Vortex Generators / Hmmm Airtabs

[zpiloto]

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.

http://members.cox.net/zpiloto/101_0070.JPG

On the front wheel well

http://members.cox.net/zpiloto/101_0071.JPG

[kickflipjr]

Cool. So were they hard to make? Seems like tin snips, a vice, and some kind of glue is all that is needed.

[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. =)

[zpiloto]

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?

[katman]

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.

[JanGeo]

Well I know a really boxy vehicle that shows greatly reduced MPG at higher speed that needs to be tested . . . my xB

[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?

[katman]

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!

[mosier]

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.

[zpiloto]

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.

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.

[JanGeo]

And my Tahoe!

Yeah but what percentage of your fuel consumption is to air drag compared to other drags of your vehicle? I know my xB gets better MPG at lower speeds and drops off over 40mph. Also think about AirTabs for $2.50 each in clear, black or white which have been wind tunnel tested.

[katman]

Yeah but what percentage of your fuel consumption is to air drag compared to other drags of your vehicle? I know my xB gets better MPG at lower speeds and drops off over 40mph. Also think about AirTabs for $2.50 each in clear, black or white which have been wind tunnel tested.

I've thought about Airtabs in the past but then thought about making some and then people post other cool stuff and I start thinking about that and I procrastinate and get nothing done!:rolleyes:
With the brush guard stuff on the Tahoe, which I don't want to take off, I know aerodynamic mods would help, but I'm having problems deciding what to use that won't change the looks too much. Clear Airtabs are a definite possibility. I've wondered about belly pans but are they effective on vehicles with large ground clearances? I never use the luggage rack so I could remove the cross bars. Then I could add a Ram Implosion Wing!

[zpiloto]

Then I could add a Ram Implosion Wing! Do you know anybody that tested that thing. It looks pretty hokie.:eek: It would be the ultimate whale tail. http://www.electrifyingtimes.com/Robert_A_Patterson.html

[ZugyNA]

I've studied the vg thing and have installed some.

I'd have to guess that the ones on the roof are in an area where the boundary layer has already separated to some extent....probably reducing their effectiveness. Maybe try moving them forward about a foot?

The ones on the deck lid are at a place where the air has pretty much separated for sure from the sharp drop at the window.

I had some on the roof of a hatchback with less slope...slightly different design of vg though...similar to the Mitsubishi kind. Found that silicone caulk is best for permanent mounting.

Good to see the accurate testing....and some positive results.


Here is a similar car with similar flows:

http://www.mitsubishi-motors.com/corporate/about_us/technology/review/e/pdf/2004/16E_03.pdf


vgs:

http://www.thirdshift.com/jack/firefly/firefly18.html

http://www.thirdshift.com/jack/firefly/firefly19a.html

Notice that he has his version of vg mounted the other direction? This plane cruises at around 60 mph.

[zpiloto]

I've studied the vg thing and have installed some.

I'd have to guess that the ones on the roof are in an area where the boundary layer has already separated to some extent....probably reducing their effectiveness. Maybe try moving them forward about a foot?

The ones on the deck lid are at a place where the air has pretty much separated for sure from the sharp drop at the window.

I had some on the roof of a hatchback with less slope...slightly different design of vg though...similar to the Mitsubishi kind. Found that silicone caulk is best for permanent mounting.

Good to see the accurate testing....and some positive results.


Here is a similar car with similar flows:

http://www.mitsubishi-motors.com/corporate/about_us/technology/review/e/pdf/2004/16E_03.pdf


vgs:

http://www.thirdshift.com/jack/firefly/firefly18.html

http://www.thirdshift.com/jack/firefly/firefly19a.html

Notice that he has his version of vg mounted the other direction? This plane cruises at around 60 mph.
Your right about the direction. I don't know how I screwed that up. I'll have to swing them around and retest. Mybe this weekend. I was disappointed with the original results. Maybe this will get it around 3%.:D

[Silveredwings]

Box drivers might be better served by adding a boat-tail to break up the inevitable turbulence behind the vehicle:

Some now well-known articles:
http://www.greencarcongress.com/2005/11/new_boat_tail_d.html
http://www.maxmpg.org/the_cap.html

PDF warnings:
http://www.nasa.gov/centers/dryden/pdf/88628main_H-2283.pdf
http://www.osti.gov/fcvt/2000-01-2209.pdf

On a vehicle with a blunted rear end (as opposed to the back of a pickup cab), it seems that the air space created by some plates does more to reduce drag than their angle of taper.

