enhanced optional DVD-ROM-based RNS-E satellite navigation system replaces the previous CD-ROM-based RNS-D option. The new trapezoidal single-frame grille, Bi-Xenon high-intensity discharge lamp (HID) headlamps, L-shaped tail-lamps, quad exhaust tail pipes, and discrete V8 badging below the side repeater indicators help distinguish the B7 from the previous B6 model. Audi S4 25quattro In June 2005, Audi announced a limited edition run of 250 special edition S4 saloon cars, celebrating 25 years of quattro four wheel drive. This exclusive model was called the Audi S4 25quattro. Available only in the United States, the exterior has unique front and rear bumpers, a carbon fibre boot lip spoiler and lower front splitter, a rear functional red tow hook, and a high gloss Phantom Black painted grille with the "quattro" emblem. 15-spoke DTM alloy wheels, along with optional dealer-fitted 'Audi four-rings' decals for the front doors complete the exterior makeover. Black and grey contrasting interior leathers, along with "quattro" embossed into the Recaro seats, together with a "1 of 250" exclusive quattro gear shift knob for the manual-only gearbox define the interior changes and act as a subtle reminder of the exclusivity that the limited numbers command. On the mechanical side, the S4 25quattro was the second Audi, after the B7 RS4 to be fitted with the latest Torsen T-3 asymmetric ATB centre differential for its quattro permanent four-wheel drive system. Under normal grip conditions, this is set with a default rearwards torque distribution bias of 40:60 front to rear, and a maximum of 100% torque can automatically be apportioned to the rear axle (and up to 80% to the front) as conditions warrant. The final drive ratios are 3.889. B8 (Typ 8K, 2009–2016) From November 2008, the latest generation of the 'Audi S4 quattro' (Typ 8K) entered factory production. It is based on the current Audi B8 A4, built on the Volkswagen Group MLB/MLP platform. Unlike the previous B6 and B7 models, the new B8 version was only available as a four-door five-seat saloon (sedan), or a five-door five-seat Avant (estate/wagon). The sport-performance two-door four-seat Cabriolet (convertible) mantle is now taken by the current Audi S5 Cabriolet and new Coupe. Unlike previous generations of the S4, only the sedan will be imported to the United States and Canada. Compared to the previous B6/B7 S4 which used a 4.2-litre V8 engine, this latest B8 S4 uses a smaller displacement 3.0-litre TFSI V6 engine, but now