quote Originally posted by Kohburn: air can't flow like that.. not to mention, haven't you ever seen water droplets run UP the rear window?

Interesting observation. I haven't seen them run up, but I have seen them just sit there like the car wasn't moving. Here is what I know. Even with 650 cfm fans running, the air moves out of the vents almost flat out to the rear sides. The ribbon closest to the window blows upward, but the ones further back blow sideways. Those rear ribbons don't get more than a couple of inches off the deck and splay out toward the edges.

I see the air move forward, and I also see droplets dry in tact on the deck right beside the fans/vents.

Check this pattern which resulted from driving a wet deck down a dirt road and simply collecting the dust.

You see the air moving under the Shadow spoiler toward the scoop. You can also see droplets dried on. If the scoop wasn't there, you would see a fan shape of dried dust extending from the back toward the rear window.

Is my illustration accurate? You bet your sweet bippy Notice I did not draw the air actually reaching the window, but rather curling up over the deck. That was my try at portraying the turbulence or "tumble" that goes on. If you look at the pic I posted of my yellow ribbon experiment, you see the air comes over the lip of the roof and down with the ribbons plastered on the window. Very little actual air movement at the surface that you would call smooth.

And yes, the wing is deployed to function as a spoiler, so we in fact do agree. Kameo's wing may actually work better due to his louvers.

Arn

Anyone else see MythBusters last week? Interesting experiment testing whether you get better gas milage (less drag) with a pickups' tailgate up or down. Now, I know Fieros are not pickups and wings/spoilers are not tailgates, but there are some similarities.

Turns out the "tailgate up" mode gave significantly better milage and here's why:

"Tailgate up" traps a rotating bubble of air in the bed causing air over the cab to flow over the bed. Less drag. "Tailgate down" allows the bubble to bleed out of the bed causing the air over the cab to flow into the bed. More drag.

How this might relate to the Fiero is interesting. Maybe a vertical wall instead of a wing/spoiler would be more efficient!

Neil

So if that is the case what about this then?

With this theory?

To increase downforce and reduce drag in the rear what about a nascar style lip spoiler and a regular spoiler.

hey Arns85GT
where did tou get your wing ???(spoiler)
extensions ? i like the look, how much taller
are they from stock?

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Somedays it isnt even worth chewing
through the restraints !!!!!!!

you guys are gonna make me start a new project aren't you?.. a mini wind tunnel using the castiron fiero model to do smoke tests

Yeah, that's right Kohburn.

It would actually be a real service to 11,868 members. Think of it, you'd become an institution

Actually the plastic models would work provided you lashed them down.

Metoady, I got them at Fiero Conversions, however I cannot recommend the quality. There are a few guys making them.

Arn

of course the best thing to do would be to do an acurate CAD model (CAD is my lively hood anyways) and do a FEA fluid analysis of it

It would be more than worth it.

I think one thing that would help these discussions would be for people to clarify a) whether they're talking about the fastback or the notchback and b) whether they've got the factory spoiler or something else. Reading about people's results, I'm convinced that airflow is different in each case.

The biggest thing making me think that is that I see no flow up over the back edge of the deck toward the front. In the various tuft tests I've done, the flow between the deck and the bottom of the wing (I have a fastback with the factory wing) is turbulent but it's always toward the rear - reverse flow (toward the back window) is from the leading edge of hte wing forward.

My previous test showed turbulent flow over the top of the wing as well. I took two pieces of welding rod and taped them vertically to the wing stands with tufts (3" is about the maximum length to clearly show flow without getting tied in knots by turbulence, lately I've been using shorter ones) at various heights, trying to determine at what height above the wing the flow off the roof becomes laminar. Based on what I saw, I raised the wing 5-1/2" above stock and drove around some more. Here aesthetics comes into play - both my boys liked the raised wing but thought it was too high. I dropped it to 4" above the stock position and did more tuft testing. At this height, flow is still laminar most of the time over the top of the wing, and very turbulent on the bottom surface of the center section (for the first time, turbulent flow is violent enough to actually unravel the yarn I'm using). I also taped over the transverse channels, and now outboard of the wing stands I have laminar flow across the bottom surface of the wing too.