[zpiloto]

On a vehicle with a blunted rear end (as opposed to the back of a pickup cab), it seems that the air space created by some plates does more to reduce drag than their angle of taper.

You are right, at least with my application. I turned the VG's around and ran the same test protocal as before with the same results:mad:.

[ZugyNA]

I got "inspired" by your 1.5% gain and made up some vgs for use above the rear window on my hatchback. I combined the Mitsubishi research and the vg design from the ultralight. Also some some oil flow testing to determine air flow direction. Will post some specifics and a pic when I get them finished.

I have some vgs on the sides of the same car (3 per side)...they are oriented the same as your roof vgs...2 vanes that point to the rear in a "V" shape.

The Mitsu research shows that mounting them around 4" from where the rear window starts was the ideal position on that car.

[zpiloto]

I got "inspired" by your 1.5% gain and made up some vgs for use above the rear window on my hatchback. I combined the Mitsubishi research and the vg design from the ultralight. Also some some oil flow testing to determine air flow direction. Will post some specifics and a pic when I get them finished.

I have some vgs on the sides of the same car (3 per side)...they are oriented the same as your roof vgs...2 vanes that point to the rear in a "V" shape.

The Mitsu research shows that mounting them around 4" from where the rear window starts was the ideal position on that car.

"Vortex generators (VGs) were studied to install
immediately upstream of the flow separation point
in order to control separation of airflow above the
sedan’s rear window and improve the aerodynamic
characteristics. It was found that the optimum
height of the VGs is almost equivalent to the thickness
of the boundary layer (15 to 25 mm) and the
optimum method of placement is to arrange them
in a row in the lateral direction 100 mm upstream of
the roof end at intervals of 100 mm. The VGs are not
highly sensitive to these parameters and their optimum
value ranges are wide."

Keep us posted with the results.:D

[ZugyNA]

Using the Mitsu research and ultralight info...I made 5 vgs from alum flashing material 2 1/2" long....with 2 vanes each set 3" apart. The vanes are about 5/8" high.

Did an oil flow test first by drawing a line 3-4" back from where the roof starts to slope down...marked 7 different points along this line...had an eyedropper of engine oil...put a good sized drop in all 7 places and drove about a mile and a half down the road at 60 and stopped. Found the center 3 flowed straight back...the 2 points in one from the ends angled in around 8* towards the centerline of the car. The 2 places right near where the roof dropped off to the side had a pretty disturbed flow...lot of buffeting here?

So they are mounted about 3" back from the "break line"...the two vgs on the ends are angled 8* inwards...glued on using silicone caulk. Each vg is 4 1/2" apart.

Expecting that each vane creates a vortex that rotates conterclockwise on the right side and clockwise on the left (looking to the back)...so that they don't tend to cancel each other out.

http://www.cpu-net.com/host/gaxir/gpics/zvgs.jpg

[zpiloto]

Using the Mitsu research and ultralight info...I made 5 vgs from alum flashing material 2 1/2" long....with 2 vanes each 3" apart. The vanes are about 5/8" high.

Did an oil flow test first by drawing a line 3-4" back from where the roof starts to slope down...marked 7 different points along this line...had an eyedropper of engine oil...put a good sized drop in all 7 places and drove about a mile and a half down the road at 60 and stopped. Found the center 3 flowed straight back...the 2 points in one from the ends angled in around 8* towards the centerline of the car. The 2 places right near where the roof dropped off to the side had a pretty disturbed flow...lot of buffeting here?

So they are mounted about 3" back from the "break line"...the two vgs on the ends are angled 8* inwards...glued on using silicone caulk. Each vg is 4 1/2" apart.

Expecting that each vane creates a vortex that rotates conterclockwise on the right side and clockwise on the left (looking to the back)...so that they don't tend to cancel each other out.

http://www.nonags.org/members/nijqk/zvgs.JPGhttp://www.nonags.org/members/nijqk/zvgs.JPGhttp://www.cpu-net.com/host/gaxir/gpics/zvgs.jpg

http://www.nonags.org/members/nijqk/zvgs.JPG
That's nice do you have any data on FE increase? Your methology is better than my stick it on there and lets see what happens.:D Have you thought about adding a couple more to decrease the space between VG's?

[ZugyNA]

Just got them on there...and am also testing other things...like the FA2000...so no mpg results.

The Mitsu research says that a spacing of 4" is ideal...mine are spaced 3" and 4.5"...Mitsu has 8 vgs...I have 10. Ideal for that car was 4" back from the "break"...mine are 3" back. I was planning on using 7 of them instead of 5.

