Hi All,

I have been thinking about getting some real world wind tunnel testing done on my car for a year or so, and it looks like I'm finally going do it this winter or this coming spring. I've found a good place with a full scale tunnel that has reasonable prices (as reasonable as a wind tunnel can be! ) and seems to be exactly what I'm looking for.

http://www.a2wt.com/

This place runs a larger wind tunnel pretty much dedicated to Nascar and Indy teams that runs 24 hours a day year round. Their smaller tunnel that I am looking at is geared toward racing teams with a more modest budget.

I have not decided exactly how I am going to do this yet. I could pay for it all out of my own pocket and keep the information to myself. I'll betcha that there are ALOT of folks out there, though, who would really like to get some aero data to help them set up their drag, time attack, or autocross car. Therefore another option, since I am not a buisiness and have nothing to sell to make money off this endeavor, is to share the cost with others who want access to the information gathered. Kind of like "hey, lets' all pitch in and do some EVO wind tunnel testing!" . . .

A third option is just like above, but to also let people or businesses loan me parts they want tested. You would then pay for the portion of the wind tunnel time testing your part took up. If the tunnel is $500 per hour and it took me 1/2 hour to put your part on, test it, then take it off - you would pay $250.

I am planning on videotaping/photographing smoke traces on key areas of the car and may even do the whole thing up with some tufts. . .

Anyway - I have a few months before making this final and I would really appreciate all input and feedback! What should I test? You've always wondered just what that XXX brand splitter will do? Does the stock wing really make any difference? Here's your chance to find out! Attached is a spreadsheet with some proposed tests laid out . . .

EVOlutionary

 

i don't have any products to test but i would be interested in helping you out so i can get he info on the stuff you have on your car now. my plan is to get the same dhp stuff that you got on your car now anyways. you can pm me more details when you are ready!

 

Id like some solid results on those APR carbon splitters. Id like to rub it in peoples faces that they dont do all that they think. haha

But honestly, Not everyone can afford voltex stuff, and almost all your tests have voltex. we all know its already wind-tunnel tested, so Id think tests on other options would be better. DHP composites make some really good offerings as well, and i see youre testing that too. good luck

 

I'm thinking of getting a DHP multi-element wing...might be interested in testing numbers before I jump and make the purchase.

Dave

 

I can work with David to have it on the car. He can probably make just the 2nd element and add it on to my current wing (the same as yours) to get some results. What I want to see is just how well that MASSIVE front end treatment you have on your car works!!

The reason I'm testing mostly DHP and Voltex stuff is because that's what's on my car. I want to find out how my setup works as a system for my own personal knowledge and benefit . . . the results can be applied to other parts as a generalization. For example - if the Voltex canards add DF to the front and take DF off the rear, you can pretty much assume any canards will have a similar effect, only in a greater or smaller magnitude. . .

I DO have access to an APR splitter on a VIII front bumper. . . I could possibly throw that into the test if there is enough interest. . .

 

I wish there was a tunnel of this scale around Seattle, I'd be all over it.

Make sure you write yourself a detailed test plan and stick to it.

 

David made mention that to do the 2nd element properly, he'd remove the large gurney flap on the trailing edge of the big wing. I beleve the big advantage of the 2 or 3 element wings is that they'll make the same downforce, but the drag will be reduced quite a bit. For slower speed events, it's probably not worth the extra cost, but I'm thinking the reduced drag will allow us to get closer to 125mph on some of the longer 'straightaways' at Pikes Peak.

I'd be happy to send you the canard assemblies for testing, but I'm not sure if you have provisions for mounting them. From what I can tell, I mounted my splitter ~3" further forward than normal based on tire clearance, which resulted in some gaps between the canard and the bumper. I'd be willing to bet that it'll fit near perfect on your bumper.

Dave

 

You going to test at AutoX speeds or circuit speeds?

 

I understand, Im just expressing that those are the two brands we know make real downforce

I wouldnt expect to see much downforce from canards, theyre actually used to create vorticies down the side of the car to keep laminar flow around the car, instead of the airflow sticking to the surface. The vorticies also help keep air from getting under the sideskirts, lowering under-car pressure.

Im interested, but for reasons other than wanting one

 

The canards he's talking about have both inside parts designed for producing downforce, then the outer canards are there for inducing the vorticies. I don't know what the technical name for the inner canard are, but they look like canards, but have a plate on the outside so that air is channeled up and over them. Used in conjunction with a splitter that has a couple degree tilt to it, they should help to balance out the big DHP rear wing.

As for the question about speeds, if possible, I'd really like to see both speeds in the 40-50mph range and also at 100mph or so.

Dave

 

Actually the big advantage is that you can keep the airflow attached to the lower surface of the wing at higher angles of attack thus increasing your downforce and drag.

If you're looking for lower drag but the same downforce you need more wing area running at a lower angle of attack. Using a 3d element that incorporates some spanwise curvature can also reduce the drag.

the 'dive planes' are probably your biggest drag contributor though. I'd ditch those first.

 

This tunnel maxes out at 85mph. I would do most testing at that speed, but would run one setup at probably 3 increments to get a rough idea of how things change as speed increases. Probably something like 40mph, 60mph, and 85mph.

You could probably use that data to interpolate what is going to happen at higher speeds . . .

On the topic of canards or dive planes. . . in the recent issue of Racecar Engineering they did a test on a Noble. The results are as follows:

. . . . . . . . . . . Cd. . . . . Cl . . . . . Cl-f . . . . . Cl-r . . . %front
w/o canard . . 0.502 . . 0.527 . . 0.128 . . . 0.400 . . . 24.3
w/ canard . . . 0.513 . . 0.521 . . 0.194 . . . 0.327 . . . 37.2

This is with a flat canard with no end plates. As you can see, although total Cl is reduced, the Cl on the front is increased significantly and the rear is decreased. This adds more front balance to the car. The reason it reduces Cl at the rear is because it "dirties" the air coming off it that eventually flows over the rear wing. . .

I would expect a canard with an end plate to have significantly more drag, but to also add more Cl to the front of the car. . .

 

The vortices may help keep the flow attached but they will not keep the flow laminar, quite the opposite. And generally you want the air to stick to the surface.

 

I may not have explained it correctly, you do not want laminar flow to stick, the vorticies keep the straighter flowing air from sticking to the surface of the car and causing drag. The vorticies are what sticks to the car surface. quick paint drawing:

 

explain to me how attached laminar flow creates more drag than huge vortices running down the sides of the car do?