A prototype for the 991.2 Porsche 911 GTS has been spied testing at the ferocious Nurburgring ahead of the model's expected debut in 2017.

The most significant change over the previous GTS is that the new car will adopt the same 3.0-liter twin-turbocharged six-cylinder engine used by the rest of the 911 family (excluding existing and future hardcore GT models).

While this engine lacks some of the emotion of the naturally-aspirated unit of the old GTS, it is both more powerful and fuel efficient and, in 991.2 GTS trim, should comfortably pump out more than the 420 hp offered up by the Carrera S. The result will be a model to sit perfectly between the Carrera S and the facelifted GT3, also due next year.

On the back of the unprecedented reception for the 911 R, there's talk that Porsche may be prompted to reintroduce its six-speed manual gearbox over the current seven-speed stick shift found within the 911 range. If this proves true, the new GTS could make use of the R's six-speed, but with modified gear ratios for more relaxed cruising.