Audi looks to be striving to catch up in the reduced-emissions department, its new S4 features a six cylinder TFSI engine that emits 30 per cent less CO2.
The completely new 3.0-litre V6 shares its ‘TFSI’ designation with the six engines in the Audi range that combine single turbocharging with FSI direct injection, but the S4 has a compact supercharger to provide an improved response over the two turbochargers.
The combination of supercharging and direct injection works in favour of fuel economy and emissions, the S4 Saloon promises to return 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).
The supercharger’s compact dimensions enable it to fit 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 440Nm torque peak available from 2,500rpm right through to 4,850rpm, enabling a 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.
The new S quattro flagship has the option of the S tronic twin-clutch automatic transmission, developed specifically for Audi models with longitudinal ‘north-south’ engine installations.
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.
Audi has even made an effort to improve weight distribution, due to the all-new chassis with repositioned front axle, and it has a new evolution of the quattro all-wheel-drive with 40% / 60% front-to-rear torque distribution and the option of a new active sport differential.
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, all three systems can be combined.
The new S4 and S4 Avant will open for order in November priced from approximately £36,000 and will reach their first UK customers in April 2009.