Audi S6
Audi made a high-performance, 4.2-litre V8 engine (parts code prefix: 077, identification code: AEC) with a Bosch KE-Motronic ECU available as an option in the original European S4s, and made the decision to continue to do so with the S6, making a version of the 4.2 available as an optional upgrade over the 2.2-litre inline five-cylinder turbo. Unlike the five-cylinder turbocharged version, the V8-powered S6 was supplied with a four-speed automatic transmission as standard, but kept the quattro four wheel drive. A six-speed manual gearbox was also available as an option.
Audi A4
The quattro permanent four-wheel drive system uses the latest Torsen T-3 centre differential, with a default 40:60 front to rear asymmetric torque distribution ratio (used first on the B7 RS4) as standard. (Previous A4 quattro models split torque with a default front:rear 50:50). The additional torque bias applied to the rear wheels helps mimic the driving dynamics of rear wheel drive cars.