Is there any new experience to report, about the effectiveness of using Vortex Generators?

No track time since the April event. Going back to Buttonwillow 6/23-25.

Will be able to get some lap times to do a 'before & after' with the AirTabs.

In any case, for an investment of only $27.50, they sure look cool! (see #52 in the background)


Click to view attachment

I am ssssoooo waiting to see if there is any difference with Air tabs.
I am just about ready to get them just for the cool factor.

For the June event I'm going to get some times with the airtabs, then switch tops with #25 and compare the times.

Without airtabs I can't stay full throttle in 5th going clockwise through the riverside turn. Rear end gets way too light and starts 'dancing'. Got my fingers crossed that the vortex generators will help get some air down to the rear spoiler!

Man I wish I lived in Kalifornia. That is WAY bigger than NPR in Lousianna.

i saw an EVO with vortex genorators on its roof yesterday...

Well so much for that shit. If the ricers guys start putting them on then I will keep them off.

UNLESS someone has evidence of it really working. then I will just paint them flat black like the targa top.

That will be interesting to see if it really can get an effect down to the spoiler. Vortex generators work best with wings, or a rear spoiler/tail section that is high enough to have the tumbling air move over them.

My good friend I met in college works for Honda now, but previously worked for a couple of Indy car design places and he really knows a lot about aero, and he doesn't think it would make any difference with the spoiler with the way the rear is designed, though it may help with the overall lifting issue. I didn't really notice the lifting with my car until I was up around 130mph or so on the front stretch of Willow (I don't think you go that fast at Buttonwillow unless you remove the bus stop and go straight down the back). My car got a bit "darty" around 130 to 140-ish. I have a 6" Sheridan spoiler and was talking about adding those tabs to see what would happen and he said maybe with a spoiler that tall, but thought controlling the air under the car would be far more beneficial than the airtabs.

We both agreed it was worth a try though for $30. I am adding a wing to mine, so I will be getting those tabs as well and have 2 lids, so I will tab one and leave the other stock to compare. It will be awhile for me though... my friends rented Buttonwillow this Thursday and I thought my car would be done, but I have had a one-month setback that is just killing me That would have been 8hrs with only 14 other cars, but oh well!

Where do you get these babies?

Here is a link that was posted elsewhere
http://www.buyairtab.com/index.php?main_pa...054559679f89fc2

A friend of mine is a retired engineering professor and we were talking about the vortex generators at one of our Porsche Saturday AM get togethers. He is very well known and respected in the engineering and PCA racing communities.

Here is what he said after I showed him a picture off the internet:

"What this picture shows are a type of vortex generator but these are WAY to
large! The next time you fly look out the window of the aircraft about where
the engines are mounted below the wings and you will see a row ( or two ) of
small one or two inch high hat appear to be tiny wings sticking out of the
wing and with a small angle to the flight direction. These produce vortices
which help keep the flow attached to the wing and increase lift

The add-on's in the picture you sent may make the owner happy but will only
increase the drag. I can't see that they will produce any help for any
thing."

wow, talk about a bummer.....

That last post kind of takes all the fun out of it...

...Except, our cars don't go 500mph.

I'd like to see some wind tunnel pics.


KT

I started this thread, because I had intended to install the Factory Mitsubishi VG. The ones you are referring to are designed for Semi's, with long straight, flat panels. As I understood, they were trying to get clean release at the rear, to lessen drag. The smaller version on Mitsu. were developed, not just eye candy. There design is to keep air attached, reducing lift, and or keeping air in the vicinity of wing/spoiler.
I still think there is potential for improved stability at speed.

That would be the EVO MR Edition. Comes from the factory like that. And they aren't just for looks either. The MR outperforms the Subaru STi, unlike the stock EVO.

I'm sure the stick on airtabs wouldn't do well at 737 speeds. Not sure if the airplane devices work well at ~120mph ?


Here is the 'operational concept' from www.airtab.com




Here is how my roof turned out
Click to view attachment

Will this help get airflow to the rear spoiler? Don't know... but worth a try for $27.50. The with & without laptimes will tell the story!

