As with all 911s, the flat-six engine is hung out the back, behind the rear axle. The GT3 R Hybrid adds two 60kW electric motors (2) that drive the front wheels. Instead of being powered by the usual nickel-metal hydride or Lithium-ion battery pack, the electric motors are powered by a flywheel power generator (4) that's connected via high voltage power cable (3). The whole system is controlled by two sets of electronic brains (1 and 5).
The flywheel "battery" is actually an electric motor that can spin at up to 40,000rpm. Whenever the brakes are applied, the front axle's electric motors go into regenerative braking mode storing the captured energy as extra rotational motion in the flywheel.
Whenever the driver requires an extra burst of energy, say when powering out of a corner or attempting an overtaking manoeuvre, the flywheel "battery" slows down its rotation, releasing power to the electric motors. Around six to eight seconds of additional power can be called upon.
According to Porsche the system is good for not only additional power, but also reduced fuel consumption. Although the company is keen to point out the GT3 R Hybrid's smaller tank, it doesn't quote any fuel economy figures.