Road and Track, May 28th, 2006
The twin-turbo flat-6 retains the same displacement as the 996 Turbo (3.6 liters), but power has been increased to 480 bhp at 6000 rpm, along with 457 lb.-ft. of torque. For those of you counting, that gives the new Turbo 133 bhp per liter, an astounding number for a production car.
More interesting is the technology behind the Turbo's newfound power: Variable Turbine Geometry (VTG), which has been used on diesels since the early 1990s, but rarely before on a production gasoline engine. Porsche says, "The heart of the technology is adjustable guide blades, which can vary in angle to most effectively guide engine exhaust flow onto the turbocharger's impeller wheel." Porsche developed its version of VTG with Borg- Warner Turbo Systems, overcoming the far higher exhaust-gas temperatures of a gasoline engine with "temperature-resistant materials derived from aerospace technology."
The result provides the advantages of both a small and a large turbo, especially improving response at low engine speeds. This is shown by a rise in torque from 415 lb.-ft. to 457, as well as in the spread of the peak torque: previously from 2700-4600 rpm, now from 1950-5000. And if that's not enough, the optional Sport Chrono Package allows a 10-second "overboost," increasing turbo boost under full throttle to bring peak torque to 502 lb.-ft.
The Turbo will be available with a 6-speed manual gearbox or a 5-speed Tiptronic automatic. A twinclutch gearbox is in the works, but don't expect to see it any time soon.
The 911 Turbo will once again use all-wheel drive to transfer its power to the road, though the system is new, with an electronically controlled multi-disc clutch replacing the previous model's viscous unit. Power is variable to the front and rear axles according to slip. Porsche claims the PTM (Porsche Traction Management) awd system is one of the lightest in the world.
The 6-piston front and 4-piston rear brakes should halt the new Turbo even more quickly, with rotors at all four corners increased to 13.8 in. The super-expensive and virtually fade-free PCCB composite brakes will be optional, reducing unsprung weight by 37 lb.
In typical Porsche fashion, styling is evolutionary, minimal changes being a 0.9-in.-wider rear, a new rear wing and redesigned air inlets behind the doors. The new Turbo will be priced at $122,900 when it goes on sale in North America this summer.
