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Recirc vs. Outside Air: What was Toyota's Intent?

Discussion in 'Gen 2 Prius Audio and Electronics' started by jimolson, Dec 3, 2009.

  1. jimolson

    jimolson Member

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    Has anyone figured out the MFD's software strategy regarding the selection of recirculated vs. outside ingested cabin air?

    At first I thought that Toyota's lawyers served their software jocks with orders to make the beast retreat to outside air after every engine shutdown, independent of the driver's desires. If true, this would square with a corporate fear of being sued by everyone who believes that he crashed his Prius while intoxicated by exhaust fumes.

    But on further examination, I've determined that the annoying retreat to outside air is mostly random and only distantly tied to engine re-starts. It is clearly tied to changing other things like temp setting or which instrument panel vents blow the air. The strategy seems to be "if he touches the MFD in any way, switch to outside air."

    Indianapolis is getting cold this time of year. My dear departed Avalon had a heater that could melt polar ice caps. This 2009 Prius has a cabin heating capacity measured in milliBTUs. When the damn MFD randomly overrides my desire for recirc and chooses outside air after a pit stop at McDonalds, you can invite frostbite on your lower extremities.

    Did I tell you that I love the 48mpg I get on this car?
     
    #1 jimolson, Dec 3, 2009
  2. Tideland Prius

    Tideland Prius Moderator of the North
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    Haven't noticed that but I have noticed that it doesn't go into Recirc (whether I'm in ECO or normal) when I have the heater running. My understanding is that it warms up faster in Recirc. Our 02 Camry did it and our 05 Prius does it. Both cars switch to outside air after the cabin has been decently warmed up. No idea why my 2010 doesn't do it.
     
    #2 Tideland Prius, Dec 4, 2009
  3. Frayadjacent

    Frayadjacent Resident Conservative

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    One thing that weighs into it is that with the AC on and set to recirc, it can dry out the cabin air.

    I had a Hyundai a few years ago that would ALWAYS turn recirc off when the car was turned off.

    I know this is not true with the Prius, as recirc stays on when I get back into the car. It will turn off if I turn off the AC system, and later turn it back on.
     
    #3 Frayadjacent, Dec 8, 2009
  4. drew_flux

    drew_flux Junior Member

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    When in auto mode,or after restart the air mix flap will do whatever the a/c ecu thinks is the most efficent mode to run.if you want full control get your local dealer to change the customise option.
     
    #4 drew_flux, Dec 9, 2009
  5. Rhino

    Rhino New Member

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    It is not that evil. A lot of cars do this - including my Toyota Sienna.

    The idea is that recirculating heated air, in a car with people in it, would cause the car to fog up. Since you are recirculating heated air, it is probably cold, so turning on the AC would not reduce the fogging since your windows, exposed to the elements, can be at -20 degrees or colder. That is, the AC is not any better than your cold window when the car is cold. So you will fog up if you heat and recirculate. So the cars are programmed to switch to fresh air after a while whenever you turn on the heat. Since it is cold, the fresh air should be dry.

    You may ask - what about when the outside temperature is only 50 degrees. It still happens because cars are not smart enough to differentiate between a little cold and a lot of cold. Whenever you have the heat on, it switches to fresh air after a while. It is a benefit to those who live in the really cold climate.

    A smarter system will drive up prices.

    Disclaimer. By reading this letter the party of the second part shall agree to hold the party of the first part harmless for any and all damage that may arise from the writings of the party of the first part including and not limited to the loss of life, destruction of the earth, moon, sun, solar system, or universe. In the even the universe is destroyed, the parties agree to binding arbitration by an arbitrator of the party of the first parts choosing but in no event shall the arbitrator be outside the territories of the United States.
     
    #5 Rhino, Dec 9, 2009
  6. fjpod

    fjpod Member

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    As long as we are on the subject of defrosting, heat/AC, outside/recirc...

    Does the 2010 automatically turn the AC compressor on when you select defrost? Based on what I see, I think no. But on some cars I've had in the past it is automatic.
     
    #6 fjpod, Dec 9, 2009
  7. Tideland Prius

    Tideland Prius Moderator of the North
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    yes. I think all new Toyotas do it now regardless of whether it has automatic climate control or manual A/C.
     
    #7 Tideland Prius, Dec 9, 2009
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