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Racesills - Increased Downforce and Drag Reductions?

Discussion in 'Roadster' started by wiztecy, Oct 7, 2014.

  1. wiztecy

    wiztecy Active Member

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    #1 wiztecy, Oct 7, 2014
    Last edited: Oct 7, 2014
    Came across Racesills online for the Lotus Elise, they look pretty interesting. Does anyone have any personal experience with racesills or ground effects on their car and noticed any drag reduction and increased down-forces? Would be nice seeing real numbers from a wind chamber comparison with/without. I could see these sills calming and reducing choppy at the lower sides and outer edges / underside of the Roadster. Aluminum and Carbon Fiber ones are available for the Elise/Exige. They may just work for the Roadster as well. They also add a second function as to protect the rocker area from rocks that get kicked up from the front wheels. Also would help keep rocks and crud getting up inside your Roadster's doors in the winter/rainy months.


    Lotus Elise Side Rocker Extensions - Lotus Exige Side Rocker Extensions

    Sector111 RACEsills


    APR-Lotus-Elise-Lotus-Exige-Side-Rocker-5.jpg
    lotusfinaled6.jpg
     
  2. Doug_G

    Doug_G Lead Moderator

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    Typically adding downforce improves rear stability in high-speed turns, but do so at the expense of increased drag...
     
  3. wiztecy

    wiztecy Active Member

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    #3 wiztecy, Oct 7, 2014
    Last edited by a moderator: Mar 13, 2016
    Doesn't appear to be all that much velocity either at those areas as well on the Roadster. The mirrors and their mounts are really hot! Look at all that red/orange/yellow.

    aerodynamic2.jpg

     
  4. TOBASH

    TOBASH Member

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    I think hundreds of pounds of battery has increased my downforce enough as compared to an Elise.

    Best,

    T
     
  5. wiztecy

    wiztecy Active Member

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    Not really interested in downforce but rather reducing drag/turblance around the car. Theory is to push the air out and away from the car, especially further back from the rear diffuser. Also having a smaller footprint on the mirrors. All these little improvements should add up unless they cause more drag! If you look at the Elise windtunnel video, right behind the rear window is a sticky place for air. The Exige should eliminate that since it has an enclosed slope running down in that area.
     
  6. supersnoop

    supersnoop Tesla Roadster #334

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    Aren't the mirrors designed to channel air into the cooling ducts?
     
  7. TOBASH

    TOBASH Member

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    Then you want to kill off turbulence.

    The upright multiple fins on some cars are meant to do that.

    I'm not sure most of us need such mods BUT if you want to kill turbulence behind the window you need to design and fit a sloped rear louver or window. A rear spoiler is not what I think you are looking for.

    Best,

    T
     
  8. wiztecy

    wiztecy Active Member

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    Nope, the mirrors and that opening came off the Lotus Elise, they were designed that way to look sporty but are a large target for wind.

    - - - Updated - - -

    I was looking at the channeled rear diffuser of the Elise and aftermarket ones that push the air in channels out past the tail a good 3-4 inches so it doesn't stick to the ass end of the Roadster. If you look at the Nissan Leaf and the Model S they have these rail channels on the back rear of the cars, so channeling back alone must help with drag.

    I agree, the rear spoiler would add more drag, I think the that part of the Roadster is in decent shape in terms of drag.

    If you look at Terry Hershner and how he worked with Vetter on making the Zero motorcycle better at aerodynamics, he told me all the improvements have added up to putting another battery pack on the bike! Motorcycles are horrible for drag/aerodynamics.

    Its fun to analyze and see where things can be improved to increase range. I don't think I'd be able to drill into my Roadster to mount all this stuff and experiment. I do like my Roadster as it is that's for sure.
     
  9. TOBASH

    TOBASH Member

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    I think the best bang for the buck then would be rear louvers that baffle the dead space and as such kill off turbulence.

    A fiberglass or aluminum version should be easily custom made.

    Side mirrors also add to drag but they are a necessity.

    That being said, I don't know the resistance coefficient on a Roadster and I don't know how much difference that area might make.

    I agree that discuissions like this are fun, but I am not sure if the drag savings would translate into serious energy savings especially as most of our driving is under 50MPH.
     
  10. wiztecy

    wiztecy Active Member

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    Drag coefficient of the Roadster appears to be 0.35:
    Automobile drag coefficient - Wikipedia, the free encyclopedia

    I think a computer model with all these experimental improvements would be the best and most inexpensive way to try them out. I agree, both sides and the mirrors are essential on the Roadster, but those big bulky wind grabbing extension arms are not hence why I like the raceview and covercraft mirrors.
     
  11. bart513

    bart513 Member

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    Those outside door sills look awesome!
     

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