Air flow stabalization

JimIsbell · 01-22-2009, 05:48 PM

Some time ago I found a product at was sold to truckers to improve the air flow around the truck. They were small plastic stick on devices that looked kind of like a cut off funnel. 6 or 8 of them placed along the forward edge if the roof was supposed to make eliminate turbulent air flow across the roof and down the back.

BUT....I forgot what they were called, where to get them, or anything.

Can anyone tell me what they are called so I can gogle them?

JimIsbell · 01-22-2009, 07:57 PM

I found it. Its called "Airtab" Gonna try them. I was wrong, they apply to the trailing edge, not on the leading edge. Might do something on the front of the front wheel wells to smooth the air across the opening.

lenwardus · 01-22-2009, 11:49 PM

IIRC a forum member did a write up on these, front and back. Limited if no success.

Dougie · 01-23-2009, 12:02 AM

They're vortex generators, and add energy to the airflow to reduce the separation of the flow from the surface. On a regular sedan shaped car, you can usefully put them at the back of the roof to reduce the separation as the air flows down the back window. They're not needed on the Insight, because it has a gentle rear window slope that in itself prevents separation. Putting them at the back is useless because you are unavoidably going to get separation at the Kamm transition anyway.

They come stock on some versions of the Mitsubishi EVO; here's a paper that talks about them...
http://www.mitsubishi-motors.com/corpor ... 16E_03.pdf

JimIsbell · 01-23-2009, 01:18 PM

Even limited success would be fine as they are quite cheap at $2.75 each.

JimIsbell · 01-23-2009, 04:56 PM

Quote:

Originally Posted by Dougie

They're vortex generators, and add energy to the airflow to reduce the separation of the flow from the surface.

The Airtab site states that they improve the air flow off the BACK edge of the vehicle reducing the drag at that edge caused by turbulence. If that is the case then they would be used at the very back edge of the car and perhaps the front edge of the front wheel wells to facilitate air flow off the aft edge of those two surfaces, not for reattaching air flow to the body. On trucks they are attached at the aft edge of the cab and on the aft edge of the trailer so they are not reattaching air to anything.

I also think they might be useful on the aft edge of the splash pan to facilitate air flow along the bottom of the car.

They are so cheap that I can buy 10 of them for less than $30 to experiment with. If there is any improvement, even minor, the cost of the Airtabs is inconsequential.

I will report back in a couple of months. Hopefully with pictures of airflow ribbons on the car.

Dougie · 01-23-2009, 07:14 PM

There are already bumps on the bottom of the bumper that do the same thing... But I encourage you to experiment!

When I was driving around with airflow tufts on my car, I decided that the biggest issue was flow separation at the sides of the windshield. So you might try putting them there...

JimIsbell · 01-23-2009, 09:55 PM

Thanks for the "heads up" I will try them there. It may be a bit difficult however since they would have to be on the glass to be in the right place and then I couldn't roll down the window. Maybe they could be fastened to the pillar in such a way that they lay just a few microns away from the glass. But there is also the problem of visibility past . It may be tricky. Maybe a few "Wrens Teeth" along the pillar itself........

rbusa · 08-03-2009, 10:56 PM

I read an online article at Autospeed website that mentioned they tried testing the Airtabs on a gen 1 Insight. Used at the back worsened observed FE. Used at the front just under the front air dam on the bottom, 4 tabs (I believe) used, didn't noticeably increase FE, tester noted that he recorded the best FE at the time with them in front but couldn't tell if it was traffic/driving style that was more of a factor than the Airtabs. The tester did note that using the tabs in the front did have a subjective improvement in higher speed stability when next to big semis and such... I'm looking at using them too in the front. Maybe in the sides as was mentioned as well. Did you ever try them out?

It would be nice to put a venturi tunnel under the Insight to improve grip at highway speeds without increasing drag too much. But then again, it might overload the short supsension travel of the rear suspension especially when loaded. The Insight has enough advances and technology to tempt one, but still leaving a bit wanting for those who want that little bit more... But you still gotta respect the engineers for what they did do with this car amongst the gorrillas... I like gorrillas too but just can't justify the gas bill, and don't like standing still with technology...

Cobb · 08-04-2009, 12:37 AM

A friend of mines used them on a geo metro. It just kept the rear window clear when it rained. No mpg increases.