The heart of the new S4 and S4 Avant is a completely redesigned engine. The 3.0 TFSI, the newest member of the Audi V-engine family, generates its power from a displacement of 2,995 cc, is equipped with a supercharger, and delivers 245 kW (333 hp). The sedan sprints to 100 km/h (62.14 mph) in 5.1 seconds, and the Avant in 5.2 seconds: they both have an electronically governed top speed of 250 km/h (155.34 mph).
The 'T' in the 3.0's TFSI nomenclature no longer merely stands for 'turbo', but rather for the concept of supercharging in general. The compressor is so compact that it easily fits inside the 90-degree V of the cylinder banks, in place of the intake manifold. Two four-vane rotary pistons counter-rotate inside the turbocharger at up to 23,000 rpm. Two charge-air coolers are integrated into the housing and are connected to a separate coolant circuit. An array of measures keeps the noise generated by the compressor to a minimum.
The engine-driven belt that powers the mechanical charger provides full thrust right from idling speed. The 3.0 TFSI delivers its maximum 440 Nm (324.53 lb-ft) at 2,500 rpm and maintains this constantly until 4,850 rpm. In fourth gear, the vehicle accelerates from 80 to 120 km/h (49.71 to 74.56 mph) in 4.4 seconds. On average, the sedan uses 9.7 liters of fuel per 100 km (24.25 US mpg), and the Avant 9.9 liters per 100 km (23.76 US mpg) – an improvement of 3.4 liters (26 percent) compared with its predecessor.
The V6 power in the new S4 and S4 Avant flows into a six-speed transmission, fitted as standard. As an option, Audi offers a dual-clutch transmission: the seven-speed S tronic. The driver has the option of driving in fully automatic mode or selecting the gears with paddles on the steering wheel or directly with the shift lever – all of which provide quick gearshifts.
The Quattro permanent all-wheel drive system transfers power to the road. Under regular driving conditions, it sends 40 percent of its torque to the front wheels and 60 percent to the rear wheels – a slightly rear-biased, sporty characteristic. Where necessary, it can vary distribution within fractions of a second.
The new, active sport differential complements the Quattro drive system and lends it greater fascination. When the steering wheel is turned or the car accelerated in a corner, power is redirected in a controlled manner to the outer rear wheel, literally pushing the vehicle through the corner. The system intervenes to counter any signs of understeer or oversteer. The active sport differential is a new type of rear-axle differential. A superposition gear was added to both the left and right sides of the classic differential; it rotates ten percent faster than the wheel's drive shaft.
The Audi drive select driving dynamics system is a technology featured on the new S4 and S4 Avant. It accesses the throttle response characteristics, the shift points for the seven-speed S tronic and supports the speed-dependent servotronic steering. With the press of a button, the driver can decide whether these systems should operate in 'comfort,' 'auto' or 'dynamic' mode. If the vehicle is equipped with the MMI operating system, a fourth mode is available which the driver can program according to his own personal tastes and preferences.
Audi drive select can only be ordered in combination with one or more of three additional technologies – the sport differential, adaptive control for the shock absorbers, or dynamic steering, which is an additional high-tech solution. Its zero-play superposition gear, which is driven by an electric motor, varies the ratio by almost 100 percent depending on the speed being driven. In terms of driver safety, the dynamic steering assists the ESP stabilization program by using steering intervention to keep the new S4 and S4 Avant on track when cornering at the handling limits. In many instances, the system renders ESP intervention superfluous.
Both the Audi S4 and the S4 Avant look athletic and muscular on the road. Some of the most striking modifications to the exterior design are the special aprons, the aluminum-look exterior mirrors, the 18-inch S-design light-alloy wheels, the side rocker panels, the restrained spoiler at the rear and the quadruple exhaust system. The xenon plus headlights with daytime running lights and the rear lights are further distinctive touches.
The interior also underscores the sporty expertise that is the hallmark of both new S models. The sports seats have electric lumbar supports and pull-out thigh supports, and the instrument panel features gray dials with white needles. They also bear the S4 emblems, as do the multifunction sport steering wheel and the key. The interior is in black, with brushed aluminum inlays. Carbon and birch wood inlays are also available, as are stainless steel mesh inlays.
Audi will begin delivery of its new S models in March 2009.