Four valves per cylinder

Engines with four valves in the combustion chamber operate more efficiently than two-valve engines, because internal gas flow is speeded up and the cylinders filled more effectively. Since they burn their fuel with greater efficiency, they generate more power and torque, with reduced consumption and exhaust emissions. Audi introduced the four-valve principle with double overhead camshafts for the 2.5-liter V6 TDI diesel in 1997. The injector nozzle could then be in the ideal position at the precise center of the combustion chamber. Another decisive advantage was obtained by giving the two inlet ports different patterns: The swirl-action port created turbulence in the intake airflow at low loads and engine speeds, which resulted in higher torque. The tangential port made the engine more dynamic at higher speeds by reducing friction. To modulate the swirl action as accurately as possible, Audi installed switchable flaps in the ports.