Vortex Generators / Hmmm Airtabs

[The Toecutter]

Basically, from multiple sources, the results were so minimal that much more accurate testing would be required.



Here's the 1st three articles of a series on vortex generators:

http://72.14.203.104/search?q=cache:...ient=firefox-a
http://72.14.203.104/search?q=cache:...ient=firefox-a
http://72.14.203.104/search?q=cache:...ient=firefox-a

And the important conclusion:

http://72.14.203.104/search?q=cache:...ient=firefox-a

So, was there a fuel economy gain (indicative of a deacrease in drag) from the fitting of the six vortex generators? Unfortunately, we don?t know. The NHW10 Prius doesn?t run a trip fuel consumption display and we simply don?t think that filling the tank each time is a sufficiently accurate way of checking the fuel consumption ? not when we?re talking a car where just 250ml difference in tank fill volume would dramatically change the results. This is one case where the fuel consumption records would need to be accurately kept over a long period if valid data were to be gained.

www.beavermotorcoaches.com/journal/archive/march_april04/airtabs.html

On The Road
A before and after test of the Airtab is difficult to quantify. There are no testing standards available; however, that being said, we found that our coach no longer displayed the seesaw effect due to oncoming big rigs. And we have noticed a marked improvement in our confidence for driving into traffic laden with on-coming big-rigs. Also, while evidence of moderate to heavy crosswinds has been displayed (trees and bushes bending on the side of the road) we have not noticed their effect on our steering. Over the 600 to 700 miles we have tested Airtabs we have not noticed the usual buildup of dirt on the rear cap or backup camera lens, including the usual road grime buildup during travel in the rain.

As for fuel economy improvements, we have not been able to establish any measurable improvement. Was the installation worth the cost? You be the judge. If increased driving confidence and the absence of dirt build-up are desirable, then so are Airtabs.

mpgresearch.info/viewtopic.php?p=5402&sid=a7cea6352302b3718247bddd8 97d6831

It looks to me like in my particular application there is no improvement in fuel economy and maybe it's actually worse. But there may be an improvement in stability in high winds.

I've read many articles and testimonials where users of these claim they reduced the effects of crosswinds though. But the effect on fuel economy seems immeasurably small. Maybe if I ever get an OBD-II vehicle, I'll have to get a scangauge and test.


I do think they could have impact if placed at the right location of a vehicle, but you'd have to do some wind tunnel testing to really know.

[GasSavers_Red]

I have a set of airtabs for the Jeep, I plan on running some tests this week to see whether or not they have an affect on FE

[MetroMPG]

(moved to the VG thread).

Originally Posted by The Toecutter

Basically, from multiple sources, the results were so minimal that much more accurate testing would be required.

Ah yes. I've seen the autospeed and motorhome references.

I wouldn't call them "tests" though - they're primarily reporting subjective results with no real effort made to control for accurate fuel consumption readings.

That said, though, I agree the results - if any - are likely to be small, and would be impossible to discern above the normal variability of tank-to-tank testing.

If the weather cooperates this week (still conditions, mild temperatures), I hope to get out to do a "controlled as possible" ABA on my test route. I'm skeptical, but willing to give it a try.

What I don't understand is why, if the company believes they have an effective device, don't they hire a 3rd party to do proper tests and publish the results, rather than rely on the dubious customer testimonials as they do on the web site. Perhaps it's saying something.

[GasSavers_Red]

Tested out my AirTabs(AT) today on a 400ish mile day trip (391.8 miles).

The Short and Sweet
#'s taken using a ScanGauge II

Baseline MPG average no AT: 19.1 MPG (@ 70 MPH)
MPG w/ AT: 20.5 MPG (@ 70 MPH)

Difference: +1.4MPG
% Change: +7.33%

Total Cost: $34.24

Recap:

AirTabs are designed for use on Tractor Trailers. A quick recap of what AirTabs are supposed to do:

• Increase gas mileage
• Cut down on vacuum region aft of a trailer by creating vortexes in the air stream
• Prevent dirt and debris build up on the rear of the trailer
• Reduce the effects of wind gusts

Conditions:
I mounted the AirTabss near the end of the hardtop. Approximately 6 inches from the rear edge. Due to the rain channels formed into the fiberglass of the top, I was unable to place the AirTabss as were recommended. Instead I mounted two AirTabss in between each rain channel and 1 AirTabs at each end channel. I'll post a picture up tomorrow to better illustrate this.



Temperatures were around 40F for the duration of the trip. The experimental duration of the trip was taken from a Safeway gas station in Fairfax to Truckee. I stopped at the same station on the way back. The 60ish miles to Fairfax from my place was used as a "Warm Up" to make sure all various parts are at optimal operating specs and temperatures.

