page_title: Audi S4
section_title: Audi S4 25quattro
hierarchical_section_title: Audi S4 / B7 (Typ 8E/8H, 2005–2009) / Audi S4 25quattro
caption_attribution_description: 2006 Audi B7 S4 "25quattro" special edition
context_page_description: The Audi S4 is the high performance variant of Audi's compact executive car A4. The original Audi S4, built from 1991 until 1994, was a performance-oriented version of Audi's 100 saloon/sedan. All subsequent S4s since 1997 have been based on the Audi A4; and as the A4 has evolved from one generation to the next, so has the S4.
  A more powerful internal combustion engine, larger upgraded brakes, firmer suspension, larger wheels, and distinctive sheetmetal, styling clues and badging have always been amongst the many upgrades the S4 receives over its mainstream 100 and A4 siblings. In markets where the even higher-performance Audi RS4 is not offered, the S4 is the top-of-the-line trim of the A4 family.
  Like its regular A4 counterpart, all S4 variants have had longitudinally oriented, front-mounted engines. A single turbocharged 2.2-litre inline five-cylinder powered the original C4 version, and a 2.7-litre twin turbocharged V6 engine was found in the B5 generation. The B6 and B7 versions shared a common 4.2-litre V8 engine, the first time that a V8 engine was placed in a compact executive car, placing it in direct competition with the BMW M3 which at the time had a 3.2 L inline 6.
context_section_description: 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.
caption: Audi "S4 25quattro" special edition (8EC)
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