Audi B7 RS 4: A Performance Icon

The Audi RS 4 is not just a car; it's a statement. Representing the pinnacle of Audi's A4 line-up, the 'RS' moniker, derived from the German 'RennSport' meaning 'racing sport', signifies a machine built with performance at its very core. Positioned above the already capable 'S' models, RS models are at the forefront of Audi's technological advancements, and the B7 generation RS 4 is a prime example of this philosophy. This powerhouse, built by Audi Sport GmbH, was a significant evolution from its predecessors, offering a blend of blistering speed, sophisticated all-wheel-drive, and a distinctive, aggressive aesthetic.

The Genesis of the B7 RS 4

While the original B5 RS 4 was exclusively an Avant (estate car), the B7 generation marked a departure, initially launching as a four-door saloon (sedan). Soon after, the beloved Avant and a two-door, four-seat Cabriolet version joined the ranks, catering to a broader spectrum of performance enthusiasts. There was no RS 4 variant based on the B6 platform, making the B7 a highly anticipated and significant release. Unveiled in February 2005, the B7 RS 4 officially hit European streets in mid-2006, followed by North America in June 2006. Its production run spanned from 2006 to 2008, with approximately 10,000 units produced globally, around 2,000 of which found homes in the USA. The Cabriolet version also graced US shores, albeit in limited numbers and at a premium.

Powertrain: The Heart of the Beast

The B7 RS 4 is renowned for its magnificent 4.2-litre (4,163 cc) 32-valve V8 engine. This naturally aspirated powerhouse was a highly reworked and high-revving variant of the V8 found in the B6 S4, boasting a redline of 8,000 rpm and a rev limit of 8,250 rpm. It featured a new cylinder block construction and shared technology with the 4.2 FSI V8 in the Audi Q7, even serving as the base for the Audi R8's engine. Significant enhancements included increased crankcase breathing, a low-pressure fuel return system, and a baffled oil sump to prevent cavitation during high-speed cornering. With four valves per cylinder and dual overhead camshafts on each bank (quad cam), the engine benefited from variable valve timing for both intake and exhaust camshafts. A cast magnesium alloy intake manifold with adjustable tumble flaps further optimised low-end combustion. On premium 98 RON (93 AKI) petrol, this engine unleashed a formidable 309 kW (420 PS; 414 bhp) at 7,800 rpm, equating to a specific output of 74.2 kW (100.9 PS; 99.5 bhp) per litre. This resulted in a power-to-weight ratio of 0.184 kW per kg for the saloon variant, which tipped the scales at around 1,650 kg (3,638 lb).

The engine's exhaust gases were managed through a sophisticated '4-into-2-into-1' fan-branch steel exhaust manifold system, feeding into four high-flow catalytic converters and terminating in twin oval tailpipes with dynamic silencer valves. Engine management was handled by two Bosch DI-Motronic electronic control units, operating in a master-slave configuration due to the engine's high-revving nature, and ignition was via eight individual single-spark coils using mapped direct ignition. The saloon version emitted between 322-329 g/km of CO2, with the Avant starting from 324 g/km.

Transmission and Drivetrain: The quattro Advantage

Power was exclusively channelled through a 6-speed Getrag manual transmission, a choice that underscored the RS 4's driver-focused ethos. The gear ratios were meticulously chosen for performance: 1st: 3.667, 2nd: 2.211, 3rd: 1.520, 4th: 1.133, 5th: 0.919, and 6th: 0.778. The B7 RS 4 was unique among Audi 'RS' models of its time as it was the only one powered by a naturally aspirated engine until the arrival of the RS 5.

The cornerstone of the B7 RS 4's dynamic capability was Audi's advanced 'third generation' asymmetric/dynamic Torsen permanent four-wheel-drive system. This system featured a default 40:60 front-to-rear torque split under normal driving conditions, a configuration designed to promote a more neutral cornering response and a more engaging driving experience. The Torque Bias Ratio (TBR) was set more aggressively at 4:1 compared to the standard A4's 2:1 or 3:1, allowing one side of the differential to handle up to 80% of the torque, while the other managed only 20%. This sophisticated system, coupled with conventional open front and rear axle differentials and a final drive ratio of 4.111, provided exceptional traction and stability. Electronic Differential Lock (EDL) acted as a safety net, monitoring wheel speeds and applying brakes to spinning wheels to redistribute torque to those with grip.