Cruise control was used for the entire duration of the trip. Cruise was set to 70 mph as determined by the stock speedo, the SGII displayed actual speed as 68 mph.

Terrain was a mix of flat land, moderate to steep climbs and moderate to steep descents along with a few miles of city driven to get to the ski park and get lunch. Elevation ranged from 50 ft above sea level to 7000ft.

Comments
Initial driving impressions earlier in the week verified the additional stability in gusty situations. We had some nice 25-30 mph gusts around my house on Thursday. Usually the Jeep gets blown around that you are conscious of your steering input, however with the AirTabss I barely noticed the wind's effect, noise rose but the Jeep did not rock around. Prior to the AirTabss when I would pass a Semi I could feel that I was driving through a thick wall of something, I could literally feel out a trucks wake, again now I barely notice anything, I have to use the SGII to figure out whether or not I'm in a sweet spot.

After my trip up to Truckee, the rear glass and tire carrier was noticeably cleaner looking than what I usually end up with. I did not have to use my rear wiper once to clear out the crud. Also the usual piles of road dust was much smaller than usual. Rather than a literal pile of sand and salt, it was more of a medium coating along the edges and a very light coating closer to the top and middle. (Will add a pic later)

As for gas mileage my trip average with the AirTabss were 20.5 beating my usual average of 19.1, an increase of 1.4 MPG. The average was computed over 268.6 miles following the exact same route, so it should be a fairly valid #.

I did notice that when shutting cruise off, usually the Jeep would feel like you hit something and generally drop 3-5 MPH, with the AirTabss you don't get that jolt nor sudden deceleration anymore, the Jeep feels like its coasting for a bit, slowing down almost normally.

Conclusions and Comments
For 30 bucks worth of plastic, not bad for a 7.3% gain in FE. But if 7% equals around 1.5 MPG this kinda sucks. 7% seems like such a nice big number and 1.5ish is so small... Ahh well whatever, breaking 20 MPG on a box isn't bad.

They don't look too bad on the hard top to boot.

Coming out of cruise and starting to coast, decelerating slowly instead of slamming and dropping in speed felt weird.

-----------------------------

I've got 6 AirTabs left that I'm got to play with to see if I can get any more improvement on other body locations.

Hopefully I've covered it well enough, please let me know if I might have left out something relevant.

Thanks

[CO ZX2]

Originally Posted by FormulaTwo

Agreed, although the tires i did not have a choice. Considering the ones I had went completely bald due to my crappy alignment. So now the alignment is my #1 priority.

The EGR box I have to go pick up about an hour from here, but havent yet.

The o2 sensor will soon follow. If I see a 10 to 15% increase off of the O2 sensor then I will be amazed. Im pretty sure the car is not going into lean burn since the ECU is seeing the o2 error, and adjusting the fuel for safety.

If any of you guys know of places to get deals on 5 wire o2's, let me know. I am going for NGk most likely, i hear bosch are crap.

I had this site saved. You might find what you need here.They have NGK.
http://www.bmotorsports.com/shop/pro...0f0bb2bad73acc

[omgwtfbyobbq]

On the basis of the scientific evidence that is available, and the results of this test, we very much doubt whether vortex generators fitted to the trailing edges of vehicles will reduce drag.

Something I've suspected is that these may be a poor choice for vehicle shapes that try to minimize the area where the flow separates, like an Insight or Prius, but boxy vehicles, like Jeeps, old hatches, or longboxes/pups may benefit way more from it.

[MetroMPG]

Originally Posted by Red

As for gas mileage my trip average with the AirTabss were 20.5 beating my usual average of 19.1, an increase of 1.4 MPG. The average was computed over 268.6 miles following the exact same route, so it should be a fairly valid #.

Just to clarify: the baseline MPG you recorded was for a round trip (both directions), and the tabs were also tested on the same round trip route (both ways)? Was the comparison made on the same day (same weather & wind conditions)?

I made up my test strips with the tabs mounted on them, but we haven't yet had a calm, mild day that coincided with enough free time to test them on my car.

[GasSavers_Red]

Originally Posted by MetroMPG

Just to clarify: the baseline MPG you recorded was for a round trip (both directions), and the tabs were also tested on the same round trip route (both ways)? Was the comparison made on the same day (same weather & wind conditions)?

I made up my test strips with the tabs mounted on them, but we haven't yet had a calm, mild day that coincided with enough free time to test them on my car.

Same route and more or less same conditions. I had gone up earlier in the month with out the AirTabs. Temperature was more on the lower side of the 40s, clear skies, light traffic, light cross wind, cruise on the whole way.

[GasSavers_Red]

I left late at 9:30 instead of 9, was trying to get up there by 12

[Ted Hart]

How many air tabs / VE tabs / vortex generators / whatever can be mounted on the head of a pin?