Component description for the turbocharger - GF09.40-P-4010TU

ENGINE 642 as of 1.6.06 in MODEL 211.0/2/6, 219.3 as of 1.6.06 

ENGINE 642 in MODEL 164.1/8, 251.0/1 with CODE (494) USA version up to Model Year 8 

Shown on model 211.020 with OM 642.920 with code (494) USA version 

Location 

The turbocharger sits at the rear between the two cylinder heads.

Task 

The turbocharger has the task of pre-compressing the suctioned in air depending on the operating condition of the engine.

Structure of the exhaust turbine 

Design 

In contrast to its predecessor (Step 2) the turbocharger (Step 3) has a turbine housing insert. This Turbine housing insert consists of the following components:

• Turbine wheel
• Return spring element
• Guide vane carrier
• Guide vane
• Adjusting ring

The installation space required for the guide vanes is achieved from a design point of view through the use of integral, aerodynamically optimized spacer bridges.

The guide vane carrier and the return spring element are screwed to the turbine housing and are therefore decoupled thermally. This has the advantage that the guide vane support and the return spring element can adapt to the respective thermal conditions without restriction during thermal expansion.

The return spring element serves to receive the guide vane carrier.

Function 

The exhaust gases of the engine are directed through the exhaust manifold into the turbine housing onto the turbine wheel. The flow energy of the exhaust gases sets the turbine wheel in rotation. This means that the compressor turbine wheel which is also connected to the supercharger shaft is driven at the same speed. The sucked in fresh air from the compressor turbine wheel is compacted, led through the charge air cooler and then led to the engine. The boost pressure is regulated by adjusting the guide vanes, that is by altering the flow angle of the guide vanes.

The pilot studs on the boost pressure positioner control rods (Y77/1) turn the adjusting ring in the turbine housing insert. The fact that the pilot studs on the guide vane also engage in the adjusting ring means that all guide vanes are adjusted at the same time.

At a low motor speed the flow cross-section is downsized by "closing" the guide vanes. In this way the air flow velocity of the exhaust on the turbine wheel is increased whereby its RPM and thus also the RPM of the compressor turbine wheel increases and thus the boost pressure increases.

At a high motor speed the flow cross-section is increased by "opening" the guide vanes. In this way the air flow velocity of the exhaust on the turbine wheel is decreased whereby its RPM and thus also the RPM of the compressor turbine wheel decreases and thus the boost pressure decreases.