I can't do the research they did...but I can generally duplicate what they say is ideal. I think they compromized for production by putting them too far back.

Though as they say..."The VGs are not highly sensitive to these parameters and their optimum value ranges are wide."

I made some previously pretty much exactly the same dismensions they used...but the doublesided tape wouldn't hold in the rain. Didn't test for flow. Didn't put them back on because of the very low reduction in CD they mention.

Sounds like IDEAL would be 4" back...spaced 4"...none at the edges....angled 15* to the tested flow...they say 1" high vgs are OK. Theirs were 2" long.

[zpiloto]

Nice job. I tried a FA 2000 knockoff that I manufactored myself with no luck. Do you have an EFIE on your O2 sensor? Without it I don't think you'll have much luck with the ECU making adjustments.

[ZugyNA]

Yep...got an EFIE. Somehow the FA2000 was set back to a lower setting where no gas was flowing...either somebody was messing with it...or I'm getting careless...but testing goes on.

Have had a problem with liquid gas building up under some conditions...got that solved by adding an extra PCV jar to catch it.

[MetroMPG]

More info I've found about VG's...

zpiloto: yours are/were not on backwards, at least according to the old web site of Gary Wheeler, an Indy car designer/aerodynamicist who originally popularized VG's for use on regular cars (if I'm not mistaken). His were oriented the same way as your photos show.

zugyNA: what's that flat black thing on the top of the rear window downstream of your VG's? It's not a spoiler is it? (Would kind of negate the VG's.)

3rd party tests: I still haven't found anything good that supports using these at the trailing edge of a vehicle (vs. the roof)... but I did hear back from the airtabs company with a report of a study done in the UK using them ahead of the tractor/trailer gap, and it appears legit.

[JanGeo]

You guys need to put a fan on the roof and have it blow backwards over the VGs and then spray a mist of water or smoke and see the air flow to check for the VGs working and the proper spacing and never mind the road testing . . . you need to actually see it working up close. Maybe a thread tell tail off of the tips of the VGs would help too.

[MetroMPG]

I thought of using a shop vac hooked up to the outlet port. ... and then immediately realized it would only generate turbulent flow, since it's blowing into still air. Same deal with the fan. Unless it's a really big fan, like, say, in a wind tunnel :)

[JanGeo]

I don't think you can cover the entire roof line but you should have a pretty good air flow at 1 inch height along the roof line if the fan is at the start of the roof - by the time the air gets to the rear of the roof it should be pretty smooth flow - not looking for 60 mph wind either - just some 10-20mph air flow. I was looking at the bottom end of my xB on a windy day and could feel the air flowing under the rear ground effect. Maybe a windy day would show the vortex created. I also have to wonder about using sheet metal for the VGs instead of a smooth aero shaped VG like the Airtab.

[zpiloto]

More info I've found about VG's...

zpiloto: yours are/were not on backwards, at least according to the old web site of Gary Wheeler, an Indy car designer/aerodynamicist who originally popularized VG's for use on regular cars (if I'm not mistaken). His were oriented the same way as your photos show.
I've tested both directions with the same results. I've also tried them at different spacing with the same results. It looks like VG just need to be there to help the flow. The spacing and orientation don't seem to make too big a difference. I saw a 1.5% increase with a 40 MPG base. I personally don't think it worth the trouble as far as bang for the buck but your base is a lot higher than mine. I spent about 8 hours on the whole project including getting material making the VG installing and testing, but then again every little bit helps.:D

[ZugyNA]

More info I've found about VG's...

zpiloto: yours are/were not on backwards, at least according to the old web site of Gary Wheeler, an Indy car designer/aerodynamicist who originally popularized VG's for use on regular cars (if I'm not mistaken). His were oriented the same way as your photos show.

zugyNA: what's that flat black thing on the top of the rear window downstream of your VG's? It's not a spoiler is it? (Would kind of negate the VG's.)

3rd party tests: I still haven't found anything good that supports using these at the trailing edge of a vehicle (vs. the roof)... but I did hear back from the airtabs company with a report of a study done in the UK using them ahead of the tractor/trailer gap, and it appears legit.

