On the M54, the intake manifold is split into 2 groups of 3 (runners) which increases low end torque. The intake manifold also has separate (internal) turbulence bores which channels air from the idle speed actuator directly to one intake valve of each cylinder (matching bore of 5.5mm in the cylinder head).

Routing the intake air to only one intake valve causes the intake to swirl in the cylinder. Together with the high flow rate of the intake air due to the small intake cross sections, this results in a reduction in fluctuations and more stable combustion.

The resonance system provides increased engine torque at low RPM, as well as additional power at high RPM. Both of these features are obtained by using a resonance flap (in the intake manifold) controlled by the DME.

During the low to mid range rpm, the resonance flap is closed. This produces a long/single intake tube for velocity, which increases engine torque.

During mid range to high rpm, the resonance flap is open. This allows the intake air to pull through both resonance tubes, providing the air volume necessary for additional power at the upper RPM range.

When the flap is closed , this creates another “dynamic” effect. For example, as the intake air is flowing into cylinder #1, the intake valves will close. This creates a “roadblock” for the in rushing air. The air flow will stop and expand back (resonance wave back pulse) with the in rushing air to cylinder #5. The resonance “wave”, along with the intake velocity, enhances cylinder filling.

The DME controls a solenoid valve for resonance flap activation. At speeds below 3750 RPM, the solenoid valve is energized and vacuum supplied from an accumulator closes the resonance flap. This channels the intake air through one resonance tube, but increases the intake velocity.

When the engine speed is greater than 4100 RPM (which varies slightly – temperature influenced), the solenoid is de-energized. The resonance flap is sprung open, allowing flow through both resonance tubes, increasing volume.

The DME determines idle speed by controlling an idle speed actuator (dual winding rotary actuator) ZWD 5.

The basic functions of the idle speed control are:

  •  Control the initial air quantity (at air temperatures <0º C, the EDK is simultaneously opened)
  •  Variable preset idle based on load and inputs
  • Monitor RPM feedback for each preset position
  • Lower RPM range intake air flow (even while driving)
  • Vacuum limitation
  • Smooth out the transition from acceleration to deceleration


Under certain engine operating parameters, the EDK throttle control and the idle speed actuator (ZWD) are operated simultaneously.This includes All idling conditions and the transition from off idle to load.

As the request for load increases, the idle valve will remain open and the EDK will supply any additional air volume required to meet the demand.

Emergency Operation of Idle Speed Actuator:

  • If a fault is detected with the idle speed actuator, the DME will initiate failsafe measures depending on the effect of the fault (increased air flow or decreased air flow).
  • If there is a fault in the idle speed actuator/circuit, the EDK will compensate to maintain idle speed. The EML lamp will be illuminated to inform the driver of a fault.
  • If the fault causes increased air flow (actuator failed open), VANOS and Knock Control are
    deactivated which noticeably reduces engine performance.


Individual Control Intake System (DISA)


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.

DISA utilizes 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.

Operating principle

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.

The vacuum tank is evacuated by the vacuum applied in the intake pipe in the partial load range. The connecting flap is closed with the aid of the vacuum unit and the pneumatic actuator.

If the switching speed is exceeded, the DME control unit deactivates the solenoid valve, i.e. it is switched off. As a result, the vacuum unit is aerated and the flap opened.

As soon as the solenoid valve switches (on dropping below the switching speed) the vacuum reservoir and vacuum unit are reconnected and the connecting flap closed.

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.

This control configuration ensures that the connecting flap always remains open in the event of a fault in the electropneumatic 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 flap is returned or opened by means of two springs:

– A torsion spring on the flap shaft

– A coil spring in the diaphragm cell

The solenoid valve is activated directly via a powerful output stage in the DME control unit.

MS43 DISA Pin Outs

MS45 DISA Pin Outs