The cars have a new eight-cylinder twin-turbo 414bhp 4.0-litre TFSI, which powers the saloon from 0-62mph in 4.8 seconds – the Avant is just 0.1 secs slower – while both have a limited top speed of 155mph.
Compared with the 5.2-litre V10 in the previous S6, this version is 25% more fuel efficient, average 29.1mpg in the saloon and 28.8mpg in the Avant. This is achieved, in part, thanks to Audi's cylinder on demand system.
Both have a seven-speed S tronic gearbox, Audi's quattro four-wheel-drive system and adaptive air suspension.
As well as being slightly longer than the standard A6 and A6 Avant, the S versions come with sporty styling inside and out, including rear spoilers, four chrome-tipped exhaust pipes, chrome detailing on the front bumper and grille.
The interior has S6 badges on the car key, steering wheel, the gearshift paddles and instruments.
Prices have yet to be revealed but Audi says order books will open towards the end of the year.
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