With another wind tunnel test approaching it might be helpful to throw out some ideas that the guys can test; this thread will provide a place to share those ideas.
I've had a couple ideas rolling around in the back of my brain for a while, things like splitters with airdams on the leading edge, trying to increase airspeed on a flat floor, etc. All have more to do with the underside of the car.
Here are my ideas:
1. Splitter with airdam on the leading edge. I think this will work better for autox types of situations where the speed differential of the air going under the splitter won't be as significant. Since the windtunnel air speeds are pretty low where you guys are going, I think this would be a good spot to test the theory. I think Cameron actually has this setup so that all he has to do is bolt it on. Not sure if he will be part of this though. This was recently tested in Race Car Engineering on a Porsche, but the airdam they used was still 3-4 inches off the ground and not surprisingly it produced worse results than the splitter alone. I'd like to see it tried with an airdam 1-2 inches off the ground. A variation would be adding dams to the sides of the splitter. This could be fairly easily tested by taping a cardboard strip to the edge of a splitter, with some triangular cardboard braces on the backside to keep it from folding under pressure.
2. Splitter with diffuser. The NASCAR COT's used a diffuser after their splitters. This diffuser was about as simple as it gets. It was just a piece of aluminum mounted at an upward angle at the end of their splitter. Their splitters were very short, and the diffusers were too. If there is room, it would be interesting to try a 12 or 18 inch long piece of cardboard at the back of the splitter, just tape to the splitter and then tilt up towards the rear. The COT had a very rough bottom so you wouldn't think that a diffuser would work, but they were talking about 80 lbs of downforce difference based on the angle of the diffuser in a video I watched. Variations on the angle of the diffuser could be checked.
3. Ground effects. It's really tough to do an aero bottom on a Z because of exhaust and drivetrain clearance, but it might be possible for the guys with larger diameter wheels to do it, particularly if you have very stiff springs. I know 74_5.0L_Z is running at about 2.75" from the bottom of the front crossmember to the ground and not bottoming with spring rates in the 400s IIRC, so if you have 5 or 6 inches to the lowest hanging piece, you could drop a floor down a few inches and still not scrape. Flat bottoms are usually mandated by rules, but aren't the best option. Contoured floors are better and obviously more difficult to fabricate.
3a. Contoured floor. Splitter with diffuser into a second venturi into a rear diffuser. Basically we're talking about aping a LeMans car, mulsannescorner.com has plenty on this if someone wants to try it.
3b. Flat floor. Much easier to make is the pro here, and theoretically much better than the rough bottom with the drivetrain and exhaust hanging down. It would be awesome just to test the flat floor/diffuser setup, but I have a couple variations. The idea behind the contoured floor is that you're creating a venturi by getting the floor closer to the ground and narrowing the opening for airflow, causing the air to speed up. If you have a flat floor, what is to prevent someone from using fences on the bottom to narrow the airflow passage on the bottom of the car and get the same effect? Essentially I'm talking about more airdam material, and making a venturi shape on the bottom of the flat floor. This could be tested with aluminum 1/2 x 1/2 x 1/16 thick angle (easy to bend to shape) double sided taped to the floor and then the cardboard fences could be taped to the angle. A further variation would be to add air from in front of the rear tires to the venturi. I think there would be a decent amount of airflow to tap at that spot, particularly if there were dams pushing air out to the side of the car behind the front wheels, as I know Mike Kelly and others either have or were planning to have.
All of the above can be tested pretty cheaply and easily. These drawings are not to any scale or anything, but I think they might help to conceptualize the overall ideas. Red or blue is a fence that could be tested with cardboard and actually be put on the car with airdam material (plastic lawn edging is what I would use).
4. Spoiler/wing combos. It is pretty well known that a spoiler and wing can be more effective than a spoiler or a wing alone, but I don't think there is a hard fast rule about what size spoiler makes the best result, so that could be tried, in particular testing the amount of increase in AoA on the wing before you get separation on the bottom side with and without the spoiler would be helpful. This would probably be useful only on the car that was tested, but if my car were going in there I would definitely want to do this test.
5. Front fender contour. I doubt anyone will do this, but I'd like to see a Z with the front fenders cut and folded in behind the wheel to the wheel well, imitating what you seen in Spec Racer Fords, Can Am cars, etc. It's not a new idea and we know it works, but I'd like to see what the result is. Would require cutting up a set of fenders and making a fender liner so that air didn't get past the opening and trapped in the back of the fender, but fenders could be grossly cut and cardboard used to push in behind the wheel and make a crude fender liner as well.
6. Fender top vents over the front wheels. Preferably alligator tooth style.
7. CFD. Anyone ever considered putting this money into a CFD model? Not sure how much that costs to do, but if you had a CFD model, you could test infinite variations without going back to the tunnel.
Edited by JMortensen, 05 June 2013 - 10:31 AM.