ok forget about aluminum wings
06-23-01, 09:11 PM
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You need to remember that any wing that you put on a street going car, particularly the IS is just for looks.
Those huge airplane wings, regardless of what they're made of are just for looks and serve little or no functional purpose.
I'm not putting on a rear spoiler at this time because the whole "wing" movement is getting out of hand. I mean I've seen three foot wings on a Neon. C'mon that car in it's wildest dream will never generate enough speed to create any beneficial downforce.
Check out the Viper, most don't have huge wings, but rather subtle ground effects.
IMO you get better aerodynamic benefits by the rechanneling of air around the car rather than trying to create downforce w/a wing.
However, if I had to get a wing, it would look like the RMM or the smaller lip spoiler by Blitz.
Those huge airplane wings, regardless of what they're made of are just for looks and serve little or no functional purpose.
I'm not putting on a rear spoiler at this time because the whole "wing" movement is getting out of hand. I mean I've seen three foot wings on a Neon. C'mon that car in it's wildest dream will never generate enough speed to create any beneficial downforce.
Check out the Viper, most don't have huge wings, but rather subtle ground effects.
IMO you get better aerodynamic benefits by the rechanneling of air around the car rather than trying to create downforce w/a wing.
However, if I had to get a wing, it would look like the RMM or the smaller lip spoiler by Blitz.
06-24-01, 12:44 AM
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I think that the dealer wings are a lil more classy than the other wings sold on the market..even tho i am really not to sure who makes then i know that they are $800 at the dealer and i would rather finace the wing with the car than pay for it in cash....or you can get a rmm spoiler
06-25-01, 02:01 PM
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Like Risk3233 said, most consumer automotive "wings" are purely cosmetic. Some of the larger, extruded aluminum serious-looking ones do generate a little bit of downforce, but that's only without the contours of a roof, rear window, trunklid, and turbulence/vortices that come off of them to complicate things. the only certainty is that they raise your center of mass, which is certainly a bad thing for handling.
In seeming contradiction, tiny lip "spoilers" and some short wings can be another matter. There's a short blurb about the Coanda effect in the July '01 R&T. Those that really want to explore the subject can head on over to the SAE website and purchase paper #2001-01-1267, which expounds on the subject in detail.
My synthesis of the R&T blurb and my own understanding of automotive aerodynamics goes as thus: An aerodymanic automobile body is itself a big wing, forcing air to travel a longer distance over the top of the car than under the bottom. Despite the minimization of drag, it generates lift. But cars rarely terminate in long tapered tails (old 911's excepted), so when air reaches the end of the car, it swirls into turbulence, which generates drag. You either have lift or drag, and you trade one off for another.
The Coanda effect is basically the tendency of a fluid to follow the contours of an object in its path. A great conceptual example used in R&T was that of the back of a spoon in the path of a flowing faucet. Instead of just lauching off the curvature of the spoon back, the water follows the contour of the spoon a bit. If you think about it, it's because the fluid is "sucked" to the surface because leaving it would generate a vacuum, which would suck the fluid back to the surface anyways.
Back to cars. Air follows the contour over the front of your car because there is no other place for it to go. But air also follows down the back of your car because not following it creates a low pressure zone which would suck it in anyways. The determinant of whether you get laminar flow smoothly following the contours (generating lift) or spilling into turbulence (generating drag) is how the rear window and trunk edge fall away from the relatively horizontal roof and trunk top. A notchback is draggy but generates little lift, while a hatchback is low-resistance but generates lift. Just about all cars generate turbulence off the edge of the trunklid, except really tapered cars such as the older 911's. The IS300 rear window is almost configured like a hatchback and hence is low resistance, but should generate some lift.
