Background:
With the front of the GTI apart during the installation of the Mabotech intake manifold, the Vibrant FMIC was a candidate for porting the inlet pipe.
A few minutes with a hand file and then polishing with a Dremel produced a smoother inlet edge.
Next up, testing the flow rate through the IC in each direction to detect any changes that might result from the porting.
Result:
Air flowing from the unported end was 178 CFM @ 28″ of H2O. Reversing the IC and flowing through the ported end resulted in a flow rate of 179 CFM @ 28″ of H2O – within the margin of error.
Conclusion:
Porting the inlet end of a Vibrant FMIC did not significantly increase airflow when measured at 28″ of H2O.
One possible explanation for the lack of change is a contribution from the silicone hose attached to the inlet. This silicone coupler connects a bellmouth, ensuring smooth airflow into the intercooler.
The silicone coupler stretches at the inlet edge, partially shrouding the inlet edge facing the airflow. This may smooth the airflow into the IC in the unported case.
Potentially, when the hose is subjected to boost pressure, it may expand outward, which may then allow a greater quantity of air to flow into the inlet end, and the porting may have an opportunity to show more benefit compared to the no boost condition.