WOTTEG

I am REALLY tired of people saying this:
There are good reasons to utilize a rear wing on any car that will be driven at speed, particularly where a neautral balance is critical or desired. Here are some contributing factors to why rear wings (and in some applications: spoilers) can benefit a car's handling (and safety) profile.

1) The shape of production coupes creates positive lift proportional to the square of speed. This force is primarily acting after the front apex on the roof.

2) The Largest pressure difference (most positive lift) is on the rear section of the body. Particularly along the taper of the rear glass where (if) the airflow remains attached to the vehicle.

3) The hood and windshield have positive pressure acting on them, increasing frontal downforce with the square of speed.

4) The weight distribution numbers of most sport coupes is biased towards the front of the car (Where the engine is located).

5) Positive rear lift at high speeds (even freeway speeds) has the effect of "loosening" the suspension's tact. Forward pitch is undesirable in racing applications, and can be unsafe as well.

At speed, rear wings help create negative lift to counteract the positive lift created by the body at the REAR of the vehicle. This is in an effort to maintain a nuetral balance for an already front "heavy" force distribution.

Spoilers serve the same purpose through a different means.
As is evident with one of the more extreme cases [VW New Beetle]. Most of the pressure differentiation is towards the rear of the car. That is why the Turbo-S Beetle has a speed-sensitive spoiler at it's rear apex. The spoiler helps detach the flow from the rear and thus helps to negate the lift.

So although the rear wheels are not driving the car, there are considerable benefits to conteracting the forward pitch that cars develop at speed.

I have seen a chart showing the New Beetle creating as much as 314lbs of Positive lift at a certain speed (?80mph?). While I have not seen comparable figures for any Hondas, I am sure that they (the integra particularly) would produce numbers that confirm this "rear lift" behavior.

There are also a number of sources available to confirm the factors mentioned above.
One is here:
http://www.autospeed.com/A_1065/P_6/article.html


Good Day.

Spade

Funny how Speed Vision World Challenge REQUIRES all vehicles be equipped with a rear spoiler.

Daemione

I heartily agree. A wing is just as useless (or useful, depending on how you look at it) on a RWD or AWD car as it is on a FWD one.

You're not going to see any benefits until 70+ mph, and personally, I don't know of many cars that are able to spin their tires while going 70.

There are certainly reasons why a large wing isn't necessary on a street driven vehicle, but drivetrain configuratin is not one of them.

kb58

I think the aftermarket wings you see on street cars are the reason for the negative posts. Ask the next Import Car kid you see about downforce and drag data on his wing and see what he says. It's all part of the Ricer look, which has nothing to do with actual performance - like stickers.

It's not ALL their fault, because none of the Rice Equipment makers have a clue about the wings either, they just know they sell. (and they're dang expensive pieces of superficiality, if there is such a word.

Yes, a REAL wing works on any car to avoid high speed oversteer, but it's rare that people know what they're buying.

Urban Business

please dont try to justify your rice wing ricer

WOTTEG

Just FYI TorteX:
My LS has no wing.
But I don't drive at track speeds, so there isn't a need for one.

Although I am working an another (more useful) aero device for my Teg. The project has become a lot more complicated (and expensive) than I first anticipated. Plus tnow that I'm back at work I don't have any time to devote to it. If I ever get it done, then maybe I'll do like BSQ does and sell my creation to other gearheads.

LudemanDan

What you are overlooking is that even though the aerodynamics argument may be true... production cars STILL understeer at the limit. So keeping the back wheels on the ground is STILL basically a non-issue (except in heavy braking or lift-throttle).
If you don't believe me, go to an autox and watch what happens when front-drivers lose traction.

So: the sole purpose of big spoilers is, still, to make perfectly good cars look perfectly silly.

Dan

P.S. Not to mention they reduce visibility.


[Modified by LudemanDan, 8:52 PM 7/3/2002]

YeuEmMaiMai

fords new mustange cobra SVT is ELECTRONICALLY LIMITED TO 155 due to the fact that the car will come off of the ground at it top speed of 175+ MPH. Spoilers or Wings can help keep the car planted

LudemanDan

Oh, also, if spoilers were really useful, wouldn't you see them on Corvettes?

frogsr

many good points here; boils down to purpose and car's intended usage. a wing is not entirely useless unless it's put on for cosmetics (which many, are).

PyroVTEC

Yes and no...

