Porsche 919 Hybrid – a bold technical concept and the most complex race car that the brand has ever put on wheels
Facing stiff competition on the racetrack has a tradition at Porsche: Since the founding of the company, the manufacturer has put new technologies and solutions to the test in motorsport. Much of what is proven on the racetracks flows into the production shortly afterwards – and on to the customer.
One of the most important test tracks for Porsche lies about 200 kilometres southwest of Paris. It is 13.629-kilometres long and is available only twice a year: the “Circuit des 24 Heures” at Le Mans. The world’s most famous long distance race and the accompanying test day two weeks prior serve as the ultimate test lab for Porsche. New technologies are put to the proof under the extreme conditions of tough competition over 24 hours. Several times per lap, the racing car reaches speeds far exceeding 300 km/h before being braked in hard and forced mercilessly over high kerbs; in scorching midday temperatures, in the cool of the night or in torrential rain… and always under the scrutiny of hundreds of thousands of spectators.
In 2015, Porsche scored its 17th outright win at Le Mans with the innovative 919 Hybrid. With this, the sports car manufacturer remains the undisputed record-winner at Le Mans. Moreover, in only its second LMP1 season, the Porsche squad won both titles in the FIA World Endurance Championship (WEC). Ultimately, it’s the customers who benefit from the many Class 1 Prototype technologies and solutions that proved successful in the WEC.
The fastest in the future: Porsche 919 Hybrid
At the beginning of the 2014 season, a new and very progressive set of technical regulations was put into force for the top LMP1 category of the World Endurance Championship (WEC). The amount of energy available per lap serves as the limiting factor in the performance of works cars. In addition, the rules specify that manufacturers must implement at least one hybrid system. The rule-makers, however, have allowed free choice of system type and of the method used to temporarily store the recovered energy, as well as the choice of engine design, the displacement and the power transmission. At the same time, the allowable fuel consumption is inversely proportional to the electrical energy that is re-invested into propulsion per lap (for more details, see the text “Porsche 919 Hybrid”). In the search for the best possible efficiency and the highest efficiency levels, Porsche engineers are thus allowed tremendous latitude in coming up with new and creative approaches. It was precisely these opportunities that provided the crucial argument for Porsche to return to top-level motorsport.
The result is the 919 Hybrid – a bold technical concept and the most complex race car that the brand has ever put on wheels. It highlights relevant technologies that hold future significance for the development of production vehicles.
A glance at the unusual engine concept of the Class 1 Prototype illustrates this: The winner of the Le Mans 24-hour race is mounted with just a 2-litre, but almost 500 hp turbocharged 4-cylinder in V configuration. That 4-cylinder technology that has already proven itself under tough racing conditions is now adopted in the new Porsche 718 Boxster – even in the classic boxer geometry and in the 2-litre 220 kW (300 hp) production version. Technology elements such as cylinder spacing, short-stroke design, central direct fuel injection and much more have been taken directly from the 919.
In addition, the 718 Boxster S combines two VTG turbochargers with variable turbine geometry for the first time with a so-called wastegate valve for even more precise regulation of the system pressure in the exhaust tract. This increases the efficiency of the entire drivetrain, and ensures that now the engine itself does not have to work against possible overpressure in the exhaust tract. In the 919 Hybrid, Porsche took a major leap forward and uses overpressure in the system to drive one of the VTG units, which is directly connected to an electric generator. This generator reroutes the generated power to a lithium-ion battery – a technological highlight used solely by the Le Mans winner in 2015.
Turbocharging: Until now turbocharging was reserved for Porsche’s top models, where it set benchmarks in terms of performance and consumption. Now, the six-cylinder flat engine of the 911 Carrera benefits from this technology that was originally developed for motorsport where it was extraordinary successful. Its conceptual advantage lies in the higher specific output, which allows for an adjustment of the displacement. Instead of following the prevailing trend of downsizing – i.e. extremely minimized aggregates – Porsche goes its own way with rightsizing and chose a comparatively large displacement of 3 litres. Through this, the engine can run longer at low revs and low speeds without the turbocharger generating boost. This improves the efficiency and especially the fuel consumption at low revs, while also providing a sporty and direct throttle response.
Hybrid drive: unlike its direct competitor in the WEC, the 919 takes a dual approach here. The first is already being used in a similar form in the Porsche 918 Spyder: during braking phases, a generator at the front axle converts kinetic energy into electrical energy. The second concept, on the other hand, is unique. An auxiliary turbine generator unit, which is laid out in parallel to the turbocharger, recovers energy from the exhaust gas stream – as a result, the Porsche 919 Hybrid not only recovers surplus energy during braking, but also under full throttle.
Storage technology: Porsche develops the liquid-cooled lithium-ion battery of the 919 Hybrid in-house. However, it has partnered with the company A123 Systems to develop the cell technology. Thanks to ongoing development under immense competition, Porsche has attained previously unheard of power densities. In the past season, the 919 was the first and only LMP1 racer to run in the top 8 MJ class (amount of electrical energy that may be used per Le Mans lap for boosting), despite a significant reduction in the overall weight of the prototype. In the meantime, the competition is now following Porsche’s lead and mounting lithium-ion batteries for the 2016 season.
