Simply stated I have found there to be 1.4 inch MP differential between ram
air, unfiltered, straight into the flow meter on the front end of the sump
as opposed to filtered alternate air sucked in from the lower cowling area.
This translates into a noticible boost of power and acceleration when
switching from alternate to ram air at 3,000 AGL.  I have not measured the
speed differential but I believe that 1.4 inches translates to about 15
ponies.

Bob Smiley
N94RJ 360 Lycoming.