>> Could you upload a copy of that report? <<


* maybe with some vgs...direction isn't that important

* flat (?) black thing is one of those 3rd brake lights...does mess up the flow

* the kind of vg I put on the ZX roof is a different design than the airtab clones made of alum. The basic vg is just a single vane usually set at a 15* angle to the air flow....the ultralight type I made for the roof just combines 2 vgs in the same piece of metal....these create 2 vortexes.

the airtab clones are made so that the air is focused and made into a non vortex type higher pressure stream...while maybe there is a low pressure area between them.

the kind used on the roof should likely be the actual vortex generators (spaced at 4"?)...while those used at the back should be the airtab clones (spaced at 1"?)?

[MetroMPG]

>> Could you upload a copy of that report? <<

I will if the airtab guy says it's OK. Waiting to hear back.

maybe with some vgs...direction isn't that important

That seems to be the case, doesn't it.

the airtab clones are made so that the air is focused and made into a non vortex type higher pressure stream...while maybe there is a low pressure area between them.

Could you show me a pic of this non-vortex type? This is the first I've heard of that behaviour. My understanding is that the airtab style also creates vortices.

[JanGeo]

The Airtabs have a definate direction to face and create a clockwise vortex and counter clockwise vortex and should be placed 4 inches apart. The idea is to prevent reverse air flow back against the rear of the vehicle which represents drag and turbulance. I wish the improvement was greater to justify the cost but I guess at some point I will get a few and try them.

[vegasjetskier]

Here's an SAE paper that describes how "vortex strakes" can be used to create an "aerodynamic boattail" behind semitrailers. See p. 13 for pics.

http://www.solusinc.com/pdf/2003-01-3377.pdf

Blue skies,

Patrick

[ZugyNA]

Could you show me a pic of this non-vortex type? This is the first I've heard of that behaviour. My understanding is that the airtab style also creates vortices.

a pic and the pattern for the airtab clones is here:

http://www.gassavers.org/showthread.php?t=1351

I don't think the airtab type create vortexes...since the vanes oppose one another....


the vgs I used on the roof are a different pattern....and do create vortexes.

[MetroMPG]

According to the airtabs website (in "How do they work"), they create vortices.

[n0rt0npr0]

According to the airtabs website (in "How do they work"), they create vortices.

Yes. Metro, I've been running my airtabs for sometime now, and when I drive through the rain, and a vehicle is behind me with thier lights on...I can significantly see the votices. Also, whenever I cruise down a dirt road above 40mph I can see them.

[ZugyNA]

All I can say is that they are symetrical, but the air hitting between the vanes is bumped up...might create a spin? Maybe there is an interaction between this higher pressure and the lower pressure air between the airtabs?

the typical vg obviously creates a spin.....

[MetroMPG]

FYI: Porsche 914 club forum - racer claims use of airtabs cut 1/2 second off his lap times by reducing rear lift:

http://www.914club.com/bbs2/index.php?s=&showtopic=52170 (http://www.914club.com/bbs2/index.php?s=&showtopic=52170&view=findpost&p=712533%20)

[ZugyNA]

vgs for Vettes:

http://www.greenwoodcorvettes.net/gc4/vortex.htm

http://www.greenwoodcorvettes.net/gc4/G4%20instructions.htm

[MetroMPG]

Info given to me by Ron Davidson at Airtabs. (Posted with permission)

[omgwtfbyobbq]

Try hosting/linking them on box.net, they have large file hosting iirc.

[MetroMPG]

Good suggestion, thanks. Previous message edited with links to files.

[vegasjetskier]

So if I'm reading that chart right, the most improvement from the Airtabs was in the bumper and lower valence area? That seems strange . . . :confused:

[omgwtfbyobbq]

From what I've gathered, any change in angle greater than ~15 degrees will result in seperation and a low pressure area. Underneath the car, the flow is very turbulent, so on a normal car, this flow is more likely to be pulled into the low pressure zone behind the vehicle compared to the relatively smooth flow over and around the vehicle, which is what's creating the pressure drop behind the vehicle. By filling this low pressure zone with air, the greatest change we see should be around the bottom.

[FormulaTwo]

So i went ahead and ordered some air tabs, at $2.50 they would be worth testing out.

The company ships them extremely fast.
They send you a little template to help you position them, and they have adhesive on the undersides.

I ordered 5 to put across my roof line in the rear.

First i cleaned the entire area with windex.
Then i cleaned it with Alcohol.
I then heated the airtab adhesive so that it would adhere even further.


On the directions it says to let them stick for around 15 minutes to make sure. Even though you can drive with them on there as soon as installed.
I waited around an hour.

Well that night i parked outside
When i got outside there was the usual dew on my car. It was probably around 50 degrees as I start my 15 mile drive to work.
I get around a mile down the road, look in my rearview and what else but something black flying off the top of my car.

