Has anyone seen this product. It seems like it could function very well if used like the factory available vortex generator. It would also be more cost effective at $2.50 a piece. I have no knowledge of aerodynamics, so let me know what you guys think.

www.airtab.com

 

This is a great concept, and is generally effective if applied correctly.

Mitsubishi did a lot of wind tunnel testing on the vortex generators (VG) for the MR. They did not try this particular (Airtab) size and design, but worked with shapes that they had previous favorable data on. The key was to find a balance between the increased drag created by the VG itself and the decreased drag resulting from the pressure increase on the back deck area.

Looking at the Mitsu data, I would guess-trapolate that the Airtabs will be less efficient than the small OEM VGs, but perhaps create a stronger effect in the wake and a net decrease in drag.

Another benefit would be to get more of the flow down to the wing and increase rear downforce. I am working on a new rear aero package which was to include the OEM VG using their data...and now I will include testing on these Airtabs as well. For my design, I really need something that will create even more pressure behind the rear window than the OEM unit...hopefully the Airtabs will do just that.

Regards,
Ethan

 

That sounds like a cool project, take lots of pictures and documentation. It would be interesting to see the effects of different aero packages on lap times. What will your aero package consist of?

The size of the airtab does seem a little large for our use but I wouldnt really consider the evo a very sleek car to begin with. I would assume the car has a fair amount of drag and lift (even with the wing) in stock form. This judgement comes from looking at numbers for road cars from this website:
http://www.mulsannescorner.com/data.html

On the airtab website a guy used them on his porsche 914. He said they were worth half a second at button willow. This was with a big wing on the back.

 

I'm sure this thread will get moved to Evo Advanced at some point.

Yeah that is an interesting site. Sure, compact sedans are not usually considered slippery But there are several aero major problems with the rear of most street cars. The Evo has a pressure buildup under the rear, too steep a rear glass (creates separation and low pressure), and a wing that seems a bit bulky and too low...etc.

My plan is to reshape the flow around the entire rear section. Bring flow closer down the glass to the deck, onto a deck wing. I'll need to bring the flow up from the diff area up through a diffuser (smooth and accelerate flow) through the rear cover into a low pressure area behind the deck. Give the rear more of an effective teardrop shape. The diffuser will be the real key to reducing lift and drag...the deck wing is just a helper to pull flow up and out. I'm experimenting with an alternative to simply throwing a huge wing/parachute on the trunk as is common practice.

Of course it's a bit of a challenge on a car with such steep glass and short deck section but it will be fun experimenting...

 

Any more development on these ideas? Or does anyone else have any useful input?

SCC has a small feature on pg 88 in the feb 08 issue.

 

Anyone else thinking about putting some of these on their roof to see what happens? I'm game as the investment is low but I just don't want to mess up my paint... should not be too much an issue however? Thoughts?

 

In the old days teams would paste short ribbons all over the body then take pictures of the car at speed to examine the air flow. Now it must be done with computers in factory race programs. Car manufacture engineers have learn from passed acquired experiments (race car data) as that vehicle downforce website shows.

 

Well, not to jack, but I wondered how well the STi's rear window spoiler worked compared to the VG - Any smarties know?

 

I read about this in SCC. Seems to work but it's awful big, at least it looks big. I don't want to be the first guy to try it thats for sure.