If the driver floors the throttle, PTM instantly directs some engine power to the front wheels to · prevent the rears from braking

If the driver floors the throttle, PTM instantly directs some engine power to the front wheels to prevent the rears from braking traction. By comparing data from the steering-wheel position sensor with other input, PTM and PSM are able to detect both under- and oversteer and redirect engine power or even apply braking to individual wheels as needed. As expected with a high- performance sports car, both PTM and PSM are active at all speeds. Always under the driver's command Given the demands and expectations of the typical Porsche driver, PSM has been designed to act seamlessly and all but invisibly. Porsche engineers programmed the system to allow the driver to fully enjoy the Turbo Cabriolet's agility and speed without coarse interference and abrupt actions. But the highly skilled, enthusiast driver who may wish to fully experience the Turbo Cabriolet's balance and ultimate handling limits can temporarily switch off PSM. Simply hitting the brake pedal instantly re-engages the system. Even more traction for the 911 Turbo Cabriolet can be had with an optional mechanical differential lock with asymmetric distribution. The differential lock is available only with the manual gearbox and provides 22 percent locking under power, and 27 percent otherwise. Safely ensconced Porsche engineers are fully aware that no matter how nimble a car may be or how skilled its driver, some accidents are unavoidable. They are also sensitive to the fact that the occupants of any open-top car can be more vulnerable than those in a car with a fixed metal roof. To ensure that the driver and passengers of the new Turbo Cabriolet are as well protected as possible, the car's designers took several critical measures. All four seats on the new 911 Turbo Cabriolet have three-point inertia-reel seatbelts. The front units have belt-latch tensioners and force limiters. The seatbelts are supplemented by dual frontal, two-stage airbags and the Porsche Side Impact Protection system (POSIP), unique in an open-top sports car. The POSIP safety system includes thorax airbags on the outside of the front seatbacks, head airbags in the doors, and side impact protectors in the doors. The head airbags are housed in the door-sill beneath the window. In the event of a side impact, both thorax and head airbags inflate, with the head airbag forming a flat cushion against the window opening. Topless and topsy turvy Keeping occupants safe in case of a rollover is problematic in an open-top car. Porsche engineers, therefore, ensured that the windshield frame is strong enough to serve as a fixed rollbar, so there are ultra-high-strength steel pipes inside both A-pillars. At the rear, a similarly reinforced, spring- loaded U-shaped rollbar deploys instantly should dedicated rollover sensors detect an impending accident. Those same rollover sensors trigger the front seatbelt tensioners to secure the driver and front passenger in their seats.