Building on the sharpened appearance of the facelifted S4 launched this month, Ingolstadt’s latest supersaloon gains an added dose of visual muscle that instantly differentiates it from its lesser sibling. A deeper front bumper with larger air ducts and distinctive vertical gills on the outer edges, a new plastic honeycomb insert for the single-frame grille and beefed-up front wings dominate the front view, while the sides are characterised by widened sills, signature matt aluminium exterior mirror housings and towering 18-inch double-spoke alloy wheels shod with 255/40 profile tyres. The rear features a small spoiler, deeper valance panel and a pair of large chrome tailpipes.
The new car sits a considerable 30mm lower than the S4 and its overall stance is improved by tracks extended by 37mm up front and 47mm at the rear.
Aerodynamic requirements have influenced changes underneath, where a flat undertray and diffuser provide a more efficient flow of air, while small ducts are employed to cool the engine and brakes more effectively.
Audi has also used its expertise in lightweight construction to keep weight down. The body is made predominantly from high-tensile steel – as with the S4 – but the bonnet and heavily flared front wings are aluminium. At 1650kg, the new car tips the scales a creditable 10kg under the S4 but is 155kg heavier than an M3.
Although Audi has only revealed a saloon version of the RS4, an estate model exists. However, it probably won’t be unveiled until the Frankfurt Motor Show in September.
Engine & transmission
The big news under the skin is the arrival of a naturally aspirated engine derived from the S4’s compact 90-degree V8. The technical details revealed so far indicate very different characteristics to Audi’s earlier turbocharged engines, with sharper throttle response and a more highly strung nature that should make it a hit with enthusiasts.
With a capacity of 4163cc, the engine gets a host of tweaks, including Audi’s FSI (fuel stratified direction injection) system that’s conducive to high revs – the electronic cut-out is at 8250rpm. Peak power is 414bhp – 70bhp more than the S4 and (crucially given Audi’s quest to top BMW) 75bhp up on the existing M3, although the replacement M3 due in 2007 will close that gap courtesy of a 400bhp V8. The RS4’s maximum torque of 317lb ft arrives at a relatively high 5500rpm, although 285lb ft of it is developed between 2250rpm and 7600rpm, which should mean a highly flexible delivery.
A more reliable performance indicator is the RS4’s power-to-weight ratio – at 251bhp per tonne, it makes the M3’s 215bhp per tonne look a little tame.
A six-speed manual gearbox channels drive through a twin-plate clutch and heavily reworked version of Audi’s quattro four-wheel-drive system. In a bid to provide the RS4 with a more entertaining feel, the characteristics of the quattro system have been heavily revised. Instead of delivering drive in a classic 50:50 front-to-rear arrangement, the new system doles out a rear-biased 40:60 split. Insiders admit there is a slight trade-off in traction, but it is a drawback they are prepared to absorb in return for improved poise and balance.
The RS4 is spectacularly fast by four-door standards. The headline figure is 0-62mph in a claimed 4.8sec – 0.8sec faster than the S4 and 0.4sec inside the M3’s official figure. Those who have experienced the new car’s standing-start acceleration say it lacks the neck-straining take-off of its predecessor’s, although this is compensated for by greater mid-range shove.