Edge

what sold me on it is I couldn't justify not taking a fairly inexpensive step to improve the efficiency of the car. this makes sense for me because i drive a lot of highway miles. around town drivers it wouldn't have much impact on.

it's not much, but 1-3% change on drag, hence gas mileage at "speed" for a couple hundred bucks is worth it. plus it helps break up that massive wedge shape that Mazda worked so hard to build into the car.

wakeech

again: there is a wing (the "arch spoiler") and a spoiler ("lip spoiler")... i challenge someone to invent a wing which decreases drag. the spoiler will cut drag, the wing increase it. (<- that's a period, friends)

...but duh, aesthetics is the main reason anyone would put something like that on their car anyways, and i really have to say: seeing the MazdaSpeed wing on the yellow RX-8 in another thread has really convinced me that i'd either go for the spoiler, or the MS wing... forget the Genuine Mazda "wing": useless.

wakeech

...this is (rumoured??) the reason why all the Mazda's for the UK and Europe are fitted with spoilers as standard equipment... or, conversly, they knew they could get Americans to pay extra for them (standard on all of our "thrift minded" Canadian models).

Harold T

I was fortunate enough to drive an RX8 company car a couple of days ago that has been making the rounds at Mazda's corporate office in Irvine. As you might suspect it was fully decked out. It had the spoiler and I found it better than I anticipated. I fits the cars rear curves quite nice and does not take away from the rear view mirror in a way that reduces visibility.

jdj1971

You may have never noticed this. But spoilers are upside down wings. Saw and felt the one in detriot. My mx-6 was this way too. Flat on the top curved on the bottom. It creates negative lift = down force. While at the same time changing the air flow/turbulance behind the car thus reducing drag as well.

Hercules

Hehe, the amount of drag we get on these cars isn't really important because I don't think too many of us will be going that fast where it makes a difference.

Let's just say its aesthetic and leave it at that. I personally like it without... some like it with. Big woopie :0

wakeech

*ahem*

sir, i don't mean you any disrespect, but i know (very well) what i'm talking about. a wing, be they generating force either up or down, is a wing. whenever you diffuse air ("stretch" it) to create a low pressure zone, there is energy needed to "pull" the air apart. the more you do this, the more energy it needs, it's really quite simple. this in effect creates a helluva lot of drag, but it's kinda neat the way downforce works: with an increase in speed, the energy needed to diffuse the air (drag) increases linearly, while the force generated (in a "simplified to perfection" model) increases exponentially... i'm not exactly sure of all the mathematical relations off the top of my head, but rest assured: wings create drag. (<- again, period)

a spoiler is an entirely different beast as an aerodynamic device: it's basically a dam for air. creating a slight high-pressure zone at the base of the spoiler, and immediately in front of it, most of the laminar flow coming over the car is influenced to distribute itself evenly over the top of the spoiler, thus creating immediately behind the spoiler a very low pressure zone, which because of the angle a laminar flow would have to follow to fill it, is filled with a small pocket of turbulence. this pocket of turbulence then effectively "streamlines" the top of the boot, and with the air given that extra kick upward discourages it from simply "spilling" over the edge of the rear deck (there forms a large 'waterfall" of turbulence at higher speeds when this happens) and flowing in a more linear, laminar fashion. this is where the drag reduction happens: you pick up some turbulence, and slap a wall on the back of your car, but reduce net turbulence behind the car (the rest of the void is filled with air streaming around the sides, and up from underneath, helping also a little with rear-end lift).

Hercules

wakeech your kung-fu is strong... :D

wakeech

...sheesh, i'm Thread Creepo 20XD6... back on topic...

my vote goes (again) to MazdaSpeed wing :D... well, i'd like it better without the ricey adjustable pillars (unessarily higher drag), but not everything is perfect... one could always just fibreglass a fairing over them afterward anyways...

Ahura

I just hope ricers don't do some research and stumble upon the Chaparrals around 1970. Mind you, this is in the early days of wings and downforce. It most likely created massive downforce, I'm sure lots of drag accompanied it. Then ground effects on the Lotus came along 8 years later



Back on topic, I will not be putting a spoiler on my car. It looks perfect as it is.

desmo996

Actually, any body passing through a medium creates drag. The larger the cross sectional area of a body, the larger the drag, hence the low profile of sport cars. Drag is also increased depending on the shape of the body, hence the shape of the wings. The real trick is to keep the flow laminar over the body, hence different shapes of wing design. But sometimes you want to create turbulent air to induce a laminar flow over the body, hence small vortex inducers on top of 727 wings to eliminate drag. I could try to explain mathematically, but who really cares?

