The design to race at 800V points to a future production car with a similar design for the consumer. Wayne Gerdes – CleanMPG – July 23, 2016 While Porsche (919 shown), Audi R18 quattro and Toyota TS050 FIA WEC Hybrid race cars move ahead with technology that can be incorporated into consumer vehicles of the future, why are the large American racing series pushing technology for a bygone era? The Le Mans Prototype Porsche 919 Hybrid is about to make its one and only 2016 appearance in Germany. The six-hour race on the Grand Prix circuit of the Nürburgring, the fourth round of the FIA World Endurance Championship (WEC) will start in just over 7 hours as of this writing. The Porsche factory is the series’ leader and will fight to defend its title. At the same time its mission is to revolutionize the technology of future sports cars. With the 919 Hybrid, Porsche developed a new field of technology at racing speed. For the “Mission E”, a fully electric road-going concept sports car was unveiled in 2015. The 919 Hybrid designers adopted an 800V technology for the prototype race car. Porsche exhausted all current technology possibilities in designing the two-time 24 Hours of Le Mans winner. Basically, it consists of a 2.0L, V4 turbocharged gasoline engine – the most efficient combustion motor that Porsche has ever built– and two different thermo and kinetic energy recovery Hybrid system(s). 2016 FIA LMP1 Porsche 919 Hybrid During braking, a generator at the front-axle converts the car’s kinetic energy into electrical energy. In the split exhaust system, one turbine drives the turbocharger while another converts surplus energy into electrical energy. The braking energy contributes 60 percent, with the remaining 40 percent produced from exhaust gas. The regenerated electrical energy is stored in a Li-Ion battery and feeds an electric motor “on demand”, meaning, the driver can accelerate and call up the energy at the press of a button. In accordance with the latest regulation changes, the power from the combustion engine is just under 500 hp and the output from the electric motor is well over 400 hp. The use of these two energy sources requires a sophisticated energy strategy. In every braking phase, energy is regenerated at maximum. On the Nürburgring’s 3.2-mile Grand Prix circuit, this happens 17 times per lap as the 919 Hybrid enters each corner. The amount of recovered energy depends on the speed at which the driver drives into the corner and how tight it is. Braking regeneration lasts until the apex of every corner at which time the driver reaccelerates. In this moment, the aim is to utilize as much of the now stored energy as possible. As the driver steps into the throttle using fuel energy, “boost” electrical energy from the battery is also let loose but in a tightly controlled manner. The combustion engine drives the rear-axle and the electric motor drives the front. The 919 accelerates out of each corner without loss of traction using AWD. At consistently high engine speeds, the pressure in the exhaust system increases rapidly and drives the second turbine which is connected directly to an electric generator. Both energy sources are limited by the FIA WEC regulations as in a driver cannot use more than 1.8L of fuel per lap and no more than 1.3 kWh (4.68 MJ) of electricity. He must calculate this carefully so that at the end of the lap he has used this amount. He who uses more is penalized. He who uses less, loses performance. Converted to the 8.469-mile lap of Le Mans, which is the scale model for the regulations, the amount of electrical energy allowed is 2.22 kWh. This corresponds to eight MJ – and that is the highest energy class stipulated in the regulations. In 2015, Porsche was the first and only manufacturer that dared to push the limits so far. In 2016, Toyota is also competing in the eight MJ class. Audi uses six MJ recovery and application hybrid system. The WEC regulations almost completely balance these differences. At speed during the overnight hours. For the Porsche 919 Hybrid, a very close look at the individual alternatives was taken. Like all, Porsche would use the braking energy from the front-axle. For the second system, two solutions were considered: brake energy regeneration at the rear-axle or through the utilization of exhaust gas. Weight and efficiency pointed in favor of the exhaust solution. With brake energy recovery, the system has to store the regenerative energy in a very short period of time, which means coping with a lot of energy but at the expense of weight. The acceleration phases, however, are much longer than the braking phases, which allow a longer period of regeneration and makes the system lighter. With the combustion engine, the 919 already has a drive system on the rear-axle. Adding more power at the rear would have made wheel spin less efficient, leading to heavy tire wear. Porsche’s 919 Hybrid system running at a very high 800 volts influences the battery design, electronics design, e-motor design and charging technology. Porsche pushed the technology available today as far as they could. The racing brand stated it was difficult to find components to accommodate the high-voltage storage medium. Porsche chose a massively parallel liquid-cooled Li-Ion battery with each individual cell enclosed in its own .7 inches high and 0.71 inches in diameter cylindrical metal capsule. In both a road and racing car, power density and energy density must be balanced. The higher the power density of a cell, the faster energy can be recharged and released. The other parameter, energy density, determines the amount of energy that can be stored. In racing, the cells must the largest of both with braking and boost matching at exactly the same speed. 2016 Porsche 919 at SPA In an electric car for everyday use, storage capacity translates into range. In this regard, the requirements of the racing car and a road-going electric car are quite different. The 919 served as the trial vehicle for the voltage level of future hybrid systems. Important basic knowledge was discovered during the LMP1 program, such as, cooling for the battery and the electric motor, the connection technology for extreme high-voltage as well as battery management and the system’s design. From this experience, the production development team gained important expertise for the 4-door concept car Mission E with 800V technology. From this concept car a production vehicle will appear by the end of the decade to become the first purely electric Porsche.