Engine and transmission: full power output
The heart of the new Audi S4 is quite clearly its engine - a newly developed V8 with a swept volume of 4.2 litres and five-valve cylinder head. This engine is notable not only for its dominant power (253 kW/344 bhp), but also at first glance for its impressive and incomparably short design.
Its dimensions - especially the length of only 464 millimetres - for the first time enable installation in what is, for a vehicle in the B segment, a very slim engine compartment.
In order to make this compactness possible, the Audi engineers have installed a chain drive for camshafts and ancillaries on the engine output side. The length could thus be reduced by no less than 52 millimetres.
The engine designers have also made a saving in terms of weight in the new engine. The weight of the pistons could thus be reduced by 70 grams for each piston to 392 grams, whilst the conrod weights have been reduced by 66 grams to 501 grams. These measures provide the basis for low frictional losses in the engine and a high maximum engine speed of 7,200 rpm.
An additional benefit: the entire V8 at only 195 kilograms total weight is just as light as its predecessor in the previous S4, a 2.7-litre V6 biturbo engine. This results in major benefits for weight balance and handling characteristics.
On the other hand, the engineers have not saved anything in terms of power. The V8's thrust enables the new Audi S4 with 6-speed manual gearbox to sprint from 0 to 100 km/h in only 5.6 seconds. It takes just 20.6 seconds to reach 200 km/h, whilst the top speed is a governed 250 km/h.
The new 4.2-litre engine provides its maximum power of 253 kW (344 bhp) at 7,000 rpm. The maximum torque of 410 Nm is available at 3,500 rpm. Even at only 1,100 rpm the large V8 provides almost 300 Nm, and between 3,000 and just under 4,500 rpm the torque plateau is always above 400 Nm.
Clearly more impressive than such figures is the combination in practice of spontaneous response to every movement of the accelerator pedal, its astonishing free revving and the hefty torque typical of a V8. And then there is the experience of an equally characteristic V8 sound - reserved and practically free of vibration in the low speed band and with a sonorous tremolo under load - that makes no secret of the engine's potential.
Power on the one hand and low emissions on the other are not contradictions for the Audi S4. Thanks to efficient exhaust emission control with primary and main catalytic converter it remains clearly within the EU IV limits.
The Audi S4 consumes 13.3 litres of Super Plus petrol every 100 kilometres (overall according to 1999/100 EC).
Power is transferred via a closely stepped, extremely precise 6-speed manual gearbox of the latest generation, with short sports-style shifts and quattro permanent all-wheel drive at the wheels. A 6-speed tiptronic gearbox with Dynamic Shift Program DSP and Sport program will extend the range in the second half of 2003.
Quattro all-wheel drive is a standard feature for an Audi S model. It ensures excellent traction and directional stability; and it reduces the influence of the drive forces on the self-steering characteristics to a minimum. The self-locking Torsen centre differential on the Audi S4 distributes the drive forces variably to the front and rear axle. This guarantees the best possible straight-line running, high driving stability and maximum propulsion.
The lightweight aluminium suspension, based on the much-praised axle design of the A4 model line, provides the ideal basis for maximum agility and, consequently, sheer driving pleasure.
Four-link front suspension and trapezoidal-link rear suspension enable maximum steering precision and clearly defined handling with excellent cornering stability. Ride comfort also benefits from this ingenious axle design because a low unsprung mass also makes for a particularly sensitive response from the suspension. The wheel carriers on the new Audi S4 are also manufactured in aluminium for the same reason. Compared with conventional steel construction this means a reduction in the unsprung mass of almost two kilograms per wheel.
A general characteristic for which the A4 model line since its first appearance has already received unanimous praise in the automotive press, and which is accentuated even more clearly on this new model. Audi's development engineers have tuned the springs, shock absorbers and anti-roll bars to improve sports performance even further. And they have lowered the chassis - and therefore the centre of gravity - by 20 millimetres.
The new S4 generation has one of the most complex and efficient rear wheel suspensions that is presently available as a standard feature: the self-stabilising trapezoidal-link rear axle, especially designed for quattro drive. Newly tuned toe-angle kinematics optimise the directional stability and the precision of the steering response even further.
Compared with the basic version, the steering of the new S4 is much more directly transferred: for the driver this is a decisive contribution to the sports-oriented handling of the agile V8 version that can be experienced in all situations. A standard feature on both the saloon and the Avant is the speed-dependent servotronic, which enables precise steering at high speeds as well as effortless manoeuvring and parking.
The braking system is also matched to the powerful potential of the Audi S4. The disc diameter of the 17-inch wheel brakes is 345 millimetres at the front and 300 millimetres at the rear. The system is operated via a new dual-rate servo. This gives the driver a sporty, firm pedal feel in the low to medium deceleration range whilst at the same time providing exceptional control of the brake force.
In the comfort braking range of up to around 0.5 g deceleration, the brake servo's ratio at factor 5.5 is at the level of the other A4 models and thus ensures especially good control. Above 0.5 g the ratio is raised to the factor 12. In this way, the deceleration increases disproportionately high to the braking force - a clear advantage for a sporting style of driving. The S4 achieves full deceleration with comparably low pedal force and with less pedal travel than on a conventional system.
The Electronic Stabilisation Program ESP 5.7 including hydraulic brake assist ensures active driving safety.
The Audi S4 will roll to the start on standard 18-inch wheels. The tyres for these alloy wheels are of size 235/40 R18.