With its sophisticated technology, lightweight components and features such as Rear Active Steering for maximum agility, the V8 FX50S Premium -- Infiniti's flagship as well as its best-selling model in some markets -- provides the ideal starting point for the FX Sebastian Vettel version. Changes including increased power, lower weight, derestricted top speed, longer gearing, increased downforce and lowered and stiffer suspension turn what is already a sports car among crossovers into a crossover supercar - the 300km/h reality of the World Champion's vision. With an already potent 5.0-litre V8 under the bonnet, relatively little needed to be done to enable the world's most special FX to hit Sebastian Vettel's maximum speed target of 300km/h. The first job was to free the car of its speed limiter which electronically restricts all other FXs to 250km/h. Even in standard form, with the VVEL V8 producing 390PS at 6500rpm, the car has plenty of performance beyond its artificial top speed, but even so more power had to be found to deliver 300km/h. No radical engine reworking was necessary to gain the extra 30PS that takes the FX Vettel concept's power output to 420PS. A new exhaust system liberates some of the extra horsepower while a reprogrammed engine ECU takes care of the rest, with no discernible difference to the V8's response or efficiency. And it sounds better than ever. In addition to the extra power is a longer final drive ratio to deliver 300km/h Autobahn speed without any detrimental effects on refinement. The longer overall gearing means the car is not as quick off the line as it could be -- but at 5.6 seconds for 0-100km/h, two tenths of a second ahead of the standard car, no one is complaining. Least of all Sebastian Vettel. Stiffer springs and re-rated dampers take the FX50's already highly focused sports chassis into a new area of precision control for the smooth-surface, high-speed driving for which the car exists. Essentially, however, making an FX to the World Champion's specification required no major changes. Like any FX in sporting S guise, the concept features dual-flow path (DFP) dampers with continuous damping control (CDC); the same wishbone front/multilink rear suspension, much of it constructed out of aluminium; opposed 4-piston (front), 2-piston (rear) calipers for the 355/350mm brake discs; and vehicle-speed variable rack and pinion steering. Rear Active Steering, an important ingredient in any FX S's blend of agility with stability, plays a key role in ensuring handling fulfils the World Champion's requirements for a road car.