New Generation N62 Engine
Chapter 3 P.8
Course Contents/Background Material
© BMW AG,
Service Training
The intake pipe is at the optimum length when the pressure
waves are at the intake valve shortly before it is closed. The
increase in pressure in front of the intake valve results in
increased air flow to the cylinders once more.
This process is described as recharge effect. The opening angle
of the intake valve remains unchanged as the engine speed
increases. The opening time, however, is reduced proportio-
nately (with conventional, non-Valvetronic engines).
Since the suction waves and pressure waves expand at sonic
speed, the suction path length must be adapted depending on
the engine speed to ensure that the tip of the pressure wave
reaches the intake valve before it is closed.
