After acquiring a velocity probe designed for measuring exhaust direction airflow I went and put the stock intake manifold back on the flow bench to measure the air velocity at the various runner outlets while all were open and a steady air stream was pushed through the manifold.  Similar to the last time, the first two runners showed the lowest air velocities.

Considering the shape of the IM plenum, the increasing velocity recorded by the velocity probe at the rearward runners is not surprising.

New for this test, and something that I will use for future evaluations, is a viewport that will allow me to precisely place the probe tip along the centerline of the intake manifold plenum.

To measure the stock intake manifold volume I covered the runner outlets, put fuel injectors in place, covered the throttle body opening, and covered the vacuum port that is located near the throttle body opening.  I then used a funnel to fill the intake manifold with water.  Once water began running out the vacuum ports at the back of the manifold I stopped filling and emptied the manifold into a larger container.  I then measured the quantity of water that was captured.

The water volume would fill 129 cubic inches.

There was some slow leakage from the coverings so the amount recorded is not exact, once the manifold was filled it was almost immediately emptied, so the amount of water lost should not be very great.  In addition, there may have been a few drops still inside the manifold.

The point of the exercise was to get an approximate idea of the volume of the intake manifold which was accomplished.

This test was done to evaluate if there is any impact on the airflow caused by the way the turbo inlet pipe is positioned inside the adapter, a reducing silicone hose, that connects the Y-pipe outlet to the turbo inlet pipe.  The transition not only is a reduction in the pipe diameter but there is also flat surface presented to the airflow by the edge of the inlet pipe that is inside the coupler.

For a reducing transition the longer, thus more gradual the transition, the lower the value for the loss coefficient.  What I was interested in finding out was if the way the turbo inlet pipe was positioned inside the reducer would have any affect on the flow rate.  Given the short range over which the inlet pipe could be varied I did not expect to see much change.

The setup utilized the RS4 y-pipe with one outlet capped off.  The other end was attached to a short piece of the turbo inlet piping.  On my car I have cut the inlet pipe into two sections roughly halfway along the length of the inlet pipe.

To facilitate taking airflow measurements at defined intervals, marks were placed on the inlet pipe every 10mm over the range in which adjustment could be done.

With the inlet pipe placed at the furthest location inside the reducer (40mm mark) the pipe and coupler looked at follows:

With the inlet pipe placed at the further position (10mm mark) the arrangement looked as follows:

The inlet was then tested for airflow quantity (CFM) at 10″ of H2O over the range of marks.

The results were:

Shown as a relative change in airflow from the baseline state, which I chose to have be when the inlet was fully inserted.

I was somewhat surprised by how substantial the change was given how little the range span varied.