Porsche 918 RSR Hybrid Concept

Jan 24, 2011

Porsche continues its development work in the field of hybrid technology with its 918 RSR.

The two-seater mid-engine coupe 918 RSR “clearly reveals what happens when the technology fitted in the 911 GT3 R hybrid and the design of the 918 Spyder are transferred to a modern, innovative super sports car,” the company said in a press release introducing the vehicle at its recent world premiere in Detroit.

With its highly-efficient flywheel accumulator, the 911 GT3 R hybrid racing car proved to be an attention magnet during competition racing on the Nuerburgring Nordschleife circuit, during the American Le Mans Series races (ALMS) in Road Atlanta/USA and the ILMC run in China’s Zhuhai.

Referred to internally as the “Race Lab,” Porsche is now transplanting the technology into the mid-engine coupe 918 RSR, the motorsports version of the 918 Spyder concept car.

Here is some information on the vehicle, supplied by Porsche Cars North America Inc.

The 918 RSR’s lines feature an elegant flow dominated by muscular wheel arches, dynamic air intakes and a pulpit-like cockpit. A visible fan wheel between the ram air intake tubes and a rear spoiler with RS Spyder dimensions additionally emphasize the racing laboratory function.

Motor racing technology includes the particularly light, torsionally stiff carbon fiber-reinforced plastic (CFRP) monocoque. The V-8 engine is a further development of the direct injection engine from the successful RS Spyder race car and now offers an output of 563 hp at 10,300 rpm.

The electric motors on the two front wheels each contribute 75 kW, i.e. a total of 150 kW, to the peak drive power of 767 hp. The additional power, which is generated during braking, is stored in an optimized flywheel accumulator.

In the 918 RSR, the two electric motors offer a torque vectoring function with variable torque distribution to the front axle. This additionally increases agility and improves steering response.

Mounted upstream of the rear axle, the mid-engine is integrated with a racing transmission also based on the RS Spyder race car. The six-speed constant-mesh transmission with longitudinally mounted shafts and straight-toothed spur gears is operated using two shift paddles behind the racing steering wheel.

The vehicle’s functional equipment underscores its puristic motor racing character. Whether it be the characteristic doors which open obliquely upwards, the air intake in the roof between the wing doors, the quick-action locks on the front and rear CFRP lids, the two roof-mounted aerials for pit radio and telemetry, the RS Spyder-like small, lateral front flics or the air splitters beneath the front lip or no-profile racing slicks on 19-inch wheels with central locking, the vehicle can be clearly recognized as an experimental racing laboratory.

In contrast to the 918 Spyder concept car, an unadorned racing atmosphere predominates in the interior of the 918 RSR. The figure-hugging bucket seat’s brown leather covering cites the history of the gentleman driver; the gear flashes on the racing steering wheel and a recuperation display on the steering column in front of the display screen supply the pilot with information.

The 918 RSR’s cockpit is split by a minimalistic console with rocker switches. Instead of a second seat, the flywheel accumulator is positioned to the right of the console.

This flywheel accumulator is an electric motor with a rotor that rotates at up to 36,000 rpm to store rotation energy. Charging occurs when the two electric motors on the front axle reverse their function during braking processes and operate as generators.

At the push of a button, the pilot is able to call up the energy stored in the charged flywheel accumulator and use it during acceleration or overtaking maneuvers. The flywheel is braked electromagnetically and adds additional power.

This additional power is available for around eight seconds when the system is fully charged. In the successful 911 GT3 R Hybrid, the additional power is also used as a consumption aid depending on the racing situation, e.g. to delay pit stops or reduce the fuel tank volume and therefore the weight of the vehicle.

The Porsche 918 RSR received the 2011 NAIAS “AutoWeek” Editors’ Choice Award for Best in Show at the Detroit Auto Show.