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Old 09-06-2011, 08:19 PM   #11 (permalink)
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Nobody has articulated the theory about how Vortex generators are supposed to help, and under what circumstances. Saying we just can't measure the difference is "logic" that can be applied to any unicorn. It really is a unicorn for all intents and purposes, and if someone comes up with a repeatable (not background noise) design/process that other ecomodders can validate, well I would reconsider it as a possible non-unicorn, but most of the time it is background noise (and a lot of hot air and wasted energy discussing it).

If the difference is that small, and requires such a large investment in design even then, then most folks here shouldn't be messing with them, better to label it a unicorn made of unobtanium until proven otherwise (no, claims about one race car is not conclusive "proof").

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Old 09-06-2011, 08:22 PM   #12 (permalink)
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I find it to be very difficult to believe that AirTabs & Vortex Generators do any good, except in very specific applications.

The reasons are these:

• If they create more thrust than the drag they produce, this would violate the laws of physics.

• The air being affected around a vehicle extends out several feet, it isn't all just within 1" of the skin. VG's seldom protrude more than 3/4" so the volume of air they have an effect on is very small compared to the huge volume that is in play, so it's doubtful that they could dramatically change the Cd.

• If they had measurable gains in fuel efficiency, we'd see them on production vehicles, you can't tell me that a cheap fix of adding these to a car or integrating them with the design of a car wouldn't be used if it could demonstrate 2-3 MPG's of difference. Car companies spend millions trying to figure out how to eek out that kind of FE gain.

• There is only 1 test I have ever see where they helped out a Mitsubishi Lancer, this took a team of engineers, a wind tunnel, and very specific placement to achieve a tiny gain in Cd. It is far beyond the reach of most people to figure out where & how to place these devices, and 95% of the vehicles made would receive no benefit from them no matter what number, where, or how they were applied anyway.

Show real reports by people other than the makers of these gimmicks showing an improvement in FE if you want to claim they work. My studied intuition says they're crap, they aren't in wide spread use commercially, and plenty of people have shown real results demonstrating they do nothing to help FE.

It is up to you to prove they do work, not up to those who are very skeptical to prove they don't. Show us real data, not hyped up marketing from someone who stands to make bucks selling these.

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Old 09-06-2011, 11:23 PM   #13 (permalink)
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The reports of semi trailers having better handling characteristics keeps coming to mind. This is a consistent report when searched online. But FE is more of a problem. If but one truck fleet used them we'd have something to go on.
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Old 09-07-2011, 09:11 AM   #14 (permalink)
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Isn't it "obvious" that for VGs to do any good, there has to be something down stream of them that can reap the benefits? (Like the trunk lid and wing on the Lancer for example)
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Old 09-07-2011, 09:50 AM   #15 (permalink)
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Quote:
Originally Posted by jakobnev View Post
Isn't it "obvious" that for VGs to do any good, there has to be something down stream of them that can reap the benefits? (Like the trunk lid and wing on the Lancer for example)
No, it isn't obvious in the slightest. Half the vg enthusiasts stick them on the very back edge of their vans/boxes, and all of them "Want to believe". They want to believe they aren't chumps...

From the airtab site:
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Old 09-07-2011, 11:28 AM   #16 (permalink)
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Aren't those ^ the wrong way round ?

EDIT - no apparently not.
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Old 09-07-2011, 11:56 AM   #17 (permalink)
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Quote:
Originally Posted by dcb View Post
No, it isn't obvious in the slightest. Half the vg enthusiasts stick them on the very back edge of their vans/boxes, and all of them "Want to believe". They want to believe they aren't chumps...

From the airtab site:
LOL! That is hilarious!
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Old 09-07-2011, 12:22 PM   #18 (permalink)
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I really think they should be tested pointing the wrong way.
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Old 04-28-2012, 05:46 PM   #19 (permalink)
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Airtabs at PATE

While I was rummaging around the swap meet I ran across a HAULMARK trailer which sported Airtab brand VGs on its trailing edge.The owner was tracked down.he's a Texas Tech guy,has maintained 40-years of logbooks on his vehicles and reported that no savings were discernible with the Airtabs.
He has many friends who are career OTR truckers.None of them report savings from them.He told me that 'soft-sided' trailers were the only thing to 'show' at the Diesel pump.
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Old 04-28-2012, 07:33 PM   #20 (permalink)
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Renault seems to think that vortex generators can reduce drag in 3-box cars.



Search for the Renault Logan ECO2

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