Edge

well, actually you don't. there are numerous causes of drag:
- frontal surface area
-- all of us can agree darts fly better than balloons
- turbulence
-- all of us can agree that turbulent air slows us down
- lift induced drag
-- all of us can intuitively guess that you pay for down force
- vortices and other funky stuff
-- all of us can agree we don't understand aero 100%

the wing arch on the RX-8 is a WING. it always will have some drag due to it's frontal surface area and how the air flows over it. if the angle of attack on the wing is such that an up or down force (let's hope down) is being generated there will also be induced drag directly proportional to the force generated. it could also be placed in such a way that no lift / force is generated and no drag would be induced.


Here's the cool part of that wing arch. Guess what? It can have the same effect. Let's assume Mazda put it on there at the correct angle and down force is being generated. This means there is a low pressure area under the arch. There is also a high pressure area above the arch, and in front of it due to the frontal area of the arch hitting the air flow. Okay, go back and re-read your description. Finally, the arch will generate a downward flow immediately off the end of it, but at a slightly higher location than the end of the deck, so it should help air smoothly fall over the end of the car. Hmmm... seems like this will have almost exactly the effects you're describing but without that lip spoiler or an air dam.

If we're going to talk aero over the car and drag, you need to consider the car as a system, not just one little piece of it. The whole car is a wing. It's also got lots of features that are generating all sorts of eddies, vortices, turbulence, you name it. Drag induced by one small piece (a fairly aerodynamic arch) is probably minimal compared to the barn door effect of lets say the mirrors? Obviously if it generates lots of down force, you will have lots of drag, but I don't think it looks like there's going to be huge down force off this arch. I suspect it's just enough to generate the desired aero effects, just like the lip spoiler.

//ejw

jdj1971

I think Edge described it well. I was hoping not to have to break out my engineering books and run formulas!

MadMax Rotor4

Word, In my opinion, the spoiler just makes it look like an other sports car. If you don't want to stand out, get a rear spoiler.

wakeech

?????

when did i say anything to the contrary?? yes, i know all about this stuff... when i say "all about" i mean i was an F1 fanatic for 3 years before becoming a rotorhead, and i know ALL about this stuff... i dont' remember the equations anymore (just fuzzy memories), but the relationships are still clear, the experimental knowlegde and outcomes are still up here *taps head*.

...this was one of my favourite places to explore:
http://www.aae.uiuc.edu/m-selig/ads/

...i'll tell ya something about nearly every single factory "wing" of this nature: they have an aerofoil profile which looks like a big, fat trapezoid. they're often configured to a 0* AOA... they often make no downforce at all. the MS wing on the other hand would actually generate some, and is of a far thinner chord, with much nicer curvature along the chord... blah, i'm rambling, this is beside the point.

never did i say that an aerofoil won't create some little amount of drag, even if not creating a net pressure difference (say, an aerofoil which is concave on both planes). you're repeating things i have already said, what is it i don't know/am wrong about??

...no, it doesn't. the drag and lift created at the back of the car is from a net upward force being generated from air above the car being sucked down behind it, and then pulled along behind it as it moves forward (the "turbulence waterfall"). the spoiler inhibits the rear of the car from collecting the air off the rear deck by physical impedence, and as i said before, with the turbulent vortex "carried" along behind it. with just a wing, there is nothing to prevent air from cascading down the aft side of the boot lid.

you seem to be under the impression that the air under the aerofoil has an upward vector after the low-pressure moment, and it doesn't: if the flow around the aerofoil is laminar, then after the moment of diffusion just tries to return to its origional state of rest. supposing that rest WAS reached before the end of the boot lid got there (duh, it wouldn't) the air would still be sucked down behind the vehicle, regardless of whether the wing was there or not. at very high speed, where there is almost no progress back toward rest, there may be some very small reduction in the contribution to turbulence behind teh car from air moving over the car, but certainly not at the level of the spoiler... not even close, by any measure.

