The Audi RS 4 is the high-performance variant of the Audi A4 range produced by Audi Sport GmbH for AUDI AG, a division of the Volkswagen Group. It sits above the Audi S4 as the fastest, most sports-focused car based on the A4's "B" automobile platform. The RS 4 was reintroduced in 2012, based on the A4 Avant instead of the sedan as did the original model.
The original B5 version was produced only as an Avant, Audi's name for an estate car/station wagon. The second version, the B7, was released initially as a four-door five-seat saloon/sedan, with the Avant following a short while later. A two-door four-seat Cabriolet version was subsequently added.
The "RS" initials are taken from the German RennSport—literally translated as "racing sport", and is the Audi marque's highest trim level, positioned above the "S" model specification of Audi's regular model line-up. Like other Audi "RS" cars, the RS 4 pioneers some of Audi's latest advanced technology. It is only available with Audi's Torsen-based "trademark" quattro permanent four-wheel drive system.
RS4 models have been produced for every generation of the A4 since 1999, with occasional gaps in production (2001-2006, 2008-2012 and 2015-2018)
Its main market competitors include the BMW M3, Mercedes-Benz C 63 AMG, Lexus IS-F (formerly) and Cadillac ATS-V (now Cadillac CT4-V Blackwing).
B5 (Typ 8D, 1999–2001)
alt=|left|thumb|Audi RS 4 Avant (UK) finished in Goodwood Green
The original B5 Audi RS 4 Avant quattro (Typ 8D) was introduced by Audi in late 1999, for main production and sale from 2000, as the successor to the Porsche / Quattro GmbH joint venture-developed Audi RS2 Avant. Like its predecessor, the RS 4 was available only as an Avant and was built on an existing platform, in this case, the Volkswagen Group B5 platform shared with the A4 and S4. Retail price was around DM 103,584. The RS 4 was available for sale in most of Europe, parts of Asia and in some Latin American countries.
Audi produced 6,030 units between 1999 and 2001.
B5 bodywork and styling
Although related to the B5 S4, many of the outer body panels were altered, with wider front and rear wheel arches to allow for the wider axle track on the RS 4. With unique front and rear bumpers and side sills, and the rear spoiler from the S4 Avant, the aerodynamic modifications achieved a drag coefficient of C<sub>d</sub> 0.34. Although the B5 S4 came in a saloon car body style, the B5 RS 4 was only available in the Avant version.
Luggage space, measured according to the industry standard VDA method was with the rear seats in the upright position, and with the seats folded flat.
B5 powertrain
thumb|left|Audi B5 RS 4 engine [[power (physics)|power (red) and torque (blue) curves]]
The engine was developed from the 2.7 litre 90° V6 'biturbo' used in the B5 S4. It displaced and had five valves per cylinder. The engine was developed and manufactured in the UK by Cosworth Technology. It featured aluminium alloy ALSi7Mg cylinder heads, cast by Cosworth, with enlarged intake ports and smaller exhaust ports, two parallel BorgWarner K04-series turbochargers, two larger side-mounted intercoolers, dished piston crowns, stronger connecting rods, larger intake ducting, an enlarged exhaust system, and a re-calibrated engine management system. The modifications increased the engine's output from and of torque to at 7,000 rpm and at 6,000 rpm. The engine was controlled by a Bosch Motronic ME 7.1 electronic engine control unit, using a Bosch 'E-Gas' electronic drive by wire throttle. It had multipoint sequential fuel injection, a mass airflow sensor, and six individual ignition coils. The engine oil was cooled by oil to water and oil to air coolers.
A six-speed manual transmission (parts code prefix: 01E, identification code: FDP) (gear ratios—1st: 3.500, 2nd: 1.889, 3rd: 1.320, 4th: 1.034, 5th: 0.806, 6th: 0.684), cooled by a NACA duct in the engine undertray, and Audi's Torsen-based quattro system, using the Torsen T-1 "automatic torque biasing" center differential, with a 50:50 default bias were standard. Final drive ratio was 4.111.
The RS 4 has a curb weight of . It can accelerate from 0- in 4.9 seconds, 0- in 11.3 seconds, and 0- in 17.0 seconds. The top speed is electronically limited to .
B5 brakes, wheels and tyres
left|thumb|Interior
Brakes were also developed jointly in house by Audi's quattro GmbH, not by Porsche as with its predecessor, the RS2. At the front they were radially vented and floating cast iron discs, diameter and thick, with double-piston floating calipers, and at the rear by discs with a single-piston floating caliper. The RS 4 needed less than to come to a full stop from a speed of .
The standard wheels were 18 inch alloy wheels (8½×18" "9-spoke"), with 255/35 ZR18 high performance tyres. Optional "winter" alloy wheels were also available, at 18 inch (7½J×18"), with tyres.
Other B5 notable features
- "Sideguard", Audi's curtain airbag system.
- Xenon High-Intensity Discharge (HID) headlamps.