Vortex generators - where's the solid data for hatchback/van benefits?

[brucepick]

Originally Posted by SL8Brick

... Vortekz doesn't recommend using the delta fins on the sides, which is kind of understandable since that would essentially make them mini canards. I think Airtabs would be more effective when mounted vertically.

What's a canard and why would it be bad?

[SL8Brick]

Originally Posted by brucepick

What's a canard and why would it be bad?

They're commonly used to increase downforce, and we all know that a downforce generating device does not an ecomod make.

The Airtabs would be better on the sides since they induce a more neutral flow...for lack of better words.

[tasdrouille]

If you use them in v shaped pairs they will work exactly as airtabs.

Btw a properly designed spoiler can reduce drag while creating downforce on a fastback or notchback.

[crexcrex]

I beleive that many answers re Vortex generators can be found by researching Citroen, France is well known for aerodynamics who am i to question experts in the field of aeronautics, these vg's are used on jet fighters as well as the piper cub i certainly do not see thwm as bieng all show and no go..............

MY VG's will be installed on my rex next week all hand made to the specs Citroen has recommended.............never though that i would be using a geometry set again.

[NeilBlanchard]

Hi,

I've got 21 AirTabs coming for my xA -- should I put them on in a straight line, or a shallow vee with the point forward in the center, or swept forward with the point at the back? I have 9 for the roof, and 6 for each side...

[bilgladstone]

As much as possible, they should be in a straight line, perpendicular to the centre line, within 10cm of the trailing edge.

That's the spec I got both from Air Tabs and Performance Products.

[crexcrex]

The buisness of airtabs is to sell you as many as you do not need, 21 is a case of overkill, 21 would be great for a semi! before i can comment re number of tabs on the roof how many inches at the widest point? I have seen them and not impressed i beleive that you will find that your drag will go up..............if i had the cash i would bet on it.

I made nine shark fin style for a crx and have installed them and used them and can feel the effect on the highway and city as the air rushes over the roof the fins divert the air down onto the glass and off the back............to reap the full benefits of the vortex generators i can only conclude that i will have to install a air wing.......not a spoiler.

I can only suggest that you check citroen the pro's on aerodynamics and arrive at your own conclusion.................speaking for my self i usually coast down this bloody hill each day. prior to using the vortex generators i would coast at 50 miles per hour and with them 60 with a head wind or not...........I made my own vortex generators and am satisfied.............bottom line is too may will cause more drag.

I am sure this entire matter is and will be open to debate.

Your typical vortex generators are four inches apart and one inch from the edge of the vehicles roof

[NeilBlanchard]

Hello,

The kits for semis include 80 AirTabs, and I'll bet that you need 2X that to do both the cab and the trailer.

They recommend 3 per lineal foot, so the clear space between the rain gutters on the roof of the xA is nearly 3 feet, so 8 or 9 will fit there. The sides are harder to be completely even, so I estimated 6 per side. 9 + 6 + 6 = 21

[crexcrex]

Without going into depth re airtabs which are wannabe vortex generators.... let me say this they are for TRUCKS and i can count on two fingers how many trucks i have seen with them. Airliners use them for fuel efficiency but i have a crx and not an airliner thus the shark fin style for automotive fuel efficiency not to make my car look pretty and the center of attention.

As i said this is going to be a free for all re airtabs and genuine vortex generators which citroen uses on thier high end cars. Hopefully you have taken the time to read as i have and study the pro's and con's....................at three per foot they may as well be on the wings of a delta wing jet............

Those are my thoughts on the subject and i am sure there are many more to come pro and con.............airtabs? would not want any as they are for trucks............

Finally ...mount them and prove me wrong and you will see that you will have more drag tie that in with your mpg and you will know for sure

[crexcrex]

Re Canards.......ducks.......agreed they are for downforce and used in racing. pressure applied to the front wheel drive equals drag as the tires are stuck to the track like crazy glue.................ecomodding? pressure equals increased tire friction and you are looking at 5 to 15 percent fuel reduction due to tire deformation, heat, sound etc............for racing and not ecomodding. Once again another area to open to discussion, surely the pro's and con's will flow as freely as wine.