Aerodynamic improve ments

[goatnipples2002]

I have been doing alot of research about the areodynamics of my GT and came up with a few ideas that others might be interested in. The wing of the fiero does damn near nothing if anything. It needs to be about roof level because of the fieros design. The diagram below shows why. If your satisfied with the wing or don't drive fast then more power to you but if you drive 100mph then you might want to upgrade your wing/spoiler. Spoilers only create downforce when they are in clean air.



Vortex Generator. This is a "VG"

It helps improve a spoiler/wings ability to create downfoce. It comes stock on the new evo 8 and many have already copied the design. The funcionality of it on a fiero hasn't been tested yet. On an evo it decreases turbulent air. It affects the boundary layer of air flow. Not sure of its effectiveness, but it's one of the hot topics right now and thought I would inform people about it. The same pattern of "bumps" can be found on the front roof of many trucks. Take a look at the way the cab roof lights are set up.....same shape and similiar pattern . Think its an accident they are set up that way.....I think not.


To increase downforce up front there are canards


There effectiveness depends on how many you have, their placement, their angle of attack and how fast you are going....yet they do add a considerable amount of downforce.


There is also the front/chin spoiler


These don't actually create downforce by themselves. They direct more air into the radiator area (depending on design). Alone these will create a more aggresive look and INCREASE LIFT, BUT when you add a hood vent or extractor scoop the chin spoiler will increase downforce. This is because the air that is being directed into the radiator has no where to exit. So if you add more air that has no where to go that will result in more lift. You add the vent/scoop and the added air has somewhere to exit. Resulting in increased downforce.
The downside of this mod is the price and if you low you fiero you will need to take extra caution so you don't scrape the spoiler.

The next best/cost effective suggestion is to take the bottom section of another aero nose bumper...flip it upside down and mount it this way. This type of bumper mod is more for looks for than function. The upside of this is that you don't have to worry about ride height and the mod can be done for very cheap. Plus it looks damn good.





The best and most important mod to keep your front end stable when driving fast is to put an extractor scoop or a hood vent directly over the radiator compartment. I have a 6x6 hole over my radiator compartment and it helped tremendously...going 130mph felt like 60mph.



I need to read more so this is it for now. Tell me what ya'll think.
(None of these fieros are mine, just posted for examples.)

[Black Lotus]

The vortex generators as used on the Evo won't work on a stock Fiero, as there is nothing to attach the airflow to (open air behind the rear roof line).
In any event, the rear roof line's sudden termination trips the airflow downward and ultimately the airflow spirals around like a horizontal tornado. If you were to look at a side view of the car and the front is pointing to the left, the airflow would be from left to right. And the "tornado" that I'm referring to would then be clockwise. As you can imagine, this would bend the overall upper surface airflow down, just far enough to impact the aft upper suface of the stock wing.
The stock rear wing acts (IMO) the equivalent to you sticking the tip of your finger into the water stream of a faucet. You can deflect the flow of the water. I think the same thing happens to the airflow behind the wing, it deflects down giving the Fiero a passable Cd.
Just my opinion from reading, my own observations, and looking at photos of the car at speed with streamers attached.

[goatnipples2002]

Sounds good.....BUT not quite how it goes. Sometimes you can't apply common logic to physics. The wind coming off the end of the roof will "swirl"....which is called rear vacuum effect and that does nothing for downforce. If the wind is "swirling" towards the back window as you say how could your wing provide any down force if there is never a chance for "clean"/non-turbulent air to pass over it? Your wing would need to in a place of clean air in order for it to be effective. This area of clean air is higher than the stock location.....it is located about roof level.

Another detail about our wings is that the angle of attack is setup for MINIMAL downforce/drag. Wings need to have a greater angle of attack when you are going less than about 150mph. Wings with a slight angle of attack are usually found on cars that are on speedways going like 200mph. They don't rely on there wings for downforce but the actual structure of the chassis provides most of the downforce. Street cars require a wing with an agressive angle so the wing can provide downforce when cornering.

The VG would delay the rear vacuum effect so that the wing could pick it up before it "swirls". VGs work on damn near all vehicles. They've had them on planes for many decades. It's not what the air does before the VG, it's what the air does after the VG as it rolls off the edge of the roof.

Now time for some details.....when air travels over your car it becomes more and more unstable and unpredictable with changing patterns which is called turbulence. So by time the wind hits the end of your roof it is extremely turbulent. The turbulent air passes over the VG.....the VG speeds up the turbulent air.....this speed increase causes a pressure reduction. This pressure is what causes the "swirl". Reduce the pressure of the trubulent air and you reduce the "swirl".

