So, I'm working in Mojave and Edwards AFB this week. Aerospace geek central. Spied a modded Miata in the parking lot of Scaled Composites today with carbon fiber VGs. Thought it was interesting. Pictures:

 

I think it looks terrible, and I really question if it does anything how it's set up. Are they supposed to smooth the air into "channels" or work together with a rear wing? I ask this because they spawned on Evo's originally from what I recall, and their wings are huge.

Also the Evo's don't have them in a "flying V."

 

Vortex generators are an effective way of keeping flow attached to a body where curvature would normally cause flow separation. Typically used on aircraft to improve stall performance or tail effectiveness. Next time you're on a 737, peak out the window, there will be a line of them ahead of the ailerons.

To actually work, they need to be optimized for a certain design point (speed) and boundary layer thickness. Not really suitable for a car (well, maybe NASCAR or land speed records).

In this case, purely stylistic. If anything, it would increase lift, not what you want for turning. What we have here is a guy that works with carbon fiber all day and is a fan of aerodynamics doo-dads -- so he's expressing himself.

 

so he's a m.net homo in other words?

 

I hope his chamois cloth tears on those when he's drying his car.

 

I would have to argue here a little bit. While they should be optimized, and will perform the best at some optimum design point, that doesn't mean they just quit working off of design condition. I also don't see where you would get the 'increasing lift' idea. By tripping the flow into turbulence, it follows the line of the hardtop along the window and the trunk a little better. When the flow separates, you get a low pressure region around the bottom of the window and start of the trunk. Low pressure above the car = lift. IF the flow sticks to the surface better, it helps get rid of that low pressure area.

 

The real question is: Is Burt wearing shoes?

 

Great way to ruin the other wise good looking car.

 

I don't have the source handy to cite (or the motivation to go find it just to dispute you), but I have seen evidence that the vortex generators on an Evo (with the OEM rear wing) and other production based cars (using wings) are effective.

It's entirely possible that those are useless cosmetic doodads. It's also possible the guy has guesstimated (or even done something more extensive) a useful position and uses them with a wing mounted on a separate trunk for track days.

In other words, while it's possible he is a poser, I don't think it's as self-evident as some would like to think.

 

I will reserve judgement until we see a picture of the mouth opening checking for the presence of an intercooler

 

To me the way those "VG"s are arranged they will do close to nothing, and thats before we talk about its effects on lift. In the EVO paper (that I think we all read) they are arranged 15 degrees or so to the airflow.

I have wishbone VGs on my car. My goal was to have attached flow get more air on my spoiler (7" tall lexan @ about 60 degrees, adjustable) and trunklid area to generate more pressure on the trunklid. While I have some data showing it did create more pressure, its inconclusive and I need more experiments with different equipment.

From what I gathered talking to Andrew B. on the phone about it, and the reading I have done while VGs definitely energize boundary layer for it to attach better, because they are attached to the rear windshield, they can also create upward lift also. So some or all of additional pressure generated on my trunklid may be negated. Or maybe not, but the point is that it is impossible to tell with the equipment I have access to. The car did feel like it had more rear end grip though, and track data shows this but once again, inconclusive.

I think VGs will benefit cars with airfoils. Probably less effective with spoilers, and probably good for nothing if you don't have any of those devices. They probably do reduce drag though, while increasing upward lift. Maybe he just wants to get better gas mileage.

I'm putting in an airfoil, so the VGs will do more good there.

I wonder why he has it in a V formation. Mine look way more rice than his btw. Looks like this, feel free to laugh!


I have a write-up about them I wrote for the guys who provided me the VGs. I'm pretty optimistic in the post, and I do believe they worked for my intended purpose. But I wouldn't call my data conclusive by any means and I wish I had the patience, time and money to do another test to make sure they work to increase downforce. But its really hard to properly measure pressure generated with the equipment I used when I have votices coming out of the back of my car (differential manometer) unless I get a proper pressure measuring device. What I should do is measure suspension travel with and without VGs but no flat, bumpless areas where I live :(

Anyways, thats my input to this thread.
Link to writeup:
http://hikickracing.blogspot.com/201...enerators.html

 

i think they would be more effective if they had a spoiler to direct the air under . ie the evo mr s

 

Yeah, mine does have a spoiler but the funny pic in the OP doesn't. However, even with a spoiler, VGs may negate some fo the additional downward lift generated. I put my money on "yes downforce from VGs + Spoiler > downforce from just Spoiler" though, based on my rudimentary tests.

I updated my blog with tufts testing results.