But a solution that broke the rules of this tradeoff was found along time ago. Remember that the Coanda effect depended on how the curvature fell away. A little too much curvature and the fluid is thrown off into turbulence on the surface. A hell of a lot of curvature, and most of the fluid is simply deflected off. A properly designed lip spoiler deflects the air off the trunklid in such a way that it doesn't swirl into turbulance right behind the car, but does so much farther away from the car, minimizing the drag it would otherwise cause. The deflection of air itself causes a downforce, and launching the air off the rear edge and forcing the air traveling under the car to travel further to meet it breaks the "wing effect" of the car body. (This of course works better if the bottom rear of your car was fitted with a smooth curve to allow the air flowing under the car to exhibit as much Coanda effect as possible. Real ground-effects such as those found on true racecars and the 360 Modena work extremely well in synergy with "launching" the over-the-car-air with a lip spoiler/small wing.)
So this is how a small, properly designed wing/lip spoiler works. Take a look at the small but functional power spoilers of the Porsche Boxster and the Beetle Turbo as examples.
In seeming contradiction, tiny lip "spoilers" and some short wings can be another matter. There's a short blurb about the Coanda effect in the July '01 R&T. Those that really want to explore the subject can head on over to the SAE website and purchase paper #2001-01-1267, which expounds on the subject in detail.
My synthesis of the R&T blurb and my own understanding of automotive aerodynamics goes as thus: An aerodymanic automobile body is itself a big wing, forcing air to travel a longer distance over the top of the car than under the bottom. Despite the minimization of drag, it generates lift. But cars rarely terminate in long tapered tails (old 911's excepted), so when air reaches the end of the car, it swirls into turbulence, which generates drag. You either have lift or drag, and you trade one off for another.
The Coanda effect is basically the tendency of a fluid to follow the contours of an object in its path. A great conceptual example used in R&T was that of the back of a spoon in the path of a flowing faucet. Instead of just lauching off the curvature of the spoon back, the water follows the contour of the spoon a bit. If you think about it, it's because the fluid is "sucked" to the surface because leaving it would generate a vacuum, which would suck the fluid back to the surface anyways.
Back to cars. Air follows the contour over the front of your car because there is no other place for it to go. But air also follows down the back of your car because not following it creates a low pressure zone which would suck it in anyways. The determinant of whether you get laminar flow smoothly following the contours (generating lift) or spilling into turbulence (generating drag) is how the rear window and trunk edge fall away from the relatively horizontal roof and trunk top. A notchback is draggy but generates little lift, while a hatchback is low-resistance but generates lift. Just about all cars generate turbulence off the edge of the trunklid, except really tapered cars such as the older 911's. The IS300 rear window is almost configured like a hatchback and hence is low resistance, but should generate some lift.
But a solution that broke the rules of this tradeoff was found along time ago. Remember that the Coanda effect depended on how the curvature fell away. A little too much curvature and the fluid is thrown off into turbulence on the surface. A hell of a lot of curvature, and most of the fluid is simply deflected off. A properly designed lip spoiler deflects the air off the trunklid in such a way that it doesn't swirl into turbulance right behind the car, but does so much farther away from the car, minimizing the drag it would otherwise cause. The deflection of air itself causes a downforce, and launching the air off the rear edge and forcing the air traveling under the car to travel further to meet it breaks the "wing effect" of the car body. (This of course works better if the bottom rear of your car was fitted with a smooth curve to allow the air flowing under the car to exhibit as much Coanda effect as possible. Real ground-effects such as those found on true racecars and the 360 Modena work extremely well in synergy with "launching" the over-the-car-air with a lip spoiler/small wing.)
So this is how a small, properly designed wing/lip spoiler works. Take a look at the small but functional power spoilers of the Porsche Boxster and the Beetle Turbo as examples.
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06-25-01, 02:18 PM
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DtEW,
Again, you da man. Leave it to DtEW to give the scientific analysis of an issue. Great stuff.
My question is as follows: in your opinion, do any of the current body kits (aka ground effects) on cars do anything in the way of improving handling through effecting downforce? Or are they as I believe, mostly for appearance.
What would be the most effective setup on the street to achieve the most desireable air flow over a car?
