Intake manifold switchover, function - GF07.61-P-3028AMG

ENGINE 156.980 in MODEL 164, 251 up to Model Year 8

ENGINE 156.982 in MODEL 209

ENGINE 156.983 in MODEL 211, 219

ENGINE 156.984 in MODEL 216, 221 up to Model Year 8

Fig 1: Identifying Intake Manifold Switchover Function Diagram

Courtesy of MERCEDES-BENZ USA

With the intake manifold switchover, switching between long or a short intake paths is possible. The vibration response of the intake air for different operating conditions is used in a specific way in order to achieve internal charging.

Better distribution of a mixture is achieved by means of variable intake pipes lengths which leads to improved combustion and thus a higher engine torque.

The intake manifold switchover is dependent on:

Engine load
Engine speed

In a deenergized condition the switch flaps are opened by spring force (short intake routes).

Short intake routes (Switch flaps opened)

The variable intake manifold switches over to short intake routes at a lower rotational speed and lower loads or at a high rotational speed. The short intake routes allow achieving a high motor speed.

Fig 2: Identifying Variable Intake Manifold Switches Routes Diagram (Switch Flaps Opened)

Courtesy of MERCEDES-BENZ USA

The switchover valve is de-energized and the aneroid capsule is ventilated in the process. The switch flaps are opened by the spring force of the vacuum unit via the gearshift linkages and release the intake route.

The switch flap shafts for the right and left cylinder head are connected at the rear in the variable intake manifold via a further gearshift linkage.

Long intake routes (Switch flaps closed)

The variable intake manifold at a low rotational speed and high loads ensures a full torque curve.

Fig 3: Identifying Variable Intake Manifold Switches Routes Diagram (Switch Flaps Closed)

Courtesy of MERCEDES-BENZ USA

The variable intake manifold switchover valve is actuated at the ground end from the ME control unit and switches the vacuum from the vacuum reservoir through to the vacuum unit. The vacuum unit closes the switch flaps via gearshift linkage, which close off the short intake routes.

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