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Thread: Aerodynamics of the new Mirage (0.27-0.31 drag coefficient varies with options)

  1. #51
    Administrator Daox's Avatar
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    Welcome to the site Martin!

    The technical specs (top speed) aren't going to be tested by the OEM for every trim level. They test it for one and use it for all. The spoiler will have some effect, but its not drastic. The fuel economy gain is also there, but again not drastic enough to show up in the testing cycle.


    Custom Mirage products: Cruise control kit, Glove box light, MAF sensor housing, Rear sway bar, Upper grill block

    Current project: DIY Nitrous oxide setup for ~$100

        __________________________________________

        click to view fuel log View my fuel log 2015 Mirage DE 1.2 manual: 47.2 mpg (US) ... 20.1 km/L ... 5.0 L/100 km ... 56.7 mpg (Imp)


  2. #52
    Hi Martin -

    It's also possible the fuel economy rules do not require the company to test every trim. They may be able to test their "high volume" trim and then its rating applies to other trims (this was the case in the U.S., which was only very recently changed because some automakers were abusing the loophole).

    Darin

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        click to view fuel log View my fuel log 2014 Mirage ES 1.2 manual: 63.2 mpg (US) ... 26.9 km/L ... 3.7 L/100 km ... 75.9 mpg (Imp)


  3. #53
    Senior Member Mitz's Avatar
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    Improvements on the 2017 model

    ... The redesign is functional as well. The front bumper features a chiseled crease for smooth airflow. The front tyre air dam is optimised, and a rear tyre air dam is added to reduce drag resistance. At the back, the new bumper is optimised for air flow while the angle of the rear spoiler has been changed to reduce lift. These enhancements reduce coefficient of drag (Cd) to 0.27.

    From:
    http://paultan.org/2015/11/19/2017-m...rage-facelift/

    Tire Dams (Wheel Spat)
    - front tyre air dam is optimised
    - rear tyre air dam is added

    Air dam is visible - not provided in the Asian models
    Attachment 4581

    I can't seem to find the difference between the old spoiler and the new one.. maybe a few degrees in the angle?
    Attachment 4582

    I plan to attach Airtabs as substitute for the tire dams and also place them at the side of the rear lamp assembly. Would this make sense?
    Attachment 4583
    Attached Images Attached Images    

  4. #54

    Comparison of original vs. revised rear spoiler

    It's not a massive change, that's for sure:

        __________________________________________

        click to view fuel log View my fuel log 2014 Mirage ES 1.2 manual: 63.2 mpg (US) ... 26.9 km/L ... 3.7 L/100 km ... 75.9 mpg (Imp)


  5. The Following 3 Users Say Thank You to MetroMPG For This Useful Post:

    3dplane (12-04-2015),Daox (02-09-2016),GrnBn (12-04-2015)

  6. #55
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    Quote Originally Posted by MetroMPG View Post
    It's not a massive change, that's for sure:

    It could look insignificant but mean alot in terms of aerodrag. The stall speed difference btw 40 and 37mph could have considerable impact on MPG.

        __________________________________________

        click to view fuel log View my fuel log 2015 Mirage DE 1.2 manual: 46.4 mpg (US) ... 19.7 km/L ... 5.1 L/100 km ... 55.7 mpg (Imp)


  7. #56
    The fact they raised the spoiler angle to reduce drag/lift in the redesign could explain why we didn't see much benefit from extending the original 2014 spoiler (me) and 3dplane's kamm extension showed no gains as well.

    If flow was already suboptimal, extending that plane further isn't going to help as much.

    What's most surprising is they didn't have it optimized in the first place!

        __________________________________________

        click to view fuel log View my fuel log 2014 Mirage ES 1.2 manual: 63.2 mpg (US) ... 26.9 km/L ... 3.7 L/100 km ... 75.9 mpg (Imp)


  8. #57
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    Quote Originally Posted by MetroMPG View Post
    The fact they raised the spoiler angle to reduce drag/lift in the redesign could explain why we didn't see much benefit from extending the original 2014 spoiler (me) and 3dplane's kamm extension showed no gains as well.

    If flow was already suboptimal, extending that plane further isn't going to help as much.

    What's most surprising is they didn't have it optimized in the first place!
    I just got MPG bump by installing vortex generators on Prius C, ~14" off the spoiler trailing edge, angled (need to post pics). Too early to call it I wanna go through several tanks, but so far I had seen MPG numbers better than before. Mirage rear spoiler looks like a good candidate for trying them, just need to convince son (it is his car and he thinks they are tacky).

    I've read your posts on airtab tests, but I think with VGs location is very important, just putting them off the trailing edge won't do much. I posted a link at ecomodder to study which shown gains from VG+spoiler, it is there if you wanna jump on it.

        __________________________________________

        click to view fuel log View my fuel log 2015 Mirage DE 1.2 manual: 46.4 mpg (US) ... 19.7 km/L ... 5.1 L/100 km ... 55.7 mpg (Imp)


  9. #58
    Moderator inuvik's Avatar
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    Quote Originally Posted by MetroMPG View Post
    The fact they raised the spoiler angle to reduce drag/lift in the redesign could explain why we didn't see much benefit from extending the original 2014 spoiler (me) and 3dplane's kamm extension showed no gains as well.

    If flow was already suboptimal, extending that plane further isn't going to help as much.

    What's most surprising is they didn't have it optimized in the first place!
    The new spoiler should be a bolt on replacement. The big question would be would the fuel economy gain ever offset the cost of the spoiler?

        __________________________________________

        click to view fuel log View my fuel log 2015 Mirage ES 1.2 automatic: 40.5 mpg (US) ... 17.2 km/L ... 5.8 L/100 km ... 48.6 mpg (Imp)


  10. #59
    Quote Originally Posted by cyclopathic View Post
    I've read your posts on airtab tests, but I think with VGs location is very important, just putting them off the trailing edge won't do much.
    Agreed on location - which is why I followed the manufacturer's instructions exactly!

    Too early to call it I wanna go through several tanks, but so far I had seen MPG numbers better than before.
    With respect, I don't have a lot of faith in tank-to-tank testing. I'd be willing to bet normal variability is greater than any small aero change will make. To truly evaluate a change, you have to try as much as possible to isolate it from other variables.

        __________________________________________

        click to view fuel log View my fuel log 2014 Mirage ES 1.2 manual: 63.2 mpg (US) ... 26.9 km/L ... 3.7 L/100 km ... 75.9 mpg (Imp)


  11. #60
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    I am with you, my regular commute variation could be as much as 5mpg due to traffic, weather conditions and unintentional drafting. If you hand measure at pump then add pump variation.

    So to get accurate data you either have to do a controlled experiment or rely on statistics.

    While mpg gain is speed dependent iI suspect the gains are not linear. VG work by increasing flow speed, so they will lower stall speed of spoiler. If the speed was 40mph and it was reduced to 30, then the biggest gain to be expected in 30 to 40 range. Without knowing car aerodynamics it is hard to guess what to look for and what to test.


        __________________________________________

        click to view fuel log View my fuel log 2015 Mirage DE 1.2 manual: 46.4 mpg (US) ... 19.7 km/L ... 5.1 L/100 km ... 55.7 mpg (Imp)


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