|Sucessfully campaigned in the 2005 & 2006 Dutch Supercar Challenge Championship by Ric Wood and partner Steve Hirst.
This Audi A4 racecar looks very similar to its roadgoing cousin with a few modifications including a large rear spoiler, low ride height, large 19inch OZ alloy wheels and a deep front airdam .
Though based on an Audi A4 chassis, the similarities are kept to the outside. On the inside, the car is outfitted with a wide range of structural and mechanical enhancements.
To build the race-spec Audi A4 touring car, the chassis is first fitted with a tubular safety cage. The cage, combined with full seam welding, supplies plenty of protection for the driver in the event of a wreck and roughly doubles the torsional rigidity of the chassis. These structural enhancements also have a beneficial effect providing improved handling. Portions of the cage extend throughout the front and rear bulkheads of the car, connecting to the suspension turrets. The end result is an incredibly strong frame that is practically devoid of unwanted chassis flex.
Underneath, the car is equipped with smooth paneling to provide improved aerodynamics over the cluttered underside of the roadgoing A4. This smooth underbelly helps the front airdam and rear spoiler to operate giving downforce which keeps the car glued to the track.
Under the bonnet, the differences between the A4 racecar and the A4 road car are many. Standard specification in the Touring Car format is a 2.0-litre, so the car has a modified version of the 1,998cc-inline four-cylinder setup that is subject to explicit specifications. One regulation states that teams cannot alter the position of the valve centers, limiting the size of the valves that can be used, however leaving the specific size and configuration of the valves up to the developer. In Audi's case, this meant 4-valves per cylinder for a 16-valve setup.
Upon opening the bonnet of this Audi touring car, the most easily recognized difference is the carbon-fiber cam cover. Below, the engine is controlled by a Bosch Motronic system, lubricated through a dry sump setup utilizing Castrol fully synthetic oil and limited to 8500rpm. Exhaust exits through a three-way catalyst.
With regulations in mind, every possible modification is made to the engine in an effort to optimize power and reliability as much as possible. In full race specification, the modified engine produced 296bhp at 8,250rpm and 188lb ft torque (225Nm) at 7,000rpm. For the 1997 season, power was bumped up to 305bhp at 8,250rpm and 217lb ft torque (260Nm). However, rules for the Dutch Supercar challeenge are much less restrictive and 550BHP was extracted from an enhanced engine build. This made the car very competitive against a very strong field. It was a particularly good car in the wet and took a race win at Siverstone in 2006
The transmission is a 6-speed sequential unit that allows for clutchless shifting. The gearshift is moved backwards for upshifts and forwards for downshifts. Though that sounds similar to Audi's Tiptronic transmission, the similarities end there. While the Tiptronic transmission is an automatic programmed to change gears based on driver inputs, a sequential shifter is a manual transmission with a hydraulically actuated clutch allowing quicker shifts than either a manual or Tiptronic could provide.
The transmission was added to handle the increased power output of the A4 Touring Car's engine and mated to a single dry plate clutch made of carbon fiber. In addition, the center, front and rear differentials of the quattro system have been strengthened to help reliably put the power to all four wheels.
While the A4 1.8T, the touring car's closest cousin, features 280mm ventilated front and rear discs, the A4 racecar has 343mm in diameter and 32mm thick vented discs at the front and 330 X 28mm discs at the rear. Audi is able to use this particularly large rear brake setup because the quattro all-wheel-drive system allows the rears to be further maximized than front-wheel-drive cars due the quattro system's ability to keep the rear wheels from locking up. ABS is not used in accordance with FIA Super Touring regulations.
Pads on the system are Performance Friction carbon-metallic and asbestos free, designed to minimize brake fade. Audi Sport developed the pad compound in cooperation with the American owned company based in Munich. Rotors are slotted. Although most teams in the multiple series choose Brembo or AP Racing, the Audi factory team uses brakes manufactured by a British manufacturer named Alcon. The system is fully adjustable from front to rear via a cockpit dial and, unlike the A4 1.8T, is not power assisted. Though rarely altered once set up for a specific venue, adjusting the balance during the race allows the driver to compensate for decreasing fuel levels that change the car's own balance. This setup, significantly larger than stock, allows for the drivers to brake much later and harder when approaching each turn.
Regulations also state that the racecar's suspension layout must be identical to that of the road car, though modifications of the setup are allowed. The A4 Touring Car rides on 8JX19 forged racing spec OZ 16-spoke alloys in dry weather and forged OZ 5-spoke alloys in wet weather to prevent confusion during pit stops. The OZ alloys are held on with center lock hubs and shod with 215/650 R19 tires.
Inside the trunk, the fuel tank is placed in the center of the car where it is also filled. "Fast filler caps" are not permitted under the FIA rules.
In the cockpit, anyone familiar with the opulence of Audi's smallest sedan might have a hard time recognizing what car they were even in, with the small exception of the top dashboard panel. Luxurious appointments such as leather seats and wood-trimmed components are replaced with bare metal, the aforementioned steel roll cage and carbon fiber composite panels.
Impact protection was a big issue for Audi, who even conducted the world's first crash test for racecars at its road car crash testing facility in Ingolstadt. An Audi 80 Competition racecar was launched into the side of an A4 racecar at 50mph in an effort to perfect their new rollbar safety system.
Audi's roll bar is a unique design that implements X-patterned bars across the front door apertures and called ìSide Impact Security Conceptî. The system also uses two layers of absorbent foam with a strong carbon-fiber partition plate attached to the rollcage. A Sabelt six point safety belts, and a Recaro racing seat further assure the drivers safety.
Standard instrumentation is replaced with various electronic readouts that are centralized more effectively to the view of the driver. On the driver's right is the sequential gearshift lever, located next to two slider controls that handle on-the-move adjustment of the front and rear anti-roll-bars. To the right of the slide controls is a dial for brake bias control. The console above the driveshaft houses the rest of the switches, which would normally be found on the dashboard of a production car.