@s90: the 911 Turbo uses a 3.6 litre engine, also the 911 GT3 , GT3 RS, Targa 4, carrera 4 cabriolet , carrera 4, carrera cabriolet and the carrera.... while the carrera S , carrera 4S, carrera S cabriolet, carrera 4s cabriolet, and the targa 4s use the 3.8 litre 
Porsche: There is no substitute.