Did you see the post on Pennock's where someone put strips on the back of his fiero? He had a rear decklid scoop facing the wing and you would assume that the air would come out of it and the vents......but the opposite happened. Guess why? Because of the "SWIRL" . Just a real life example of what I was trying to explain.
Here's the link http://www.fiero.nl/forum/Forum2/HTML/064636.html

Found this one too...it's old but it has some good stuff. http://www.fiero.nl/forum/Forum2/HTML/060770.html

You do have a point about ours car having a different flow pattern than most other cars. I left links in the 1st post and here that explain it better than I. I don't claim to be a aerodynamists or physicist so if i am wrong please correct me.

This is the research done by the mitsubishi enegineers that designed the VG.
http://www.mitsubishi-motors.com/cor...004/16E_03.pdf

[Black Lotus]

Originally Posted by goatnipples2002

Sounds good.....BUT not quite how it goes. Sometimes you can't apply common logic to physics. The wind coming off the end of the roof will "swirl"....which is called rear vacuum effect and that does nothing for downforce. If the wind is "swirling" towards the back window as you say how could your wing provide any down force if there is never a chance for "clean"/non-turbulent air to pass over it? Your wing would need to in a place of clean air in order for it to be effective. This area of clean air is higher than the stock location.....it is located about roof level.

Another detail about our wings is that the angle of attack is setup for MINIMAL downforce/drag. Wings need to have a greater angle of attack when you are going less than about 150mph. Wings with a slight angle of attack are usually found on cars that are on speedways going like 200mph. They don't rely on there wings for downforce but the actual structure of the chassis provides most of the downforce. Street cars require a wing with an agressive angle so the wing can provide downforce when cornering.

The VG would delay the rear vacuum effect so that the wing could pick it up before it "swirls". VGs work on damn near all vehicles. They've had them on planes for many decades. It's not what the air does before the VG, it's what the air does after the VG as it rolls off the edge of the roof.

Now time for some details.....when air travels over your car it becomes more and more unstable and unpredictable with changing patterns which is called turbulence. So by time the wind hits the end of your roof it is extremely turbulent. The turbulent air passes over the VG.....the VG speeds up the turbulent air.....this speed increase causes a pressure reduction. This pressure is what causes the "swirl". Reduce the pressure of the trubulent air and you reduce the "swirl".

Did you see the post on Pennock's where someone put strips on the back of his fiero? He had a rear decklid scoop facing the wing and you would assume that the air would come out of it and the vents......but the opposite happened. Guess why? Because of the "SWIRL" . Just a real life example of what I was trying to explain.
Here's the link http://www.fiero.nl/forum/Forum2/HTML/064636.html

Found this one too...it's old but it has some good stuff. http://www.fiero.nl/forum/Forum2/HTML/060770.html

You do have a point about ours car having a different flow pattern than most other cars. I left links in the 1st post and here that explain it better than I. I don't claim to be a aerodynamists or physicist so if i am wrong please correct me.

This is the research done by the mitsubishi enegineers that designed the VG.
http://www.mitsubishi-motors.com/cor...004/16E_03.pdf

"rear vacuum effect"
Well, that's some new terminology for me....
"how could your wing provide any down force".
Never said it did or would.
"They've had them on planes for many decades."
I know, I was just contemplating some located on the underside of the leading edge slats on a brand new 737 sitting inside the Boeing Renton factory building.
"Did you see the post on Pennock's where someone put strips on the back of his fiero?"
Yes I did. That's what reinforced my OPINION of what the airflow patterns are at the rear of the Fiero.
Obviously we are two different people, who look at the same data and reach different conclusions.
We can just leave it at that.

[goatnipples2002]

No problem man. The only reason I started researching the subject and posted was because I wanted to go faster without doing anything mechanical. I figured that a fiero has never seen a wind tunnel unless the owner did it. You are intitled to your own opinion i am just trying to help.

[fierangero]

i have a strong feeling that the spoiler does, even minimally, create downforce. i look back i can see the wind blowing against the spoiler when im driving, and around 110 or so the front end starts to lift, partially due to the downforce on the rear (kinda like hondas with spoilers, except not as detrimental since we are rwd) so while its not as effective as it could be, adding additional downforce to a car that will most likely never see the other side of 140 mph is akin to putting full sandbags in the trunk, you get the force effect but without any real benefit

[goatnipples2002]

The reason your front end raises is not because of rear downforce it's because of the pressure under the hood. When you go fast enough the air that goes to the radiator has ni where to go so the front end becomes a "kite". I bet you don't have a scoop (facing backwards) on your hood to let the air out....do you? Try that and your kite effect will be gone. I put a 5"x5" hole in my hood right above the radiator compartment and at 120-130mph it feels like 60mph. I have no lift, my responsiveness at 120mph is perfect....considering my old ass suspension. Aerodynamics has alot to do with speeding and the cars ability to "cut" through the wind instead of "plowing" through the wind. Read my 1st post all this is explained. If you add downforce to the rear you MUST add it to the front....vice versa. Aerodynamics is the one thing that can increase top speed and E/Ts without doing engine work.