It is funny how the first thing that pops into your head when you realize something has just taken flight off your car is denial.

Did not have time to go back and get it because I was heading to work.
When i make it to work i get out and sure enough there is an airtab missing....

So i tug on the others to see if they are loose also. Each of the remaining tabs slid around in the remaining dew on the roof.

:mad:

So i wasted $2.50 this week, thats an entire gallon of gas.
I have to find a way to try and restick these things.
We have 3m adhesive tape at my work which is used on vent visors etc...
but i feel like that may be too thick.


http://www.buyairtab.com/images/airtab/AT_Black.gif

[thisisntjared]

weird....

[nonnef]

So i went ahead and ordered some air tabs, at $2.50 they would be worth testing out.

The company ships them extremely fast.
They send you a little template to help you position them, and they have adhesive on the undersides.

I ordered 5 to put across my roof line in the rear.

First i cleaned the entire area with windex.
Then i cleaned it with Alcohol.
I then heated the airtab adhesive so that it would adhere even further.


On the directions it says to let them stick for around 15 minutes to make sure. Even though you can drive with them on there as soon as installed.
I waited around an hour.

Well that night i parked outside
When i got outside there was the usual dew on my car. It was probably around 50 degrees as I start my 15 mile drive to work.
I get around a mile down the road, look in my rearview and what else but something black flying off the top of my car.

It is funny how the first thing that pops into your head when you realize something has just taken flight off your car is denial.

Did not have time to go back and get it because I was heading to work.
When i make it to work i get out and sure enough there is an airtab missing....

So i tug on the others to see if they are loose also. Each of the remaining tabs slid around in the remaining dew on the roof.

:mad:

So i wasted $2.50 this week, thats an entire gallon of gas.
I have to find a way to try and restick these things.
We have 3m adhesive tape at my work which is used on vent visors etc...
but i feel like that may be too thick.


http://www.buyairtab.com/images/airtab/AT_Black.gif


I've used Gorilla Glue to glue things on the body of cars before. Holds on nice and tight but if you pry it off they tend to pop off without ruining the paint at all.
I emailed them about it out of curiosity, and they said it was because the glue could "foam out" on the clearcoat but it couldn't actually attach to it.

I'd put a few drops somewhere to test it on your paint first, anyhow(just in case). Good Luck! :D

[red91sit]

hmm that's very peculiar they fell off that quickly! If i were you I'd contact the air-tab company, they seem like a real consumer focused company, I'm sure they will either send you a new one, or atleast recommend a great way to attach them

[JanGeo]

Hey I wanted to test them on my xB which as you know is a big square box with lots of turbulance in the rear - you would not believe the dirt that piles up back there. So what kinds of polish have you been using on the roof? Sounds like maybe you should have heated the painted surface after you cleaned it with alcohol. I think if I were to add them to my roof line I would attach them to the rear hatch in the gap between the roof and the hatch by hooking them on the leading edge of the hatch. Next time used a clean tissue with some Acetone on it to prep the surface. Maybe safety string the back ends together too and then some really sticky clean packing tape over the leading edges. You may have to compound the painted surface to break through the glaze to get them to stick better, mask off the area with tape first and bust the shine on the paint a little - you should be able to polish it back up if it you don't keep them on.

[MetroMPG]

Silly question: how are you going to determine if they work / don't work? (Assuming you can keep them stuck on the car :) )

[FormulaTwo]

Good question Metro, I need to order a supermid. I am going off of my tank to tank info for now. Its hard to keep up with all the things my car needs. I still need a 5 wire o2 (mine is shot), the EGR box, and an alignment so i dont kill the Potenza's.

With all I have done to the car lately I have somewhat expected a FE gain, but my averages seem to be leveling off, Maybe due to outside temps.

Thanks for the info on the gorilla glue Nonnef, I may try that. Is it more like super glue, or a silicone type of glue?
I have also thought about tapeing the leading edges like Jangeo said, because the edge did not sit as flush as i would have thought. Which could lead to more of them flying off.


I will let you know how these turn out and post some pictures.
I also need to post pics of the LED brake lights since i havent done that.

[zpiloto]

Good question Metro, I need to order a supermid. I am going off of my tank to tank info for now. Its hard to keep up with all the things my car needs. I still need a 5 wire o2 (mine is shot), the EGR box, and an alignment so i dont kill the Potenza's.

