The fresh air inlet is located under the passenger side, windshield on the firewall behind the windshield washer tray. I suspect flexible duct pipe (aka., similar to dryer vent hose) could be routed to a high pressure area. Bob Wilson
Thanks Bob. It seems like as I am driving air will only come through the vents when the fan it turned on. On other cars I can have outside air flowing from the vents without the fan. Is that possible in the Prius as is or would I have to duct it per your suggestion? I assume they did this to reduce drag?
I just know where the inlet is located and have no clue about the actually pressure at that point. I've never liked it because of the risk of picking up hot air from the engine compartment. But the windshield wiper pan may have some aerodynamic magic that is supposed to provide positive airflow. I just don't know. My car has rain-guards on the rear windows so I usually don't have to worry about air flow and keeping out the wet. Bob Wilson
Technically, I think if you remove the cabin air filter and leave the glove box open, you will get fresh air as there is nothing between the windshield tray and the cabin filter except ducting.. (As all the leaves and crap sitting on top of the filter prove). You could remove the cabin filter and line the bottom with foil or make piece or cardboard to keep debris from falling into your fan and internal ducts. This would allow some fresh air forced in from driving. However, I think you are better off running the fan on low and not recirc. The reason for this is you are forcing the air out across the HV battery. I'm not sure if it would work as well just leaving the cabin open to the outside.
