New-generation sports sedan hits the Nurburgring for performance testing.

The upcoming 2019 Audi S6 has been spied again, this time around the iconic Nurburgring race track in Germany.

Spotted with next to no camouflage, the blue sedan in the images gives us a fairly clear indication of what to expect from the mid-tier performance A6, which is likely to be revealed early next year.

As with most Audi 'S' models, the S6 gets a subtle body kit and a quad-tipped exhaust as its main distinguishing features from the standard A6 family, while bigger wheels and brakes complete the look.

Expect the production model to sport several 'S' badges scattered around the exterior and interior, including on the front grille and on the boot lid.

What will really set the S6 apart from the A6 is what lies under the bonnet – anticipated to be a version of the Porsche-derived 2.9-litre twin-turbo V6 that does service in the RS4 and RS5, along with the Porsche Panamera and Cayenne.

It's unclear whether the S6's version of this powerplant will match the 331kW/600Nm outputs of the RS4 and RS5, though considering the current model's 4.0-litre twin-turbo V8 makes 331kW and 550Nm, it's a pretty safe bet.

That grunt will be sent to the tarmac via an eight-speed 'Tiptronic' automatic with torque converter paired with Audi's quattro all-wheel drive system. With that in mind, 0-100 should take a smidgen over 4.0 seconds.

Audi will offer the S6 in both sedan and 'Avant' wagon forms as it has previously – though it's a sedan-only proposition in Australia at the moment – while the next-gen RS6 flagship will likely continue to be offered solely as a wagon.

In terms of timing, the new S6 will probably be revealed early next year, with Australian deliveries to commence either very late in 2019 or early-2020.

Following the reveal of the S6, the RS6 will join the line-up as well. Stay tuned to CarAdvice for all the latest.

Click on the photos for the full gallery