To assess the amount of additional air that can pass through the turbine housing with the wastegate door open I loosened the nut holding the wastegate shut.  I positioned the nut at the end of the wastegate rod, so that the nut was flush with the end.  This position was selected for ease of repeatability and because it allows the door to open to the maximum extent while the nut is still on the actuator arm.

The position allows the door to open a good amount, though far from being fully open.  In order to determine where the door placement is when the actuator rod is fully extended I’ll need to attach a pressure source to the wastegate canister and observe the door opening.

The airflow through the turbine housing with the door closed versus open is shown below.

No surprise the airflow is significantly higher with the wastegate door partially open.