Handling question and my quick fix

Discussion in 'Prime Accessories and Modifications' started by mister2cool, Oct 28, 2019.

  1. mister2cool

    mister2cool Junior Member

    Joined:
    Sep 26, 2019
    63
    33
    3
    Location:
    New Jersey
    Vehicle:
    2020 Prius Prime
    Model:
    Limited
    I don't know if anyone else noticed this but this is my experience.
    When I first got my Gen 2, I noticed that it was quite unstable when driving on highway when I came up close to a large vehicle like a tractor trailer. I guess it's the aerodynamics of the car being very low drag, it is very sensitive to turbulent air around a massive object moving at high rate of speed. Basically the car would bounce around side to side quite a bit. Out of desperation, with some F1 inspiration, I added 4 vortex generator on the rear roof bar figure they wouldn't hurt even if it doesn't do anything. I was totally surprised by the night and day difference they made reducing the bouncing effect to unnoticeable.
    A month later Toyota came out of TDR version of Prius aero treatment that included those roof diffusers [​IMG]

    Fast forward to this month, I noticed the same bouncing effect on the Prime. I am a little disappointed that they never considered this an issue but perhaps it's the price to pay for low drag. I installed the remaining pieces I had and problem went away.
    I know some might think this is total gimmick but it actually made a difference for me. Just want to share my experience in case anyone else is bothered by the same issue.
     
  2. Washingtonian

    Washingtonian Active Member

    Joined:
    May 26, 2017
    387
    367
    0
    Location:
    Western Washington
    Vehicle:
    2017 Prius Prime
    Model:
    Plug-in Advanced
    Interesting. I wasn't aware of the problem and hadn't heard the term "vortex generator". I assume you attached them to the black plastic panel between the roof and rear window. Could you share a picture of them on your Prius?
     
  3. schja01

    schja01 One of just a few in Chicagoland

    Joined:
    Apr 22, 2005
    964
    628
    0
    Location:
    Chicagoland
    Vehicle:
    2018 Prius
    Model:
    Prime Advanced
    I always attributed the “squirliness” to the weaker sidewalls of the stock tires.
     
  4. Tideland Prius

    Tideland Prius Moderator of the North
    Staff Member

    Joined:
    Oct 2, 2004
    40,028
    11,543
    41
    Location:
    Canada
    Vehicle:
    2018 Prius Prime
    Model:
    Technology
    [​IMG]

    There are vortex generators on your mirror base as well as one on the taillight.
     
  5. mister2cool

    mister2cool Junior Member

    Joined:
    Sep 26, 2019
    63
    33
    3
    Location:
    New Jersey
    Vehicle:
    2020 Prius Prime
    Model:
    Limited
    I am sure those sidewalls are weak but that wouldn't really come into play if you are going a straight line on highways.

    Those little nubs first showed up on my Subaru STi 15 years ago, under the side mirrors. Supposedly they helped to smooth out the airflow past mirror. Then they showed up in force on the rear roof line of EVO and Gen 2 STI. If you watch racing, you'll notice those and little fins are used extensively to modify airflow around curved surface to delay the flow layer from separating away from the surface . They really don't do anything until higher speeds, and even our highway speed is marginal. We usually drive around 80 MPH on highways (speed limit 65) and there was enough effect to be noticeable. Basically the principle is to keep a bit more air flow following the rear window and hopefully reach the spoiler to provide just a little extra down force to keep the tail stable.

    Honestly I initially hoped those to act more like tiny vertical stabilizer as I didn't think the hatch on the Gen 2 had any spoiler effect but I was pleasantly surprised.

    This is what it looked like on my old Gen 2.
    [​IMG]
    I'll take a new picture later with them on the Prime.
     
  6. Rob43

    Rob43 Senior Member

    Joined:
    Sep 24, 2014
    950
    640
    0
    Location:
    VA, BMW Race Car, BMW R1200R, BMW 330Ci, Ford F350
    Vehicle:
    2013 Prius v wagon
    Model:
    Prime Advanced

    I find this statement very far from accurate... the last time I checked, nobody is driving on a sheet of glass inside a vacuum.

    My Prime was at its worst at highway speeds, it porpoised back n forth and simply didn't feel good the faster it drove.

    The instant I installed my 17x7" wheels & 205/50-17 Ultra High Performance A/S tires, Problem Solved.

    The best part is ALL handling (feel) at all speeds is remarkably better, plus dry and wet weather grip (safety) is now outstanding.



    Rob43
     
  7. mister2cool

    mister2cool Junior Member

    Joined:
    Sep 26, 2019
    63
    33
    3
    Location:
    New Jersey
    Vehicle:
    2020 Prius Prime
    Model:
    Limited
    No doubt that nicer tires would help but that's a whole different conversation. Good hear that there's more than one way to solve this issue.
     
