Opinions on VGs
 

As expected, my experimental vortex generators didn't survive the winter. So, I'm going to try out replacing them with ones made from tent stakes. While looking for black plastic ones, I found some long steel stakes. I might be able to get three VGs out of one stake, which will mean saving a little cash. Plus, I can buy them individually, and am not limited to getting 4 packs.

Painting is required with both types. The only plastic stakes I found were bright yellow. The metal ones will need it to prevent rusting. So, between the two, which would you use?

Plastic. It's easier to work with (mostly), and if they come off they will do less damage to anyone behind you. You would need to use adhesion promoter to make paint stick, unless you get paint made specifically for plastic.

I like simple

How would you install them?

I used aluminum flashing and stuck them down with silicone caulking. Been on since last summer and they're not going anywhere. If you can, let the car sit for a day or two just to make sure they're really on. There was a bit of wiggle for a few days so just make sure they haven't moved. You can cut the flashing with a decent pair of scissors and clean up the sharp corners with sandpaper or a file.

I chose the second design (black on a blue roof). Half an hour with a sharpie, a protractor, scissors and something straight to fold it against. Paint them and sick 'em on.

[URL="https://www.gassavers.org/showthread.php?t=1482"]

BTW this is the mod that brought me here.

I was leaning towards the plastic without considering the possiblity of them coming out while driving. The metal stakes I found are a heavier gauge than flashing.
My old VGs were delta wings cut from the wood paint stirrer sticks. Attached them with double sided tape. Except for the cheap spray paint starting flake off, they held up fairly well. I didn't start losing them until I had to pull out the snow broom. If given a wider base, they might still be on there.
I should check out the aluminum flashing. I didn't because I thought it comes in rolls or sheets and would have to be folded into the L shape. Those plastic/metal strips used to protect wall corners are another consideration.

I'd be sort of nervous of the steel unless it were attached pretty solidly.

Did a quick search and there are some pretty inexpensive vortex generators out there for sale. Not sure how good they are, but it's a thought.

IMO, VGs are pretty well into the "Never pay anyone for them" category; you should DIY or skip it.

trollbait, you are familiar with some of the other threads where people have posted their DIY VGs? The one that comes to mind is from someone who made them from CDs.

Some are less than $20. Of course they might suck.

Make 'em. It's easy.

Don't be nervous about steel 'cause they're aluminum. No rust and super light (for better FE).

And cheap. Made mine out of scrap.

Plus they make that cool pattern on the window with a dusting of snow. It proves they MUST work!!;)

I didn't see the one about using the CDs, but I'm using the post I believe SloSaturn used as a guideline. The HHR has the squared back end, so I was going to try the the basic 4in strake at a 15 to 20 degree angle along the edge. Likely have some on the sides also. Depending on how much material is left over, maybe even do some tuft testing on the hood.
Found a can of plastic spray paint at home. The safety angle was the deciding factor, but this helped. An inch height is recommended for the VG, so I'll check the tent stakes and corner protectors dimensions. I'm guessing the protectors will win out on price, but the tent stake tips would look better on the hood.

I opted for making mine out for .020 sheet aluminum and mounted them with 3M indoor/outdoor double sided tape which covers the entire bottom surface. These suckers are not going anywhere. I think the key it to prepare both mating surfaces properly. Dont paint the bottom surfave of the DIY VG's and throughly clean the rooftop surface with alcohol.


https://www.fuelly.com/attachments/fo...577d791918.jpg

https://www.fuelly.com/attachments/fo...31778a571a.jpg

Looks great!

Did you do any tuft-testing before installation?

Do you have a gaslog before installation?

Yeah I did the tuft testing before and after installation. I was amazed at the tuft test results before installation. At 15-20 MPH the tufts started dancing around in all directions. At 25-30 the tufts actually started to move UP the window, opposite direction of "expected airflow". I only drove about 1 mile reaching 50 MPH before I realized just how messed up the airflow was on the back of my Mustang.

So after I installed the VG's and did the same drive test, they layed down perfectly as the sir was flowing over the back of the car like it should have been. So the VG's worked perfectly.

Since my VG's are kind of a DIY rip off of the Airtabs, with similar dimensions, I used the Airtabs specs for spacing. Spaced 4" on center. But I screwed up my count on the manufacturing. My roof width at the install point was 48". So I would have needed 11 VG's spaced 4" to cover the roof properly. At first I did 9 of the spaced at 4" and had a 6" dead zone on the drivvers side. Sure enough, I had some drivers side tufts that acted erradiicly. So I busted out the sheet aluminum, stencil and shears and made 1 more. I then respaced the 10 (should have been 11) to be like 4" then 4.25" then 4.5" on center to span the width of the roof.

As far as data...

I have only collected a small amount of data with the VG's. Only 4, 1/2 tank runs. So, only time will tell the real deal. As a side note, these 4, 1/2 tank runs were with my stock 5.0 Mustang spoiler removed. I did not want to damage it while standing on the back of the car installing the VG's.

Before VG's 22-27 MPG
After VG's 24-29 MPG

The results are promising. And I have noticed that the back of the car feels more stable, even without the spoiler,. I've had this Mustang for 10+ years and have completely rebuilt it from the ground up to be a road racer. However, it is my daily driver so a ANY minor difference in the handling or performance is something I pick up on right away.

I am new to the forum, but will keep with it and post any relevant results as they become available.