Basic Charging Pressure

PRINCIPLE OF OPERATION, BASIC CHARGING PRESSURE





Basic Charging Pressure--provides the basis for boost pressure control.

Basic charging pressure is adjusted mechanically by means of the push rod between the diaphragm unit and the turbo wastegate.

If basic charging pressure is too low, pressure buildup will be too slow when the accelerator is depressed with sluggish engine response when the throttle is opened abruptly.

If basic charging pressure is too high, negative boost pressure adaptation will take place and maximum boost pressure cannot be attained. There is also a danger of damage to the engine as sufficiently low pressure for knock control will not be achieved.

Basic charging pressure should be 0.40-0.03 bar.

After adjustment, the push rod should be prestressed by at least 2 turns (2 mm) when hooked on. The purpose of this is to ensure that the wastegate is completely closed when not activated.

On new turbo units the basic charging pressure tends to be at the upper tolerance limit with two turns of prestressing. Nonetheless, there must never be less than two turns (2 mm) of prestressing.

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