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What can I add/install onto the Prius to reduce highway air drag/vortex movement?

Discussion in 'Gen 3 Prius Accessories and Modifications' started by h1ph0panonymous, Oct 24, 2023.

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  1. h1ph0panonymous

    h1ph0panonymous Junior Member

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    2014 Prius
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    Four
    Before I bought this 2014 Prius 4 model a month ago I was driving a 2017 Ford Fusion SE for six years, nothing special, no spoiler, no fins, just a bullet shaped car that never caught air drafts on the highway unless I was stuck in traffic 10 feet right behind a semi truck catching it’s box shaped air vortex draft or a 50 mile per hour wind gust which would make all traffic shift positions slightly.

    But with this Prius I have now I feel like I’m literally catching every slight gust, every cars draft from behind them and BESIDE them on the highway. I don’t mind it overall but it makes me looks like I’m driving drunk or distracted which I don’t want if cops are near by.

    What can I add to my car; side mirror fins, rear roof fins, underbody fins, a spoiler, etc...which one of these actually stops the effect I’m experiencing on the highway?

    maybe it’s because the car is 1000 pounds lighter than what I used to drive idk
     
  2. Leadfoot J. McCoalroller

    Leadfoot J. McCoalroller Senior Member

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    That's a bingo!

    The longer wheelbase of the Fusion also helped with high speed handling.
     
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  3. TMR-JWAP

    TMR-JWAP Senior Member

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    Tires make a difference also, including something as simple as inflation pressures.
     
  4. bdc101

    bdc101 Member

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    Your Prius is only a couple hundred lbs lighter, but the wheelbase on the Ford is 6 inches longer. Additionally, it's tires are much larger (30mm or 40mm larger width) and probably made more for general roadholding than efficiency. Fins aren't going to do anything to keep you from being tossed about by gusts, I would get bigger tires is probably the best suggestion. Or a good alignment. More toe in and more camber would help with dynamic stability, at the cost of efficiency.
     
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  5. Vman455

    Vman455 Senior Member

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    Dynamic stability is complex and affected by a variety of factors, including aerodynamic stability (surface area, side force, yawing moment, yawing moment change with yaw angle), suspension and tire factors, and vehicle loading.

    You can measure stability using steering angle as an indicator. I found that shifting a 300 lb load moved the center of gravity of my car 3 inches, and this change was measurable in the steering angle in a constant crosswind, logged on an OBD scanner. Read more here. More on aerodynamic stability in general can be found in Julian Edgar's Vehicle Aerodynamics: Testing, Modification & Development (2023).

    [​IMG]
     
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  6. bdc101

    bdc101 Member

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    Only question is, how does one go about finding a constant crosswind? And verifying that it is constant for the duration of your test?

    I will be happy to read your link later though - ex-FSAE member here, now an advisor for the local solar car team.
     
  7. Grit

    Grit Senior Member

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    I have side and rear side splitters, they work great stabilizing straight line driving.
     
  8. h1ph0panonymous

    h1ph0panonymous Junior Member

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    You made those thingy-ma-bobbers on the bottom skirt front and rear?

    looks cool, I see you lowered it too but winters coming, not trying to sled around.
     
  9. jzchen

    jzchen Newbie!

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  10. jzchen

    jzchen Newbie!

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  11. Vman455

    Vman455 Senior Member

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    Oh nice, I thought about joining FSAE but Solar Car seemed more up my alley.

    I check weather forecasts and wait for a day with suitable predicted conditions, build everything I'm planning on testing so I can quickly install or remove it to shorten test time to a minimum, and use an anemometer to check wind speed. Depends where you are, too--here in the flat Midwest in the winter, it's relatively easy to find suitable days for crosswind testing (windy but not gusting); where I grew up in mountainous Washington probably not so much (although I've never tried it there). I've abandoned many a test when conditions changed. By its nature, testing in the real world will be subject to variable conditions, so when I do things like coastdowns I also run statistical confidence tests on the results.