Munich 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.
The new RS4 deviates from the engineering concept of its predecessors in more ways than one. The turbocharged engine has been replaced by a normally aspirated, high-revving V-8; the Quattro drivetrain for the first time features a rear-wheel torque bias; and the four-door sedan doubles the number of available body styles.
The move away from turbocharging is a big departure. The new direct-injection V-8 is ultraresponsive and addictively light-footed in the way it summons more power and whips up more torque. With 414 hp, the 2006 RS4 will accelerate from 0 to 62 mph in a stellar 4.8 seconds. The 4.2-liter unit musters its maximum brio at 7800 rpm; from there, you have another 450 rpm to play with before the limiter gently intervenes at 8250 rpm. The torque curve plateaus at 5500 rpm, where 317 lb-ft are on tap, but it is worth knowing that 90 percent of the twist action is available between 2250 and 7600 rpm.
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 switching the Quattro drivetrain from a 50/50 to a 40/60 front/rear torque split, 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. Only when pushed to the point where ESP interferes does a blink of torque steer remind you that quattro is Italian for "four."
Like nearly every current Audi, the new RS4 suffers from a disappointingly harsh ride. Shod with optional 35-series Michelin Pilot Sport tires on nineteen-inch wheels, the RS4 is quite bad at coping with high-frequency transverse ridges. The staccato suspension is particularly tiring at autobahn speeds, when the car fights every expansion joint, every piece of patchwork tarmac, and every lateral groove it can find. While the underdamped steering tries to jerk off your wedding ring, the overly taut spring and damper settings convert the thinly padded, tight-fitting bucket seats into masochistic massage pods. Lowered by 1.2 inches and widened by 1.5 inches in front and 1.9 inches in back, the RS4 doesn't track as stoically as its lesser stablemates. On winding, uneven two-lanes, the front and rear axle pitch and the vertical body movements that seem to rotate back and forth around the car's longitudinal axis can affect the directional stability. It's a dynamic oddity: in a car so expressively devoid of emphatic body movements, what little compliance there is tends to work against you.
The Dynamic Ride Control (DRC)-introduced in the RS6-has been updated here and effectively suppresses yaw, roll, dive, and squat by diagonally linking the two pairs of dampers hydraulically. This wholly mechanical system provides a confidence-inspiring, ground-hugging cornering attitude that is particularly awesome on smooth tarmac, where the RS4 occasionally will lift a leg or two when going ten-tenths.