DWS964

Where does the cabin air flow exit the body? I know there are the two small plastic flappers behind the rear interior panel, under the seat belt retractors. But where does the air go from there?
I have a theory that part of my HVAC air flow issues are due to this pathway being plugged.
When I had the rear panels off for the install of my DAS roll bar, I should have used a blower to see where the air exited - but I got in a hurry with my excitement.

Rocket Rob

Good question. I'll be curious to hear the answer. The only thing I can offer are these diagrams but unfortunately, they doesn't show the exit.

elbeee964

Ok - this might be a stretch, but...

...through the little tiny headliner holes, and on out through the roof line vent holes above the rear window.

It would be a natural as those roof-line vents approximately mark the start of a partial vacuum area that blanket's the aft top-side of the 911. (And lifts our tail ends so wonderfully, sans lift-spoiling tails.)
So, these vents would freely draw out interior air to the outside world.

At least that'd be my best guess for now.

jimq

mine exits when I lower the top

DWS964

Thanks for (well, some of) the answers. I should have been more specific on "cabin air in a COUPE". One of the reasons I suspected that something is wrong with my cabin air exit flow is that I get a significant increase in the flow of air from the dash vents when I slightly open a window or the sunroof.

I have part/most of the answer - after re-reading the section in Adrian's book, and some threads here on RL. And it confirmed I was on the right track.

The bottom line answer is that the air exits from an opening in the FRONT wheel wells. If you remove the forward fender liner, you will see a 2-3" (50-75mm...) diameter hole in the frame rail. This is open all the way through the frame/rocker back to the opening behind the rear interior panel under the seat belt retractor. That is where the little plastic flapper check valve resides. Flapper Link. Adrian refers to this as the air extraction system. He also describes this as the "clink" noise you often (but not always?) hear when you slam the door shut. I don't believe this is correct (or unless there is yet another flapper device in line somewhere). I believe the "clink" is from the differential pressure boxes that are in line between the heat exchangers and the supply air to the mixing valves in the HVAC unit.
I am not sure what happens in the "extraction" system for cabin air flow exit when the "recirculation" button is pushed on the CCU. Adrian's description implies that something changes in the "extraction" system.
So, tonight I will connect a blower and then a vacuum to the hole in the front fender well and see if and where I get air flow. The cabin air flow would have to exit through the same vents as the AC condenser fan and oil cooler fan under the bumper, and would seem to me those would interfere with the flow of cabin air.

elbeee964

Just as I thought; it's Not those rear window-top vents!

foxford

So, what are those vents along the top of the rear window for?

DWS964

Mystery solved, mostly

I hooked up a vacuum to the port in the front fender well and confirmed air flow entering the vent area under the seat belt retractor. Not sure if I sucked anything out of the pathway. I reversed the vacuum and blew back through the hole and into the cabin - some debris blew out, but not much. My small flapper boxes have been removed during the DAS bar install - if they were still in place, there theoretically would have been no air flow back into the cabin.
Also, noted that the fender liners have a partition to separate the cabin air extraction exit from the areas of the AC condenser and oil cooler.
I learn something every day about this car.