Periodic pressure fluctuations are produced in the intake pipe by the induction strokes of the cylinders. These pressure waves run through the intake tube and are reflected at the closed inlet valves. The intake tube length precisely adapted to the valve timing ensures that a pressure peak of the reflected air wave reaches the inlet valve just before the end of its opening range. A post-charging effect is achieved in this way. This post-charging effect conveys a larger volume of fresh mixture into the cylinder.
Individual Control Intake System utilises the advantages of short and long intake pipes.
Short intake pipes or intake pipes with a large diameter have the effect of producing higher output values in the upper engine speed range together with lower torque values in the medium engine speed range. Long intake pipes or intake pipes with a small diameter develop high torque in the medium engine speed range.
A headpipe is arranged ahead of the oscillating tubes of the two cylinder banks.
When the connecting flap valve is closed, the headpipe and oscillating tube together act as a long intake pipe. The pulsating gas column produces a distinct increase in torque in the medium engine speed range.
The connecting flap between the two cylinder banks is opened in order to increase the output in the upper engine speed range. As a result, the dynamics of the headpipes is reduced to a large extent. The short oscillating tubes which are now effective enable higher output values in the upper engine speed range.
If the switching speed is not reached, the DME control unit activates the electric motor to close the flap. If a certain speed is exceeded, the flap is opened again.
The switching speeds for activation and deactivation are shifted with respect to each other (hysteresis) in order to avoid opening and closing in rapid succession.
The return or opening of the lid is by means of a torsion spring on the flap shaft
This ensures that the connecting flap always remains open in the event of a fault in the electrical flap operation. This ensures the complete engine output is available in the upper engine speed range (e.g. for overtaking). The basic setting of the flap is therefore ”open”.
The electric motor is activated directly via a powerful output stage in the DME control unit.