Less than a year ago Porsche wowed Geneva show goers with its futuristic environmentally friendly supercar, the 918 Spyder Concept. At this 2011 Detroit auto show it went one better, evolving the Spyder into the RSR – a hardtop racer.Fully validated by its colour scheme and styling cues from legendary Zuffenhausen endurance racers such as the 908 and 917, the RSR arguably makes for an even more arresting shape than its Spyder sibling.The racing theme is no marketing stunt either, the Detroit show car boasts Porsche chief test driver Walter Röhrl’s name emblazoned on the door, indicating a very real works racing effort in the near future.Inside the RSR deletes one of its seats in favour of a flywheel accumulator, which looks for all the world like something out of the Millennium Falcon. For the rest it is racing-spec with paddle shift gears, classic Le Mans brown leather trim and a tiny steering wheel.The 564kW 3.4-litre V8?Technically the RSR can summon a combined peak power output of 564kW, courtesy of a 3.4-litre V8 and dual electric motors servicing the front wheels. The V8 engine cranks up to 10 300rpm and is the latest development of Porsche’s (very) successful RS Spyder endurance racing powerplant. Supporting the V8’s 414kW contribution to the RSR’s performance are dual 75kW electric motors driving the front wheels, totalling 150kW of silent shove for an eight second burst when the cockpit mounted flywheel accumulator is fully charged. Charging the RSR’s electric power system is a reverse kinetic function on the front wheel electric motors, whereby brake force energy is captured during deceleration and stored in the flywheel accumulator, boasting a peak rotor speed of 36 000rpm. DON’T TOUCH: The RSR’s passenger seat replacement, a flywheel accumulator. Not to be touched with wet hands we think… Porsche says an accumulator is far lighter than a lithium-ion battery set, enabling the company’s engineers to retain the low mass and agility for which the brand is known. Looks like the real thingFor true Porsche endurance racing enthusiasts those 19-inch centre-locked deep dish alloy wheels (replacing the Spyder’s rather odd self-ventilating items) are a welcome styling upgrade.Add the prospect of an acoustic blend of 10 300rpm worth of V8 and a six-speed transmission (turning straight-cut gears), and this should authenticate Porsche’s latest show car concept in full. Even the colour, a new hue called 'liquid metal chrome blue', contrasts with the orange centre-car colour bar much as the original Porsche Gulf Oil livery would. The 918 RSR carries the number ‘22’ livery in a bid to pay tribute to the 917 which won Le Mans in 1971, posting a distance record over the 24 hour endurance race – 5 335km – that stood until the completion of the 2010 event. Such historical inference is not purely for heritage marketing either.Much as the 911 GT3 R Hybrid, the RSR is expected to race – most likely debuting at the Nuburgring 24 hour race in May.