Porsche has once again played a pioneering role in utilising the 800-Volt technology in the 919 Hybrid. The doubling of voltage compared to conventional 400-Volt systems shortens the charging time and saves weight, for example, through using thinner and lighter cables to conduct energy. Most of the components needed here had to be specially developed. With the Mission E four-seater concept car, Porsche demonstrated the advantages of the groundbreaking 800-Volt technology at the Frankfurt Motor Show (IAA) in 2015. As part of the “e-volution” project, a first 800-Volt test car based on the Porsche Cayman now exists. It benefits directly from the expertise gained in the development and racing of the Le Mans prototype.
The two permanently excited synchronous motors of the Mission E concept car have passed the test as a Motor Generator Unit (MGU) in the 919 Hybrid. With a system output of 440 kW (600 hp) they drive Porsche’s first all-electric sports car and combine this with an impressive driving range of more than 500 kilometres, needing just 15 minutes to charge 80 per cent of the electrical energy. The decision has already been made to develop and manufacture a production version based on the Mission E concept by the end of the decade.
Combustion engine: the DFI turbocharged petrol engine of the 919 Hybrid features an unconventional V4 layout, and a relatively low displacement of 2.0 litres. It is the most advanced and efficient downsizing engine that Porsche has built so far and is a trailblazer in terms of its injection technology. The four-cylinder engine also impresses with exemplary efficiency in terms of its friction losses. The engine was comprehensively optimised for the 2015 season. Despite its lower weight and greater stiffness, it now offers even better combustion efficiency. With the new regulation restrictions, the vehicle will tackle the 2016 season with almost 500 hp.
From the 800-Volt technology to cell development and battery management through to the cooling system, packaging and engine technology: Porsche gained expertise in the WEC, and it remains with Porsche. Production vehicle development specialists can access data from the LMP1 project. Some engineers even work in a dual role – on both the motorsport and street-legal vehicle sides. This assures direct transfer of information and experience.
On a direct path to series production – Porsche 911 RSR
In addition to the 919 Hybrid, Porsche campaigned the 911 RSR as a works-entry in the WEC. Both racing car models are rolling research labs, albeit with very different job descriptions. While the Class 1 Prototype offers a glimpse of the potential future and serves primarily as the pre-development platform, the 911 RSR offers insights that can be directly and quickly transferred to series production. Innovations developed for this racing car often very quickly benefit the 911 GT3 RS. It serves as a direct link between the racetrack and everyday driving, before other road models benefit. Here too, the primary focus is on relevant technologies and efficiency.
Keyword aerodynamics: Many specific details from the racing car make their way into production vehicles. They range from the contour of the front spoiler lip to the geometry of cooling air channels, temperature management and aerodynamic design of the underbody and the two wings.
Keyword driving dynamics: the concept for the dynamic engine mounts that are standard in the new GT3 RS were also derived from the 911 RSR. The electronically controlled system prevents undesirable engine movements that could disturb self-steering behaviour while driving in a sporty style. As a result, the GT3 RS reacts less to load alteration, and is much more stable in fast bends. At the same time, it reduces the transmission of vibrations and noises to the body, especially while idling, which contributes to the refinement of the vehicle.
Keyword lightweight design: the new 911 GT3 RS is ten kilograms lighter than the 911 GT3, making it a prime example of systematic weight reduction. The front and rear lids are made of carbon fibre, the rear window is made of a thin polycarbonate material, and other lightweight components made of alternative materials were derived from the 911 RSR, in which they were tested. The magnesium roof of the GT3 RS also follows an idea from the RSR. The same applies to the weight-optimised 12-Volt lightweight battery, which replaces conventional and much heavier lead batteries.
Efficiency as the decisive parameter for production and racing
With the 919 Hybrid and the 911 RSR, Porsche tests and explores relevant technologies. In times of increasingly stringent emission and fuel economy standards – which pose great challenges to high-performance sports car manufacturers in particular – one thing is most important: efficiency, i.e. the best possible relationship between input and results. Like no other topic, efficiency is the key to the countless Porsche successes in motorsport. Long before the brand scored its first outright victories at Le Mans, the manufacturer had seized efficiency trophies such as the “Index of Performance” and the “Index of Thermal Efficiency” time and again. These were special awards early on in the 24 Hours of Le Mans. As early as 1955 Porsche secured the fuel consumption category for the first time with the 550 Spyder. Even the 917 was able to pocket efficiency prizes in the historic wins of 1970 and 1971. Most recently, between 2007 and 2011, the 911 GT3 was unbeaten in its class in terms of fuel efficiency and won the Michelin Green X Challenge. It all comes down to this: developments that prepare the groundwork for victories and titles also serve as models of very fuel-efficient and low-emission production models.
The revolutionary efficiency regulations that were newly created in 2014 for the FIA World Endurance Championship allow great advances in development. An example of this: the best-performing 919 Hybrid car completed 348 laps of racing last year and converted 585 kilowatt-hours of energy into propulsive power. This amount of energy would be enough to power a Volkswagen e-Golf – one of the most efficient electric cars of the compact class – over a distance exceeding 4,600 kilometres. This is roughly the distance between New York and Los Angeles. In 2015, the 919 Hybrid of the 8-MJ class boosted 780 kilowatt-hours of energy. With this increase of more than 30 per cent, the e-Golf could cover an additional 1,500 kilometres.
Whatever the Porsche engineers develop to secure successes in motorsport – in the end customers benefit as well. This is because efficiency-boosting technologies, which have a positive effect on the competitiveness of a racing car, also benefit the production models. In the medium to long term this pays off in the form of even greater driving pleasure and improved performance data, and also with optimised fuel consumption and emission figures. At Porsche, the sports car of the future is being created at racing speed.