Going 110-120mph in a Civic... it would really help if there was something to reduce dartiness and general nervousness of the car at that speed... The smallest movement of the steering wheel creates a large movement at those speeds... if there was a rear airfoil on my car minimizing the positive lift, I would sure feel much more confident at those speeds.

Then again, when the hell do we go that fast anyway in the States...

earl

When we first built our race crx, it went about 120 mph in the quarter mile. A year later it's going 156 mph. The difference in aerodynamics between those two speeds is huge. I would not have believed all the gremlins we chased to try to make it right. Looking into a small flush wing for the rear now.

WOTTEG

Just a note, drag on cars pulls at an angle, not backwards. The difference in pressures above and below a car "draws" the low pressure from the rear so that it's force acts at angles. It usually is a combination of forces either acting back-and-up (as in production cars), or back-and-down (as in race cars). This is the same with downforces, that is why most downforce devices also create drag. Engineering (mostly race engineering) has drasticly reduced the drag incurred by these devices while increasing their potency, but the force of drag is there none the less.

LudemanDan

Take a look at the body of C5 corvettes (especially the rear face area). I hardly think the shape of a corvette is comparable to that of an Integra or civic, don't you?

C5's have a number of functional aero devices built into the body. One is the lack of a protruding rear bumper. The curvature between the underside of the vehicle and the vertical rear face, encourages the negative pressure left behind the vehicle (drag) to "seep" forward under the car. This encourages negative lift (downforce) much like rear diffusers do for race cars. As earl has stated, the effects of such devices are surprisingly effective at high speed.


An interesting tangent for this thread would be to look at the Honda Insight's aero engineering. It's design has the lowest Coefficient of Drag [0.25] exhibited by any production car to date. (Slipperier than even the 0.29 C5 Vette!) You can note such things as the front wheel wells that encourage air out the SIDES of the car as opposed to underneath. Covered rear wheel wells. Flares beneath the body prior to the wheels to reduce the drag created by the tires. And one trait that is also noticed on corvettes: a rear overhang on the apex of the trunk. While not as pronounced on the C5, because the C5 has a larger width to work with. This has beneficial aero characteristics too.

Last though: for all the "Fundamentals" or "Universal Characteristics" of how the forces of fluid dynamics act on shapes, it is still known to be a Black Magic; an Art. Innovation continues to change peoples perspectives and understandings.

Good Day.

Lsos

The thing with aftermarket wings on cars is that two types of people use them: the ricers and the extremely hardcore guys. By hardcore, I mean people like this dude I heard of with a huge wing on his Eclipse. Apparently he races around the Inner Loop here in Rochester (city streets), and he's been quoted as saying "it really helps keep the car planted at 150+mph". I'm not going to say he's smart, but he's freaking hardcore.

So its the ricers or the hardcore dudes. No one in between has a wing.

bmm89

OEM case and point, AUDI TT recalled and lip spoiler installed due to cases of flipped vehicles when rearend gave out...

owen_the_soyboy

WOTTEG, I give you props for trying to educate these nutters here, but sometimes they are a lost cause.... good luck in your fight

I would NEVER have removed the rear wing from my GSR sedan since I used it for track schools where speeds of 130 mph+ were achieved on every one of the 100 or more laps, for almost 3 hours total a day. The rear wing is helpful in reducing rear lift/wobble during hard braking from 130 mph.

I hate superficial wings on street only cars.

I laugh at all of the hypothetical talk on this topic... you guys (LudeMan, etc) should go to a track school and take your cars up to 130+ for one session of 20 minutes of laps, THEN remove your wing for the next session and see if you like it that way. Until then, these are just guesses from you right?

WOTTEG

Owen:
I think Lude_man_Dan has a great deal of track experience under his belt. He deserves a little more respect than his posts here are incurring.


Just an FYI about the "End-plates" seen on the ends of wings. [This excludes "smaller" wings tacked onto the outer edges of wings like those made by Arospeed (called ?winglets?). I will make no comments on those. ]

"End-Plates" <u>increase</u> the effective negative lift of the wing greatly. Like "Gurneys" (which are btw named after the man who pioneered them) they increase downforce gains, <FONT COLOR="#FF0000">but with a more modest compromise in drag</FONT>. <FONT COLOR="#00dd00">Edit: This is incorrect. The end plates actually DECREASE drag. I'll explain below.</FONT>

How do they do it?

