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Do any Prius aero mods actually reduce drag?

Discussion in 'Gen 3 Prius Accessories and Modifications' started by Robert Holt, Apr 21, 2015.

  1. Robert Holt

    Robert Holt Senior Member

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    We do about 70% long-distance highway driving in which aerodynamic drag becomes a dominant factor in overall efficiency . So do any of the aerodynamic mods have either wind-tunnel data proving a reduced Cd , or have solid pre-post modification mpg data that confirms an increase in overall efficiency?
     
  2. mrbigh

    mrbigh Prius Absolutum Dominium

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    The CD on the Prius III is the best it can be in the market for the retail price of the vehicle.
    Can it be improved, yes a little bit......
    Solid wheel covers, enclosing the rear wheels body panels.
    Full covering the front grill.
     
  3. Toppcat

    Toppcat Member

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    Yes there are little modifications that will reduce cd but will it be worth it? 1st aero mod is to keep the body clean free of rough spots like fall out by clay baring. It and keep it waxed! This will reduce the air friction, protect the paint and looks better. Won't reduce cd by much but every bit helps! Next lowering springs this will reduce cd a little and improve handling will affect ride quality!
     
  4. Vman455

    Vman455 Senior Member

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    Short answer: Yes.

    Longer answer: According to Gary Eaker, former GM aerodynamicist and owner of the A2 wind tunnel, the following almost always reduce drag on cars they've tested:

    -Lower the ride height
    -Block the grill
    -Add a front air dam
    -Seal the back of the hood to the cowl
    -Remove outside rearview mirrors

    And, mods with no effect on Cd:

    -Wax/smooth paint
    -Golf-ball dimples
    -Taping seams
    -Smoothing rivets

    Ideally, you should tweak the car in a wind tunnel to get the best results, as different designs can have complex interactions and downstream flow can affect upstream flow and vice versa. But there are lots of modifications that get very predictable results. On my Prius, I have solid wheel covers (pizza pans bolted to the stock wheel covers), lower grill blocked, passenger mirror removed, and lowered on Tein H-tech springs. I think it would be great fun sometime to take my car to A2 and see just where it is now and what can be done to improve Cd further.
     
    JerryCS, j12piprius and wjtracy like this.
  5. LDB

    LDB Member

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    The answer is probably yes, there are things that can be done at a cost of many dollars that will yield positive results saving many pennies.
     
  6. Mendel Leisk

    Mendel Leisk Senior Member

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    Just brainstorming:

    1. Remove the antenna (assuming you're not needing it).
    2. Remove rear wiper.
    3. Remove front license plate. (or do some sort of aero mod to the holder?)
     
    Robert Holt likes this.
  7. Robert Holt

    Robert Holt Senior Member

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    1. I've seen the "shark fin" replacement but not any completely interior or flush exterior replacements, have you?
    2. Safety concerns prevent me removing rear wiper.
    3. For winter, how about a combo 100% lower grill block plus smoothly integrated license plate holder? Anybody make those? Is it legal to have a bent license in a bent holder set flush in a nose cone?
    4. Is the right rear view mirror legally required? If not, has anyone replaced it wth a inside camera pointed out thru the small side window back along the side of the car? With a suitably-sized display screen just inside that window on the dash, I think you could have equivalent right side rear vision.

    Hello, modders?
     
  8. Vman455

    Vman455 Senior Member

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    I've removed the passenger side mirror, and only recently put the driver side mirror back on the car for some upcoming road trips through states that require it. Most states do not require exterior mirrors at all; a small convex mirror mounted on the A-pillar will eliminate any blind spots if aimed properly and is much cheaper and easier to set up than a camera system. You can check your state's mirror laws on the Ecomodder Wiki (should come up on a simple Google search).

    I've been using this setup for the past year and a half:
    [​IMG]
     
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  9. E46Prius

    E46Prius Active Member

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    I removed rear wiper. Removed antenna, replaced with $7ebay unit (functional) =), and no front plate. I plugged holes with BMW parts. Painted them silver.

    [​IMG]

    [​IMG]

    I have two more mods on my car since then.. i'll post updated pics soon =D
     
  10. Robert Holt

    Robert Holt Senior Member

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    Inside mirrors look very interesting.
    Must check state regs.
    Virginia requires front license plate.
    Thanks for ideas.
     
  11. ryankokesh

    ryankokesh Junior Member

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    I used the H&R Sport Springs to lower it a bit and it seemed to help ever-so-slightly in the mpg department. Probably wouldn't have done it if I hadn't been doing the shocks/struts. Honestly though the ride didn't seem any worse than stock. Plus it looks a lot better (imho), and the handling is definitely improved. Makes on/off ramps much more fun. :)

    [​IMG]Untitled by Ryan Kokesh, on Flickr
     
  12. DtEW

    DtEW Active Member

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    I'd be worried about having a mirror explosively launched into my face by the airbag right behind that pillar.

    Otherwise seems like a great idea for reducing frontal surface area.
     
    #12 DtEW, Oct 13, 2015
    Last edited: Oct 13, 2015
  13. Vman455

    Vman455 Senior Member

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    Alternatively, you could mount a mirror to the top of the door panel, right next to the window, but you'll need something more complex than a simple L-bracket. If I take the driver's mirror off in future, I'll probably go that route.
     
  14. xliderider

    xliderider Senior Member

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    Check out the images tab after googling automotive boat tail mod. ;)