[RandomTask]

First off goat, never to trust a site thats trying to sell you something... period.

Second- You ask for help, then when you get it, you tell the people they are wrong...

Third- "Vaccum Effect"? You mean drag? A VG is used to decrease drag, not provide downforce. The only thing a VG could be considered to help is the reducing the boundary area which may at the slightest level (I'm talking .0000001%) exchange some parasitic drag for lift induced drag. But its main function is to elminate drag, not provide downforce. Putting a VG at an sharp edge is almost worthless.

"If you add downforce to the rear you MUST add it to the front....vice versa" --- False, or what, your car will spontaneously explode?

The reason for the Fiero's high drag co-efficient is its sharp (almost 90 degree's) after the roofline. This creates a low pressure area-- aka drag-- (this is also why those vents are designed to let heat out, not push air in) perhaps this is what you meant by vaccum effect?

You want to reduce drag and get some more down force on the fiero? Make a smooth, rounded panel that covers the rear decklid that extends to both pillars, roofline, and rear of the trunk. Only then would a VG be useful on the car.
You need to take a course in fluid dynamics, ...

And if you think I'm talking out of my ass, I invite you to critisize me. I've worked at NASA Langley wind tunnel for over 2 years and would like to hear what you have to say.

[goatnipples2002]

Originally Posted by RandomTask

First off goat, never to trust a site thats trying to sell you something... period.

I don't trust their products If you knew abour aerodynamics you would understand that they are only reciting basic aerodynamic theories and principles. So that is the only reason I posted that site.

Originally Posted by RandomTask

Second- You ask for help, then when you get it, you tell the people they are wrong...

I never asked foe help.....I started this post to help others understand how to improve their fieros and share what I learned from my research.

Originally Posted by RandomTask

Third- "Vaccum Effect"? You mean drag? A VG is used to decrease drag, not provide downforce. The only thing a VG could be considered to help is the reducing the boundary area which may at the slightest level (I'm talking .0000001%) exchange some parasitic drag for lift induced drag. But its main function is to elminate drag, not provide downforce. Putting a VG at an sharp edge is almost worthless.

NO, drag and vacuum effect are two different things.
I tried to keep it simple but here.....

Aerodynamic drag - The drag produced by a moving object as it displaces the air in its path. Aerodynamic drag is a force usually measured in pounds; it increases in proportion to the object's frontal area, its drag coefficient, and the square of its speed.

Rear vacuum aka FLOW DETACHMENT (a non-technical term, but very descriptive) is caused by the "hole" left in the air as the car passes through it. To visualize this, imagine a bus driving down a road. The blocky shape of the bus punches a big hole in the air, with the air rushing around the body, as mentioned above. At speeds above a crawl, the space directly behind the bus is "empty" or like a vacuum. This empty area is a result of the air molecules not being able to fill the hole as quickly as the bus can make it. The air molecules attempt to fill in to this area, but the bus is always one step ahead, and as a result, a continuous vacuum sucks in the opposite direction of the bus. This inability to fill the hole left by the bus is technically called Flow detachment. See the diagram below.

Flow detachment applies only to the "rear vacuum" portion of the drag equation, and it is really about giving the air molecules time to follow the contours of a car's bodywork, and to fill the hole left by the vehicle, it's tires, it's suspension and protrusions (ie. mirrors, roll bars). If you have witnessed the Le Mans race cars, you will have seen how the tails of these cars tend to extend well back of the rear wheels, and narrow when viewed from the side or top. This extra bodywork allows the air molecules to converge back into the vaccum smoothly along the body into the hole left by the car's cockpit, and front area, instead of having to suddenly fill a large empty space.
The reason keeping flow attachment is so important is that the force created by the vacuum far exceeds that created by frontal pressure, and this can be attributed to the Turbulence created by the detachment.

Originally Posted by RandomTask

"If you add downforce to the rear you MUST add it to the front....vice versa" --- False, or what, your car will spontaneously explode?

When 1 side of your car has more downforce than the other it allows the pressure under/above the car to be unequal which leads to lift (the enemy).

