Crucial in the development of the Le Mans prototype were the newly created and revolutionary racing rules for this class as they relate to energy efficiency. In 2014, it will not be the fastest car that wins the World Endurance Championship series and the 24 hours of Le Mans, rather it will be the car that goes the furthest with a defined amount of energy. And it is precisely this challenge that carmakers must overcome. The 919 Hybrid is our fastest mobile research laboratory and the most complex race car that Porsche has ever built.

—Matthias Müller, Chairman of Porsche AG

The hybrid powertrain of the Porsche 919 Hybrid. The V4 gasoline engine with direct injection and turbocharging is integrated in the chassis as a mid-engine. The batteries at the center of the vehicle supply the electric motor at the front axle with energy. Click to enlarge.

The high efficiency of the Porsche 919 Hybrid is the result of a balanced overall concept. The drive system is based on a 2.0-liter V-4 gasoline engine that is compact and lightweight. The engine is a structural component of the chassis, and reaches a maximum engine speed of approximately 9,000 rpm.

It features direct injection, a single turbocharger and thermodynamic recovery capabilities. The compact unit outputs around 500 hp (373 kW).

Two different energy recovery systems harness energy to replenish the batteries and provide power. The first system is the innovative recovery of thermal energy by an electric generator powered by exhaust gases. The second hybrid system is a motor on the front axle utilizing brake recuperation to convert kinetic energy into electric energy.

The V-4 gasoline engine of the Porsche 919 Hybrid features direct injection, turbocharging and an energy recovery system for the exhaust gases. Click to enlarge.		The single electric motor distributes its power to the two front wheels via a differential as needed. The advanced energy management unit for the battery is located near the center of the vehicle. Click to enlarge.

The electric energy is then stored in water-cooled lithium-ion battery packs from A123 Systems (earlier post) and when the driver needs the stored power, the front motor drives the two front wheels through a differential during acceleration. This gives the Porsche 919 Hybrid a temporary all-wheel drive system, because the gasoline engine directs power to the rear wheels, just like the 918 Spyder.

Intelligent management of electricity was a focus of the racing engineers who designed the 919 Hybrid. Efficient use of available power helps to achieve an optimal lap time. The driver can select several automated driving modes that effect vehicle dynamics. Race traffic, course layout and weather conditions are all taken into consideration when selecting the driving mode. The developers had a chance to experience these adverse conditions with the 911 GT3 R Hybrid—which used a flywheel KERS—during the running of the Nürburgring 24 hour race in 2010 and 2011.

The allowable fuel consumption depends directly on the amount of electrical energy the driver can use per lap, known as the Boost function. There are four classes of racecars with electric boost levels ranging from 2 to 8 mega joules (MJ). Porsche is developing the 919 Hybrid for the “Premiere class" with an energy recovery capacity of 8 MJ.

This requires high-performance energy recovery and storage systems, which are larger and heavier than the other classes. A flow meter limits the amount of fuel flow creating a challenge to balance the hybrid system between the use of electric energy and gasoline engine power. For example, at the 24 Hours of Le Mans, the turbocharged gasoline engine is driven at full load for 75% of the 8.48 mile lap and only has 1.23 gallons of fuel available.

Despite the addition of many new technical systems, race regulations have reduced the specified minimum vehicle weight by 66 lbs to 1,918 lbs compared to the prior year. This ambitious requirement has Porsche engineers optimizing the smallest details, using the right material in the right place for the intended purpose.

As in Formula 1 racing, the chassis of the new Porsche 919 Hybrid consists of a carbon-fiber monocoque, combining lightweight materials and a high degree of torsional rigidity. The multilink suspension and 14-inch wide Michelin race tires are an important prerequisite for performance in all conditions.

The Porsche 919 Hybrid must not exceed a length of 183.1 inches, a height of 41.3 inches, and the width must be between 70.8 and 74.8 inches. The aerodynamics have been analyzed during some 2,000 hours of wind tunnel testing since February 2012. The adjustable aerodynamics add to overall efficiency of the racecar, reduce air drag while supplying increased cooling needed for the hybrid drive, and increase down force needed for high speed corners.

A new Porsche team of more than 200 employees was formed to develop and implement the development center in Weissach.

Porsche 911 RSR. The 470 hp, 4.0-liter 911 RSR is the successor to the 911 GT3 RSR, which Porsche customer teams have driven to numerous victories and titles all around the world in endurance championships since 2004, including finishing first and second in their racing debut last year at the 24 Hours of Le Mans.

The rear wheel drive 911 RSR is based on the seventh generation of the 911 Carrera, type 991. Its wheelbase has been lengthened by 3.9 inches and a new wishbone front suspension replaces the previously used MacPherson strut. The lightweight racing gearbox is a special new development by Porsche Motorsport; the six gears are shifted by paddles on the steering wheel.

A central focus in the development of the 911 RSR was to attain balanced weight distribution. The center of gravity is significantly lower than the previous model. Carbon-fiber is used in the front and rear fenders, front and rear lids, the doors, underbody, wheel arch panels, rear wing, dashboard and center console. In addition, all windows are made of very thin and lightweight polycarbonate. The familiar lightweight lithium-ion battery of the GT street models also makes a contribution towards weight savings.

The 911 RSR has a redesigned front end and the new rear wing provide for optimal aerodynamic balance and contributes to greater stability. Even more precise steering response leads to better vehicle handling at slow to moderate speeds and was attained by optimizing front suspension kinematics. Further improvements to the structural rigidity result in more precise steering response. The new engine air intake system was optimized with a new air filter geometry, which contributes towards reducing the effects of contamination on power output. The new FT3 safety fuel tank has a lowered center of gravity and enables improved filling under race conditions.

Live telemetry that is permanently transmitted to the command station via the car's roof antenna ensures that engineers are always well informed of all relevant vehicle data with over 200 measurement values. In addition, all data is stored on a memory card in the vehicle.