Have you ever seen an airplane land or take off with a "swirl" of air shooting off of the wing tips? The swirl is caused by the High pressure below the wing intruding on the low pressure above the (airplane) wing. This effectively reduces the lift at the edges of the wing <FONT COLOR="#00dd00">and incurs a substanial ammount of drag</FONT>. By utilizing an "end-plate", the pressure differences are maintained over the surface of the wing. This also delays the formation of the "swirl trails" until further behind teh wing, thus reducing drag as well. There is a generic formula for the benefits of end plates on a wing's downforce. Maybe someone knows it. I'll take a stab at it:

Contrasting two wings with the same surface area and cross section,
wing A has no endplates;
wing B has endplates.
For every 5% of the wing's total width added to the height of the end-plates, wing B's effective surface area (downforce) is increased over Wing A's by 25%. I'm sure the point of diminishing returns (at least for HIGH downforce racing wings) comes when the endplates height reaches close to 25%-33% of the wing's width.

Now I'm not certain about the numbers above, but you get the idea: maintaining the pressure difference between the wing's top and bottom surfaces is the objective. And it is effective in race applications.

There is a nice picture of the NSX-R floating around here somwhere; It shows an additional endplate just inside of the outermost edge of the wing. This no doubt is there to isolate the majority of the wing from pressure differences caused by the body-wing connecting structure. ( Just something else to look at )

Good Day.


[Modified by WOTTEG, 10:18 AM 7/9/2002]


[Modified by WOTTEG, 10:20 AM 7/9/2002]


[Modified by WOTTEG, 10:23 AM 7/9/2002]


[Modified by WOTTEG, 10:24 AM 7/9/2002]

LudemanDan

Heh- I've been autoxing for about a year, and I've never driven on a track. Thanks for standing up for me though. Believe me, if I wasn't a college student, I'd be ALL OVER the tracks (in more ways than one).

Observation: the way many spoilers out there are constructed/ connected to the trunk, I'd be afraid to lean on them for fear of damaging them. So remind me, how much downforce are they supposed to be sending to the tires? (hopefully not more than your trunk latch can support!)

Dan

LudemanDan

Follow-up: WOTTEG, your argument about how aerodynamics effect steering and sticking at high speeds makes sense. I suppose I'll start subscribing to the idea that a spoiler serves some function on FWD cars when they hit the track. I doubt they're useful in autox though.

And I still think most cars look cleaner without 'em.

Dan

Bnjmn

150 on the inner loop? There are only a handful of sections smooth enough to support much over 100...

EARL- what have you done on the CRX to make it stable? I'm planning on entering the One Lap of America race with my CRX and there are a couple high speed road courses (Road Atlanta among others).

Thanks
Ben

WOTTEG

Yeah, I agree, I've oly seen one Auto-X. But from what I could see: the speeds at that event didn't stay high enough to Require a wing. The course was very "Technical".

I have wondered about the rear trunk or hatch lids, and how they support the force created by wings. I've never leaned on my trunk, but I'm sure when serious racing teams beef up the downforce created by their wings, they choose to reinforce the rear deck-lid too.

dohcsideSi

as for the first part of your sentence ummm i'm gonna pretend you didn't say that, and about the corvette.. why would you need a spoiler when you spent 90% of your development stage in a wind tunnel... ......gm sucks they couldn't bring anything out with even a little ***** on the style side (ie... viper, which does have a spoiler), they just keep turning out garbage on the pontiac end.

WOTTEG

Just a bump to correct a few things on my post concearning end plates.
I had to edit that post about 5 times before the HTML converted correctly.

DOHC-DX

that's why you all should invest in Z10 or compEng radius rods before aerodynamics

Avante

Being an engineering student, I really love having these discussions on technical stuff. I think as pointed out by many already, aerodynamic needs have nothing to do with being either FF, FR, or 4WD, every race car will benefit from increased downforce. The only problem is that increased downforce by exterior devices such as canards and rear wings causes drag, therefore creating a need to have a compromise between drag and downforcare depending on the type or track. This is why on most modern race cars, a lot more research is being spent on undercar structures such as ducts and diffusers to reduce lift and create downforce without taking a penalty in drag. but anyway, Id say that more than 90 percent of people with wings on their car do it soley for looks, Im sure that there certainly are people who dont understand anything about aerodynamics at all that jut plop a giant wing on their trunks and think they will go faster. To this day, I am yet to see anyone with a civic with a GT wing installed properlly. If you look at any race car with a properlly installed wing, the attachment points of the wing are usually connected to bars under the trunk that are attached to either the roll cage or the chassis.