Re cheap raised stands - I got 4 pieces of M6x1.00 threaded rod and some splice couplings and 4 pieces of 1/2" CPVC pipe - I run the extended wing mounting bolts thru the pipe to an aluminum plate on the deck. The pipe takes the compression loads and makes it easy to vary the height and angle of the wing ( cut the front pieces shorter, for instance). Looks ugly right now, but I'm making non-structural fairings with the same cross-section as the factory stubs. Bondo and paint on foam, and Voila! Raised wing.

quote Originally posted by fojo: At this height, flow is still laminar most of the time over the top of the wing, and very turbulent on the bottom surface of the center section (for the first time, turbulent flow is violent enough to actually unravel the yarn I'm using). I also taped over the transverse channels, and now outboard of the wing stands I have laminar flow across the bottom surface of the wing too.

yes this is another reason I've tried to explaint o people that the stock "wing" was designed as a spoiler and not as a wing -- the bottom surface has to be smooth so that the air will flow faster over the bottom than the top in order to create downforce..

however at the stock height, as a spoiler, it has proven to reduce the drag coefficient of the fiero - both notchback and fastback

quote Originally posted by Kohburn: yes this is another reason I've tried to explaint o people that the stock "wing" was designed as a spoiler and not as a wing -- the bottom surface has to be smooth so that the air will flow faster over the bottom than the top in order to create downforce.. however at the stock height, as a spoiler, it has proven to reduce the drag coefficient of the fiero - both notchback and fastback

On a standard airplane, the bottom of the wing is flat or flatter so that the curved top of the wing has air moving faster over it, to create lower air pressure so the wing can lift upward.

On the Fiero the inverse would be true. The air crossing the bottom of the wing would have to be moving faster to push the wing downward. Of course we all know this does not happen. There is not enough air movement under the wing to create this effect AND the air is moving from back to front while the air on top of the wing is moving front to back.

In other words, in it's stock location is useless as a wing. It is also marginal as a spoiler. That is the reason IMSA got rid of it PDQ and everybody who has experimented with it has dropped it.

Raising it into the air stream well above the deck might cause some downward force, but at even 5" off it is pretty insignificant. It does, however, appear to smooth the air flow, if for no other reason that it is separating the air masses that are moving in opposite directions.

I still like your idea Kohburn to create a wind tunnel.

Arn

quote goatnipples2002 said: So if that is the case what about this then?

*AHEM*

Mine probably isn't big enough to get the full effect, though. It only sticks out about 4" from the decklid.

quote Originally posted by Kohburn: I've been correcting misconceptions about this for years, and probably will continue to do so

Your 4" just isn't big enough to be really effective.

This pic that Kohburn posted shows a spoiler that is big enough to work. Notice it sticks out close to a foot.

I personally switched out my wing for the Shadow spoiler only because the wing just didn't seem to go with the large scoop. Neither is particularly effective in my book, although both do reduce the turbulence a bit and therefore the difference in drag coefficient

And thanks to Kohburn for posting it.

Arn

So if it must stick out farther than stock what about this

Or would a taller wing/spoiler and a bent metal lip spoiler be better

[This message has been edited by goatnipples2002 (edited 11-22-2005).]

quote Arns85GT said: Your 4" just isn't big enough to be really effective. This pic that Kohburn posted shows a spoiler that is big enough to work. Notice it sticks out close to a foot.

The IMSA spoiler is about half that size, and was good enough for the IMSA racers. So I don't think the spoiler really needs to be that huge. I bet that thing makes some hellacious downforce, though.

[This message has been edited by Blacktree (edited 11-22-2005).]

quote Originally posted by Arns85GT:

thats the spoiler i was talking about, if i understand what everyone is saying air comes from under the spoiler twoards the window right? would that spoiler allow air to go into a scoop on the decklid, or would the stock one or something similar?

Whether air would go into it or not depends on the pressure differential between the ends of the path - is pressure under the car higher than pressure on the deck?

The air moves under the Shadow Spoiler with some force as you can see. Yes it does blow into the scoop. My air cleaner got nice and dusty on this test.

Arn

Hey Gunnie,

I am going to the junkyard tomorrow, and I need to know what model taurus that you got the chin spoiler off of, so I can get it, I found on my trip from IA to CA, I REALLY needed some downforce in the mountain passes, and something to stabilize the front end and plant it a little better, and I am not about to cut a hole into my hood. Much as I'd like to, I don't have the glassing skillz or the money to buy the Warber hood.
I find that my rear end is planted well enough, it's the front end that's got me worried. I am thinking of perhaps putting some extra weight under the front decklid to make the front end heavier and hopefully, therefore, stickier.

Pics of yours would be GREATLY appreciated.

I need some serious front end downforce on my GT... that Aero nose doesn't seem to be worth a damn thing for me so far as stability is concerned....... The GT still feels unstable. I think I am going to get the wheels re-balanced and get an alignment.

