styling The C6 RS 6 Avant was launched in April 2008, and the four-door saloon/sedan was available from August 2008. Constructed from steel in a monocoque (unibody) design, the RS 6 uses lightweight aluminium for its front wings (fenders) and bonnet (hood). Visually, the RS 6 differed from the related S6, having flared front and rear wheel arches (fenders), harking back to the original Audi Quattro, to allow for a wider wheel track. It also had no front fog lights to allow for larger frontal air intakes (for the two side-mounted intercoolers (SMICs), and additional radiators). The ten (per side) front light-emitting diode (LED) daytime running lights (DRLs) are located within the main headlamp housing on the RS 6 in order to increase the size of the air intakes, whereas similar LEDs (but five per side) on the related S6 are found adjacent to the fog lamps in the lower front bumper. LED lighting technology was also used in the rear lights. The RS 6 also included adaptive headlights, which swivel around corners in conjunction with steering wheel movements. The facelifted Audi A6, released as a 2009 model, received similar front and rear-end LED lighting styling to that pioneered on the RS 6. Luggage capacity, measured according to the VDA 'block method' in the Avant ranges from , to . C6 powertrain The engine (parts code: 07L, identification code: BUH) of the RS6 was what Audi claimed to be the first all-aluminium alloy even firing 5.0-litre () 90° V10 twin-turbocharged ("biturbo"), Fuel Stratified Injection (FSI), with a dry sump lubrication system. This engine is related to the naturally-aspirated V10 found in the Audi R8, S6 and S8, but the RS 6's engine has around 400 unique parts. The engine has four valves per cylinder, with chain-driven double overhead camshafts, and variable valve timing for both inlet and exhaust camshafts. Charged intake air is cooled by two side-mounted intercoolers (SMIC)s. The engine is controlled by two Bosch DI-Motronic MED 9.1.2 engine control units, which act as 'master' and 'slave': two ECUs are required due to the high revs the engine can achieve. It also uses mapped direct ignition system with ten individual direct-acting spark coils, an electronic drive by wire throttle (Bosch "E-Gas"), cylinder-selective knock control, and cylinder bank adaptive lambda control, utilising eight lambda sensors. A total of seven radiators and four electric cooling fans are needed to cool the