I'll post back after our June BW event.

I am very interested to see what you determine! I think the best way to know how well these work for you is if you can get up to high mph in a sweeper turn. BW only has one and it isn't really that long (not like T7 thru T8 at Willow Springs). If you get better rearend grip and can get a higher mph thru a sweeper, then those tabs are working. To clarify - if the car wants to oversteer at 105mph without the tabs, but you can run through at 105 or faster without oversteer with the tabs, then they are working.

I agree there will definitely be more drag with their size. The issue always exists with anything aero - how much drag can you handle v. increase to handling performance (though on a smaller degree with smaller generators). If you have the HP to pull the generators through the air, and they help you go faster, the driving benefit outweighed the drag cost.

Getting the air to tumble over the rear section of the car may just be enough to reduce the crazy lift the car creates otherwise. I will gladly pull them through the air to get that benefit. Hard to say without a wind tunnel (which who has one of those ) or just some good old fashioned testing. BTW, if you have a full scale wind tunnel in the SoCal area, you are my new best friend!! Probably have a whole new club of best friends

Speeds below 100mph are probably worthless as the car doesn't experience a bunch of lift at the rear anyway. Hard to hit speeds much above 100mph at BW though, just through the bus stop and the sweeper after it. But they go by so fast...

BEST OF LUCK - if they work a lot of us will benefit on the larger tracks like Willow Springs!

I'm going to say they make an improvement.

KT

numbers will tell.
all else is conjecture.

They're cute!

Unusual observation for a Race Forum, reponse?

They look cool, I hope they have some benefit.

So any word on the track testing?? Faster slower or just cute sorry cool.

There seems to be a couple of potential solutions, Subie rear window diverter, Mitsu vanes & these vortex generators. I wonder if any really work in our targa configuration?

Where can I find the Mitubishi vanes? at least a picture.
Subie window diverter?
I imagine something in the middle size wise.
Then test it old school tape a bunch of yarn on the deck lid and up the duck tail fin.
I am sure the caw catcher air dam make my car more like a brick through the air anyway.

Vortex Generator test this weekend!

Running Friday-Sunday @ Buttonwillow and will be running stock & the 'vortex' top to get lap times.

Should be fun if the 4 holds up in 100 degree plus heat!

Looking foward to the results

KT

I was searching around and found Vortex generators used on airplanes.
They however wer putting them on the leading edge of the wing in an effort to keep air flow against the control surfaces.

Little bitty things not more than an inch high and 2-3 inches long.
My point is I guess the results or affesct depends on where you place it.

Results are in!

914 Vortex Generator Test, 6/23-25 Buttonwillow Raceway, Track Configuration #1, Clockwise


Subjective results:

Observation #1: Substantial difference in the rear end feel going clockwise around the Riverside turn. Previously the rear would get very 'light' and start twitching around through this turn, limiting throttle to about 50% in 5th. With the vortex generators I could actually feel the rear end 'squat' over 100 and could keep about 90-95% throttle through this turn! Appears that the vortex generators are helping reduce the air turbulence behind the back window and getting some air flow to the rear spoiler.

Observation #2: Previously would only have to 'lift' exiting Riverside to make the R to L transition going up to Lost Hills. With the increased exit speed from Riverside, this is now a 'brake' (a 'tap' is not enough! Almost went farming the first time through )

I was not expecting this much difference. As a matter of fact with all of the feedback on why this wouldn't work, I was wondering if I would notice any difference at all. I'm very happy with the results


Objective results:

Times showed a 1/2 second improvement, or about 6 car lengths through this section. I'm sure there is more out there as I work with this new setup.


Summary:

Even if the times did not improve I'd keep the vortex generators just for the increased stability and confidence in high speed handling. The rear end skating was too much 'excitement' for me...

Question now is, will the increased drag slow me down on other tracks?


More info on the AirTabs I used at: http://www.airtab.com/

Hope this test and results was of value to some of you!

Thanks for the update.

I would like to try them.
Are they adhesive applied?

Removable?

Thanks, again.


KT

Hey KT,

They come with double sided adhesive tape. Just a peel and stick installation.

