Curious about how well balanced the flow is across the intake manifold runners led to performing this test. A Mk7 GTI intake manifold is the subject of this flow test.
The GTI intake manifold is attached to the flow bench using an adapter that supports exhausting airflow from the bench through the intake manifold throttle body opening.
First air is exhausted out of the intake manifold with all runners open. Then the port flaps are closed to assess the affect on airflow.
Next each runner is flow tested individually. To do this one runner is left open and the other three are blocked with a piece of foam.
The foam block is inserted into the runner to sufficient depth to keep from being blown out during the flow test.
Flow testing is conducted at 16″ of H2O.
With all runners open the Mk7 GTI intake flows 458 CFM @ 16″ of H2O. With the intake flaps closed the manifold flows 326 CFM @ 16″ of H2O.
These results are shown on the chart:
The blocked runner setup is shown below:
Flow readings for each runner are shown on the chart:
The maximum flow difference is 4% with a measurement margin error of approximately 1%.
Uniformity of airflow between the runners seems good (emphasizing this is an opinion).