WG Nut Effects

Next up I wanted to see if creating a smoother transition for the airflow going into the turbine housing would make a difference in maximum airflow.  Commonsense says that adding a bellmouth to the entry would help smooth out the airflow and give higher numbers.

turbine_inlet_bellmouthIn this case it did not.  My guess is that the airflow into the housing is not great enough for a difference to be detectable with the equipment I have.  There may have been an increase, but if there was it was tiny.

The second order of business was to see how opening the wastegate flapper door gradually affected the airflow through the turbine housing.

I loosed the nut on the wastegate actuator arm to the point where the disk that covers the wastegate port could just start to spin.  From there I made single turns of the nut, one 360 degree rotation about the actuator arm, and took an airflow reading with the flapper door open the amount corresponding to that one turn.

I repeated that process until I reached the end of the actuator arm and the nut was flush with the end.  That turned out to be ten complete turns.  Airflow through the housing for each position of the flapper door is shown below.


I was thinking there might be a point where the airflow jumped significantly, but that was not the case as the amount of airflow increased almost linearly with each turn of the nut.

Turbine Airflow Varying Wastegate

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.

k04_wg_nutThe 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.

wg_open_vs_closedNo surprise the airflow is significantly higher with the wastegate door partially open.

AN line collection

What started out as an oil line upgrade has expanded to include fuel lines and shortly wastegate signal and actuator lines.


I purchased the oil lines when I decided to swap out turbochargers and replace the stock oil lines.

(L) Induktion Lines (R) AU Tuning Lines

I had on hand a set of Induktion oil lines that had been purchased for a previous setup, but the more robust lines being sold by AU Tuning were an appealing alternative, which became an easy decision when the Induktion lines were sold off.

I started to DIY a set of fuel lines for use with an SRM intake manifold that was modified to fit an RS4 throttle body.  Not too long into that project the aggravation of trying to cut and fit the fuel lines, coupled with my concern about having fuel spraying inside the hot engine compartment due my own ineptness at building this type fuel line led me to contact Marc aka ‘cinesnow’, a forum member on the Audizine website who had developed the oil lines I now had a pair of.  I inquired about having a set of fuel lines built up and he agreed to help me out.

srm_im_fuel_linesA couple of weeks later I had a set of very solid fuel lines for use with my modified intake manifold.

When I removed my K03 turbochargers for a rebuild I began to think about how I could better hook up the sensors on my car.  One in particular is set up to monitor the compressor housing pressure via the signal line.  Normally I have a sensor tee’d into the silicone hose but it occurred to me that an AN fitting might work well in that role.  I knew that  Marc had designed a set of wastegate and signal lines with AN fittings and stainless hose and so I contacted him to see about having a line slightly modified to accept an AN fitting with a port for a pressure sensor.  He thought this would not be difficult and had a set worked up with the modification I had requested.  That pair of lines should be arriving soon, especially good timing since my K03’s are due back from being rebuilt shortly.