Automotive Intelligence - the web for automotive professionals and car enthusiasts
October 21, 2008
The “T” in the 3.0’s TFSI nomenclature no longer merely stands for “turbo”, but rather for the concept of supercharging in general – extensive testing on the big V6 has proven the superiority of mechanical charging. In conjunction with direct injection it is far superior to twin turbochargers, both in terms of packaging and of starting performance and responsiveness.
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 just 4.4 seconds. Thanks to the extremely short gas paths, the sonorous, supercharged V6 responds spontaneously to the throttle, even more so than a naturally aspirated engine of the same displacement.
Furthermore, the new 3.0 TFSI achieves exemplary fuel efficiency. 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 Audi technology of gasoline direct injection was what made this great efficiency possible in the first place. Unlike conventional concepts, it allows the compressor to be located behind the throttle valve. In view of the low density of the intake air at loads below supercharging level and when coasting, its rotors are free-running and the amount of power required to drive them is low.
The V6 power in the new S4 and S4 Avant flows into a six-speed transmission, fitted as standard, which shifts quickly and precisely. As an option, Audi offers a state-of-the-art dual-clutch transmission – the seven-speed S tronic is extremely dynamic and highly efficient. 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 impressively quick gearshifts. The gearshift feel is dynamic, comfortable and very precise – typically Audi.
The seven-speed S tronic consists of two separate transmissions and uses two multidisk clutches that control the various gears. The large K1 clutch guides the power via a solid shaft to the pinions for gears 1, 3, 5 and 7. A hollow shaft rotates around the solid shaft; it is connected to the compact K2 clutch, which is integrated within its larger counterpart and controls the pinions for gears 2, 4, 6 and reverse gear.
The quattro permanent all-wheel drive system transfers power to the road with supreme ease. 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 quattro drive system ensures safe self-steering characteristics, high stability and excellent traction in comparison with rear-wheel-drive competitors.
The new, active sport differential ideally complements the quattro drive system and lends it even 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. For the driver, this means reduced effort at the steering wheel and even higher lateral acceleration.
Audi will begin delivery of its new S models in March 2009.
(Oct. 14, 2008)