Tested: Airtabs on a mini van, A-B-A - no measurable effect
 

See also: http://ecomodder.com/forum/showthrea...olla-2390.html

---

As promised, here's the low down on the A-B-A test that I did using my brother's 2005 Pontiac Montana minivan: long wheelbase version, 3.5L V6, automatic.

http://ecomodder.com/imgs/van-side.jpg

As I mentioned in the van Kammback thread, conditions were ideal. Zero wind, and no traffic on my favourite testing route, and a cruise control functioning perfectly (unlike the one in my Firefly, which quit while testing the Kammback).

Here's what I did:

1) OEM roof racks were removed, holes covered with tape.

2) Vehicle was driven for approximately 25 minutes / 20 km in sub/urban and rural highway conditions to bring the vehicle up to operating temperature. Ambient conditions:

October 5, 2008 - 18:00
10 C / 50 F
71 % relative humidity
102.5 kpa pressure
0 wind

Cruise control was set once for the entire A-B-A series, at 55 mph / 88.5 km/h. Cancelled with the brake at the end of each run and "resumed" for subsequent passes between the same markers each time. Fuel consumption taken from a ScanGauge II, reset and read at the same markers each run.

3) 4 bi-directional "A" runs were done, averaging 33.65 mpg (US).

4) Airtabs were installed on the top & sides of the van (following mounting instructions on their web site, except they were taped on their leading & trailing edges, rather than peeling off the adhesive backing and sticking them on).

5) 3 bi-directional "B" runs were done, averaging 33.8 mpg (US)

6) Airtabs were removed, and 2 more 2-way "A" runs were completed, averaging 33.92 mpg (US).

Average of all "A" runs: 33.72 mpg (US)

Standard deviation of all the "A" runs: 0.36 mpg

Raw data:

Pics:

Below are the OEM roof racks. I think those are aftermarket cross bars though:

http://ecomodder.com/forum/attachmen...1&d=1229128839

Air tabs shown - placement only. For the actual test, they were taped across the full leading edge, and on the trailing tip, so they sat flush against the sheet metal:

http://ecomodder.com/imgs/van-airtabs-back-roof.jpg

Side placement. I was advised by the distributor that where the airtabs were set on an angle (rather than perfectly vertically), to increase the spacing between them slightly. So the ones behind the side window area aren't the usual "4 inches on center" layout.

http://ecomodder.com/forum/attachmen...1&d=1229128839

air tabs
 

Shucks! I was at the store with my fingers on the package of air-tabs when my "Yes Men" monitor brought me news of your testing,so I put them back and grabbed a can of sky lubricant instead. Big thumbs up for the info!

When you did this test on the Corolla, I wasn't moved much, since the AirTabs site doesn't make huge claims about small cars. They're geared towards big rigs, trucks, and vans. But now you've tested a van. Unbelievable! I really wanted to believe they'd work. I couldn't feel any difference on my truck either, but I hoped it was because I hand-made them. Heck, I still wanna believe they work on something. I think you need to test a big rig next. :)

My hopes and dreams are dashed to the ground. Curse you, cruel world!

So Frank, I take it that you're in no mood to assist with the next test? I need someone with a mallet & awl to help me put golf ball dimples all over a VW Bug... :D

Glad you proved it. Now, the bad part is i just got 8 of them delivered today for the liberty. I guess i should now put them on the front under belly pan i made for it, do you think will it help down under?

I would be delighted to help! :)

VGs drag reductions properties are highly dependent on chord placement on an airfoil, you must have placed them wrong *sarcasm*.

Good job for your rigorous testing. Lets hope this puts the final nail in the coffin that VGs do not affect overall drag enough to make a significant impact on fuel consumption in everyday driving of light duty passenger vehicles.

Of course, Darin's rigorous testing has demonstrated only that AirTabs have no empirical effect on aerodynamics of light duty passenger vehicles. Still to be determined is the degree of effect of AirTabs on the foot of the driver. ;)

But hey, if the placebo effect can improve your fuel efficiency by 5-10%, isn't that a good thing? LOL.

Maybe that should be my next mod: I'll install placebos all over the Prerunner! It has to work. After all, the miraculous effects of placebos have been thoroughly proven in more scientific studies than any other product in history. If someone can get me a pack of convincing literature and a few diagrams and photos, I'll make a DIY version.

Pics added to the first post.

EXCELLENT points, akashic.