Motorsport – FIA WEC Audi R18 hybrid technology. The 2016 FIA World Endurance Championship begins at Silverstone later this month, with the debut of the all-new R18. Martyn Pass examines the sportscar which Audi hopes will record its 14th Le Mans victory in June…
For the FIA World Endurance Championship (WEC) and the Le Mans 24 Hours, Audi is emphasising focal areas in the 2016 season: The Audi R18 that has been redesigned from scratch has almost nothing in common with its predecessor. It features a more radical aerodynamics concept, including a new safety cell, its hybrid drive system is battery-operated for the first time, the V6 TDI engine has been revised, and new system solutions have been added. As a result, Audi’s LMP1 sports car is more powerful, more innovative and clearly more efficient than its predecessor, consuming less fuel than any of the generations before it.
While the new R18 is Audi’s strongest race car to date, with a power output of more than 1000 hp delivered by the TDI and hybrid powertrain, it consumes 10 per cent less fuel than before. The FIA WEC regulations have been providing manufacturers with incentives to build increasingly efficient race cars since 2014. Starting in the 2016 season, the competition will intensify as the upper limit for fuel consumption will decrease considerably, by 10 megajoules per lap at Le Mans. ‘The result is a race car that manages energy even more effectively than before. This is an objective we’re pursuing for our road-going automobiles as well,’ says Head of Audi Motorsport Dr. Wolfgang Ullrich. ‘This type of motorsport continues to set an example for automotive engineering. For Audi, production relevance has been a core topic of all racing programs for 35 years.’
The development engineers at Audi Sport were challenged to enhance the efficiency of the Audi R18. As a result of switching to the 6-megajoule class, the hybrid system, due to the regulations, now recovers 50 per cent more energy. The car’s aerodynamics concept is fundamentally new. Nearly all vehicle systems have been refined or redesigned.
Consequently, energy consumption decreases, the race car has become lighter, and allows for more favourable packaging of the component assemblies. This has resulted in an R18 which, even visually, clearly differs from its predecessor.
No other race car embodies the philosophy of optimised aerodynamics as consistently as the LMP1 sports cars and the new Audi R18 has a significantly altered exterior, with the proportions of the front end and the cabin within the overall vehicle length changed and its conspicuous nose clearly slimmer than before.
‘The new proportions influence weight distribution and aerodynamics,’ explains Jörg Zander, Head of Technology at Audi Sport. ‘Our most important objective was to improve airflow.’ At the front end, airflow has to be directed across the top of the race car and between the wheel wells, enter the cooling ducts through the bodyshell, and optimally approach the underfloor. ‘In this process, vortices must be avoided, as this costs energy,’ says Zander. Undesirable vortices and turbulent flow would reduce the energy in the airflow and increase resistance.
The smaller the space which the monocoque – the central stressed structure and safety cell of the race car – occupies in this area, the larger are the clearances for low-loss airflow. Thanks to the new proportions, the new Audi R18 directs airflow even more effectively to optimally approach the underfloor. At the rear, the air exits again through the diffuser.
As a result, it produces a major portion of the downforce under the race car, which is beneficial in cornering. Audi developed a new monocoque, modified the proportions within the prescribed maximum length of 4650 mm, and designed all the component assemblies accordingly.
Also new are the dimensions and positions of the prescribed openings in the front wheelarches. They are intended to reduce undesirable aerodynamic lift effects in the case of lateral airflow. Their areas have been enlarged by 45 per cent compared with the 2015 season.
This new concept requires innovations in many other areas. The suspension is a case in point. Due to the new monocoque, the mounting points for the front suspension have significantly changed. To make them more compatible with the position of the driveshaft for the hybrid system, the new mounting points have been rearranged. Suspension kinematics have been significantly revised.
Wishbones featuring a new design are now used for wheel guidance and the lift and roll spring-damper elements are actuated by pushrods at the front. The rear suspension kinematics have also been optimised. As in the case of the previous-generation vehicle, the spring-damper elements are controlled using pullrods. Optimum balance of the race car in all speed ranges is guaranteed by balancers of the Linked Suspension System (LSS) in the chassis.
The transmission is a new design as well. Audi’s simulations revealed that the optimised engine allows a very good spread of gear ratios with minimal rpm jumps even in combination with a 6-speed instead of the previous 7-speed unit. As a result, the engineers managed to further reduce the weight of the transmission. In the other areas of the vehicle’s structure, Audi rigorously pursued its lightweight design approach as well, while retaining the high torsional stiffness of the chassis.
In addition, new solutions for the actuators of individual systems of the Audi R18 help reduce weight. While in the previous-generation vehicle electrical actuators were still operating in the braking, transmission and engine systems, the new Audi R18 uses an all-new development of a high-pressure central hydraulic system. The regulations prescribe a minimum weight of 875 kg for the LMP1 hybrid sports cars. In spite of a more powerful and therefore necessarily heavier hybrid system, Audi does not exceed this limit.
