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  1. #1
    FEP Senior Member BMW Rider's Avatar
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    Oct 2014
    Location
    Calgary, Alberta, Canada
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    949

    Default Air vent flow - exhausting from the interior

    This is probably a unique issue and I'm looking for ideas on where to create an outlet for air flow through the interior. This is on my non-AC 79 coupe with the outside air vents in the dash. Since I have used a trunk mounted fuel cell and sealed off the interior with a rear firewall and plugged all the gaps with fire proof foam, the interior is pretty air tight. The only way I can get any air coming in is to open a window to let it out. I assume that in a standard state, these cars leak enough air out through various parts of the inside to create decent air flow from the dash vent. Or is this typical? It would be nice to be able to close the window at highway speeds to lessen the noise.

    I'd like to figure out somewhere to create outlet vents so I can roll up the windows and still get some air through the vents. Obviously cutting holes into the trunk area would be defeating the firewall, so I would like to figure out where else I could accomplish this without it being obvious and where I'm not assaulting the paintwork. The other concern is possibly allowing a backflow of dirty air into the car so the vents would ideally go to a clean air space. I have thought about some flex hose to route the air to the back end of the car somewhere too. I have a length of 2" high temp vent hose that I mistakenly ordered instead of the 3" I needed for the brake ducting.

    Thoughts and ideas from those who are intimately familiar with the construction of the fox body are welcomed.

  2. #2
    FEP Super Member gr79's Avatar
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    Jun 2009
    Location
    SE Michigan
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    5,141

    Default

    Mine (also non-ac) leaked so much no problem with air exchange, drafts.
    Cigar smoke dispersal is fast. Smoke flow is a good test. Incense sticks, etc.
    Ha. Get a halloween stage fogger to really see whats up inside.
    Was going to get one to check for vac leaks.

    Heater has hard time keeping up below 32, slow defrost almost like a VW.
    The fan is sort of weak needs a higher speed i think like a/c cars have.
    Checked the HVAC doors and ducts with a snake cam were ok. Heat is warm not hot. Core is good.
    Oh well gives engine time to warm up. Then its ok. Wish it worked great like my Ranger's HVAC.
    Hopefully ongoing rust repairs and sealing have improved the situation.

    When the heater or def is turned on, the fan comes on low automatically. That is a safety item per manual.
    I would think if no air was coming out of vents, the car was too tight.
    Any routing to back of car will suck in exhaust fumes- monoxide.
    Did test mine as is with a 9v CO detector. Was ok.

    Have always cracked the window 1/4-1/2" to relieve some pressure, even in winter.
    Speeds the fan up a bit.
    Added window visors to be able to open when raining or when parked on hot sun days.
    They did cut wind noise and buffeting down too when windows are open.

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