Basic Boost Pressure

Basic boost pressure provides the basis for boost pressure control.

Basic boost pressure is adjusted mechanically on the pressure rod between the diaphragm unit and the turbo wastegate.

If the basic boost pressure is too low, the build-up of pressure when the accelerator is depressed will be too slow. As a result, the engine responds sluggishly when the throttle is opened quickly.

If the basic boost pressure is too high, negative boost pressure adaptation takes place and maximum boost pressure cannot be attained. There is also a risk of damage to the engine as a sufficiently low pressure is not achieved in connection with knock control.

Basic boost pressure should be 0.40 ± 0.03 bar.

After adjustment, the push rod must be prestressed (tightened) at least 2 turns (2 mm) (on hook).

The purpose of this is to ensure that the wastegate is completely, closed when not activated.

On new turbo units the basic boost pressure tends to be at the upper tolerance limit when the push rod is prestressed 2 turns. However, prestressing must never be less than 2 turns (2 mm).

When basic boost pressure is checked, it should be noted that the pressure drops at high engine speeds and rises in the case of low outdoor temperatures.