In short, yes! Everything goes to the wind tunnel. But are they sharing... unfortunately no.

 

The car definitely gets light in the rear during high speed sweepers. Quite a noticeable difference (for me at least) even just riding in an S2000 with a wing and one without on the same track. There is a thread on here someplace on the big a** wing that Jason R. created with driving impressions from different drivers. That is the thread that first got me thinking about a wing. A few ride alongs have made it pretty clear as well.

hmmm ... maybe I should go for the 70" monster!?

 

the number (if my memory serves me correct) that has always been thrown around by jzr is 90lbs of lift at 100mph.

 

Does anyone know the respective angles at the glass for the soft top, honda hardtop, and mugen hardtop?

I was reading in the McMillen book on race car vehicle dynamics and their were some interesting points made about aero. One thing they mentioned is that air will not fully follow a rear profile with more than a 10 degree angle on it. However, it will follow somewhat up to about 28 degrees. Then you start to just create huge turbulence and drag from 28 to 32 degrees. After 32, you actually create less drag/turbulence/lift than at 30 or so because the air doesn't even "try" to follow the body anymore.

Just from glancing at it, it seems like the honda tops might be very close to that 30 degree turbulence problem McMillen mentions.

Anyway, it would seem to me that to find the best minimum height for efficiency of the wing, you would want to create a line at a 10 degree downslope from the top/back portion of the roof and then make sure your wing is at or above that line.

JZR? Thoughts? Did I basically explain it right?

 

Well, first off, it's Milliken & Milliken - McMillan prints high school textbooks.

The higher up the wing gets, the more rear wheel loading (and front wheel lightening) occurs as the result of the drag force's moment about the car's cg.

While I think there is truth to the rear profile studies, in action things are a bit more complex, especially on a production-based car. Think of how the effective profile changes when going from full throttle to threshold braking with soft streetable springs - it changes at least a few degrees, though maybe less on a stiffer car. Then there's the bars that hold the soft top, making the roof surface not so smooth, who knows what that does to airflow. That the Moon Racing (I think that was the team name, some sort of JGTC race car) built a hardtop that slopes nearly all the way to the rear of the car is telling.

As much as I like researching and putting book knowledge to use, I still think the best bet here for the layman would be to eyeball an initial setting and iteratively go from there. A wing with a mount adjustable for height as well as angle, along with a large-diameter skidpad (aka T2 at Willow) would be valuable tuning elements to find out what works best for the car.

The AABAUW on Davepk's car in OTC '03 was just right in T2 at Willow Springs - all 4 tires right at their limit. In T8 it was a bit too much, but the sense of security was nice at 140+. Unfortunately, T8 at 140 without the wing was NOT so bueno

As for stock aero characteristics, the figure I've seen quoted is 88lbs. of rear lift @100mph, with neutral front aerodynamic behavior. IIRC the source was an old German race team who built a Silverstone S2000 to compete in some sort of Nurburgring endurance race. They were using both the Mugen ducktail spoiler and the Mugen wing in conjunction, and had some funny-looking disc wheels.

 

I remember that picture!


It had those old school rallye type wheels! Big centers and tiny spokes. I was actually going to incuire about that car and the mods, etc.

Glad someone was thinking along the same lines!

 

Dude, I'm lucky I even got that close. I've got a hangover from last night's Valentine's Day "events."

I never saw the car you're talking about, but I think I know the type of wheels you're talking about. The logic behind them is supposed to be that they channel air inward to the brakes for cooling. Last I heard, they were used experimentally decades ago but it was eventually determined that they don't work. I'm surprised someone's resurrecting the idea now.

 

Uh, ok.

I was wondering what happened to Will last night.....

 

Where's the third Stooge? How come he never posts anymore?

 

You guys are lucky. I run an enormous rear tail, but the net effect is not very dramatic. A stock 911 body like mine generates about 270 pounds of lift (combined front and rear) at 100 mph (at 150 mph, the lift increases to about 400 pounds). Even with the Porsche Turbo tail and front spoiler, the figure only improves to about 50 pounds of lift at 100 mph. My huge elevated wing makes my car just about neutral, but I get no meaningful net downforce, and my drag coefficient is over .50.

If you're compressing your suspension at speed, then you guys must be getting hundreds of pounds of actual downforce from those big wings.

Modern technology and wind tunnels do have benefits.