layout, and provide room for a potential hybrid system. Additionally, it is equipped with a diesel particulate filter, which resulted in the car's quiet engine note and relative lack of exhaust soot. The engine weighed 25% lighter than the R15's 5.5L V10 and was a similar weight to the R8's 3.6L petrol V8. It is claimed to develop over and of torque. The engine uses a single Garrett (Honeywell Turbo Technologies) TR30R VGT turbocharger in a hot valley (hot vee) configuration, as opposed to the twin TR30R configuration of both the Peugeot 908 HDi FAP and the previous Audi R15 TDI.
The R18 uses a new 6-speed gearbox custom-designed by Xtrac which was controlled electrically rather than pneumatically, saving weight by eliminating the pneumatic system.
As per the new rules for Le Mans in 2011, the car featured a stabilisation fin on the engine cover. Additionally, the R18 was Audi's first car to feature LED headlights.
The R18's launch event was held on 10 December 2010 in Ingolstadt. After private testing of the initial specification of the car at Sebring, the R18 appeared at the 2011 12 Hours of Sebring in March with a major revision which Audi referred to as 'Evolution 2' but did not compete in the race, which was instead competed by an updated version of the R15 plus. According to Audi, the Evolution 2 revision was lighter than the initial specification.
2012: R18 ultra and R18 e-tron quattro (RP2)
For 2012, Audi introduced a new car called the R18 ultra and R18 e-tron quattro for the non-hybrid and hybrid versions, respectively, which won Le Mans. Both the Ultra and e-tron quattro R18 were run at the 2012 24 Hours of Le Mans. Development of the RP2 began in February 2010.
Both the hybrid and the non-hybrid used the same new chassis, known internally as RP2, which could accommodate an electro-flywheel hybrid system at the front axle. The ultra is identical to the e-tron quattro, except the hybrid system components are removed and replaced with ballast at the same mounting points. To improve visibility, the lack of which contributed to the R18's severe crashes in the 2011 24 Hours of Le Mans, the windows were enlarged and head restraints reworked. An indentation was added to the roof below the engine air intake to feed cleaner air to the engine, resulting in an increase to engine power. Due to the additional weight of the hybrid system, Audi focused on weight reduction, which resulted in the car being lighter than the RP1 R18.
The 3.7L turbodiesel engine was designed to accommodate the RP2's hybrid systems, including a compressed-air reservoir hybrid system powered by the turbocharger that could be used to prevent turbo lag, though the system was banned before it was used in competition.
The R18 e-tron quattro's hybrid system consisted of a electric motor mounted on the front axle within the monocoque, which stored recuperated energy in an electromagnetic mechanical flywheel located in the passenger seat area of the cockpit. The flywheel unit is supplied by the Williams F1 team, which originally designed it but never used it in F1, and consists of a composite flywheel held under vacuum with a maximum speed of 45,000RPM. The electrical energy generated by the MGU-K front motor is transferred to the flywheel unit through wires, which then spins the flywheel using an electromagnetic clutch to store the energy kinetically. The flywheel's energy can later be deployed by converting it into electric energy through the electromagnetic clutch to power the MGU-K front motor, which was only allowed above by regulations. While the hybrid system is deploying, the car has a total of over .
In addition to the changes required by the regulations (reduced air intake restrictor and 60-litre fuel tank) the car was completely reworked to reduce weight. These changes included Xtrac sequential electrically activated 6-speed racing gearbox with gearbox housing made of new carbon-fiber composite with titanium inserts, carbon clutch, changes to the carbon-fiber composite aluminum honeycomb monocoque built by Dallara, single Garrett (Honeywell) turbocharger with boost pressure limited to absolute, Bosch MS24 engine management, 1 x diameter air restrictor, OZ magnesium forged wheels, Brembo brakes in a Formula 1-style 'cake-tin' housing, and Michelin Radial 360/710R18 front and 370/710R18 rear tires.
