quote Originally posted by 85fiero_fanat: I know that the decklid vents are to let air out, but adding a vent to the back of the decklid would allow air to flow out the back, and air would be forced down into the ducts which would create a loop of air helping cool everything.

If you forced air in you would likely cause the air to neither move up or down. You want the high preasure under the car to lift the heat up and out. The extra vent you are talking about would be good, but do not try to reverse the natural up-flow of air.

With yarn pieces attached at the roof line that are just a little longer you can likely pick up the turbulence that is occurring immediately above the vents.

This is a really good opportunity for us to understand this air pattern. When I did mine, I used long ribbons which just plastered themselves against the window and I didn't have a mounted video camera at my disposal. (This is very cool research BTW.)

I wish www.myfiero.com was working today. The old pics I have from Eclipse following me showed that with the Shadow spoiler the air was moving under and over the spoiler in the center unlike the Fiero wing which appears to be successfully getting the air to move over the wing to the back instead of forward.

Is it possible that one could fab a pair of rear facing scoops that look nice, and use them instead of the grills? That would eliminate some of the turbulence but would it allow the air to flow better?

Arn

Blacktree, good work, it's admirable to do actual research to get information rather than just making wild assumptions. Changing to yarn is a good thing, as you can tell it's much better at showing flow in any/all directions and at indicating "dirty" air because it's not as stiff as the paper. Some food for thought on the engine vents, you may want to consider re-running the test using a stock vs. modified vent on the same side of the car. You showed video of left vs. right vents with stock vs. modified (respectively). It would be a more worthwhile comparison to do stock vs. modified while viewing the same side for each type. You mention how much more freely the modified vent flows, but for all you/we know, the right side vent flows more air on your car whether it's modified or stock.

If you were really feeling ambitious, you could modify your stock vent to remove the bottom panel of the leaf catcher so it has stock top appearance but much less material to impede flow. Some people have even gone so far as to modify it so they could re-attach the bottom panel with screws for the fall season (to actually catch leaves). Then you could do a stock vs. leaf catcher removed vs. mesh screen comparison of the same (right?) side. I know that from a looks perspective, removing the leaf catcher really looks sharp and still has a stock look to it.

Bryce

I was wondering how long it would be until somebody caught that. Unfortunately, those two decklid vents are the only two I have. And all the local salvage yards are out of Fieros. Anyone willing to donate a right-side decklid vent?

quote Originally posted by Arns85GT: I wish www.myfiero.com was working today. The old pics I have from Eclipse following me showed that with the Shadow spoiler the air was moving under and over the spoiler in the center unlike the Fiero wing which appears to be successfully getting the air to move over the wing to the back instead of forward.

Air rushing over and under the wing will likely create lift, similar to air getting under the chasis creating lift. If the air is only traveling over the top, you are more likely to get downforce. Am I thinking wrong here?

quote Originally posted by Electrathon: Air rushing over and under the wing will likely create lift, similar to air getting under the chasis creating lift. If the air is only traveling over the top, you are more likely to get downforce. Am I thinking wrong here?

"Air rushing over and under the wing will likely create lift"

I don't think this is true.

Air rushes over and under an airplane wing. The wing produces lift because the lower surface of the wing is flat and the upper surface of the wing is curved. This creates a difference is the path of the air as it traveles over and under the wing which results is lower pressure on the top of the wing relative to the pressure on the bottom side of the wing. The difference in pressure is what yields the lift on the wing.
If you were to turn the airplane wing upside down, with the flat surface on the top, the wing would produce a net downward force which is what the wings on cars are supposed to do.

I'm pretty sure that the above info is correct, however my last Physics class was a few decades ago. I hope this helps.

~Bob

------------------
"Its nice to be important.
Its more important to be nice."

The Fiero wing is upside down. Look at it closely. The top side is straight and the bottom is curved.

Arn

Fantastic thread. I have noticed when the spoiler is wet there doesnt seem to be any movement of the drops. I have a notchback Look a the IMSA racers and you will notice the rear spoiler stands high of the deck! I bet the Dodge spoiler works far better! I know that GM will put a rear spoiler on just to add value to the vehicle. Look at the Grand Am rear spoiler I dont think they ran it through the wind tunnel. I have notice over the years of selling Pontiacs/GM's they will add an item to make the vehicle look better. I love the second gen trans ams. Real spoilers, air foils and vents that worked!

Thanks for the thread

[This message has been edited by solotwo (edited 06-05-2008).]

quote Originally posted by Blacktree: Today, I took some video of the decklid vent gratings. I compared a stock vent to a modified, free-flowing one to see if there would be a noticeable difference. Unfortunately, I couldn't get a good camera angle from inside the car. So I had to mount the camera behind the back window. I was concerned that heat (both from the hot Florida sun, and from the engine compartment) would damage the camera. But it survived unscathed. You can see the video in my original post on Page 1. I decided to consolidate all the results there, so people wouldn't need to scroll through several pages of conversation to see it all.

