Audi has rearmed its S4 with a more potent powertrain and chassis. A lighter, supercharged and intercooled 24-valve 3.0-liter V-6 supplies more torque but slightly less power than the retired 40-valve 4.2-liter V-8. An Eaton blower spinning up to 23,000 rpm skews the torque curve down the rev scale and up the lb-ft register. Between 2900 and 5300 rpm, 325 lb-ft of torque is available, versus the previous V-8's 302 lb-ft at 3500 rpm. The power curve is dead level at the high end, with 333 hp available from 5500 rpm to the 7000-rpm redline (compared with the previous S4's 340 hp).
Driveline upgrades include a new seven-speed dual-clutch automatic with a gear ratio spread 32 percent wider than the outgoing six-speed Tiptronic's range for improved fuel mileage.
A new active rear differential uses a clutch-activated gearset overdriving the outside rear wheel to diminish understeer in tight bends. While the Quattro AWD system relies primarily on mechanical manipulation of torque distribution, electronic systems help out during snow and ice driving. The variable-ratio power steering and gas-pressure dampers also are actively controlled.
For improved handling and road feel, the front axle is shifted six inches forward, and the steering gear has been mounted ahead of the front wheels to an aluminum subframe, which is in turn rigidly attached to the S4's steel unibody.