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Old 05-24-2006, 07:56 PM   #1
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Vortex Generators / Hmmm Airtabs

Wanted to see if installing vortec generators on the roof, trunk and front fender would improve FE. Did 4 runs on a 7.5 mile north south section of highway with cruise control set at 60. Did runs with a clean car, with VG on roof, VG on roof, trunk, and front fenders. Temperature was 93 and winds were out of the south at 15mph. VG's were made from hand out of aluminium.

#1N #2S #3N #4S
Clean car 42.0 38.4 42.1 39.0 AVG 40.38

VG on roof 42.6 39.2 42.8 39.1 AVG 40.93

VG/roof/trunk/ff 42.9 39.1 42.9 39.0 AVG 40.98

That's only a 1.5% increase in FE and it looks like the VG anywhere but the roof are ineffective.



On the front wheel well

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Old 05-24-2006, 08:14 PM   #2
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Cool. So were they hard to make? Seems like tin snips, a vice, and some kind of glue is all that is needed.
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Old 05-25-2006, 02:39 PM   #3
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I think the roof is the only place you're going to see an improvement, since the rear window is at a greater than 11 degree angle, the boundry layer seperates from the window and causes greater drag. Or so says the things I've read and studied. =)
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Old 05-25-2006, 06:56 PM   #4
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Quote:
Originally Posted by Bunger
I think the roof is the only place you're going to see an improvement, since the rear window is at a greater than 11 degree angle, the boundry layer seperates from the window and causes greater drag. Or so says the things I've read and studied. =)
That's kinda what I figured out. The gain not really worth the effort. Do you think that it might show a better improvement on a box vechile or mini van placed on the roof and sides on the rear end?
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Old 05-25-2006, 10:19 PM   #5
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Definitely better on a boxier vehicle. You might try moving the VGs from the front fenders to the rear, just before the curve to the rear bumper and I use the term bumper loosely.
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Old 05-26-2006, 01:01 PM   #6
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vg

Well I know a really boxy vehicle that shows greatly reduced MPG at higher speed that needs to be tested . . . my xB
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Old 05-26-2006, 06:38 PM   #7
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a set of vortex generators

I like. If you were to sell a couple of those vortex generators to a fellow gassaver for his roofline, what would you charge him?
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Old 05-26-2006, 07:19 PM   #8
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Quote:
Originally Posted by JanGeo
Well I know a really boxy vehicle that shows greatly reduced MPG at higher speed that needs to be tested . . . my xB
And my Tahoe!
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Old 05-26-2006, 07:59 PM   #9
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I know it may be some trouble to try the test again, but your vortex generators might be too close to the trailing edge to be of benefit. On plane wings, the generators are closer to the front of the wing, to keep the air attached over the surface of the wing. You might want to try moving them forward a few inches, and see if there is any difference.

One thing that might be of interest is this quick doc on the generators, on the wikipedia (http://en.wikipedia.org/wiki/Vortex_generator), where it says they actually increase drag.
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Old 05-26-2006, 08:39 PM   #10
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Quote:
Originally Posted by tomauto
I like. If you were to sell a couple of those vortex generators to a fellow gassaver for his roofline, what would you charge him?
I don't have any left to sell. I have 2 left over and I would just give them to you if I had a bunch extra any way. If you want PM me your address and I can send you the paper pattern I used to make them. Just copy the pattern on to cardboard(for durability) then use the carboard cutout to copy on to the aluminium. Then cut out the pattern and bend with a pair of plyers. The whole shooting match was less then ten bucks at Lowes or Home Depot and took about 3 hours to make 45 of them. The aluminum was $6.00 for a ten foot roll and the 2 sided tape was under $5.00.

Quote:
I know it may be some trouble to try the test again, but your vortex generators might be too close to the trailing edge to be of benefit. On plane wings, the generators are closer to the front of the wing, to keep the air attached over the surface of the wing. You might want to try moving them forward a few inches, and see if there is any difference.
I don't think I'll test them again. It a pretty small gain. With such a small amount of data it really a toss up that they help at all on this car. The roofline is where they have them on the new cars and my cars rear end is rounded on the top and the sides so not much help there.
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