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Airtab Vortex Generators and testing

5K views 5 replies 5 participants last post by  dingo7 
#1 ·
Hmmm.. This is more informational than a product review but I couldn't find an "aero" section on this forum.

Okay, so the testing methods and equipment aren't that awesome but here are some data and conclusions I've gathered. I'll be quoting from my blog post. Please check out the link for more information.



First Test
I first did a "lab test" using a differential manometer. This manometer works by measuring the air pressure differences at its two nodes. I mounted one 3.5 inches away where the spoiler edge meets the trunklid, and another node at the rooftop. Now, I have no idea if the rooftop is an accurate representation of ambient pressures or whatever pressure that acts with the spoiler pressure to generate lift, so I won't be able to calculate accurate lift figures. But it would conclusively tell me the differences between the two tests. So, in short, it is perfect for comparisons.

My first test was a failure. I mounted them 2.5 inches apart (thats 6.5 inches apart from center-to-center), about 13 inches from the rear edge of the roof--at the maximum manufacture recommended parameters. The test results weren't that great. I found out position of the VGs are pretty critical. Although the first test showed that the VGs were not working, I've seen this particular design work from different tests on the internet (link), so I wasn't convinced. I had to do another test with adjusted mounting positions.

Unfortunately I had to return the manometer before I could do another test. School was starting soon too, I was running out of time. I decided to do the second testing on the track.
At the last track event, I ran two consecutive sessions on the same aero settings, one with and one without four Airtab® VGs installed much closer to the rear edge of the roof, about 2.5" apart between the VGs. The VGs are supposed to be installed 0.75" apart, but I just wanted to do a quick and dirty test. I placed them in the center 2 feet of the roof, and ignored the edges since my spoiler probably generates the most pressure in that area.

Because I don't drive at pro-level, it was really hard to analyze the data from my amateur-level DAQ setup. Fortunately, temperatures, fuel levels, tire wear were all at a similar level because I didn't waste much time between sessions. Unfortunately, and probably because of my inconsistent driving, maximum velocity of both sessions and best laptimes are equal. What to do? After staring at my charts for a long time, I decided to look at a sector laptimes for turns 2 and 3. These turns are constant radius, and I am fairly consistent here, and I take the same line every time I go through it. Perfect.

Sector times, Averaged
Session with no VGs: 13.22
Session with Airtab® VGs: 13.15

Samples were from six runs each with and without the Airtabs®, with one or two outliers removed from when I was doing warm-up and cool-down laps or when I made a big driving mistake.
The 0.07 second difference in this section means there was an appreciable amount of lateral force generated. Calculations based on this data show that the increase in lateral force, or grip, was 1%. I got the answer of the question I've been asking for months; They work!
My best use of the VGs was not necessarily to make an huge difference in available traction through radically increased downforce levels. Yes, the Airtab® Vortex Generators made the car faster, but it also allowed me to adjust the car's balance to inspire more confidence to drive more consistently. More consistency = more improvement!
Installation is very simple. Plot out your mounting points, mark them (I use painter's tape), remove backing and stick them on. They can be painted also.

Remember the original intent of the Airtab® vortex generators. They are supposed to reduce drag. I'm sure they are doing exactly that on my car for a certain extent, but a car with a spoiler is not the best platform to test that on.
Other notes: Total laptimes went from 62.8 to 62.1 in the same day. This includes adjustments to tire pressure, however. Last fast time from another session was 62.4. Temps were 5-7 degrees higher that time and tires weren't heat cycled as bad. I'm still on old Azenis and these guys age fast each event. Test area is about 13 seconds of the entire course.

One thing I wish I had done is my own tufts tests. I just relied on Keith-FM's statement that flow separation begins about 1-1.5 inches rearward from the edge of the rooftop.

Links to manufacturer:
Aerodynamic Fuel Economy Savers for Road Vehicles
To purchase
Airtab - Airtab® Improve Stability, Reduce Spray, Save Fuel

If you do buy some, please note that I referred you :) I don't get paid anything for this, and I solicit all of the products I want to review, but I'd like to have some happy people around me so I have more leverage when I move on to bigger, more serious things with real money sponsorship involved.
 
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#4 ·
Other notes: Total laptimes went from 62.8 to 62.1 in the same day. This includes adjustments to tire pressure.
There are so many parameters that could be different between your laps not to mention the most major one - your driving style. I don't mean that on purpose you tried to skew the results but it's always better if the driver is not aware if the thing is attached or not.
Anyway the best way to test it, is the mythbuster's way. Measure gas and do a long straight line measurement of mpg with very similar conditions.

My feeling is that even if it's effective it would definitely not make a difference on 0.7 sec on a 62 sec lap - The tire pressure on the other hand can make a huge difference.

If you do buy some, please note that I referred you :)
:fp:
 
#6 ·
Holy fucking variables, This is old news and started on the evos. They just help disturb the wind to create a bit more downforce. If you want them to work just take the measurements off a mitsu vortex generator.

 
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