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IAA ’03: The new Audi S4 Cabriolet

Another Audi sports model with a strong personality is about to leave the starting grid: the Audi S4 Cabriolet. It combines the acknowledged qualities of the Cabriolet with the powerful V8 engine from the Audi S4 and the safety of the quattro driveline. Restrained visual changes underline its sports character.

Design and equipment

The new Audi S4 Cabriolet expresses its supremacy by adopting a deliberately restrained appearance. A closer look, however, reveals that this stylish, sporty body is indeed subtly different in its basic form and proportions from the remaining Audi A4 Cabriolets: the bumper has large air inlets, the xenon headlights have a titanium-coloured surround behind the glass and the outside mirror housings have been given an aluminium finish. At the rear, one sees the powerful exhaust tailpipes on both sides that are typical of the Audi S models. The Audi S4 Cabriolet runs on 18-inch cast aluminium wheels of S design with 235/40 R 18 tyres.

Inside this Cabriolet too, it is immediately identifiable as an S4. The instrument cluster has characteristic grey S dials and special dial needles. For the inlays, customers can choose between carbon fibre, piano finish, brushed aluminium and birch. The car’s sporty character is emphasised by the three-spoke leather-covered sports steering wheel with S emblem. There are shift paddles behind the steering wheel on cars with the six-speed tiptronic transmission.

For firm lateral location and excellent comfort on long journeys, the standard sports seats have a wide range of electrical position adjustments; combined Alcantara and leather upholstery is used, and there is a lumbar support and an adjustable thigh support.

The V8 engine: a torrent of power

The Audi S4 Cabriolet’s eight-cylinder engine develops 253 kW (344 bhp) at 7000 rpm, and delivers a massive 410 Newton-metres of torque to the crankshaft at 3500 rpm. Such impressive figures are a sure sign of the superiority of this large-capacity, naturally-aspirated engine with its five valves per cylinder. Possibly even more impressive than its peak power output is the immediacy with which it responds to every movement of the accelerator pedal, and its remarkable willingness to run freely up to high revs. The exhaust system produces a deep, sporty note, always present but never obtrusive.

The Audi S4 Cabriolet sprints from 0 to 100 km/h in only 5.9 seconds, and reaches a top speed of 250 km/h, at which point the governor cuts in smoothly.

The eight-cylinder engine surprises the onlooker in yet another way: it is shorter and more compact than any other engine of this type and size, measuring only 464 millimetres from front to back. Audi’s engine developers achieved this by moving the chain drive for the camshafts and auxiliaries to the output end of the engine, thus reducing its overall length by 52 mm. The weight is also extremely low for an engine with eight cylinders, at only 195 kilograms. This has definite advantages in terms of the car’s weight distribution and road dynamics.

From the six-speed close-ratio gearbox of the latest model generation with a precise shift action and short lever travel, the power is delivered to the 18-inch diameter cast aluminium wheels. The selector mechanism is decoupled, which largely prevents load-reversal movements or vibration from being transmitted to the gear lever inside the car.

Available as an optional extra, the six-speed tiptronic transmission with dynamic shift program, additional Sport programme and shift paddles on the steering wheel it combines sports-style progress with the convenience and relaxed driving of an automatic transmission and is therefore ideal for smooth, relaxed travel in an open car.

The sports suspension: aluminium makes the car agile and light on its feet

The weight-saving aluminium running gear consists of four-link front and trapezoidal-link rear suspension, and is designed to ensure maximum steering precision and clearly defined road behaviour with excellent lateral stability. Ride comfort also benefits from this ingenious suspension design, since low unsprung weight makes the suspension more responsive to road-surface irregularities.

Like the S4 saloon and Avant, the S4 Cabriolet has firm sports suspension settings which are an important precondition for agility and thus for pure driving pleasure.

Servotronic power steering is standard equipment; it varies the degree of power assistance according to road speed so that the correct combination of steering precision and light action is always obtained.

The quattro driveline: driving fun and ample traction

The new Audi S4 Cabriolet has quattro permanent four-wheel drive as a standard feature. It can therefore translate engine power into optimal progress in any conditions and exploit the dynamic potential of its aluminium running gear with a new degree of supremacy. There is no other term for this but “top-class driving pleasure”.

Cabriolet: emotions under an open sky

Driving a convertible is definitely one of the most emotionally satisfying forms of automobile transport – particularly in a car with such a timelessly elegant body and wonderfully responsive engine. But elegance and power need to be accompanied by a body of no-compromise high quality before one can be certain that every journey will be pure pleasure.