For a complete test, you should do the same thing with the vents swapped to the other side of the car as there are different components on each side of the car.

In order to do that, I need the appropriate vents. Like I mentioned above, I'm having trouble finding decklid vents locally. Wanna help?

Everything I've seen has shown a lower drag coefficient on Fieros with wings as opposed to Fieros without. If that's true, then the wing acts like an airplane wing and has lift.

quote Originally posted by 85fiero_fanat: Everything I've seen has shown a lower drag coefficient on Fieros with wings as opposed to Fieros without. If that's true, then the wing acts like an airplane wing and has lift.

Drag and lift have nothing to do with eachother...you can add a ton of drag (or remove it) without affecting lift or downforce at all. What you said doesn't make any sense; with the same logic, one would argue that reducing coefficient of drag to improve fuel economy (by cleaning up airflow at seams, wipers, etc.) would add lift and change handling, which obviously is not how it works.

Bryce

quote Originally posted by Nashco: Drag and lift have nothing to do with eachother...you can add a ton of drag (or remove it) without affecting lift or downforce at all. What you said doesn't make any sense; with the same logic, one would argue that reducing coefficient of drag to improve fuel economy (by cleaning up airflow at seams, wipers, etc.) would add lift and change handling, which obviously is not how it works. Bryce

Any form of down force creates drag. Therefor, if the wing created down force, it would create drag, which would then raise the drag coefficient of the car. I know that you can adjust drag without changing down force, but down force creates drag.

quote Originally posted by 85fiero_fanat: Any form of down force creates drag. Therefor, if the wing created down force, it would create drag, which would then raise the drag coefficient of the car. I know that you can adjust drag without changing down force, but down force creates drag.

Downforce can contribute to drag, but you said that the wing creates lift because it reduce drag and that is simply wrong...

The wing is not located in the dominant air flow stream. It is in general an upside down air foil but, anyone can see in light rain, that the droplets do not move on the top surface, meaning that the air foil principle cannot work. The top of the wing is shielded from the air stream by the cockpit.

The wing only acts as a smoothing device for the air tumbling up the tail and murging with the dominant air stream. It reduces drag by reducing the turbulence on the tail end. By mounting it up about a foot, you would soon find it functioning as a wing, and if angled appropriately would actually produce some down force. However, it would look way too ricey for me and I am still thinking ground effects skirts with side vents is the optimum way to go for downforce. But hey, I'm no engineer either.

Arn

quote Originally posted by Arns85GT: The wing is not located in the dominant air flow stream. It is in general an upside down air foil but, anyone can see in light rain, that the droplets do not move on the top surface, meaning that the air foil principle cannot work. The top of the wing is shielded from the air stream by the cockpit. The wing only acts as a smoothing device for the air tumbling up the tail and murging with the dominant air stream. It reduces drag by reducing the turbulence on the tail end. By mounting it up about a foot, you would soon find it functioning as a wing, and if angled appropriately would actually produce some down force. However, it would look way too ricey for me and I am still thinking ground effects skirts with side vents is the optimum way to go for downforce. But hey, I'm no engineer either. Arn

But none of those things listed really give down force on the rear, and that's why a wing is normally used when rear down force is needed, because it's the easiest to create down force with, and the easiest to adjust down force with. Has anyone thought about adding a wing right behind the cockpit, kinda like on the Ferrari 512's? It seems like the area behind the cockpit is what creates the most drag. A wing right there might help out. If not that, why not create a little spoiler to the back of the cockpit.

example...

Hey Mike, I have a number of extra vents for notchbacks that you can have to run tests with. Also have rims like you mentioned last night. Give me a call. Harry

------------------
87 GT Maroon 3800SC & White Formula

quote Originally posted by Electrathon: fiero turbo scoops: The ugly scoops that stick over the roof? Too ugly and dorky looking to use no matter if they work or not.

Nicely put.

Nice testing. You give an idea of what is happening around the wing and the vents. The big picture has been referred to several times and that is the fact that from the rear window to the rear of the car is not aerodynamic. If there was a piece of glass like bubbajoexxx put on his highly modified Fiero then you would have a nice airflow from the rear window to the rear of the car and a wing mounted in the stock location would get "clean" (well, cleaner) air to flow from front to rear. This is assuming that the front of the car does not create too much turbulence prior to the rear window area. Also, keep in mind that air on the sides of the car are flowing in vortices's starting just past the notch back side panels or the more sloped side panels of the fastback. So really all you get with the stock car is a bunch of turbulence behind the rear window and a slightly lower air pressure. If I were to mount fans they would blow upward and out of the vents to help rid the heat most efficiently.