...this is what i'm not getting: that's not what my post was about in the first place, it was about RX-8 Zoomster's statement about the wing being lower drag than the spoiler; it isn't.

also, yes, you CAN just talk about the aerodynamics of a specific area inside a system, and this is how windtunnel research is done. of course there are big picture considerations which have to be addressed (and note never did i say anything to the contrary, as you seem to suggest), but there is certainly merit to analysing specific areas.

Edge

uh, my impression of your argument is, "OMG the wing arch will generate HUGE amounts of DRAG! (especially induced drag 'cause it's generating lift) Why would you want that POS?!" My answer is it's going to have drag from various sources, potentially greater than the lip spoiler, but it can have drag reducing effect on the entire car just like the lip spoiler.

by the way, I think multiple years/courses in aerospace, aerodynamics, fluids, etc probably are sufficient for me to figure out what the heck is going on around this spoiler, but i could be wrong.



okay, so what? your earlier arguments were about the sky falling because there'd be so much more induced drag. now you tell me it's not going to generate lift, hence minimal induced drag. probably has more drag than the lip, but not that much more.



uh, i was pointing out that your end of the world drag scenario was not accurate (as in i think there's less drag involved than you do). and the net pressure difference can happen to any air foil regardless of shape as long as it's at the right angle of attack, but we normally talk about symetrical air foils (top 1/2 looks like bottom 1/2 ) at 0 degrees AOA doing this.



we disagree. i said (and specifically went back to fix my post because i typed in the wrong direction the first time) that there would still be a downward flow off the back of the car, but it would be happening from a slightly higher departure point (namely the end of the wing instead of the end of the deck). It also will be more energized to push off the back of the car because of the low pressure zone under the arch (assuming downward force generated). Air is accelerated under that arch if it's working correctly so, as all the air streams try to come back together again, they should be more laminar, but also more energized and at a better position to get the hell away from the back of the car. i'd have to know the AOA and a bunch of other stuff to actually predict the angle the air would take off the back of the wing, I don't think it will over come the downward trend of all the air coming over the car, but I do think it will have the effect of simulating a longer back deck, then when the turbulence finally starts acting on the area behind the car the car will be farther upstream.

Conceivably with absolute miraculous engineering you might even get the vortex to rotate up away from the car instead of down, but then if you get it to rotate down properly you might even recover some of that energy (try searching on klein-fogleman air foils for more on using vortices in this way)


The amount of drag generated by a wing arch generating down force is probably greater than the drag generated by a lip spoiler. However the point of RX-8 Zoomster's post was his opinion that the effect on the overall system (read entire car aerodynamic performance) would be better. He thinks the wing arch is more effective at providing better aerodynamic performance than the lip spoiler. It has nothing to do with whether the lip spoiler is a bigger or smaller barn door than the wing arch.

I agree with his opinion based on the concept that the arch wing can provide both functions, overall reduced drag and probably some down force if it's designed and placed correctly. If it hasn't been done, then it's just a piece of eye candy doing me no good, but that's a different story.

Last word, I know we test parts of aerodymic systems in wind tunnels, etc. However, when it's all said and done and you want the right answer, you put the whole thing in the tunnel and see what the heck is happening. Lots of aircraft that never got the full tunnel test had very serious problems once produced, even when all the parts worked great in isolation.

Efini 8

well, damn u people post way too much info. so I just skip it... personally I am getting the spoiler because the mazdaspeed one is ugly and a bit ricey for my taste. the lip kit which is hardly anything I skipped because I am putting another aftermarket kit on the 8

Edge

You bet! I'm done. Unless somebody says something bad about my mother, I don't have anything more to say on this.

Racer X-8

My 15 yr old son totally abhors the typical nonfunctional wing. It's old hat. Argyle. Loose it.

I agree with him.

If it looks nonfunctional, it is (whether it really is or not). Loose it.

I wouldn't do my RX-8 with a functional wing, not until I were to relegate it to actually racing it. Classical beauty - maybe so. I'm more into romantic beauty here. Otherwise, I'ld be buying an EVO VIII. No wings/spoilers on my sweet thing's rear end, please! Looks good enough all by itself.

Spoiler - maybe but probably not. I'm gonna have to see one for real and decide it's really worth it - probably isn't.

A good artist knows when to lay the brush down.