    #7 mister2cool, Oct 29, 2019
    Last edited: Oct 29, 2019
  8. mister2cool

    mister2cool Junior Member

    Joined:
    Sep 26, 2019
    63
    33
    3
    Location:
    New Jersey
    Vehicle:
    2020 Prius Prime
    Model:
    Limited
    Tideland Prius and Washingtonian like this.
  9. Rob43

    Rob43 Senior Member

    Joined:
    Sep 24, 2014
    950
    640
    0
    Location:
    VA, BMW Race Car, BMW R1200R, BMW 330Ci, Ford F350
    Vehicle:
    2013 Prius v wagon
    Model:
    Prime Advanced
    Now just get at least 3+ PriusChat forum members to buy, install, and verify your results at highway speeds.

    If you can get enough independent test results form PriusChat members that reasonably confirm your hypothesis, I'm sure many of us would also implement your aerodynamic idea.



    Rob43
     
  10. mister2cool

    mister2cool Junior Member

    Joined:
    Sep 26, 2019
    63
    33
    3
    Location:
    New Jersey
    Vehicle:
    2020 Prius Prime
    Model:
    Limited
    Just to be clear. I am not trying to convince anyone that you should do this. I experienced what I felt was troublesome handling issues but it's also because I drive pretty quick in the left lane a lot of times and pass a lot of crazy tractor trailers. I also came from driving mostly RWD & AWD sports cars so the deficiency was clearly obvious. The situation may or may not apply to others, especially if you usually cruise at more modest speeds. Better wheels and tires would help at any speed!
    I just wanted to share my experience in case if someone feels the same challenge and it's a cheap fix to test out.
     
    benagi likes this.
  11. mister2cool

    mister2cool Junior Member

    Joined:
    Sep 26, 2019
    63
    33
    3
    Location:
    New Jersey
    Vehicle:
    2020 Prius Prime
    Model:
    Limited
    I just discovered modification forum.. I guess this thread belongs there. Do we have mods that can move threads into proper place?
     
  12. vvillovv

    vvillovv Active Member

    Joined:
    Mar 19, 2013
    834
    294
    0
    Location:
    NY
    Vehicle:
    2017 Prius Prime
    Model:
    Prime Plus
  13. mister2cool

    mister2cool Junior Member

    Joined:
    Sep 26, 2019
    63
    33
    3
    Location:
    New Jersey
    Vehicle:
    2020 Prius Prime
    Model:
    Limited
    Wow, I assume this article was directly translated from another language, probably Japanese. It's making me forget how to write completely sentences in English. I honestly had a very hard time understanding the article.

    What really caught my attention is the interior photo. The layout doesn't look anything like a Prime with a traditional shifter setup and hand brake. Wasn't Prius C was the only one that had that layout?

    Now this would have been an awesome interior for the Prime.. :cool:
    [​IMG]
     
  14. vvillovv

    vvillovv Active Member

    Joined:
    Mar 19, 2013
    834
    294
    0
    Location:
    NY
    Vehicle:
    2017 Prius Prime
    Model:
    Prime Plus
  15. MTN

    MTN Member

    Joined:
    Feb 26, 2017
    51
    57
    2
    Location:
    SB, CA
    Vehicle:
    2020 Prius Prime
    Model:
    LE
    My money is on placebo.

    Toyota spent a lot of money in shaping a Prius - if $1 of plastic would make a meaningful difference, they'd install them. Yes I've seen them on STIs and EVOs OEM/factory - those are meant for high speeds (think 100mph+) and are incorporated with a large, rear wing.
     
    Rob43 likes this.
  16. mister2cool

    mister2cool Junior Member

    Joined:
    Sep 26, 2019
    63
    33
    3
    Location:
    New Jersey
    Vehicle:
    2020 Prius Prime
    Model:
    Limited
    Funny that we said the exact same thing about that exact photo!

    Yeah but they probably didn't anticipate anyone flying around in these going 80+ passing large trucks who are also going quite fast. As I mentioned earlier, the "bouncing around" really only happens at higher speed in some pretty specific conditions. That's what prompted me to look towards aero factors to find something that might help.
    If you take away the lower hatch window, the rear spoiler on Prime\Prius really isn't that much lower than where the wing was on those Sti\Evo, right in the middle of the rear view mirror, and much higher than where you would find a spoiler on most other cars.
     
  17. CraigCSJ

    CraigCSJ Active Member

    Joined:
    Sep 2, 2004
    278
    140
    0
    Location:
    San Bernardino, CA
    Vehicle:
    2017 Prius Prime
    Model:
    Prime Advanced
    I tried six vortex generators on my Prime. On freeways I drive 65 mph In right lane, and car bounces a bit when going over places where pavement is broken by trucks. After a 50 mile drive, vortex generators made the Prime feel more controlled going over the bad spots, and also made it seem as if fewer small steering moves were needed to keep centered in lane. Plan to keep them on car. Thanks for bringing attention to vortex generators, especially that Toyota racing uses them.
     
    mister2cool likes this.
Loading...