As predicted, Porsche has used this week’s 2011 Detroit Auto Show to unveil a new iteration of its 918 Spyder concept, the 756 horsepower 918 RSR race car. Sharing much in common with last year’s Spyder plug-in hybrid concept, including its advanced mid-engine platform, the new Porsche 918 RSR also features a V-8 hybrid drivetrain but there are a few key differences.

Unlike the plug-in hybrid system that featured in the 918 Spyder concept, the Porsche 918 RSR utilizes a setup similar to the one in the 911 GT3 R Hybrid race car where an electro-mechanical flywheel is used to store kinetic energy created under braking.

In the case of the 918 RSR, a 555 horsepower V-8 is paired with twin electric motors contributing an additional 201 horsepower. The V-8 engine is a further development of the direct injection engine from the successful RS Spyder race car and can freely rev to 10,300 rpm. It sends power strictly to the rear wheels via a six-speed paddle-shift transmission, while the twin electric motors power each of the front wheels, respectively.

Porsche 918 RSR

Porsche 918 RSR

These motors rely on power generated during braking and stored in a flywheel that spins up to 36,000 rpm. When the driver needs an additional boost in power, he or she simply presses a button inside the cabin and this in turn kicks in the electric motors. This additional power is available for around eight seconds when the system is fully charged. The two electric motors also offer a torque vectoring function with variable torque distribution to the front axle. This additionally increases agility and improves steering response.

Like the 911 GT3 R Hybrid before it, the new race car is now set to be used as a test-bed for the further development of hybrid systems in motorsport. An appearance at the Nurburgring 24 Hours in the summer is considered extremely likely, according to Porsche. On its debut in the race last year, the 911 GT3 R Hybrid led for more than eight hours.

Porsche could then wheel out the production version of the 918 Spyder in early 2012. It is unlikely to rush it out, preferring to further develop the hybrid systems and avoid overshadowing the arrival of the next-generation 911 at September’s 2011 Frankfurt Auto Show.

In the meantime, check out live shots of this stunning beauty direct from the Detroit show floor by clicking here.