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Old 07-18-2008, 02:03 PM   #11 (permalink)
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There were some interesting threads on gassavers about these. One guy was doing some rough testing using strips of ribbon attached to the back glass of the car. Reported that with the vortex generators in place that there was less whipping of the ribbons up to highway speeds. It would seem to mean that the wake had less of a negative pressure zone on the back.

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Old 07-18-2008, 02:06 PM   #12 (permalink)
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Sure, but I want to see some coast-down test results, not "well some ribbons don't move as much" tests. If that was a reliable FE test, people would buy ribbons instead of scanguages.
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Old 07-18-2008, 02:54 PM   #13 (permalink)
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don't scangauge's just estimate fuel usage? Tuft tests accurately show the airflow around your car

I will be doing some coast down tests for another idea I have, might as well do a before and after VG test also.

Oh, hit 55 mpg for my last tank with the vg's
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Old 07-18-2008, 02:57 PM   #14 (permalink)
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Yeah, scanguage is for fuel usage, but if you install an aero mod and it clearly uses less fuel, then you know it works. Straight ribbons does not necessarily equate to lower .cd, i'm thinking.
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Old 07-18-2008, 04:09 PM   #15 (permalink)
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Sure, but I want to see some coast-down test results, not "well some ribbons don't move as much" tests. If that was a reliable FE test, people would buy ribbons instead of scanguages.
Agreed. I hope I didn't imply that was a legitimate test. I would rather see tank numbers.

I'm still a rookie at this aero-lingo. Could someone fill me in on coast-down testing and tuft testing?
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Old 07-18-2008, 04:24 PM   #16 (permalink)
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Coast down testing

Tuft testing
or look at how VinceHX set it up in an earlier post
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Old 07-18-2008, 05:06 PM   #17 (permalink)
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Hi Carlo,

And -- how do they work?
Ahhh, I can't prove a thing, . Look at azraelswrd's post because it is helpful regarding how to do a coast-down test. My problem is, there is *no* place I can think of in LA to do this test. Because I don't have a "boxy" car like a Scion xB or a Jeep, I can't even perceive any road-stability benefit. If I could perceive increased road stability in a cross-wind, that would imply aero-improvement to me. Here is what they look like (I still need to add some below the window, just lazy as usual) :



As others have done, you could "make your own". If you are leery of the aesthetics, you could use business card magnets to move them around. A possible defect to magnet attachment is that I think the VG needs to be symmetrical in relation to the wind. The Evo-style VGs are angled to the wind. If those were magnetically placed, they would probably be "pushed" into line. Also, for side mounting, I wouldn't recommend magnets because gravity is "pulling" them down, increasing chance of loss and/or misalignment.

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Old 07-18-2008, 05:24 PM   #18 (permalink)
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Here is my understanding of it.

Vortex generators will do absolutely nothing on the trailing edge of a vehicle. The whole purpose of the vortex generator is to basically slow the air down and create a thicker boundry layer so it can follow a steeper angle such as a rear windshield. This increases pressure on the rear windshield and reduces pressure drag. The vortex generators are not going to slow the air down enough to make a near 90 degree turn to put pressure on the backside of your car unfortunately.
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Old 07-18-2008, 05:32 PM   #19 (permalink)
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Daox -

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Originally Posted by Daox View Post
Here is my understanding of it.

Vortex generators will do absolutely nothing on the trailing edge of a vehicle. The whole purpose of the vortex generator is to basically slow the air down and create a thicker boundry layer so it can follow a steeper angle such as a rear windshield. This increases pressure on the rear windshield and reduces pressure drag. The vortex generators are not going to slow the air down enough to make a near 90 degree turn to put pressure on the backside of your car unfortunately.
I am confused (as usual, ). At the Airtab site, they are installing them on the trailing edge of 90-degree turns :"

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Old 07-18-2008, 07:00 PM   #20 (permalink)
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Hi y'all,

Well, I ordered 21 black Airtabs (9 for the roof, 6 for each side), which came to $52.50 plus ~$11.50 FedEx shipping. I'll report back with some MPG results...

I thought about these compared to the Vortekz fins -- the Airtabs work individually, whereas the Vortekz work in a group; and so the latter really would only work on the roof. They also seem like they cause a pair of "larger" vortices. The Airtabs also have a lot more technical info and a lot of (authentic sounding) testimonials.

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