Audi's new allroad quattro station wagon comes with a choice of a 2.7-L gasoline engine or a 2.5-L V6 turbodiesel. The interior of the Audi allroad quattro. Cutaway view of the Audi allroad quattro's drivetrain and chassis. The Audi allroad quattro's rear axle with air suspension. The allroad's 2.5-L V6 turbodiesel engine with variable turbine geometry. The Audi RS4 quattro is being built by Audi at Ingolstadt and quattro GmbH at Neckarsulm.

The allroad (lowercase initial letter as with "quattro") production car is based on the Audi A6 avant station wagon and was seen at this year's Geneva Motor Show. It is Audi's vision of what a dual-role station wagon should be. It comes with a choice of a 2.7-L, 184-kW (247-hp) gasoline engine or Audi's 2.5-L V6 turbodiesel producing 132 kW (177 hp), both driving through a six-speed gearbox. It has been 20 years since the first production Audi quattro appeared in sporting coupe form, and now "quattro" simply means an Audi four-wheel-drive system, without necessarily signaling a sporty model.

Until recently, the quattro capability of its sedans gave Audi owners added security on slippery surfaces and some limited off-road capability. But the company felt more could be done with the system, and the A6-based allroad is the result. With a more aggressive stance (it is slightly higher) than the regular A6, and with extensive body protection plus stainless steel undertrays front and rear, the allroad is a distinctive model. Significant mechanical elements include a four-level air suspension with both automatic and manual operation. Manual versions of the car are available with a low-ratio transfer gearbox.

Audi opted to fit the allroad with an air suspension to not only provide the level of ground clearance necessary for off-road work but to also ensure the ride and handling standards of a regular car, together with a low center of gravity and improved aerodynamics. Air suspensions are likely to be seen on more of Audi's models in the future. Ground clearance can be varied by a maximum 66 mm (2.6 in) with four delineated ride heights between 142 mm (5.6 in) and 208 mm (8.2 in). The car has automatic leveling. Central to the air suspension's efficacy is the air supply unit and an electronic control system. These are fitted at the rear of the vehicle. Each road wheel has a ride height sensor that detects ground clearance and adjusts the relevant air spring strut separately until the correct ride height is restored.

The lowest ride height is for optimum travel at speeds above 120 km/h (75 mph). Normal ride height is 25 mm (1.0 in) higher and is suitable for driving on firm surfaces up to 120 km/h, according to Audi. Another 25-mm (1.0-in) clearance is obtained in raised suspension Level 1, suitable for both gentle and rough off-roading. Road speed can reach 80 km/h (50 mph) in this mode. Above that speed, the suspension lowers automatically. Level 1 is selected automatically when the vehicle is parked with the automatic ride height control activated. Raised suspension Level 2 adds another 16 mm (0.6 in) to the ground clearance to provide the maximum 208 mm (8.2 in) for extreme terrain. A dashboard press-button system allows for automatic or manual height adjustment. An LED display indicates height chosen, flashing as it rises or lowers. Electronic interlocks prevent too high a ride height being selected. Even in manual mode, the body will lower if pre-determined speeds are exceeded. After 30 seconds of travel at speeds above 120 km/h (75 mph) the lowest ride height is automatically selected. If automatic is selected, the body will rise again from low to normal height as speed is reduced.

According to Audi, the low range option for manual allroads reduces overall gearbox ratios by a factor of 1.54, giving a 1000 rpm road speed in first gear of 4.9 km/h (3.0 mph) against 7.9 km/h (4.9 mph) in the regular range. Low range can be selected at speeds up to 30 km/h (18.6 mph) by fully declutching and pressing a gearshift-mounted button. Low range can be used at up to 50 km/h (31 mph) when audible and visual warnings are given. If ignored a governor cuts in at 70 km/h (43.5 mph).

The Audi allroad follows established quattro techniques with a Torsen self-locking center differential between the rear axles. This enables up to two-thirds of the engine's power to be switched between axles to meet demand. An electronic differential lock is effective up to 100 km/h (62 mph).

