vortex generators in front of rear wheels

[JeffD]

Another VG data point to throw into the mix....
I tried Vortex Generators in front of my rear wheels and attempted my first ABA testing (Actually BABA). Found a flat stretch of road, 54 mph using cruise control (never shut the car off so it was the same each time), no AC, relatively calm but humid out. Couldn't help but have a few cars passing me going the other way. I don't know where other folks live, but it's hard to find a good testing spot around here.
Anyhow, these are the numbers:

With VG's
North: 29.8, 30.9, 29.4, 29.6
South: 31, 30.4, 29.9

W/o VG's
North: 30, 29.6
South: 30.7, 30.5, 30

I don't see much difference.
Has anyone got data for VG's in front of rear wheels?

[Sporty Modder]

So I averaged out your data points
30.179 with vg's
30.1 wo

There are not enough data points to get a real feel for the advantages/disadvantages.

[CitroX]

usually vg's make very little difference on cars thus it's hard to see a difference in mpg. And I doubt that putting them in front of a wheel is a good idea. Covering the wheel arches or adding some flow deflectors would give a better result. I would try tuft testing.

[ChazInMT]

As I keep trying to point out when I see VG Gimmicks discussed, Skin drag is not the enemy of fuel efficiency with vehicles, it is pressure/form drag that we must address.

By messing with air only an inch or so away from the skin of the car, air which is already decidedly non-laminar...meaning it is already vortexing...these devices accomplish nothing.

If you want to improve your cars aerodynamics, you need to make changes in the shape of the car, this will affect the pressure, hopefully reducing drag.

Buffeting the buffeted air 1" from the skin of a car which is creating effects on the air many feet out from the skin in every direction is like wondering why the flow of a 6 foot deep river isn't changed by more than a tiny fraction if there is a stony bottom or a smooth one.

When you look at VG's in the big picture, they're a joke. You will never gain a discernible change in fuel efficiency with VG's alone.

[euromodder]

In that position, I'm not too sure what the VGs would or could accomplish.

Creating an air blanket over the wheel well is a bit too ambitious, I'm afraid
A cover for the wheel arches would have more effect.

[Xist]

Originally Posted by ChazInMT

When you look at VG's in the big picture, they're a joke. You will never gain a discernible change in fuel efficiency with VG's alone.

We need to sic MythBusters on them!

[sendler]

Originally Posted by JeffD

VG's in front of rear wheels?

The vortex generators may be too close to the wheel openings to set up a good stream along the panel before it disappears. try moving them forward a foot.

[Frank Lee]

I'd try moving them back about 5 feet.

[JeffD]

Should have known I was in for it . The idea was to add a bit of turbulence to the BL to get past the wheel well without flow separation. Thought it was worth a try. At least give me style points for using painters tape that matches my truck so well .

Maybe it'd work better if I was going as fast as a jet instead of 55? Anyhow, just a data point in case anyone else was considering it.

Closing off the arch would be better, but not sure I'm that ambitious.

CitroX: I am curious to understand what you mean by flow deflectors. Something like spats?

[euromodder]

Originally Posted by JeffD

Should have known I was in for it . The idea was to add a bit of turbulence to the BL to get past the wheel well without flow separation.

The wheel well is a very high turbulence area - bad aerodynamics and a spinning wheel ...
VGs will have a tough time fighting all that existing turbulence.

It wouldn't be easy to design and position VGs to blanket the wheel well.
If it's possible at all ...

Maybe it'd work better if I was going as fast as a jet instead of 55?

On aircraft, VGs are used to keep the airflow on the wing / fuselage.
In front of a wheel arch ... there's nothing much to keep the air onto.


Did you decide on the truck's color to match the tape ?
That's dedication