Wings/Spoilers make a difference in drifting?

[Dc2TyP3R]

Do wings/Spoilers make a difference in drifting, what types make a difference and would it be a good idea to get them? I know they create down force but how much of a difference is there?

[Whisky]

Want the short version? The answer is no.

Want the long version? Ok...

First, "spoiler" and "wing" are not the same thing. A spoiler is a device designed to "spoil" lift. By definition a spoiler only gets airflow over one surface, and the other side is attached to the car. The spoilers you see on street cars are generally not effective, and only cause drag if they have any effect at all. This is primarily because they are designed for looks rather than function, and because the rest of the car is designed for the same purpose. On a genuine racecar, one designed to minimize airflow separation and direct air to a functional spoiler, it might be useful, but even in D1 there are no purpose-built racecars, only modified street cars.

A wing, on the other hand, gets airflow both above and below, and is designed to create a downward force. Unfortunately, the same problem as above occurs. The air that actually reaches the wing has already separated and is now turbulent and useless. If you were able to extend the wing above the roofline and well behind the rear deck, you might see some small benefit, but that brings me to the next problem.

Street cars, and professional drift cars, rarely see speeds over 80 mph, and actually spend most of their time in the 30-60mph range. Assume for a moment that you did happen to have a well-designed car-body, and a functional wing on the back. The car would almost definitely be illegal for drift competition use, but hey, just for the sake of argument, lets assume you actually have a useful wing. Since "downforce" increases as the square of the car's speed, the downward force generated by the wing at drifting speeds is basically nothing.

I'll give you an example: if the car is moving at 60 mph and then accelerates to 180mph, the speed has tripled, but the change in downward force created by the wing has increased nine times. So lets say you have a big GT wing, and its designed to create 500lbs of downforce at 180mph. If you drove the car at drifting speeds, say 45 mph, you are getting 1/16 of the wing's downforce, a whopping 31lbs. That 31 lbs is not going to help you in any way.

But whats even worse with drifting is that the air moving over the wing is at an angle, sometimes a very high angle. Even with the use of winglets (those vertical plates on the ends of the wing meant to keep air from spilling over the sides) you are only getting about 1/4 of the wing's effective surface into the airstream, and the airfoil is all wrong when the air is hitting it at a sideways angle. So you aren't even getting your 31 lbs. In fact, all you are getting is increased drag.

There is, however, one benefit to a big huge GT style wing on a street car built to be a D1 drifter, and thats "overall impact." The big wing looks cool, and you get style points for looking cool. Thats it. Thats the only advantage to big wings in drifting.

If I were you, I would spend my money on an LSD and entry fees to events like Just Drift and Drift Day. By the time you get good enough to need a wing for style points, you'll probably be driving someone else's car for them, and they will pay for the big wing.

[gwilo_drifta]

Unless u have a crazy fast car, you won't need it.

Don't worry too much bout looks man, just poor the money into the engine, lsd and suspension.

[rlngtngku]

hey whisky, what about those big whale fins you find on old porsches and such?!

They can't really have air flowing below them at all cause the bottom is basically the car!

Good Example

[REVLIMIT]

Well actually a spoiler can change the way a car drifts...but this is mostly due to the fact that your adding 15-25lbs to the back of your car. I noticed that when I had my old APR on my car it would drift a lot differently then when I took it off. The back end wouldn't slide as much as I would like it to when it was on.

[Whisky]

Originally posted by rlngtngku
hey whisky, what about those big whale fins you find on old porsches and such?!

They can't really have air flowing below them at all cause the bottom is basically the car!

Good Example

Lol, but thats not downforce, you could throw a sandbag in the trunk and get the same thing. BTW, I dig the 3rd gen f-body drifting, thats good stuff! Long wheelbase and plenty of torque, makes sense to me.

With regard to the Porsche whale-tail, thats a huge spoiler, and I suspect is probably is fairly functional at higher speeds, but a lot of the purpose there was to get air to the engine. The old Porsches with the whale-tails were rear engined, and air-cooled, so it was a functional part of the car even if it didn't spoil much lift. I have no idea how useful it was as a downforce-generating device, I've never seen one in a wind tunnel. Not everything that looks aerodynamic is, its not all as intuitive as it might look.

[Parry]

I think he's forgetting the speeds at which that Porsche was built to operate.

Good post up there Whisky

[NismoSigma]

Im just shottin the wind here, but since the spoilers are obviously for asthetics only. Are spoilers are supposed to give you better handling in a turning situation, and if so that it was possible to drift at higher speeds in order to make function properly?

[Whisky]

Originally posted by NismoSigma
Im just shottin the wind here, but since the spoilers are obviously for asthetics only. Are spoilers are supposed to give you better handling in a turning situation, and if so that it was possible to drift at higher speeds in order to make function properly?