-Mulholland GT

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1986 GT Getrag 5-speed

MULHOLLAND GT

[This message has been edited by Mulholland_GT_Racer (edited 11-24-2005).]

You may not want to cut a hole in your hood but that by far is the best way to improve downforce, cooling and stability.

It seems that the consensus is that the stock spoiler/wing needs to be moved further back and raised to increase down force and reduce drag.

Has anyone made any type of brackets or arms that will do this with the stock wing?

This might help
An old cray supercomputer (heh) air flow on a Fiero

This is a good topic, as I want to see a better design.
As for not being any help at legal speeds, well,... why do any mods if you drive at legal speeds.

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"DRIVE IT LIKE A FIERO"
'84 Fiero, engine to be determined
'87Blue GT 3.4L Swap Completed!!!!!!!!
http://www.lasvegasfieroclub.com/

quote Originally posted by Mulholland_GT_Racer: Hey Gunnie, I am going to the junkyard tomorrow, and I need to know what model taurus that you got the chin spoiler off of, so I can get it, I found on my trip from IA to CA, I REALLY needed some downforce in the mountain passes, and something to stabilize the front end and plant it a little better, and I am not about to cut a hole into my hood. Much as I'd like to, I don't have the glassing skillz or the money to buy the Warber hood. I find that my rear end is planted well enough, it's the front end that's got me worried. I am thinking of perhaps putting some extra weight under the front decklid to make the front end heavier and hopefully, therefore, stickier. Pics of yours would be GREATLY appreciated. I need some serious front end downforce on my GT... that Aero nose doesn't seem to be worth a damn thing for me so far as stability is concerned....... The GT still feels unstable. I think I am going to get the wheels re-balanced and get an alignment. -Mulholland GT

GT- I'll put batteries in the digital and go out and get some pictures. Then I'll see if I can figure out how to post them. The chin spoiler came off a 92 Taurus, 4 door. That is all I can say, it is a solid fiberglass one. And it works for me. It took most of the float feel out of the front when your going--- oh say--- the speed limit--- or a little over! I am making splitters to put at the ends, in front of the tires. They aren't on yet.

quote Originally posted by gunnie: OK, I give up. How do you put a picture on here? Or if I send you one will you post it here for me. Thanks

i beleave all you have to do is click the blue button alllllll the way at the bottum of the sreen that says pennock's image poster

I tried---- it's a 1 hour download out here on the farm. Last time I tried to download it, it started fighting with my other photo programs (one for my camera and the other for my daughter). I can e-mail the photo to someone if they will post it. Any takers?

Gunnie

Here's the photo Gunnie sent to me (cropped and filtered):

shweet.

I'll see if I can find one when I hit up the junkyards in Wilmington tomorrow.. Hopefully they'll have a set of sideskirts for me in addition to that taurus bit. I am thinking that maybe the instability at high speeds might have something to do with the wheels being off-balance or slightly misaligned or something.

Oh well, I imagine I'll figure it out at some point.

Thanks a lot to Gunnie for posting the info and to Blacktree for posting the photos!!

This is a great thread, let's keep it going!!

-Mulholland GT

PS:
I want to cut a hole in the hood, but I'm very apprehensive about doing it because I have ZERO glassing skills, and I can't have it repainted when I'm done. I was thinking maybe put a set of sunbird vents or something in there so that I won't actually have to do a lot to the hood to allow the extra airflow out of the front compartment.

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1986 GT Getrag 5-speed

MULHOLLAND GT

[This message has been edited by Mulholland_GT_Racer (edited 11-25-2005).]

Nice idea Gunnie!

Based on your picture from that angle I started wondering if it would be possible to get the air to flow upward through the inlet (cut top section of the inlet and curl up bottom section of the inlet) and going through the top section of the rad and up out a hood vent that is infront of the spare tire wall?

I already have a hood vent and noticed a big improvement in front end lift at 80mph but I didn't want put it too far back and have to cut into the spare tire compartment. Is there enough room to do this without creating too much drag? What should be considered the maximum degree before you start to experience too much drag, 30 degrees, 45 degrees?

Thanks.

quote Originally posted by Arns85GT: On a standard airplane, the bottom of the wing is flat or flatter so that the curved top of the wing has air moving faster over it, to create lower air pressure so the wing can lift upward. On the Fiero the inverse would be true. The air crossing the bottom of the wing would have to be moving faster to push the wing downward. Of course we all know this does not happen. There is not enough air movement under the wing to create this effect AND the air is moving from back to front while the air on top of the wing is moving front to back. In other words, in it's stock location is useless as a wing. It is also marginal as a spoiler. That is the reason IMSA got rid of it PDQ and everybody who has experimented with it has dropped it. Raising it into the air stream well above the deck might cause some downward force, but at even 5" off it is pretty insignificant. It does, however, appear to smooth the air flow, if for no other reason that it is separating the air masses that are moving in opposite directions.