The soft top of the Audi S4 Cabriolet retracts fully into the body when open. Nothing disturbs the characteristic shoulder line that extends smoothly along the top of the body. But even with the soft top closed, the silhouette retains its dynamic, harmonious effect. The gentle curve of the soft top emphasises the car’s low-slung proportions and the mild wedge-shaped outline of the body.

Another typical Audi feature is the outstandingly high quality of the interior materials and workmanship on the Cabriolet. The interior decor is perfectly matched to the body styling and contributes greatly to the overall visual elegance of the Audi S4 Cabriolet.

The body: sets the class standard for freedom from vibration

Even in the early planning stages, Audi’s body developers worked systematically on the structure of the body and simulatde its reaction to movements of the suspension and the mechanical assemblies.

The result of this development process is that no unpleasant levels of either high- or low-frequency vibration reach the passenger area on any of the roads commonly encountered anywhere in the world.

Driving pleasure also profits directly from the bodyshell’s high rigidity; with its direct steering, the S4 Cabriolet can be steered with great precision through corners, aided by a special steering column mounting that takes the specific pattern vibration in an open-topped body into consideration. The steering column mounting has an additional support, with the module cross-member linked to the cross-beam below the windscreen – measures that are crucial for keeping vibration at the steering wheel down to the lowest possible level.

At an early design stage, when grades of material and joining techniques are decided upon, measures are taken to maximise strength and rigidity. For example, more than half the weight of the body-in-white is accounted for by high-strength or extra-high-strength sheet metal.

Optimised panel thicknesses and improved spot-welding quality have helped to raise the potential operating life of the body structure considerably. In addition, the body has been reinforced by a rigid bolted-on frame at the front with supporting diagonal struts at the front and rear.

A high level of crash protection

The Audi S4 Cabriolet’s A-posts are optimised in cross-section and contain high-strength reinforcing tubes – a most important safety feature if the car should roll over.

In the occupant area, the body sills have been optimised in terms of sheet metal gauge and cross-section, to increase their strength and provide optimal protection for the occupants. High-strength tube is also used in the seat structure, so that occupant safety is enhanced in the event of a side-on impact.

The doors in particular have to be designed with safety in mind. In conjunction with structural reinforcements in the sills and a strengthening cross-member below the rear seat, special impact absorbing beams in the doors ensure a high standard of safety. Crash resistance, even in the side impact test against a post, is on the same excellent level as the S4 saloon.

Finally, there is a double bulkhead at the rear that also adds to the strength of the body.

All-round safety

Seat belts with belt force limiters and belt tensioners at all seats are part of the comprehensive safety equipment, as are the full-size front and side airbags. The latter are integrated into the front seats and protect the occupant in the head and thorax areas.

If the car should roll over, an active roll-over protection system in the double rear bulkhead adds to the occupants’ safety. Two sensor-controlled protective hoops behind the rear seats are triggered off in a fraction of a second and, together with the extremely rigid windscreen frame, help to maintain an intact ‘survival zone’ for all the car’s occupants.

Active safety is maintained at a high level by the Electronic Stabilisation Program ESP, which is standard equipment and includes an hydraulic brake assist function.

Weather protection and much more – the soft top

Standard equipment on the Audi S4 Cabriolet is an electro-hydraulic soft top, which closes at the touch of a button in under 30 seconds. The button only needs to be pressed once to either open or close the soft top. The side windows move down slightly and up again to aid the process, and in the Audi S4 Cabriolet there is no locking handle to be released manually or tonneau cover to be detached.

A lever in the boot raises or lowers the soft top compartment, so that a much larger luggage space becomes available when the soft top is closed.

A heated, scratchproof glass window is just one of the reasons why the Cabriolet’s lined soft top is entirely suitable for winter driving. It has three layers of cloth and is sewn to high standards of accuracy to ensure maximum occupant protection, resist climatic effects and provide a standard of acoustic insulation worthy of a fine car such as this.

The soft top linkage can scarcely be detected from outside the car; the upholstery material is held taut to avoid any ‘ballooning’ effect. The harmonious outline of the roof that blends so well with the Cabriolet’s body is retained when the car is travelling fast.

Inside the car too, the soft top has a completely smooth surface. This is most attractive to the eye, and therefore adds to the luxurious impression created by the interior decor and trim.

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