This thread has been dormant for a while, but I'm going to revive it. I've started on another aerodynamics experiment. This time, I'll be filming the airflow patterns on the hood and rear deck, from above. In order to do this, I built a camera mount that sits on the roof. It places the camera about 3 feet above the roof, giving it a good view of the hood and rear deck.

I decided to enclose the camera in a box, for several reasons. First of all, I don't want the camera falling off the car due to the wind. Second of all, the enclosure provides protection against the elements (and flying bugs). And third of all, I'm hoping the enclosure will reduce wind noise enough that the sound won't have to be muted.

The box is made of cheap 1/4" thick plywood, glued together. The window is just a piece of clear acrylic. And there's a sheet of aluminum in the floor to give the camera mount (which uses a suction cup) something to stick on. The support frame is made of PVC pipe. The whole rig will be strapped to the car with tie-down straps.

Here are a few photos:







With this setup, I hope to find out 3 more aspects of the Fiero's aerodynamics: how the air flows over the decklid (with different spoiler configs, and with no spoiler), how hood vents affect the airflow over the hood, and how the pop-up headlights affect airflow over the hood.

After I get some data, I'll post it up.

The wing is a spoiler. It's supposed to clean up the air behind the car. The back of a Fiero is like a pickup truck, a low pressure are that sucks air through the engine vents, where it curls under.

Real wings get "clean air", and are usually mounted much higher, i.e.: Subaru Sti, Mitsubishi Evo, those then serve to push down the rear end of the car.

In terms of aerodynamic efficiency, the aero notchback with wing is the most efficient. The Fastback the least efficient. The fastback panels/back end are more for looks/cosmetics than actual aerodynamics.

btw, thanks again for these aerodynamics experiments. They're really interesting to watch, and we learn a lot.

If you can get good camera angles, could you mount some tell tales on the sides of the car, and on the front and rear bumpers? I'm really curious about the direction of the airflow.

If you have a sunroof, could you do the same test with the sunroof tilted and removed? I've always been curious how it affects aerodynamics.

quote Fiero Aerodynamics Experiment

Wouldn't that be a Fiaerodynamics Experiement?

Sorry, no sunroof. Also, my experiments are conducted on public roads... which are usually busy with traffic. So having a camera pod hanging off the side or back of the car would be asking for trouble. I'd love to have a deserted airfield or something similar to play on, but there isn't anything like that around here.

I'd like to know what having the headlights up does to the aerodynamics myself... they're awefully big, I bet they make all kinds of drag.

I tend to agree with what was said earlier about how the decklid vents function... The sharp drop-off of the passenger compartment to the deck area, would definitely create a significant low pressure zone, which SHOULD pull air up through the compartment and vents... but, I imagine that there is a sharp difference on the underside as well, which probably neutralizes alot of this effect. Maybe adding a under-car scoop to pull some air up into the compartment and through the vents could help keep it cooler.

IMO, there are really only 2 cars I've seen with spoilers that I thought looked better with them than without them, that's an 80's Camaro, and some Fiero's... I'm thinking about getting one to install on my gold Notchie... but, I haven't looked into the different styles yet.

http://www.youtube.com/watch?v=zT7j6O-Hvus
Here what pop-ups do on a c5.

If you ever want to experience the aerodynamic drag of the headlights for yourself, just take out the sunroof/t-tops and stick your hand out. Then, flip on the lights, and put your hand out again. There's a noticeable difference. The wind going over the car with the lights down is still fast and high-pressure, but with the lights up, it's high-pressure, uneven, and buffeting. For what it's worth, my Dad refuses to take his Fiero on night road trips because the loss of mileage from the extra drag.

quote Originally posted by ManMadeChickens: If you ever want to experience the aerodynamic drag of the headlights for yourself, just take out the sunroof/t-tops and stick your hand out. Then, flip on the lights, and put your hand out again. There's a noticeable difference. The wind going over the car with the lights down is still fast and high-pressure, but with the lights up, it's high-pressure, uneven, and buffeting. For what it's worth, my Dad refuses to take his Fiero on night road trips because the loss of mileage from the extra drag.

lol, I don't have any such portals to the top of my car... yet :P My head practically sticks out of the ceiling anyways, being 6'6" tall... still, plenty of leg room in that little car. Everyone laughs and asks how I fit in there :P The plus side is, the shifter is really nice for me to use, which I guess alot of people complain about.