Chassis and Handling: Dynamic Ride Control

Audi's innovative Dynamic Ride Control (DRC) 'Sports Suspension' system was a key feature of the B7 RS 4. This ingenious setup utilised a fluid hydraulic linkage between diagonally opposing front and rear suspension dampers. This linkage actively counteracted vehicle pitch and roll, ensuring a flatter cornering attitude and enhanced stability. The suspension arms, crafted from lightweight magnesium/aluminium alloy, employed a multi-link design – four arms with a virtual steering axis at the front and trapezoidal arms with unequal length track control arms at the rear. This sophisticated setup precisely located each wheel while minimising unsprung masses. Hollow tubular anti-roll bars were standard front and rear, further contributing to reduced body roll. Compared to standard B7 A4 models, the RS 4 sat 30 mm (1.2 in) lower, with an optional 'Sports Suspension Plus' reducing the ride height by an additional 10 mm (0.4 in) and increasing damper stiffness. The axle track was also widened significantly over standard A4s; the front track was increased by 37 mm (1.5 in) to 1,559 mm (61.4 in), and the rear by 47 mm (1.9 in) to 1,569 mm (61.8 in), contributing to improved stability and grip.

Braking and Wheels: Stopping Power and Style

The B7 RS 4 was equipped with a formidable braking system designed to match its performance. The standard brakes featured two-piece construction, with cross-drilled, radially ventilated cast-iron discs floating on aluminium alloy hubs. This design not only reduced unsprung mass but also mitigated heat transfer to the wheel bearings. The front discs measured a substantial 365 mm (14.4 in) in diameter and 34 mm (1.34 in) thick, paired with Brembo monoblock eight-piston fixed calipers. At the rear, drilled, vented, and floating iron discs of 324 mm (12.8 in) by 22 mm (0.87 in) were employed, featuring single-piston floating calipers and an integrated mechanical handbrake. For those seeking ultimate stopping power, an optional Audi ceramic front brake system was available from the 2007 model year onwards, comprising carbon fibre-reinforced Silicon Carbide composite discs (380 mm diameter) with grey Brembo six-piston calipers.

In key markets like the UK and Japan, the standard wheels were striking 19-inch alloy wheels (9Jx19" ET29 "7-arm double spoke") shod with high-performance 255/35 ZR19 96Y XL tyres. This 19-inch package was also an option in North America and other European markets. Earlier models, however, came standard with 18-inch alloy wheels (8½×18" "9-spoke") fitted with 255/35 ZR18 tyres.

Bodywork and Interior: Aggression Meets Refinement

Visually, the B7 RS 4 was an assertive machine, a clear departure from its more understated predecessors. The saloon variant featured a drag coefficient of just 0.31. The bodywork was constructed from fully galvanised steel with an aluminium unibody, utilising aluminium for the front wings and bonnet. Distinctive flared front and rear wheel arches, wider than those on the S4, accommodated the increased axle track. Unique front and rear bumpers, side sills, and a rear spoiler from the S4 Avant contributed to its aerodynamic profile.

The interior was a blend of sporty luxury and driver-centric design. Standard features included unique carbon fibre interior trims, a lap timer integrated into the central Driver Information System, aluminium pedal caps and footrest, and subtle RS 4 logos. The Recaro shell-type RS race bucket seats (not available in North America) offered exceptional support with electrically inflatable side bolsters and adjustable lumbar support. In North America, more traditional Recaro seats, identical to those in the B6 and B7 S4, were offered, including lower side airbags. Luggage space varied by body style, with the saloon offering 460 litres (16.2 cu ft) with the rear seats up and up to 833 litres (29.4 cu ft) with them folded. The Avant provided 442 litres (15.6 cu ft) with seats up and a cavernous 1,354 litres (47.8 cu ft) with seats folded.

Safety Features: Protecting Performance

Safety was paramount in the B7 RS 4's design. The high-strength steel body shell featured laser beam welding of major seams, enhancing structural rigidity and creating controlled deformation crumple zones. Standard safety equipment included two-stage driver and front-seat passenger frontal airbags, and Audi's 'Sideguard' head protection curtain airbag system, which covered all side windows. Lower side airbags were also available for the rear seats, and front and outer rear seatbelts featured pyrotechnic belt pretensioners.

Awards and Legacy

The Audi B7 RS 4 received critical acclaim during its production run, earning accolades such as Top Gear's 'Most Surprising Car of the Year' in 2005 and winning the 'World Performance Car' category at the International World Car of the Year awards in 2007. Its combination of a screaming V8, sophisticated quattro all-wheel drive, and engaging driving dynamics cemented its status as a true automotive icon and a highly sought-after modern classic.

Frequently Asked Questions

What does 'RS' stand for in the Audi RS 4?
'RS' stands for 'RennSport', the German term for 'racing sport'.

What engine does the B7 RS 4 have?
The B7 RS 4 is powered by a 4.2-litre (4,163 cc) naturally aspirated V8 engine producing 414 bhp.

What is the drivetrain of the B7 RS 4?
It features Audi's permanent quattro four-wheel-drive system.

Was the B7 RS 4 available as an estate?
Yes, alongside the saloon and cabriolet versions, the B7 RS 4 was available as an Avant (estate).

What transmission options were available for the B7 RS 4?
Only a 6-speed manual transmission was offered.