2007 Audi RS 4

An Audacious Audi

Audi's beloved A4 line has a new flagship with more power than a Corvette.

Audi's 340-hp S4 sedan is one of the most desirable luxury sports cars — an impeccable design teamed with V8 firepower. But Audi's new RS 4 sedan is about to make the S4 look rinky-dink in comparison.

Until now, the S4 has been the hot-rod version of Audi's A4 sedan line — one of the most popular and attractive entry-level luxury-sedan ranges on the market. All the A4 models — A4, S4 and RS 4 — have tasteful, straightforward exterior styling marked by big grilles and graceful proportions. But when it goes on sale in June with a base price of $66,000, the super-exclusive RS 4 will set new standards for souped-up midsize sedans.

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The Audi RS 4 won't necessarily turn any more heads than the S4 does; its styling cues are designed to be subtle, not extravagant. But the RS has a sharp exterior that hides a ferocious, 420-hp, 4.2-liter V-8 engine under its hood. While the S4 is for people seeking a hotter version of the A4, the RS 4 will be more of a limited-edition model designed for Audi enthusiasts, collectors of fine automobiles and people for whom exclusivity is a top priority.

To put the power of the high-revving RS 4 engine (top speed is 8,250 rpm) into perspective, compare it with the race car-like, 400-hp, 6.0-liter V-8 in General Motors' Chevrolet Corvette sports car. The RS 4's engine has 5% more power and 50% more horsepower per liter, making it a model of efficiency and engineering smarts. And, like other Audis, the RS 4 will channel its power through all-wheel drive.

Corvette engineers like to say their car has plenty of "get up and go" — the ability of the engine to pin your head against the headrest any time you mash the throttle, regardless of how fast you're already going. The RS 4 will have this quality too, thanks to its ability to deliver 90% of its torque (peak torque is 317 pound-feet) anywhere from 2,250 to 7,600 rpm. The RS 4 can accelerate from zero to 62 mph in 4.8 seconds.

Audi instructed its engineers to optimize the RS 4's power-to-weight ratio, and the company said in a recent statement that "virtually every component was checked and cross-checked for minimum weight." For example, the RS 4's front-wheel arches and engine compartment lid are made of lightweight aluminum, just like most components of the chassis and suspension.

A final touch aimed at performance drivers is the RS 4's modified electronic stability-control system, which gives the driver a bit more freedom than a conventional unit would, as the RS 4's system intervenes later and for a shorter period. This gives experienced drivers more room to push the car around before the computers feel a need to correct traction losses.

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Some manufacturers build a performance derivative of a normal car and make it look over-the-top. Consider Subaru's hot rod WRX STi treatment of its Impreza sedan, which turns an innocuous vehicle into an electric blue cop-magnet with an enormous rear wing and hood scoop.

Audi has taken the opposite approach with the RS 4's design. You might have to be a connoisseur to spot the differences between the hot rod and the regular A4.

Such subtle modifications as new wheels and additional air-intake scoops in front set the RS 4 apart. In the rear, the RS 4 features two large tailpipes as well as what Audi calls a "discreet but highly effective" spoiler integrated in the trunk lid. The RS 4 sits one inch lower than the A4 and has a wider front and rear track.

Inside, the RS 4 has similarly subtle modifications that make it stand out a bit from the A4. The biggest difference is the inclusion of racing-style bucket seats.

Note: The RS 4's on-sale date came from Audi's media Web site. By publication time, the company had not responded to requests for confirmation.

Forbes Fact

From its beginning, Audi has had a focus on performance cars and racing. According to the Beaulieu Encyclopedia of the Automobile, "the Audi marque came about because of August Horch's disagreement with the other directors of Horch Motorwagenwerke. He believed strongly in competitions; they thought them a waste of time and money." So Horch left and founded Audi, which continues today to have a dominating presence in motor sports, especially at the 24 Hours of Le Mans endurance race.