2009 audi s4 sedan avant 026Enlarge Photo
The completely new 3.0-litre V6 shares its ‘TFSI’ designation with the six engines in the Audi range that combine single turbo charging with FSI direct injection, but the newcomer actually bucks the trend by using the alternative method of forced induction – a compact supercharger chosen because it delivers keener response than even two turbo chargers could achieve.
The supercharger’s ultra-compact dimensions enable it to fit easily inside the 90-degree V of the cylinder banks, and as a result the gas paths to the cylinder are extremely short, resulting in throttle response that even a naturally aspirated engine of the same displacement can’t match. With the compressor’s help the new unit generates 333PS and a healthy 440Nm torque peak available from 2,500rpm right through to 4,850rpm, enabling an appropriate 0-62mph sprint time of just 5.1 seconds for the manual Saloon (Avant manual 5.2 seconds). Top speed is limited electronically to 155mph.
Perhaps more unexpectedly, the combination of supercharging and direct injection also works very much in favour of fuel economy and emissions, the S4 Saloon offering the potential to cover up to 29.1mpg – a 27 per cent improvement over the V8-powered S4 – while emitting 225g of CO2 – 30 per cent less than its predecessor (S4 V8 manual 322g/km).
New twin-clutch transmission
An equally radical departure for the new S quattro flagship is the addition of the S tronic twin-clutch automatic transmission, developed specifically for Audi models with longitudinal ‘north-south’ engine installations, to its options list.
Thanks to advanced electro-hydraulic controls and the alternate use of two clutches, the new seven-speed transmission, which made its debut in the Q5 SUV, delivers a lightning fast manual shift with virtually no interruption of the engine’s power delivery. At the flick of a lever it can also be transformed into a full automatic, without the drain on power output or fuel economy normally demanded in return for the convenience of ‘hands-free’ shifting. This is reflected in fuel economy which actually betters the manual version, with 30.1mpg recorded on the combined cycle test, equating to CO2 output of 219g/km.
The advances don’t end there for the latest S4. It not only now carries itself with even more composure thanks to the optimum weight distribution made possible by its all-new chassis with repositioned front axle, but is also even more agile thanks to a new evolution of quattro all-wheel-drive with 40% / 60% front-to-rear torque distribution and the option of a new active sport differential.
Wheel-to-wheel torque transfer
Making its debut in the S4, the active sport differential enables the quattro system to not only transfer torque between the front and rear axles to counter traction losses, but also between the rear wheels. 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 car through the corner. The driver benefits from reduced steering effort and a feeling of even greater adjustability and control.
The upgrade from ‘standard’ quattro to quattro with active sport differential will be available at extra cost as an element of the optional Audi drive select adaptive dynamics system that is also new to the S4. In its simplest form Audi drive select enables the driver to fine-tune throttle response, steering assistance and transmission shift points (where S tronic is fitted) via dashboard-mounted buttons to suit personal preferences or prevailing road conditions.
S4 drivers can choose from three distinct Audi drive select option packages – Audi drive select with damper control for even greater suspension adaptability to the road surface, Audi drive select with dynamic steering allowing alteration of the actual ratio of the steering for optimum feel and Audi drive select with upgraded quattro drive featuring the active sport differential. Alternatively, for the ultimate S4 driving experience, all three systems can be combined.
As befits the latest in an illustrious line of S quattro models, the new S4 will ride 20mm lower than standard versions on specially tailored ‘S’ sports suspension and 18-inch ‘S’ design alloy wheels. Other familiar hallmarks of the series will include the aluminium-look door mirrors, xenon plus headlights with LED daytime running lights, special ‘S’ front and rear styling treatments and black painted brake callipers bearing the S4 logo. For the first time in an Audi model at this level, the S4 is also enhanced visually by distinctive LED rear lights.
Inside, the ‘S’ theme is subtly conveyed by sports seats upholstered in leather and Alcantara, and by ‘S’ embossing for the exclusive silver-faced dials and the multifunction sports steering wheel. The already high specification in the appreciably more spacious cabin can be augmented by options such as a 505-watt Bang & Olufsen audio system, the Audi Music Interface with iPod connectivity, adaptive cruise control, the Audi side assist lane change assistant, the Audi parking system advanced and adaptive light swivelling headlamps for improved corner illumination.