RS is Audi's ultimate prefix, surpassing the S models and denoting maximum performance. U.S. buyers have only seen one RS model: the 2003 RS6, a wild-child A6 rumbling with a blown, 450-hp V-8. But the RS6 was actually the third Audi RS, following the 1994-95 RS2 (based on the Audi 80 wagon) and the 2000-01 RS4, a 375-hp, twin-turbocharged screamer fashioned from the first-generation Audi A4 Avant. A move away from turbocharging is a big departure. The RS4's new naturally aspirated, direct-injection V-8 is ultraresponsive and addictively light-footed in the way it summons more power and whips up more torque. With 420 hp, the 2006 RS4 will accelerate from 0 to 62 mph in a stellar 4.8 seconds. Whereas the most recent RS, the RS6, had a five-speed automatic, the new RS4 is fitted with a six-speed stick shift. The shift linkage is quick and slick, and clutch action is light and progressive. The transmission sends torque to all four wheels, but the rears get priority. By altering the Quattro drivetrain from a 50/50 to a 40/60 front/rear torque split for use in the RS4, Audi wants to zoom in on BMW and Mercedes-Benz. Now that the rear wheels get a bigger share of the action, the front wheels can concentrate on turn-in and braking. This results in light and linear steering, though it's still not as telepathic and communicative as those fitted to the best rear-wheel-drive competitors.
Borrowed from the Lamborghini Gallardo, the huge brake rotors (14.7 inches front, 12.8 inches rear) kill energy with the finiteness of a master switch, again and again, with great determination and only gradually showing faint traces of fade. In the wet, the discs are intermittently swept dry to improve response and stopping power. Americans may be unfamiliar with the RS4, but when it finally arrives stateside this spring, they're unlikely to mistake it for a generic A4. The go-faster Audi boasts bloated and Botoxed bumpers front and rear, plenty of brightwork, additional air intakes, fat fourteen-spoke wheels, and two chromed tailpipes of pornographic diameter. Inside, we find overstyled bucket seats, classy bespoke instruments, the increasingly ubiquitous but totally pointless starter button, and a fancy steering wheel with chromed spokes and a racing-car-style flat bottom. Your left thumb is invited to push the S button, a controversial move that quickens the throttle response, ups the in-cabin noise level, and pneumatically narrows the side bolsters until it hurts. The cockpit is well laid out and well put together, but the presentation is on the ritzy side, and the driving position is too high up. In more ways than one, the new RS4 is a move in the right direction. The brawny, normally aspirated engine is much more involving than the turbos; the brakes, grip, traction, and roadholding are simply sensational; and the recalibrated Quattro hardware removes several layers of indifference from the steering and the drivetrain. That's the good news. The bad news is a substandard ride, with its effect on the vehicle dynamics. And while the updated Quattro technology surely helps, the feedback from the chassis is still insufficiently three-dimensional. The new RS4 is a more rewarding drive than the cold and soulless RS6, but it's still a little too cool and polished to light the fire of hard-core rear-wheel-drive enthusiasts.