CHANGING THE GAME; Audi alters its performance-car recipe with an engaging new sedan.(Audi launches new car, Audi RS4)

Byline: GREG KABLE

Audi's 4.2-liter, 420-hp V8-powered RS4 made its world debut at Geneva, and the car marks an important change in the Volkswagen division's sport-sedan quest: To further its high-end performance-car aims, Audi has ditched turbocharging in favor of a bigger, highly strung naturally aspirated engine. This is a move Audi insiders say will be repeated in coming years on new-generation Audis, including a new RS6, RS8 and the anticipated production version of the Le Mans concept.

The engine is just the first step in a broad-based engineering program by Audi's quattro division, which aims-yet again-to garner the respect paid to its German performance rivals, BMW M and Mercedes-Benz AMG. This time, it might work.

The RS4 employs a re-engineered quattro all-wheel-drive system, putting down the power with a distinct rear-wheel bias. Lightweight body panels, aluminum-intensive suspension and a reworked interior boasting a more driver-centric ambience also highlight the new model. Audi says the changes make the new four-door a more engaging car to drive than the previous 2.7-liter, 381-hp twin-turbo V6-powered RS4-Audi expects it to run with the standard-setting BMW M3. On paper, it looks able.

Building on the appearance of the facelifted and re-powered S4 launched late last year (AW, Jan. 24), the RS4's shape looks more muscular, which instantly differentiates it from its lesser siblings. There is a deeper front bumper with larger air ducts and distinctive vertical gills on the outer edges. A plastic honeycomb insert for the single-frame grille and beefed-up fenders dominate the front view, while the sides have widened sills beneath the doors, signature matte-finished aluminum exterior mirror housings and towering 18-inch double-spoke alloys for 255/40 tires.

A small rear-deck spoiler, a deeper valance panel and a pair of large chrome tailpipes enhance the rear aspect. The car sits 1.2 inches lower than the S4, and the track has been widened: 1.5 inches in front, 1.8 inches in the rear. A flat undertray and diffuser provide a more efficient flow of air beneath the car. Small ducts cool the engine and brakes more effectively.

Audi used its expertise in lightweight construction to keep the RS4's weight down. The body is made predominantly from high-tensile steel, like the recently restyled S4, but the hood and front fenders are aluminum. Tipping the scales at 3630 pounds, the new car is 22 pounds lighter than the S4, but 341 pounds heavier than the weight BMW quotes for the M3.