However, since Porsche engineers know full well there are times when the roof may have to be · raised quickly while on the move, t

However, since Porsche engineers know full well there are times when the roof may have to be raised quickly while on the move, the roof mechanism may be operated at vehicle speeds up to 30 mph (50 kph). Roof operation on the fly takes about 26 seconds. As with the previous model, the Turbo Cabriolet may be ordered with an optional hardtop. The aluminum roof weighs only 73 pounds (33 kg) and has a heated glass rear window, which conveniently receives its necessary power from the roof's rear attaching points. Coupelike aerodynamics Critical to the engineers and designers at Porsche was that the new 911 Turbo Cabriolet deliver the same high-speed driving experience as its sibling, the Turbo Coupe. This meant, among other things, that the open-top model be equally aerodynamic and stable at high speeds as the fixed-roof version. Like the 911 Turbo Coupe, the new Turbo Cabriolet has a drag coefficient of 0.31 when its soft top is closed, despite the fact that the roof is fabric, not metal. Equally impressive is the fact that the new 911 Turbo Cabriolet, with its roof closed, has the same low level of lift forces as the Coupe version. This car marks the first time that Porsche aerodynamicists have been able to accomplish this feat. As a result, lift forces on the front axle at the car’s top track speed of 193 mph (310 kmph) are only about 18 kg, or 39.6 pounds. This translates to solid steering feel and superb stability for increased driver confidence, regardless of speed. Sitting back solidly unlike any other Even more astounding is that the new Turbo Cabriolet benefits from approximately 27 kg (59.4 pounds) of downforce at the rear axle. That makes the new 911 Turbo Cabriolet the only production convertible in the world with rear downforce. To get optimum downforce, the Turbo Cabriolet's rear split wing extends a total of 65 millimeters or 2.56 inches, which is 30 millimeters or 1.18 inches further than the rear wing of the Turbo Coupe. The wing moves out automatically at 75 mph (120 kph). The wing retracts automatically when the car slows below 40 mph (60 kph). As with other 911 models, the Turbo Cabriolet's underside is virtually smooth, practically covered front to rear. This careful attention to the underside keeps turbulence to a minimum as the airflow beneath the car is controlled. This required six polypropylene panels beneath the manual gearbox model's body. They cover almost twice as much area as on the previous model. A steady, cool but quiet breeze Proper drivetrain cooling is ensured by three radiators. As with the Turbo Coupe, radiators are mounted behind vent openings in front of both front wheels. A third radiator is installed in the center of car's nose and is fed by large intake scoops. In addition, the intake scoops for all three radiators are connected to provide very efficient air distribution. At 186 mph (300 kph), 4000 liters of air per second flow through the radiators. To minimize resistance, Porsche aerodynamicists developed a deflector blade to direct the air out of the center radiator. This guides the air down to the floor without creating any lift forces in the process.