quattro permanent four-wheel drive quattro permanent four-wheel drive is a typical feature of all high-performance Audi models. Since revolutionising the car world when first unveiled 26 years ago, permanent four-wheel drive has long since found its way into virtually all vehicle categories - and not just at Audi. Almost one in three Audi cars sold is currently a quattro; by the end of 2005, around 2.5 million Audi vehicles with quattro permanent four-wheel drive had been built. quattro ensures excellent traction and lateral stability and minimises the effect of propulsive power on the vehicle's self-steering properties. This is a precondition of the car's tremendous cornering speeds and high dynamic stability. A Torsen differential in the new Audi Roadjet Concept - with its longitudinally installed engine - automatically ensures the optimum distribution of power between all four wheels. The name Torsen is a combination of the terms "torque" and "sensing". The Torsen differential is a self-locking worm gear. The advantage of this is that the locking action is only prompted by the driveline. Yet this type of differential accommodates differences in speed when the brakes are applied and when cornering. The power is normally split 40:60 between the front and rear axles, producing particularly dynamic self-steering behaviour. In extreme cases, up to 80 percent of the propulsive power can be diverted to one pair of wheels if slip is encountered. Chassis The Audi dynamic suspension layout of the Roadjet Concept is based on proven sports technology: the refined four-link front suspension acknowledged as a typical Audi feature, and the self-tracking trapezoidal-link rear suspension carried over from the Audi A8 and A6. The 20-inch wheels with size 245/45 R20 tyres are an impressive feature. All this results in a driving performance that stands up to any comparison in respect of dynamism and which sets the standard with regard to ease of control, even on rough terrain. This is also due in no small measure to the speed-dependent servotronic power steering featured as standard, supplementing the precise handling of the Roadjet Concept with even more sensitive steering precision. Audi dynamic steering makes its first appearance on an Audi car; this superimposed steering system adjusts the steering ratio as a function of road speed. It affords a smoother ride at high motorway speeds in the form of a more indirect ratio, coupled with directional stability that is resistant to slight movements. When the Roadjet Concept is driven sportily on winding roads, on the other hand, a more direct ratio that permits high steering precision and a swifter response by the driver represents the optimum. Another new feature is the electronically adjustable dampers that cover a variety of characteristics ranging from comfortably soft to sportily firm. Electronic systems As a technology demonstrator, the Audi Roadjet Concept embodies the proverbial "Vorsprung durch Technik" not merely in its drivetrain. It comes complete with a raft of other systems that will be finding their way into series production in a few years' time, thus paving the way for driving fun, safety and comfort. Audi drive select Only a minority of car owners can afford the luxury of having three cars parked in front of their house to give them maximum flexibility in choosing the right car for every occasion, depending on whether comfort, manoeuvrability or dynamic behaviour is what they require. The Audi Roadjet Concept fulfils all these requirements in a single car. Because Audi drive select allows the driver to preselect three highly distinctive configurations for the engine, transmission characteristic, steering and shock absorbers. The result is a car that can be enjoyed in three utterly different ways. The basic setting is the "dynamic" mode; it is activated automatically at the start of every journey, and its overall concept reflects the expectations that Audi drivers typically have of what their car should feel like to drive in terms of both dynamism and comfort. The driver is informed which mode is currently active via the centre display in the instrument cluster. If the driver selects the "comfort" mode by pressing the button on the control in the steering wheel, the shock absorbers adopt noticeably softer settings in order to filter out bumpiness in the road surface even more effectively. The Servotronic requires lower steering forces, and dynamic steering establishes a more indirect spectrum of ratios. The engine and transmission respond gently to use of the accelerator. This setting is perfect for relaxed driving over long distances, above all on straight roads such as motorways. The "sport" mode, on the other hand, lends the Audi Roadjet Concept a decidedly sporty driving feel. The shock absorbers now adopt a firm response and the steering ratio is direct. The engine responds more spontaneously to the throttle and the transmission's shift points move higher up the engine speed range: the ideal basis for active driving pleasure on winding roads. Over and above the three basic configurations, Audi drive select provides scope for varying individual parameters between the levels dynamic, sport and comfort. It is for instance entirely possible to combine sporty shock absorber settings with a relaxed, easy-action steering response. Pages: [1] [2] [3] [4] [Gallery]

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