Even if the spoiler/wing were raised, it would probably provide very little down force. As you mentioned, the shape is wrong. Now, it may be possible to reshape the spoiler to more closely resemble a wing. Then raising it may help with downforce. I don't know that it would be necessary to refabricate the underside of the spoiler. I have considered adding a rub strip that had been removed from one of my Neon's to the leading edge underneath the spoiler. I am thinking that it might be possible to add a lip to the top rear of the spoiler which might be more like flaps on an airplane (reversed to provide down force instead of lift). Finding the sweet spot might be a little tough though.

I have a spoiler with 7" (or are they 10" raised stantions) and a couple extra spoilers. Might just have to try some of these ideas.

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FierOmar

quote Originally posted by Mulholland_GT_Racer: Had another thought.. I believe it was Kameo earlier in the thread that mentioned using Canards on the Fiero. I have no problem whatsoever with using canards or other aero dealies so long as it will help me rid the car of that scary shakey feeling I sometimes get over 75-80mph. From what I've heard the Fiero is supposed to be a stable car to 120, but I feel like maybe there's something wrong with mine because after 95 or so I get freaked out. I don't drive those speeds on a regular basis, but speeds do get really up there just keeping with traffic on I-15 and I-80... I took my 1979 280ZX to 140mph in basically stock form, so I am wondering what's wrong with teh Fiero that's making it so... iffy at higher speeds. I'd like to be confident that my front wheels are going to stay planted and that my steering inputs are going to continue to be effective. I also imagine that with the added downforce I'd have a lot more control and feel more secure on the highways. Anyways, long post short what would I use to make myself a set of canards, where should they be mounted on the aero nose, and at what angle? I am thinking that perhaps some cut aluminum (hello home depot, lol) or similar lightweight yet sort of strong alloy that's cut to the curve of the body would go nicely and improve aerodynamics like I've seen on MR2s, NSX's and the like. I believe a good example would be the Autobacs NSX. Canards like that, right? -Mulholland GT

The things that you speak of that your Fiero is doing sounds like you may have worn shocks and struts. I know that the old 3 bounce method that is effective on heavy cars to check shocks doesn't work on a Fiero due to it's lighter weight. I had an 86 GT that passed the bounce test but had worn shocks and struts, after replacing them Koni adjustables on putting them on about 80% firmness the GT rode like it was on rails. But you may want to pull them and check.

As for the canards there is a kid on here that everyone makes fun of his GREEN car but I do believe that he has some of the very things on his, which personal I think would work fine for air flow. I believe they're carbon fiber too, which would work better than aluminum. Slitters would also work if you had a chin spoiler like mine that is parallel with the road from the wheels to the front of the car.

quote Originally posted by kamikaze7: Nice idea Gunnie! Based on your picture from that angle I started wondering if it would be possible to get the air to flow upward through the inlet (cut top section of the inlet and curl up bottom section of the inlet) and going through the top section of the rad and up out a hood vent that is infront of the spare tire wall? I already have a hood vent and noticed a big improvement in front end lift at 80mph but I didn't want put it too far back and have to cut into the spare tire compartment. Is there enough room to do this without creating too much drag? What should be considered the maximum degree before you start to experience too much drag, 30 degrees, 45 degrees? Thanks.

I'm not for sure understanding what you are asking. If you have a hole in your hood the air will exit out through there. If you want to force more of the air upward you could install a belly pan from the spoiler to the radiator which would be basically flat. The hole in the hood would have to be large enough to relieve the air or you would lift the front. A condition most of us are trying to correct.
For the question maxium degree and drag you must know the amount of area and wind speed. Next time you are driving down the road at 60 put your hand out the window. Depending on your hand size notice the drag/force against it at different angles. This relates to the pounds of force being transmitted to your car (handling). Remember you have to have the extra horsepower to push all of this along. Bigger is not always better!

[This message has been edited by gunnie (edited 11-25-2005).]

Thanks for the info.

I would basically like to have 60-80% of the air going through the mouth exit through the vent in the hood to create additional downforce. To accomplish this without having to cut into the spare tire compartment for the vent and without creating too much additional drag is the challenge.