Would modifying the lines of a car w/either a rear spoiler or aero kits affect the drag coefficient of the factory numbers? If so, to what degree?
Again, you da man. Leave it to DtEW to give the scientific analysis of an issue. Great stuff.
My question is as follows: in your opinion, do any of the current body kits (aka ground effects) on cars do anything in the way of improving handling through effecting downforce? Or are they as I believe, mostly for appearance.
What would be the most effective setup on the street to achieve the most desireable air flow over a car?
Would modifying the lines of a car w/either a rear spoiler or aero kits affect the drag coefficient of the factory numbers? If so, to what degree?
Last edited by Risk3233; 06-25-01 at 02:27 PM.
06-25-01, 08:50 PM
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Originally posted by Risk3233
Leave it to DtEW to give the scientific analysis of an issue.
Leave it to DtEW to give the scientific analysis of an issue.
It's all theoretical with me.Anyways, I don't believe that any consumer aftermarket body kit improves anything other than appearance (and questionable in some instances) on a car.
"Well, what do you say about airdams? Any moron knows that the less air you keep from getting under the car, the better."
The answer to this is that you must remember that just about all airdams funnel air into the grille, and the grille leads into the engine compartment. For production cars, the biggest exit out of the engine compartment is through the bottom, which puts the "dammed" air back underneath the car. Notice that front-engined true race cars are just about always equiped with substantial engine compartment vents on either the front fenders or the hood of the car.
Even the entire issue of limiting airflow underneath the car is pointless considering the ride height that even extremely lowered cars ride need to ride at to be street driveable.
As quite a few car companies (Citroen, Lincoln, Audi and Lexus come to mind) figured out through the years, the best setup for the street (with the emphasis on aerodynamic efficiency/reduction of lift, general utility, conventional car structure) is the automatic ride-height adjustable suspension. The LS430 Ultra Premium package has this because it is a relatively easy feature addition to an air suspension system. It maintains a high ride eight for slow speed driveway/dip negotiation, and lowers to a reduced height as speeds increase.
In terms of the aftermarket parts, I would not invest in body kits in an attempt to improve aerodynamic performance. Invest in them for the looks, which is as good as a goal as any as long as one truly understands what they will and will not achieve.
I am considering between the L-Sportline lip spoiler and the TRD spoiler. It might contribute to a reduction of the beforementioned Coanda effect, but I desire it mostly to attenuate the "long bumper" look that has resulted from the North American 5-mph bumper certification.
06-26-01, 06:55 PM
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DtEW
Even though Dtewm get technical on us...he still gets his point across and believe me it is good that he does that because there is never a question after this man speaks his mind...great stuff DteW....
06-26-01, 08:28 PM
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Hey, you guys are too kind. 
Truthfully, don't take anything I say (or anyone else, for that matter) at face value. I try to convey the information that I've gathered and thoughts I've had on them the best I can. I do try to make sure there aren't any obvious contradictions. However, the info I give and the insights shared are only as good the info I get, which leaves plenty of room for error.
I guess if there is a point I'm trying to make, it's that you should form insights of your own from after weighing the opinions of others. You might discover that so-and-so was right. Or that there were caveats that they were unaware of. Or they might even be outright wrong. Then share. It is through this "intelligent skepticism" that we can approach the asymptote that is truth.
(Now was that "asymptote of truth" part cheesy or what?
)
Truthfully, don't take anything I say (or anyone else, for that matter) at face value. I try to convey the information that I've gathered and thoughts I've had on them the best I can. I do try to make sure there aren't any obvious contradictions. However, the info I give and the insights shared are only as good the info I get, which leaves plenty of room for error.
I guess if there is a point I'm trying to make, it's that you should form insights of your own from after weighing the opinions of others. You might discover that so-and-so was right. Or that there were caveats that they were unaware of. Or they might even be outright wrong. Then share. It is through this "intelligent skepticism" that we can approach the asymptote that is truth.
(Now was that "asymptote of truth" part cheesy or what?
)
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