It doesn’t get as much attention as the increased power, but the 911 Turbo’s new all-wheel-drive system is the first actively controlled AWD system in a 911. By comparison, the system in the Carrera 4S uses a mechanical viscous coupling to transmit power to the front wheels, only reacting after rear wheel slippage is detected. The new electronically-controlled AWD system in the 2007 911 Turbo, called Porsche Traction Management (PTM), uses sensors to constantly monitor changes in driving conditions such as acceleration, wheelspin, oversteer, and understeer. PTM then reacts within milliseconds to deliver perfect levels of power to all four wheels for optimum performance and control.