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Rear Window Attack

Discussion in 'Gen 2 Prius Main Forum' started by rcroft, Jun 8, 2005.

  1. rcroft

    rcroft New Member

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    Here's a fun one...

    Has anyone ever driven with just the rear windows down?

    It's 95+ degrees here today, so I was driving with all the windows down while the air conditioner woke up. Once I started getting cold air, I began to roll up the windows, starting with the front ones.

    I was traveling at about 32 mph when I got the front windows up and then suddenly I was attacked with an onslaught of a 5-10 Hz sound booming through my car. It was nearly incapacitating and I could feel significant pressure on my ear drums. It was enough to make me feel a little dizzy. It felt like the whole car was shaking.

    At first I thought it was the engine or drive train, so I completed rolling up the windows so I could hear it better. As soon as I rolled up the rear windows, it went away.

    After a little experimenting, I discovered it happens between 30 and 35 mph with the greatest effect happening around 32-33 mph.

    For those who wish to reproduce it, I had the cargo shade closed (covering the cargo area), which probably makes a difference.
     
    #1 rcroft, Jun 8, 2005
  2. mikepaul

    mikepaul Senior Member

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    <div class='quotetop'>QUOTE(rcroft\";p=\"96768)</div>
    World's biggest bassoon reed, probably...
     
    #2 mikepaul, Jun 8, 2005
  3. KCPrius

    KCPrius Member

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    I know that sound....my daughter likes to roll the windows down in back (FWIW, it will also do it with just the front passenger window down). Thwup thuwp thwup thwup......it's LOUD.
     
    #3 KCPrius, Jun 8, 2005
  4. oly_57mpg

    oly_57mpg New Member

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    Funny you should post this... Someone called CarTalk during last weeks show with this very same... complaint. The brothers did an ok job at explaining the reason to the caller… but she didn’t get it…

    As everyone should know... The Prius, more than any car, is very aerodynamic. A delta of the surface area will also change the aerodynamics, ergo thuwp thuwp thuwp... Because… Air passing over the open window(s) is compressed inwards (similar to the Ferrari air duct design) into the car. Once the pressure inside of the car is greater than the pressure outside of the car, the air will try to escape (violently; see thuwp). It also increases the drag coefficient quite a bit.
     
    #4 oly_57mpg, Jun 8, 2005
  5. AngelFish

    AngelFish New Member

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    Don't like that about the prius. It's the one thing I really don't like about the car. My dog - he REALLY hates it.
     
    #5 AngelFish, Jun 8, 2005
  6. jamarimutt

    jamarimutt New Member

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    This has been reported and discussed previously. Someone called it helicoptering.
     
    #6 jamarimutt, Jun 8, 2005
  7. Beacher

    Beacher Member

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    Many of the cars I have owned have done this, at least to some degree. Most of them thwump enough that it is annoying. I think that's one of the main reasons they let the driver lockout passenger windows. Quite handy, especially for those of us with kids!
     
    #7 Beacher, Jun 8, 2005
  8. KTPhil

    KTPhil Active Member

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    Oh, for the days of vent wings... they eliminated that booming completely. I wish those little windows in front were wings...
     
    #8 KTPhil, Jun 8, 2005
  9. DaveG

    DaveG Member

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    If you open your front window a crack, you can usually reduce/eliminate it.

    Dave
     
    #9 DaveG, Jun 9, 2005
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