With all I have done to the car lately I have somewhat expected a FE gain, but my averages seem to be leveling off, Maybe due to outside temps.


Your throwing your money at the wrong things. I know there expensive but fix the O2 sensor that will give you a better FE increase (10-15%) then air tab and LLR tires combined not to mention that the environment will thank you to.

[FormulaTwo]

Your throwing your money at the wrong things. I know there expensive but fix the O2 sensor that will give you a better FE increase (10-15%) then air tab and LLR tires combined not to mention that the environment will thank you to.


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.

[JanGeo]

The Gorilla glue is a urethane glue that reacts with moisture and foams up - I don't think that is what you want to use - maybe a good rubber cement or even silicone adhesive which will not damage the paint with some overlap but I don't think that it will stand up to water and rain and snow. The real problem is that all Glue is temporary and since the Airtabs are probably ABS plastic you have the other problem of using something that will stick to that also. Maybe some 3M spray adhesive. . .

[Silveredwings]

How about pop-rivets or sheet metal screws? :D (just kiddin')

But if you're just doing test, what about duct tape?

[FormulaTwo]

Alright well, here we go.....


I decided to reinstall them using 3m tape, like what is used on vent visors etc...
We have plenty of this at my work for me to play around with.

I tried it out on one just to see how high the airtab would actually sit with the 3m tape under it. It did not exactly sit flush, but definitely a good strong hold.

I took electrical tape and taped off the front edges, and part of the sides. This should smooth out airflow onto the airtab, and maybe hold the tab a little better.

So far so good, it looks a little awkward only having 3 tabs installed right in the middle of the rear of the car.

To be installed correctly I will actually need 4 more.
They say to install them 4" from center to center. No more than 10 inches from the rear of the vehicle.


Honestly I do not feel must difference in the car on the highway. I know there have been reports of increased stability etc... Then again there are only 3 up there, which probably wouldn't do too much if these things worked anyway.

I may tape some tufts all over the rear of the car this weekend, so I can get an idea of what the air is doing back there.
I will need someone to help with this, maybe video tape- take pictures...


from what i read.....

# Tufts that move around chaotically are a sign of drag.
# Tufts that move in the direction opposite to the airflow are a sign of high drag.
# Tufts that stay in line with the airflow are a sign of lower drag.

anything else to look for?
I will def post pics when i get them

Too bad none of you FE guys are from around here.
Could start up our own backyard FE skunkworks.

[JanGeo]

Try driving in fog or a dusty road I heard the vortex is really easy to see at 40mph and up. Put one on your hood?

[cfg83]

FormulaTwo -

Alright well, here we go.....


I decided to reinstall them using 3m tape, like what is used on vent visors etc...
We have plenty of this at my work for me to play around with.

I tried it out on one just to see how high the airtab would actually sit with the 3m tape under it. It did not exactly sit flush, but definitely a good strong hold.

I took electrical tape and taped off the front edges, and part of the sides. This should smooth out airflow onto the airtab, and maybe hold the tab a little better.

So far so good, it looks a little awkward only having 3 tabs installed right in the middle of the rear of the car.

To be installed correctly I will actually need 4 more.
They say to install them 4" from center to center. No more than 10 inches from the rear of the vehicle.


Honestly I do not feel must difference in the car on the highway. I know there have been reports of increased stability etc... Then again there are only 3 up there, which probably wouldn't do too much if these things worked anyway.


I am guessing that you need to start from a crummy aerodynamic place to begin with, like a Semi, in order to feel improvement. Also, the Semi's in the pictures are *covered* with them at the end. The one picture of the Honda CRV might be what you should look to accomplish.

I wonder if you can do a before/after coast test. It will be hard to keep things equal unless you have a "perfect road" to work with. Test must be done with same prevailing wind/temp/humidity conditions.



I may tape some tufts all over the rear of the car this weekend, so I can get an idea of what the air is doing back there.
I will need someone to help with this, maybe video tape- take pictures...


from what i read.....

# Tufts that move around chaotically are a sign of drag.
# Tufts that move in the direction opposite to the airflow are a sign of high drag.
# Tufts that stay in line with the airflow are a sign of lower drag.

anything else to look for?
I will def post pics when i get them

Too bad none of you FE guys are from around here.
Could start up our own backyard FE skunkworks.

I would really appreciate seeing your "Tuft Setup" in order to see how to set that up.

CarloSW2

[MetroMPG]

It will be hard to keep things equal unless you have a "perfect road" to work with. Test must be done with same prevailing wind/temp/humidity conditions.

