The Porsche 996 is the internal designation for the Porsche 911 model manufactured and sold between 1998 and 2005. It has since been replaced by the Type 997. Both body styles were used in 2005, depending on model. At its debut, the 996 featured the most significant changes to the Carrera model since its 1963 introduction. Most important among these is the water-cooled engine, replacing the previously air-cooled engines. More stringent noise regulations and higher customer expectations for both refinement and a higher performance 4 valve per cylinder engine made the switch necessary. The 996 Carrera (not GT2, GT3 and Turbo models) engine is designed with what Porsche calls integrated dry sump oiling. This integrated dry sump engine does not have an oil scavenge pump in the crankcase to pump the engine oil to a separate holding tank outside the crankcase as a true dry sump design would have. The only scavenge pumps in the 996 engine are in the camshaft boxes and the oil is pumped from there to the bottom of the crankcase as it would be in any wet sump engine. Other changes include a sleeker body with a more steeply raked windshield and a re-designed interior.