Functional wings on suitably designed vehicles are designed to do almost nothing but help in turning. Without getting into coefficient of friction (an often misused engineering term) too heavily, its fair to make a rough generalization that a tire's ability to grip the road is proportional to the weight placed on that tire (but NOT at a 1:1 ratio). Since added vehicle weight is bad for a number of reasons, aero downforce helps cornering and braking by increasing weight on the tires without adding mass to the vehicle. In a straight line the wing will actually slow you down (there is no downforce without some drag).

The problem with drifting, at any speed, is that you are by definition getting the car sideways. When you bring that tail out, your frontal area has become the side of the car. Its about as aerodynamic as a brick. There is no way to build an efficient wing that will provide downforce with omnidirectional airflow. Now, if you had the wing on a turnplate of some kind and a gyro... yeah right.

[NismoSigma]

Ok thanks for clarifying that. All this physics stuff confuses me but at least I try to understand it.

[malcolm]

Unfortunately, the same problem as above occurs. The air that actually reaches the wing has already separated and is now turbulent and useless.

um, no.

on all but a few modern cars, the airflow stays attached over the roof. Even with something like a Toyota MR2 (AW11, or SW20), a wing mount 5" off the rear decklid would be effective.

There is no way to build an efficient wing that will provide downforce with omnidirectional airflow.

well, actually, a lot of the WRC teams have come close:



basically what happens is that as a car goes sideways, the length of the chord of the wing increases. (the air is going diagonally... if the car is sideways by about 45 degrees, then the length of the chord of the wing would be about 1.4 times longer). What Subaru did was they put in big strakes so the air that flowed under the wing would be running parallel to the car, no matter how much the car was sliding.

here is a diagram that shows all the terms. this is an airplane wing, so to produce downforce, you'd need to flip the design, so the curved part is on the bottom.





Basically, you COULD make a wing that would be effective for drifting, but it would be huge, and likely ugly too. You would need lots of big strakes like on the Subaru above, but you would also want it to be a multi-element wing, like this one:





So, if you use a wing like that, and make it work, you would most likely be able to generate 80-100 lbs of downforce at 45 mph. In a 45 mph drift, it would produce a little less, considering the air would be pushing against the strakes... However, it would also act like a rudder, and want to steer you straight. This wouldn't be a bad thing, considering you would be able to throw the car in a little harder, and be able to run a bit more angle, because the endplates and strakes would want to push you straight again.

Interesting project that would likely be banned from pro drifting shortly after someone tries it. A simple rule to prevent it would be to make strakes illegal, and limit the cars to single-element wings (thus making them only useful for asthetics).

[malcolm]

Here is how you would want to mount the strakes, and the green lines represent the airflow as the car is drifting:

[Whisky]

Thats a little more into it than I had intended to go in answering his question, as his question was pretty straightforward.

I don't disagree that the use of custom made multi-element wings on a drift car could have some benefit. I'm quite familiar with the Subaru WRC rear wing and the purpose of the strakes, but that also comes at a loss of efficiency. Budgets and speeds are greater in WRC then they ever will be in drifting.

Airflow separation is largely dependent on the car, but even F1 teams have been forced to bring the wings down and in to prevent such huge downforce gains. Your best aero gains come from minimising frontal area, whihc is essentially impossible with drifting since the whole side of the car becomes frontal area at times.

On the speed issue, a recent Racecar Engineering article focused on a Formula SAE project working to develop low-speed aero downforce. If I recall correctly they had some success, but the car was ugly as can be. I'm out of town now, but when I get back I'll post more specifics about the article and what the team was able to accomplish.

I'm glad to know I'm not the only one here that knows what angle of attack, separation points, and wing chord and camber are. We should keep this going Malcom, see if we can come to any interesting conclusions...

[malcolm]

don't worry Whisky, I am on a Formula SAE team, and I bought that exact issue for that exact article.

I figure that the addition of a wing wouldn't make too much difference, percentage-wise for "frontal area" in the middle of a corner when the side of the car also counts partially toward that frontal area. a little wing sticking up would be hardly anything.

Also, the wing wouldn't be difficult or expensive to manufacture. Take some foam, cut/shape it with a hot wire, and then wrap the foam with fibreglass... weld up some simple steel or aluminum mounts. Bond a piece of steel or aluminum to a small portion of the underside of the wing, weld a tab, and then mount that to the aforementioned mounts. make some some endplates to mount the other elements, and make little supports for the center of each element. Then take 0.040" aluminum sheet (sign material), and cut it to shape underneath the profile of the wing for the strakes. Attach them to the wing similarly to, but less extensively than the structural wing-mounts, and then just a simple L-bracket to attach the bottom of each strake to the trunk/decklid/etc... Cheap, and relatively straight-forward. I am sure I could do all this for about $200, or less.

About mounting wings on racecars... sure, a higher wing is usually better for downforce, but I still don't agree that wings are useless on road-based cars unless they are above the roofline. Now, this is far from a CFD drawing, but this is just what I think would happen with a wing mounted about half-way from trunk-height to the roofline on a car like a Mazda RX7 or a 240 SX (one of the fastbacks).

