Audi's hottest convertible TT is spied being put through its paces at the Nurburging ahead of late 2016 launch

Audi 's stylish TT Roadster is about to get a whole lot more sporting, as our snappers have caught the RS model undergoing track testing.

is about to get a whole lot more sporting, as our snappers have caught the RS model undergoing track testing. It's expected to launch at the end of this year after the TT RS coupe.

As you'd expect, it will share the same powertrain as the coupe, which is almost certainly the turbocharged five-cylinder unit found in the RS3mega-hatch. In that form it produces 362bhp, but Audi may tune it even further to increase the performance gap between it and the 306bhp TT S.

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Audi will be benchmarking it against the newly released Mercedes SLC 43, which (conveniently) also has 362bhp thanks to a twin-turbocharged V6. But more driver-orientated cars like the flat-four turbo Porsche 718 Boxsterwill be considered as a target.

It will be able to handle any extra grunt thanks to the four-wheel drive system, while expect the choice of a six-speed manual or dual-clutch automatic transmission. With the latter fitted, expect to 0-62mph time to drop to - or even below - the four second mark.

Spotted testing alongside the TT RS Coupe, the Roadster styling upgrades appear relatively subtle behind the disguise. A lowered ride height, beefier front air intakes and a larger rear spoiler can be expected for production, while the tell-tale oval exhaust pipes also feature.

Will the Audi TT RS Roadster be better than the Mercedes SLC 43? Let us know your thoughts below...