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As far as I know, the ventilation fan is for the LIV-P to recirculate air in the cabin, and mounts on the rear bulkhead.  When pressurized, the tail NACA scoop is inoperative.  For the unpressurized planes (and the pressurized ones at low altitudes) the NACA scoop provides plenty of air when in flight.  But on the ground the scoop is inadequagte, and the option is to keep the door open a crack, holding it with one hand.   I hate to bake in airplanes, and I have an unpressurized IV.  The factory ventilation fan is a centrifugal unit that tucks nicely up at the top of the rear cabin bulkhead on the P versions, but is not an easy installation for the unpressurized birds without such a bulkhead.  I chose to use a 4 inch diameter axial flow blower I got at West Marine This 12 volt unit is used to ventilate engine bays on boats prior to starting.  I discarded the Lancair ducting aft of the baggage area, and built a duct with a bulge to accommodate the axial flow fan.  An access door in the duct permits installation and maintenance.  The unit puts out almost two inches of water static pressure and moves several hundred cubic feet per minute depending on back pressure.  I am using the big eyeball units to maximize flow so that I minimize pilot cooking prior to engine start.  If anybody is interested, I can provide more details.  I also used a three inch diameter unit from the same source to drive defogging air across the wind shield.  Fred Moreno

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