2013-spec R18 e-tron quattro (RP3)
The 2013 R18 e-tron quattro is an evolution of the 2012 RP2 R18 e-tron quattro. Though designated RP3, several RP3 monocoques are simply rebadged RP2 chassis, and the crash structure, headlights, suspension, and gearbox were also carried over from the RP2. The RP3 continued to use the same 500 kJ flywheel accumulator system designed by Williams Hybrid Power as the RP2, but the MGU-K motor was replaced by two Bosch Motor Generator Units driving the front wheels with water-cooled integrated power electronics, providing the car with four wheel drive (quattro), and a smaller 58-litre fuel tank. The hybrid system, as per the regulations, can only deploy energy at speeds above . Unlike the 2012 R18's MGU-K, the upgraded MGU-K could fully charge the flywheel at tracks shorter than the Circuit de la Sarthe; this increase in performance led to Audi dropping the non-hybrid ultra model for 2013 onwards.
Significant aerodynamic changes include the addition of rear wing extensions which exploited a loophole in the regulations, and the addition of a blown diffuser system, which utilizes engine exhaust gasses to block turbulent airflow from the wheels from interfering with the airflow within the rear diffuser; this necessitated the use of a splitter to feed exhaust gasses from the exit of the single turbocharger to a slot adjacent to the inner surface of the rear wheels. The use of off-throttle exhaust blowing, which burns fuel off-throttle to maintain exhaust gas supply to maintain the blown diffuser effect, resulted in the 2013 R18 to consume 21% more fuel to cover only 1.5% more distance than the previous year at the 2013 6 Hours of Silverstone, as noted by media outlets.
The e-tron has six automatic modes that are driver-selectable on the steering wheel. The modes manage engine mapping, short bursts accelerating from corners, quattro four wheel drive, wet weather, etc. Allan McNish said "I don't have to press a button ... It does it automatically ... It is like traction control."
2014-spec R18 e-tron quattro (RP4/5) For 2014, Audi introduced an all-new car, internally called the RP4. Unlike previous Audi LMP1 cars, which were designed with help from Dallara, this new version of the R18 was built in cooperation with Italian motorsport engineering firm YCOM.
Changes from 2013 R18 e-tron quattro include the introduction of blue laser beam backlights with a yellow phosphor crystal lens complementing the LED headlights, a revised V6 TDI engine with an electric turbocharger, upgrades to the flywheel accumulator system and an exhaust heat recovery system. The system captures the thermal energy from the exhaust and can add power to either the turbocharger or the flywheel accumulator system. Audi later opted not to race with the second Energy Retrieval System, which is known as a Motor Generator Unit-Heat [MGU-H] in Formula One, because it did not result in the performance gain engineers had hoped for and was therefore considered an unnecessary risk to take. The aerodynamics have been heavily revised in accordance with the new rules: the width is reduced by 10 cm, the height is increased by 20 mm and there are a new set of front wings. The exhaust-blown diffuser on the 2013 model has been banned and removed. The safety monocoque has been strengthened with additional fabric. Wheel tethers and extra crash structures are also added to the car. Finally, there are numerous smaller upgrades to vision and ergonomics to improve drivability.
For 2014, updates to the car, now called the RP5, focused on reducing aerodynamic drag. Notable changes include the removal of the side mirror pods, integrating the mirrors onto the front fender bodywork instead.
2016-spec R18 (RP6)
On 29 November 2015, Audi Sport debuted the redesigned R18 that the team planned to race in the 2016 FIA World Endurance Championship season. The new R18 featured significantly altered aerodynamics, including a raised nose similar to pre-2014 Formula One nose designs, air scoops above the front fenders, integrated mirrors, and other body modifications. The KERS for the 2016 R18 had also been changed from a flywheel system to a lithium-ion battery, and had been upgraded from the 4 MJ class to the 6 MJ class for additional boost. The engine remained the same 4.0 L turbodiesel V6. Audi dropped the e-tron quattro name badge for the 2016 season.
Audi raced two R18s all across the 2016 WEC season. They finished first at Silverstone; however, an irregularity concerning the underbody of the winning car resulted in post-race disqualification; Audi decided not to dispute this decision. They won at Spa-Francorchamps and Bahrain, and finished third at Le Mans. They finished second in the Manufacturers' Championship.
Technical data Technical data R18 TDIultimatecarpage.com, retrieved 2011-10-13 (RP1)R18 ultra (RP2)R18 e-tron quattro (RP2)R18 e-tron quattro (RP3)R18 e-tron quattro (RP4)ultimatecarpage.com, retrieved 2012-03-03R18 e-tron quattro (RP5) Audi R18 (RP6)ultimatecarpage.com, retrieved 2016-11-20 Engine 120° V6 turbodiesel