Definitely worth the $27.50. However I'm still wondering what the effect will be for the tracks where I did not have high speed issues. Buttonwillow is the only track I've run so far where there is a 5th gear sweeper. Most are just straights at that speed where the car was ok without the vortex generators....

Greg

Awesome. They *should* increase top speed too by reducing all that drag in the rear end....keep us posted as you get more experience! Who's going to build a targa top with the smaller vortex fins??? (like on the Evo and another, yellow 914 racer I've seen a photo of)

The AirTab site has a new photo showing airflow off of a 'square back' roof configuration . Good pic of how it helps get air down to the rear spoiler on a 914..

Greg - it's good to hear they were working for you. Not to be too much of a devil's advocate, but did you swap the roof with the stock one from the Orange car to see if you could directly correlate the advantage being the tabs? Just asking as you mentioned you planned to do this...

This rules out any advantages possibly gained by track conditions that day v. previous days you have been there (tires stuck better, less/more wind velocity at a different direction, etc).

I think they are bitchin' and intend to get some for my car, but just wondering if you did a direct comparison within the same day with/without.

Im going to buy some...

Good question! I did try both tops. With the stock top the rear end still gets light and twitchs.

Next experiment is to see what happens to my times at tracks without a high speed sweeper. I'm thinking I might need to use the stock top at Laguna, Thunderhill, etc. if the extra drag of air to the rear spoiler slows me down. Probably only need the vortex generators at Buttonwillow, California Speedway, etc.


Let me know how they work for you

It will be a few months before I have my car back together, but I have 2 tops and will have a huge rear wing at roof height. I intend to try and see the difference on Willow thru T2 and especially T8 sweepers in terms of how they help/hurt airflow to my wing. I have never had a wing before to begin with, let alone tune the airflow to it.

Considering the big difference they seem to make for you, I suspect that they may even reduce overall drag for you. The tabs add a little drag by punching into the air, but the fact they are apparently combatting the mess that typically happens in the area behind the rear window that wants to lift the back up, they may actually reduce overall drag. Hence why they work for semi trailers to begin with - they drag thru the air but fix the vacuum behind the rear that sucks the truck backwards, hence reducing overall drag and increasing mileage. For us, screw the mileage - we hold power constant (WOT ) and go faster.

At least that is the plan, right Thanks for letting us all know how it worked out! This may help a lot of us fellow racers quite a bit. I removed my huge spoiler and went to a wing because of lift issues - maybe the spoiler would have been enough if it was actually working. Too late for me find out...

BTW - nice looking car too! Both you and Trekkor have 2 of my favorite, great looking "non-flared" cars.

Anybody tossed them under the car, say in front of the engine on each side and notice a reduction in head temps? If it works well up top, it should work down under so to speak.

essentially what the "flaps" do..... you thinking these would improve over the stock flaps?

AA

Possibly YES, looking for any advantage I can find, if it helps at 7.50 a side I would do it in a heart beat, I have the stock flaps installed, but will be switching to a bigger engine, and want the additional cooling help any place I can get it.

I know Joe Ricard mentioned it somewhere between the 27 914 boards we now live on, but I have not seen numbers. You know with out flaps my head temps where 345, with them I am now running 325, with vortex generators, I now run head temps at 0 degrees Kelvin

Absolute zero could be fun brings up a whole new set of problems thou. But I could stop paying to have parts cryroed!

from a science/engineering standpoint.... thats way funny LOL

Have a look here:

http://www.prfprod.com/

These are much smaller than the AirTabs and come in sheets 12" wide with two, three or four rows of VGs. Four sheets will do the roof. I've ordered some of the two-row type to mess with and will let you know what I find.

These look like the same ones that are on the yellow Wayne Baker car that you might have seen at the track...

Hi Mike,

Those do look like what is on Wayne Baker's car




I've been happy with my setup. Anxious to hear your results.

Here is another vendor that I just came across recently. Closer to aircraft style



http://www.vortekz.com/

Greg

I took the photo, so I can answer the question. Yes this is the car he drives. He explained to me someone else owns it.