The current 997 Porsche 911 is still being updated for its mid-cycle refresh, with only the standard Carrera, Carrera 4, and Targa, and GT3 receiving the update. Still in the works are the new Turbo and the GT2 models, though they too are drawing near to their expected unveiling. Last year a test mule was spotted in Germany by our spy photographers, confirming that Porsche engineers are already well underway testing the next-generation 998 model, and soon after that Porsche's chief of research and development, Wolfgang Dürheimer, revealed some details of what to expect for the next-gen 911. Now we have new images of the 911 Carrera doing some high speed laps of Germany’s Nurburgring circuit.

Speaking of the new car, Dürheimer said, "'it will be even more competent, even sexier, even more unique. The design can of course only be evolutionary, but beneath the skin, almost anything is possible," reports CAR magazine. The 998 version of the car, known internally as 'project 991', will feature a few radical departures from the 911's long-running classical styling.

The changes are out of necessity more than anything, but they will be noticeable. First, pedestrian protection rules in the EU will require a change to the nose section of the car, likely meaning a larger and more collapsible bumper section. The rear of the car will also be changed, but for aerodynamic improvement.

Clear differences between the 998 and the current 997 model are the more upright headlights, a slightly longer body, and the side mirrors now positioned at the side of the doors and not at the window.

Other new features for the car will include heavy use of lightweight carbon-fiber materials and active aerodynamics - surfaces that react to what the car is doing, and how fast it's doing it. Expect adjustable front and rear spoilers plus dynamically opening and closing air intakes.

It’s still too early to determine what changes Porsche has in store for the engine lineup, but expect to see the familiar flat-six engine range carry over with only minimal updates – possibly for emissions and economy standards. The new PDK dual-clutch gearbox will also carry over as will a standard six-speed manual. Rumors of a possible four-cylinder addition to the 911 lineup, effectively bringing back the 912, and the revival of the 914 are shaking things up, however, at this point nearly anything seems possible.

According to Dürheimer, the next 911 won't make sales floors until late 2011, but we expect to see much more of the car from spy photographers as it develops. Click here for more shots of the high-performance Turbo model and the Cabrio.

2011 Porsche 911 test mule spy video