Don't forget fully warmed up drivetrain/tires. (Takes much longer than the engine does to reach stable operating temps.)

--

Coincidentally, someone loaned me a box full of air tabs yesterday. So I'll also be running an airtab test sometime in Nov.

[JanGeo]

I was thinking of molding the air tabs into a rear spoiler and then add the spoiler to the top of my xB rear hatch. They wouldn't blow off that way.

[rh77]

There was a similar thread on this a while back

Vortex Generators (http://www.gassavers.org/showthread.php?t=995)

The Mitsubishi Evo vortex generators were the subject of examination, and was tested by the manufacturer. It turns out that it improves aerodynamics by a fraction of 1%.

RH77

[n0rt0npr0]

Don't forget fully warmed up drivetrain/tires. (Takes much longer than the engine does to reach stable operating temps.)

--

Coincidentally, someone loaned me a box full of air tabs yesterday. So I'll also be running an airtab test sometime in Nov.

Very cool. Will love to see your finds on these!

[MetroMPG]

I went out looking for some thin but stiff plastic yesterday to mount the tabs in line in one big strip, so I could remove & reinstall them all at once. But I didn't find what I was looking for.

--

ALSO - going to merge this thread with the original one, so the VG information isn't scattered around the site...

[MetroMPG]

Very cool. Will love to see your finds on these!
The Australian AutoSpeed web site recently ran a 4-part series on VG's.

[JanGeo]

Yeah well they need to try it on a vehicle with a LOT OF DRAG back there like the back of my xB!!

n0rt0npr0 - how big a box did you get of them AirTabs - want to send some my way??

[MetroMPG]

Yeah well they need to try it on a vehicle with a LOT OF DRAG back there like the back of my xB!!
I think you may be onto something there. The Insight is a poor vehicle to use in these tests because its already highly optimized to minimize rear wake with significant boat-tailing.

I agree that IF the VGs can positively influence rear wake when mounted near the vehicle trailing edge, you'd more likely see the results if the Cd is bad to begin with, like your xB or my hatchback.

I still plan to try this. Just need to locate a strip of plastic or something that I can use to collectively "quick release" the rows of VGs from the top & side of the car in between A-B-A's.

[JanGeo]

Thinking about some plastic strapping material they wrap boxes with - pulled tight over the roof without any glue so it comes off easy - mount the leading edges of the airtabs to it with tape and strap it to the gutters or around the rear hatch opening or even fasten it to the rear wheel wells with hooks and put some VGs on the side too!

[n0rt0npr0]

n0rt0npr0 - how big a box did you get of them AirTabs - want to send some my way??

I only purchased what I needed which was 11 of them. And damnit, I can't say whether they've made any difference or not because I've been trying to source a 93 GM 6 cylinder computer for $20 since I got them. Ain't found one just yet. My computer keeps on resetting its fuel table optimum - verified by a Tech1 scanner. Yeah. My tank to tank FE has been eerily close for quite some time now.

[smartzuuk]

If someone wants to define their test expectations and send me some VG or whatever, how about trying it on a smart?

[Ted Hart]

I had a '77 Gremlin (remember them?) with a small scoop-type wing mounted up-side down over the rear hatch window. This served to keep the dust and raindrops blasted off the rear glass. It worked extremely well! Isn't this the same sort of thing the vortex generators (supposedly) do?
Better MPG? The thought never occurred to me...such a tiny gain! MPG gains come from HP reduction...while maintaining a given velocity! People don't seem to appreciate this simple truth...it takes power to move a mass at some velocity. Burning gas makes the power. Less gas (more MPG) to move at the same speed is what a higher FE is about! Stirring the air a bit takes no power...and doesn't make any, either! Small wiggles on a MPG read-out are likely caused by the "noise" of the real world.

[MetroMPG]

I remember those glass-clearing deflectors on the back of one of my parents' station wagons when I was a kid.

I would say those would make aerodynamics worse, not better. They increased projected frontal area, and as they blast air down the rear window, they would increase pressure drag aft of the deflector and increase the size of the trailing wake.

http://www.phoenixgraphix.com/amc/1973gx.jpg

VG's could also increase projected area, but the theory (as I understand it) of placing them at the trailing edge of a vehicle is the tight vortices they create are supposed to extend the effective aerodynamic length of the vehicle: since the vortices would be drawn inwards in the low pressure area, they supposedly create a "virtual" boat tail, and minimize trailing wake.

[MetroMPG]

I've been in touch with my Airtabs contact again.