By the way BlackTree, that's a really mean looking Fiero, I like it. Though, the big PVC tower and wood box kind of ruins its good looks :P [/off topic]

[This message has been edited by Twilight Fenrir (edited 01-09-2009).]

Here is a camera set up that is a bit less cumbersome:
http://tinyurl.com/8z6484

------------------
My Car Site
www.flexyourrights.com
Just say NO!! to Automatic Transmissions!!

Be aware that your camera mount will highly affect the airflow in the rear and probably the front too. If I were you I would find a friend to tape from another car.

If any did provide downforce, why is it that if you dont lock your trunk, it blows open....not closed. Ive seen it happen. It doesnt necessarily have anything to do with the assist springs. My V8 GT had an added on wing so the springs just barely held it open. If you parked on a hill, or even the slightest breeze hit it, down it came. A lot of times Id go to shows and just let the lid set closed but not latched so I could get in and out all day without using a key. Id always forget to push it down to latch it and soon as Id hit the freeway up popped the drag chute.

quote Originally posted by FieroBobo: "Air rushing over and under the wing will likely create lift" I don't think this is true. Air rushes over and under an airplane wing. The wing produces lift because the lower surface of the wing is flat and the upper surface of the wing is curved. This creates a difference is the path of the air as it traveles over and under the wing which results is lower pressure on the top of the wing relative to the pressure on the bottom side of the wing. The difference in pressure is what yields the lift on the wing. If you were to turn the airplane wing upside down, with the flat surface on the top, the wing would produce a net downward force which is what the wings on cars are supposed to do. I'm pretty sure that the above info is correct, however my last Physics class was a few decades ago. I hope this helps. ~Bob

Thought Experiment: How does an aircraft fly inverted then? Bernoulli's Theorem explains only a portion of total lift for typical aircraft. A clue - Angle of incidence.

quote Originally posted by FieroWannaBe: http://www.youtube.com/watch?v=zT7j6O-Hvus Here what pop-ups do on a c5.

Cool video. I would expect the effect on a Fiero to be very similar. However, my camera will be looking at the turbulence from above instead of the side. I want to see just how much of the airflow over the hood is "spoiled" by the headlights. I'm guessing it will be quite a lot... probably 1/2 to 2/3 of the hood's surface area. But we will see in due time.

quote Originally posted by ICouldaBeenAV8: Thought Experiment: How does an aircraft fly inverted then? Bernoulli's Theorem explains only a portion of total lift for typical aircraft. A clue - Angle of incidence.

Because, they have so much speed behind them they overcome MOST of the negative airfoil. Besides, they have flaps beyond just the wing. If an aircraft is going fast enough with it's flaps all the way down (relative to the pilot) It will stay airborne. If you just plain flipped it over without compensating, the plane would plumit.

If you look at an airfoil from an airplane designed to fly upside down, it will have a laminar airfoil. This means that there will be similar amount of curve both above and below the wing. This is not the most efficient airfoil for flight but it is the best for flying both right side up and upside down. An airfoil designed for maximum efficiency will be very bad for inverted flight. It may fly in level flight inverted if the aircraft has a high enough power to weight ratio. (I call that the Soviet rule. If it does not fly, add more power.) Most "Wings" on cars that are designed for downward force are low speed, high lift airfoils. They are only designed to make lift in one direction. IMHO the Fiero "wing" is pure decoration. It looks cool though so I am considering leaving it on my car.

http://www.kineticart.co.uk...dStudioSimulator.asp

I appreciate and applaud your thread and ingenuity, but don't you think your PVC support will be heavily influencing the airflow that you're wanting to see on the back end of the car?

------------------
RickN
White 88GT 5spd
White 85GT Auto
White 99 F250SD 7.3PSD 6spd
1956 Ford 860 Tractor w/ Freeman Loader

Why not just mount the camera inside the car?

quote Originally posted by cptsnoopy: If you look at an airfoil from an airplane designed to fly upside down, it will have a laminar airfoil. This means that there will be similar amount of curve both above and below the wing. This is not the most efficient airfoil for flight but it is the best for flying both right side up and upside down. An airfoil designed for maximum efficiency will be very bad for inverted flight. It may fly in level flight inverted if the aircraft has a high enough power to weight ratio. (I call that the Soviet rule. If it does not fly, add more power.) Most "Wings" on cars that are designed for downward force are low speed, high lift airfoils. They are only designed to make lift in one direction. IMHO the Fiero "wing" is pure decoration. It looks cool though so I am considering leaving it on my car.

Downwash.

I'm tuned in.

------------------
"A guy know's he's in love when he loses interest in his car for a few days." -Tim Allen

He who dies with the most toys... still dies.


Check out my restoration!

[This message has been edited by Fierology (edited 01-17-2009).]