The interior of the allroad is similar to the regular A6 avant wagon. Performance of the manual vehicle includes a top speed of 236 km/h (147 mph), a 0-100 km/h (0-62 mph) time of 7.4 s, and an average fuel consumption of 12.8 L/100 km (18.4 mpg). Unladen weight in this form is 1795 kg (3957 lb).

Audi's other new offering is the remarkably quick permanent-four-wheel-drive quattro RS4, the ultimate version of the regular A4 Avant station wagon. It has a 2.7-L V6 bi-turbo engine producing 280 kW (380 hp). This is sufficient for a 0-100 km/h (0-62 mph) time of only 4.9 s and a 0-200 km/h (0-124 mph) time of 17 s. Maximum speed is theoretically governed to 250 km/h (155 mph), although this AEI editor bettered that figure to reach 269 km/h (167 mph). Quattro GmbH's explanation for this was that possibly an element of tolerance was present in the car's limiter system.

The RS4 was created by quattro GmbH and developed in conjunction with Audi AG. It is being built jointly by Audi at Ingolstadt and quattro GmbH at Neckarsulm. Quattro GmbH was founded in 1983 to legally protect the brand name "quattro." Audi, Cosworth Technology, and quattro GmbH were all involved in the development of the RS4. The basis for the engine is the less powerful unit fitted to the Audi S4. In RS4 form, it provides a constant torque of 440 N•m (325 lb•ft) between 2500 and 6000 rpm. Of added significance is that it also has an unusual power plateau, achieving its 280 kW (375 kW) at 6100 rpm and maintaining it to 7000 rpm.

Stephan Reil, Technical Director of quattro GmbH, told AEI that achieving such figures for a road-going 2.7-L car required extensive reworking of the engine. High stress components including crankcase, crankshaft, connecting roads, and pistons were redesigned. In fact, almost all areas of the engine were changed, including a completely redesigned cylinder head; larger flow-optimized intake and exhaust ports for reduced charge-exchange losses; modified air ducts with enlarged cross-sections on the intake and thrust sides; larger KKK K04 turbochargers with a maximum absolute boost pressure of 220 kPa (32 psi); intercoolers with optimized pressure loss and a surface some 30% larger; and a back-pressure-optimized exhaust system with two primary and two main metal-based catalytic converters. Cosworth Technology casts the cylinder head and assembles the engine, which has a specific output of 106 kW (142 hp) per liter and a power-to-weight ratio of 4.26 kg/kW (9.4 lb/hp).

Audi allroad quattro's low-range transmission for the manual version.

Although the RS4 has a similar appearance to the basic A4 and sportier S4, only the hood and roof have been adopted from the outer panels of that car. The RS4 has an overtly "muscular" presence, with three large, frontal inlets for water, oil, and charge-air cooling. This design is echoed at the rear. There are vents in the side of the front apron. Wheel arches are flared by 35 mm (1.4 in), with the contour continued in the rear doors. The car has wide alloy wheels carrying 255/35 ZR 18 low-profile tires.

"The diameter of the ventilated brake discs is 360 mm (14.2 in) on the front axle and 312 mm (12.3 in) at the rear," said Reil. "Fourteen steel pins connect the cast friction ring to the aluminum brake-disc chamber. With its 'floating' arrangement, this joining technology, adopted from the world of motorsports, improves the stability of the brake discs, particularly when exposed to extreme loads and high temperatures." The car also has ESP (electronic stability program). "This combines the established functions of the ABS with EBD (electronic brake force distribution), EDL (electronic differential lock), ASR (anti-slip regulation), MSR (engine drag torque control), and the higher level yawing moment controller," added Reil. The RS4 is lowered by 20 mm (0.8 in) compared with the standard A4. Aluminum is used for some suspension parts. The car has a six-speed gearbox. Equipment includes Recaro sports seats.

Stuart Birch

AEI August 2000