Completed flow testing on an unmodified RS4 intake manifold.

One observation while testing the RS4 intake manifold was how much further up inside the runner the fuel injector sits.  Comparing the placement to that of the S4 intake manifold the RS4 fuel injector sits approximately 40mm from the exit where on the S4 intake manifold the fuel injector is approximately 22mm from the runner exit.

Not too surprisingly the RS4 intake manifold flowed on average 27% more than the S4 intake manifold based on measurements taken at 10″ of H2O.

One interesting result from the topmost picture is the airflow velocity out of the lowermost runners of the RS4 intake manifold.  With the larger runner, as compared to the S4 intake manifold, the air velocity is even lower for a given depression.  The lower right runner had airflow velocity (feet per second) in the single digit range.