Turbochargers with variable turbine geometries and charge-air pressure actuators
WARNING: This page does not describe the selected car, but rather 7 other vehicles, including the 2017 BMW X3, 2016 BMW X3, 2015 BMW X3, 2014 BMW X3, and 2013 BMW X3. However, it is still accessible from the selected car via links, so may be relevant.
A turbocharger with variable turbine geometry and without a "wastegate" valve is used for turbo pressure control.
On the exhaust side there are adjustable blades on the outside of the turbine on rotating bearings. Those blades vary the force applied to the turbine by the exhaust, thereby altering, as required, the charge-air pressure generated by the turbocharger.
The adjustable blades are adjusted by a control lever on the turbine housing. The steering column adjustment lever is activated by an electrical charging pressure actuator (electric motor with worm gear and control electronics). The charge-air pressure actuator is mounted directly on the turbocharger and cannot be replaced separately.