Upcoming performance wagon hits the 'Ring.

The next-generation Audi S6 Avant has been spied during performance testing at the Nurburgring this week, ahead of an anticipated reveal later this year.

Distinguishing this prototype from regular A6 Avants is the quad-tipped exhaust – a dead giveaway for Audi S models – along with the subtle bodykit, bigger wheels and brakes. This vehicle also rides lower than the standard A6.

While this vehicle is largely undisguised, we reckon the final production version will get some subtle refinements to the overall look, a unique set of wheels, and plenty of S badging inside and out.

The powertrain is yet to be confirmed at this stage, but rumours suggest the new S6 will be powered by a version of the 2.9-litre twin-turbo V6 motivating the Porsche Panamera, along with the Audi RS4 and RS5 twins.

In smaller Audi RS models, that engine develops a meaty 331kW of power and 600Nm of torque, matching the power output of the current 4.0-litre bi-turbo V8 with an additional 50Nm of torque.

That grunt will be channelled to the tarmac through an eight-speed automatic transmission and Audi's quattro all-wheel drive system. Expect a 0-100km/h figure in the low 4.0-second bracket.

Audi is yet to confirm an official reveal date for the new S6 sedan and Avant, though we're expecting the new performance models to debut in the coming months – potentially just before or around the same time as the Paris motor show in October.

With that in mind, Australian deliveries will likely commence early in 2019. Following the S6, the A6 range should be completed when the all-out RS6 flagship launches a few months after.

Stay tuned to CarAdvice for all the latest, and head to the galleries section for more photos.