Hybrid pioneer Audi, the first manufacturer to have won the Le Mans 24 Hours with an energy recuperation system, was using a flywheel energy storage system from 2012 to 2015. Now the time is ripe for the next step. In the future, a battery will be accumulating the energy. Electrokinetic technology is being replaced by an electrochemical storage system.
‘The flywheel accumulator definitely proved viable for the lower energy classes,’ explains Thomas Laudenbach, Head of Electrical, Electronic and Energy Systems at Audi Sport. ‘But due to the fact that we now have to process even more energy than before, a technology change suggested itself.’ The previous flywheel accumulator guaranteed high power density, Now, favourable energy density has to be achieved as well, as Audi is switching to a higher hybrid energy class. Starting in the 2016 season, the amount of energy will increase by 50 per cent to 6 megajoules. When comparing this level with the one from the 2014 season, the engineers have even tripled the amount of recuperated energy within this period of time.
For the first time, Audi will be relying on a lithium-ion accumulator as the hybrid energy storage system. Since 2009, the batteries for the electrical system of Audi’s LMP sports cars have been based on this technology. The production-based cells of the new hybrid storage system use advanced and powerful cell chemistry and are serially connected.
The system is located within the high-strength safety structure in the monocoque and separately encapsulated once more. Electrical and electronic safety systems monitor various parameters – from individual cells through to the overall high-voltage system – and will intervene if necessary. The shut-off logic naturally includes crash detection.
The energy stored by the system is generated by an MGU (Motor Generator Unit) at the front axle. The Audi R18 converts the rotary motion of the front wheels into electrical energy when the driver brakes before entering a turn and feeds it into the storage system. This way, the hybrid sports car utilises energy that would otherwise be lost.
If the race driver accelerates again on exiting the turn, the current flows in the opposite direction to power the MGU. As a result, the front axle of the R18 helps accelerate the race car again. A low-temperature cooling circuit, which is separate from the engine cooling system, cools the battery cells, MGU and power electronics.
From the 2016 season on, there will be a track-specific limitation imposed on power output in addition to the previous energy classes. Although the MGU may recuperate any desired amount of energy, it may now only supply 300 kW (408 hp) in the race at Le Mans.
Audi has designed its MGU for an output of more than 350 kW (476 hp) in order to recover as much energy as possible. The reason is that even when braking at high speed, the braking phases of an LMP1 race car last only three to five seconds. The high system output helps efficiently recover the required energy. At Le Mans, the system may only supply 300 kW during subsequent acceleration. Accordingly, the energy from the hybrid system will be available for a longer period of time. This limit does not apply to the other FIA WEC rounds. By opting for the 6-megajoule class, Audi has presented its most powerful MGU so far.
In 2012, Audi started with about 150 kW (204 hp) of electrical power output. To date, this level has far more than doubled. Conceptually, the previous and the new MGU are akin to each other, but the power electronics, stator and rotor are new developments. This generation of the hybrid drive system delivers high output and develops strong torque, as a result of which the loads acting on the components that transmit power to the front axle increase accordingly. Audi uses a limitedslip differential at the front axle to transfer torque with minimal loss.
The developers of the hybrid drive system were allowed to increase output. The engine development team headed by Ulrich Baretzky was confronted with the opposite challenge for the 2016 season. The 4-litre V6 powerplant receives clearly less fuel, which initially reduces its output. Two factors have to be considered in this respect. Audi switched to a higher hybrid energy class – and the regulations allocate less fuel to race cars which recuperate large amounts of energy.
This aspect results in a deficit of about 3 per cent. At the same time, another change is taking effect. The speed of the LMP1 race cars continually increases. To control it, the officials of the FIA, the WEC and the Le Mans organiser ACO allocate clearly less fuel energy to the hybrid race cars. ‘This is a development which, as a manufacturer, we principally support in order to control the lap times,’ says Dr. Wolfgang Ullrich.
The basic concept of the V6 TDI engine dates to 2011. With its double-flow VTG mono turbocharger, 120-degree cylinder bank angle, the exhaust gas side within the V angle, and innovative detailed solutions the unit tends to be regarded as unusual. The initial displacement volume of 3.7 litres increased to 4.0 litres in 2014. ‘We’re now using the basic engine concept for the sixth consecutive year. This shows how sound the basic idea still is,’ says Ulrich Baretzky. ‘Due to efficiency increases, we partially compensate for the lower amount of fuel.’
Among other things, the turbocharger is now lighter and more efficient. Externally, the V6 TDI has changed as well. Individual components are now arranged differently in order to make room for the new aerodynamics concept. The prescribed limitation of the charge pressure to a factor of 4 does not change the engine’s torque of more than 850 Nm.
The higher efficiency pays off, as the fuel cell capacity of the race car has been reduced further as well – by 8 per cent to 49.9 litres. The efficiency increases of the race car are remarkable in a historic comparison. The current V6 TDI consumes 32.4 per cent less fuel than the first generation did in 2011.
