Porsche 918 RSR debuts at 2011 NAIAS: swaps lithium for flywheel

For its big return to the North American International Auto Show after a three year absence, Porsche unveiled a brand new race car concept, the 918 RSR coupe. The 918 is a blend of two hybrid models introduced in 2010 to much acclaim, the 918 Spyder plug-in hybrid concept and the 911 GT3R Hybrid race car.

The RSR adds a competition ready hard-top to the 918 and ditches the lithium ion batteries in favor of the electromechanical flywheel hybrid system used on the 911. After running very competitively at several races in 2010, the 911 hybrid finally broke through with a victory in the finale of the Intercontintental Le Mans Cup in Zuhai, China.

The flywheel hybrid system is more suitable for competition applications than a battery thanks to its compact dimensions and higher power capability. Electrical energy from regenerative braking is stored in a flywheel spinning at 40,000 rpm and then released when the driver needs it for acceleration. The 911 hybrid was able to achieve 25 percent better fuel efficiency than the standard 911 GT3 which was hugely beneficial in endurance racing.

In the 918 RSR, the flywheel is paired with the 563 horsepower 3.4-liter V8 previously used in the LMP2 RS Spyder for a combined output of 767 hp. Porsche has not announced any specific competition plans for the 918 RSR yet since it doesn’t really fit into any existing class. However, American Le Mans Series spokesman Bob Dickinson acknowledged that it could run in a demonstration class in that series at the 911 did at the 2010 Petit Le Mans. We’ll most likely see the 918 debut in the Nurburgring endurance series and the 24 hour race at the famed track in May, just as the 911 hybrid did last year.

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