I'll pass my test outline by him before I do the runs to make sure I don't find out after that I did something wrong (ie. placement/orientation).

He has already suggested testing in 2 separate configurations for a hatchback:

- tabs along the trailing edge of the roof only;
- tabs on the roof edge plus along the trailing edge of the sides

[FormulaTwo]

I mounted mine along the trailing edge of the roof, without any on the sides. I still have a few extras that I have not installed. let me know how your A-B-A testing works out. I may install those later on.

http://i31.photobucket.com/albums/c368/formulatwo/4inches.jpg

[JanGeo]

I'm not sure of the size of these but they are supposed to be a certain distance apart or else the vortices don't form properly. Putting them too close together will make the adjacent vortexes interfere with each other.

The problem with the rear high wing is that it produces drag where as a vortex generator does not (not much anyway).

[MetroMPG]

For standard Airtab size (I'm not even sure if there's more than one size), spacing = 4 inches on center (minimum).

[JanGeo]

Ok the are 4" on centers and 3.25" wide so 3/8" between each so they are pretty close to each other. I would have thought they would be further apart to allow the vortex to be bigger.

[FormulaTwo]

mine are mounted 4" to the centers

i also thought they would be mounted further apart than they were

[Ted Hart]

Ok the are 4" on centers and 3.25" wide so 3/8" between each so they are pretty close to each other. I would have thought they would be further apart to allow the vortex to be bigger.

There is / was a question 'way back when... "How many angels can dance on the head of a pin?" My standard answer : "Ball point or fountain?" LOL!
These tabs remind me of this scene.... But I DO appreciate the pic of the Gremlin! Wonderful! I couldn't get outta that ride soon enough! "Sicks" cylinder / automatic / power nothing / steering wheel like a Greyhound bus ... but it rode well with the large sway bars I put under it, front & rear...and the stiffer shocks I put in. Bench seats, no radio, just back & forth to work / stores. Deja Vu? In my "rear-vu" mirror I could see at last! No dirt, no rain beads! It worked for this! MPG gain? With a slip-n-slide automatic? Who even cared? I bought it off the lot (new) and I needed a ride, NoW!

[MetroMPG]

I'm thinking I may try to run 2006's last experiment this week

[omgwtfbyobbq]

I'm eagerly awaiting the results! :)

[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:FC627CVnp6sJ:www.autospeed.com/cms/A_3058/article.html+%22Blowing+the+Vortex,+Part+1%22&hl=en&gl=us&ct=clnk&cd=1&client=firefox-a
http://72.14.203.104/search?q=cache:J5DSKpwH_hIJ:www.autospeed.com/cms/A_3060/article.html+%22Blowing+the+Vortex,+Part+3%22&hl=en&gl=us&ct=clnk&cd=1&client=firefox-a
http://72.14.203.104/search?q=cache:_WAu_dIfke8J:www.autospeed.com/cms/A_3059/article.html+%22Blowing+the+Vortex,+Part+2%22&hl=en&gl=us&ct=clnk&cd=1&client=firefox-a

And the important conclusion:

http://72.14.203.104/search?q=cache:4ODW2R2sUO0J:www.autospeed.com/cms/A_3061/article.html+%22Blowing+the+Vortex,+Part+4%22&hl=en&gl=us&ct=clnk&cd=1&client=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=a7cea6352302b3718247bddd897d6831

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.

[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).

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.

[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.
http://lostleagues.com/wp-content/uploads/2006/12/at_lines.gif
http://lostleagues.com/wp-content/uploads/2006/12/at_lines_2.gif

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]

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/product_info.php/cPath/103_107/products_id/357?osCsid=db65131ed7862594ac0f0bb2bad73acc

[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]

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.

[Red]

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.

[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?:D

[Red]

Or how many pins can be mounted on a VG? :P

Further testing(going to school/work for 2 weeks) shows that unless its a long trip 100+ miles, the airtab have next to no effect on FE. They have increased my stability in windy situations, so I'm going to leave them on.

On the flip side though an increase in milage over a long trip could just be due to highway gas milage, thus making airtabs useless.

[JanGeo]

I think the problem is that your energy use is more a function of the engine efficiency and not the drag caused by the aero of the vehicle. If more of your energy usage was from poor aero drag then reducing the aero drag would have increased your FE. I may just have to get some and try them on my xB.

[Red]

With the recent rain to confirm, the airtabs are keeping my back glass completely dry under reasonable speed, 40mph+. Anything lower and my hatch resumes its usual water attracting habits.