This progress is even more substantial in a comparison with the original year of 2006. Back then, Audi used TDI technology for the first time. Thanks to this technology Audi has since clinched eight victories, a distance record, plus two world championship titles. Today, Audi’s LMP1 race car with the current engine uses 46.4 per cent less fuel at Le Mans and yet it still achieves lap times that are 10 to 15 seconds better than a decade ago. All of this is possible thanks to the sum of all the advances that have been made in the areas of aerodynamics, lightweight design and the powertrain.
In terms of safety, the LMP1 race cars will continue to set standards in the future as well. Audi complements the exacting requirements of the regulations by in-house research that far exceeds these rules. In the field of active safety – the detection of hazards and accident prevention – the Audi drivers can draw on a wealth of tools. While the driver information monitor in the cockpit to display race control flag signals is prescribed, Audi assists its drivers with a number of additional solutions.
For instance, Matrix LED headlights combined with Audi laser light optimise the light beam of the race cars that can reach speeds of up to 340 kph. Since 2015, Audi customers have been able to order laser light in the second generation of the Audi R8 as well. Matrix LED technology has also been making its way into a growing number of model ranges.
Particularly good rearward vision is provided by a lightweight and energy-efficient camera system that requires minimal energy in combination with an ultramodern AMOLED screen that serves as a digital rear-view mirror. Since the 2001 season, the drivers and pit crews have been keeping an eye on tyre pressure using a tyre pressure monitoring system. And, last but not least, the Audi R18 automatically controls brake force distribution with respect to the hybrid system in the respective operating condition.
In the event that an accident cannot be avoided, the passive safety systems take effect. The monocoque consists of a high-strength CFRP structure with an aluminium honeycomb core and has a front crash nose for energy absorption. In 2011, Audi was the first manufacturer to use a single-piece monocoque.
The cell has been provided with additional side impact protection, as Nylon layers integrated into the cockpit walls prevent the intrusion of objects. In rear-end collisions a CFRP structure at the transmission absorbs the impact energy.
Double wheel tethers have been successfully used since the 2014 season, to reduce the risk of wheels separating from the race cars in accidents.
Finally, the high-voltage protection systems ensure that the electrical currents in the hybrid system can be safely controlled. There is no other motorsport discipline that uses an equal amount of high technology to protect the driver before or during an accident.
Be it in terms of the performance capabilities and safety of the race cars to the furthering of efficiency and innovations – in the sum of all technological features, the LMP1 class remains unique around the globe and therefore of utmost relevance for the future of the automobile.
Britain’s Oliver Jarvis will get his WEC title aspirations underway in the 6 Hours of Silverstone on Sunday, April 17 and the Cambridgeshire driver is totally focused on achieving glory for the Four Rings…
‘I can’t wait to get my second full WEC season underway and hope that my teammates Loïc, Lucas and I can continue as we finished the end of last year on a good run. Despite not getting the ‘headline’ results, we really came together as a team and had a strong end to the 2015 season.
‘Last year for me was a big learning curve, with two new team-mates and with the majority of tracks being totally new to me. However, with our performances from Le Mans onwards, we can head into the 2016 season full of confidence. I think having last year as a full-time WEC driver under my belt will be invaluable for me this year as we aim to go out and fight for victory, not just in the 24 Hours at Le Mans, but also to win the world Championship.
‘2016 is especially exciting as Audi has developed and built a completely new [R18] sports car. It was no secret last year that one of our biggest weaknesses, compared to our competitors, was the lack of hybrid power. This year, however, as we change from flywheel to battery technology and step up from 4MJ to 6MJ, we hope to have eliminated this weakness and therefore really be in a position to take the fight to our rivals in LM P1.
‘With such strong competition in the form of Porsche and Toyota, it’s important to continually develop and move forward and I really think the new car is a big step in the right direction but that said, the new Audi R18 will still be relatively new when we arrive at Silverstone. It won’t be until the qualifying session on the Saturday that we will know if the hard work has been enough. Our competitors will certainly not have stood still over the winter either!
‘I love the first race of the year as it’s that time where all the guessing stops and you really get to see where you are in the competitive order. For me, personally, it’s also fantastic to be able to open the season with my ‘home’ race at Silverstone. Last year I headed into the race weekend not expecting to particularly enjoy the track, based on my experiences in a GT car there, but was instantly blown away by how well it suited the likes of LM P1 cars with the added downforce.
So this year I can’t wait to get back and get going on what proved to be one of the best tracks of the year with its fast, flowing and committed corners. Last year we certainly had the pace to take the victory at the opening round so I hope that this year is no different and we are able to stay out of trouble to give ourselves that opportunity.’
‘The efficiency increases of the race car are remarkable in a historic comparison. The current V6 TDI consumes 32.4 per cent less fuel than the first generation did in 2011…’
‘Hybrid pioneer Audi was using a flywheel energy storage system from 2012 to 2015 but Audi will now be relying on a lithiumion accumulator as the hybrid energy storage system…’
‘This type of motorsport continues to set an example for automotive engineering…’
‘Our most important objective was to improve airflow…’