I'm wondering if there is enough room/angle from the entrance of the mouth to the hood line where it meets the spare tire compartment to do this without creating a "wall" type deflector.

The rest of the air will flow under the car and there is plenty of room to create a deflector for it.

Thanks again.

As far as canards go I would assume that they would need the same angle of attack as a spoiler. The diagram I posted suggest somewhere between 55-70 degrees. Test each and see what you like more.

The main reason for high speed instability is front end lift. The lift increases with the speed because the rubber piece that grabs air and directs it into the radiator compartment after that it has no where to go. Once it hits this dead end it lifts your front end and causes the front wheels to not make as much contact as they need to. So adding an extractor scoop would be best then vents. As long as the scoop stops about a foot before the top of the hood. Adding canards or splitters to a stock front end wouldn't help that much if any. Adding them to a vented/scooped hood would magify the effects of the scoop/vents. After i put my small extractor scoop on my front end stays planted to the road...even when I max the 4 speed out at 130mph.

This site has good info on the use of different aerodynamic devices. For those that want to make their own canards here are 2 different templates. They do sell things, but if you can ignore their overpriced stuff they have some good info. http://www.aprperformance.com/techarticles_canards.php

This is the scoop that I currently have.

I have a hole in my hood that is only about 5" by 5" and it flows good enough to keep me planted at 130mph plus I have the ORIGINAL shocks on my car from 86...(upgrading to Konis/QA1 in the spring). There really is no benefit if you cut past the radiator/spare tire well seperating line. Many have said to get the best flow out of the hood you should cut UPTO the seperator, but if you need to increase the size of the hole go as wide as the scoop/vent will allow. And if by deflector you mean something to direct the air onto the radiator compartment then look under the front end and you will see a "deflector".

[This message has been edited by goatnipples2002 (edited 11-25-2005).]

Gunnie,

I got the Taurus chin spoiler but it looks like it needs some cutting to be adapted to the Fiero Aero nose. It looks like it's wider than the Fiero's nose, and I am wondering what exactly you did to make it fit. My dad suggested I cut about 3'' out of the middle and use Bondo, glue and reinforcement to reconnect the two pieces. Is this what you did or what would you suggest to get it to work??

Goatnipples,

I am really afraid of cutting into the hood, because if I do then I might screw up the rest of the car's finish.
I need to get it cut to size and put it onto the car before I head back to Iowa this coming Friday or Saturday.

Could you post some photos of the scoop that you have mounted on the hood?
How did you do your scoop? If it's not too hard I think I might just do that and gain some high-speed stability, because at present driving above 80mph or so is REALLY unnerving.

By the way, where did you get/how much was the scoop you have? I kind of like it.

---

Thanks a lot guys!

-Mulholland GT

PS: I got new sideskirts and a new intake manifold at the Pick-Your-Part today, so goodbye cracked-up skirts, and hello ported manifold!!!

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1986 GT Getrag 5-speed

MULHOLLAND GT

[This message has been edited by Mulholland_GT_Racer (edited 11-25-2005).]

[QUOTE]Originally posted by Mulholland_GT_Racer:

Gunnie,

I got the Taurus chin spoiler but it looks like it needs some cutting to be adapted to the Fiero Aero nose. It looks like it's wider than the Fiero's nose, and I am wondering what exactly you did to make it fit. My dad suggested I cut about 3'' out of the middle and use Bondo, glue and reinforcement to reconnect the two pieces. Is this what you did or what would you suggest to get it to work??

I didn't cut any out. You will have to cut some reliefs at the corners to allow you to follow the contour of the Fiero. The only thing I cut off was after I mounted it I cut a pie shaped piece off each end so it was parallel to the ground.
PM me your e-mail and I will send picture.

hey gunnie
i have the same problem as mulholand
the chin spoiler is about 4 to 6 inches too wide
do you have any side pic of it
cus i dont see any way accept cutting it to get it to fit
hummmmmmm
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somedays it isnt even worth
chewing through the restraints

Look at the picture that was posted of the spoiler installed. I did not cut it shorter! When you align the opening the sides will be wider than the Fiero. I had to cut reliefs in the top and bottom of the Taurus spoiler to get it to follow the radius of the Fiero towards the tires. After I bolted it up I cut the bottom edge off (in a pie shaped piece). That was it. I pan on putting splitters on the ends to finish it off, but it works the way it is. I'll take a picture tomorrow morning and send to whoever gives me their e-mail address. I can do that but can't figure out how to put pictures here. SORRY

Hey Gunnie, drop me another email with the new photo and I'll post it for ya.