Variable Intake System

ENGINE 606.912 in MODEL 210.020

Model 210.020;

only to 05/96

Fig 1: Identifying Variable Intake System Components Location - Model 210.020 To 05/96

Courtesy of MERCEDES-BENZ OF NORTH AMERICA.

The resonance intake line switchover valve (Y22/7) is located on the engine side.

Model 210.020 as of 06/96

Fig 2: Identifying Variable Intake System Components Location - Model 210.020 Of 06/96

Courtesy of MERCEDES-BENZ OF NORTH AMERICA.

The resonance intake line switchover valve (Y22/7) is located on the engine side.

Task

At lower engine speeds, to improve the torque curve without impairing performance in the rated speed range by varying the length of the intake manifold.

The 1-5-3-6-2-4 firing order makes this engine especially suited to variable intake, because dividing the intake system at cylinders 1-3 and 4-6 allows for simultaneous intake into three cylinders from three separate resonance pipes at an ignition angle of 240° crankshaft.

Design

One pneumatically activated variable intake manifold flap is built into both the intake line and the intake manifold (99/2, 99/4).

The resonance intake line switchover valves (Y22/7) and the resonance intake manifold (Y22/6) are installed below the intake manifold between the 4th and 6th cylinder.

These valves are actuated by the IFI [ERE] control module (N3/7).

Function

During the suction stroke, the pistons generate a strong vacuum which, when the intake valve is open, sets the air present in the intake manifold into motion. The inflowing air produces a considerable amount of kinetic energy. When the intake valve is closed, head pressure is generated which immediately begins expanding in the opposite direction. The amount of pressure produced is a factor of the mass of gas present in the intake manifold. Rapidly alternating acceleration and deceleration of the air column creates vibration, the frequency of which is dependent on the length of the intake manifold. When engine timing matches air column vibration, resonant vibration of the air column produces a charging effect. Because the vibrations of the air column are a factor of engine speed, resonant vibrations for any one specified intake manifold length can only be improved within a certain rpm range.