[zdss14]

sorry to go off topic, but even the subarus mirors are areodynamicly designed! so cool

[malcolm]

Originally posted by Whisky
I'm quite familiar with the Subaru WRC rear wing and the purpose of the strakes, but that also comes at a loss of efficiency.

remember, we're not talking about a perfect wing... just something to give the rear a bit more grip.

...speeds are greater in WRC then they ever will be in drifting.

true, hence my suggestion for a multi-element wing, unlike the single element WRC wing.

Airflow separation is largely dependent on the car

true, to an extent. however, with cars like an MR2 that have no rear "fastback-style" window, even though the flow has seperated, it will continue a path much like one where it is attached to a fastback, but instead of being attached to the glass, it just flows over a big layer of turbulence

interesting case in point: For the longest time, I would drive my AW11 MR2 with the rear decklid open, just to let out a little more heat from the engine bay. It helped a little bit, and the lid always stayed down. That car had a few problems, so we got another one (we're not big spenders... cheaper to replace than repair!). The next one had a sunroof. Shortly after, I am driving down the highway, and I decide to pop the decklid to let the engine run a little cooler... all is good. Then I decide I should give myself the same treatment, and open the sun roof. all is good... then I notice that the decklid seems to be floating up about 45 degrees from horizontal.

I figure that the airflow with the sunroof down came down and attached to the back of the car just before the decklid, thus pushing it down. However, when I put the sunroof up, it was just enough to engulf the decklid with turbulence and lift it up. It seemed that the air just attached later, and a particular swirl of turbulence just picked it up.

Therefore I would deduce that even on that car, with no fastback, a wing mounted even 4" off the trunk would be effective. Perhaps it wouldn't be as effective as if it was roof height, but still, it would work reasonably well.

...focused on a Formula SAE project working to develop low-speed aero downforce. If I recall correctly they had some success, but the car was ugly as can be.

I've seen a few, and yes, most are ugly. I saw one car that used single element wings, which are useless for low-speed stuff like auto-x. Another (UTS, I think...) used multi-element wings, but I don't think they were big enough for the low-speed course, and there wasn't enough of an angle of attack. There was a third one, and I think they got it right. When I go home this weekend, I'll check rummage through all our magazines and try to find out more.

We should keep this going MalcoLm, see if we can come to any interesting conclusions...

for sure

[Whisky]

I think you misunderstood. Perhaps I phrased it poorly, but I did not mean to suggest that adding a rear wing would make any significant change in frontal area. I was simply trying to say that management of frontal area is of prime importance in aerodynamics, and that when a car is sideways its frontal area is obscene.

Regarding separation points, I agree that the air is unseparated along the roofline, but nearly every street car will suffer from some separation at the back of the roof where the rear gless slopes downward. Hence the effectivenesss of your sunroof as a spolier.

I don't dispute that there is still airflow down along the glass and off the rear deck of any car (even dropping the tailgate in my F250 made a difference in highway fuel efficiency), but I do still maintain that it has largely separated and is capable of providing very little downforce close to the decklid. My earlier comment that it is now "useless" was a generalization meant to keep the point simple.

The most interesting aero aspect of drift cars, to me, is cooling. To that end, I saw a car at the D1 driver's search (McKinney car maybe? Erns would know) with a vertical fin pointed straight forward off the nose. Essentially it directs airflow into and thru the intercooler and radiator in similar fashion to the strakes on the Subaru car. When I saw it I immediately - and still do - wondered why nobody else does this. Its not pretty, exactly, but were it made out of expensive materials people might think it was cool I would be more impressed by body kits if they were also functional in directing air to cooling ducts for the radiator, intercooler, oil cooler, etc.

Controlling airflow under the car might also prove more useful for a drift car than any rear wing.

[malcolm]

ahh, I see where you're coming from. But one thing to remember is that there are almost open engine rules... so if you increase the drag of the car, you can always add more power to offset that (well, budget permitting).

Controlling airflow under the car might also prove more useful for a drift car than any rear wing.

hmmm... interesting. The problem would be, where would you place the "nozzle" for the ground effects? The front of the car? surely the flow would become detached by the diffuser if it had to go that far... Through the side?

Here is a little mock-up of what might work. the yellow box has a view of the diffuse with strakes at from the back (it would be the left hand side of the diffuser... the right side would have the strakes curved the other way to allow the air to flow under them easier... or should it be the other way around so that it catches the air, pushing it up, perhaps acting like a little splitter/air-dam arrangment? hmm). The car is in the red box with the ground-effect tunnels laid out.

[malcolm]

Its not pretty, exactly, but were it made out of expensive materials people might think it was cool I would be more impressed by body kits if they were also functional in directing air to cooling ducts for the radiator, intercooler, oil cooler, etc.

Actually, imagine that, integrated with a splitter, and more strakes to direct air over the nose as well. It might not look pretty, but it would look aggressive for sure.

If i was more into drifting, and had a dedicated car for it, I would go nuts on aero and do some testing...