Originally Posted by RandomTask

The reason for the Fiero's high drag co-efficient is its sharp (almost 90 degree's) after the roofline. This creates a low pressure area-- aka drag-- (this is also why those vents are designed to let heat out, not push air in) perhaps this is what you meant by vaccum effect?

The major cause of the high drag co-effient is the slant on the windshield. The rear window creates a problem with flow detachment. Low pressure is not drag. The bottom of the fiero was designed to allow air come up for cooling not in. And No that is not what I mean by vacuum effect.

Originally Posted by RandomTask

You want to reduce drag and get some more down force on the fiero? Make a smooth, rounded panel that covers the rear decklid that extends to both pillars, roofline, and rear of the trunk. Only then would a VG be useful on the car.
You need to take a course in fluid dynamics, ...

You are correct about the panel idea, it would help greatly. I am not sure if a VG would work without it. In theory yes, but in the real world...who knows. I study alot of AERODYNAMICS. Plus the vortex generator was researched, desighned and tested on the Mitsubishi Evolution 8...never intended for the Fiero, but I talked about it because it sounded useful and was found to be funtional on other vehicles. So I thought why not the fiero. I believe it would help with the problem of our back windows.

Originally Posted by RandomTask

And if you think I'm talking out of my ass, I invite you to critisize me. I've worked at NASA Langley wind tunnel for over 2 years and would like to hear what you have to say.

I don't assume you are talking out of your ass, but it seems that our terminology is different. For a nasa guy seems like you are rusty, time to start studying again. Do you still have "connections" at the tunnel? I only repeat what I read in the books.

Did You ever get a chance to put a Fiero in the tunnel?
What do you suggest needs to be done to the Fiero to increase its performance/downforce?
What about.....canards?...chin spoilers?.....ground effects?.....roof scoops?.....naca scoops?.....vortex generator? have you had any experience with these mods?

I am not critisizing you (anymore ). I would really like to see what you do know.

[fierangero]

hrm...iirc the owners manual was touting the low Drag Coefficient (.377) of the fiero. sure its not an '05 vette (.27), but its fairly efficient for an 80's car (efficiency rating of .65)

as far as the vacuum after the sharp roofline, that is correct, i remember having many arguments with truck owners saying "if u put ur tailgate down, it goes faster/better gas mileage" i just laugh at them and offer to sell them a turbonator

[RandomTask]

Originally Posted by goatnipples2002

I don't trust their products If you knew abour aerodynamics you would understand that they are only reciting basic aerodynamic theories and principles. So that is the only reason I posted that site.

I never asked foe help.....I started this post to help others understand how to improve their fieros and share what I learned from my research.

NO, drag and vacuum effect are two different things.
I tried to keep it simple but here.....

Aerodynamic drag - The drag produced by a moving object as it displaces the air in its path. Aerodynamic drag is a force usually measured in pounds; it increases in proportion to the object's frontal area, its drag coefficient, and the square of its speed.

Rear vacuum aka FLOW DETACHMENT (a non-technical term, but very descriptive) is caused by the "hole" left in the air as the car passes through it. To visualize this, imagine a bus driving down a road. The blocky shape of the bus punches a big hole in the air, with the air rushing around the body, as mentioned above. At speeds above a crawl, the space directly behind the bus is "empty" or like a vacuum. This empty area is a result of the air molecules not being able to fill the hole as quickly as the bus can make it. The air molecules attempt to fill in to this area, but the bus is always one step ahead, and as a result, a continuous vacuum sucks in the opposite direction of the bus. This inability to fill the hole left by the bus is technically called Flow detachment. See the diagram below.

Flow detachment applies only to the "rear vacuum" portion of the drag equation, and it is really about giving the air molecules time to follow the contours of a car's bodywork, and to fill the hole left by the vehicle, it's tires, it's suspension and protrusions (ie. mirrors, roll bars). If you have witnessed the Le Mans race cars, you will have seen how the tails of these cars tend to extend well back of the rear wheels, and narrow when viewed from the side or top. This extra bodywork allows the air molecules to converge back into the vaccum smoothly along the body into the hole left by the car's cockpit, and front area, instead of having to suddenly fill a large empty space.
The reason keeping flow attachment is so important is that the force created by the vacuum far exceeds that created by frontal pressure, and this can be attributed to the Turbulence created by the detachment.

When 1 side of your car has more downforce than the other it allows the pressure under/above the car to be unequal which leads to lift (the enemy).

The major cause of the high drag co-effient is the slant on the windshield. The rear window creates a problem with flow detachment. Low pressure is not drag. The bottom of the fiero was designed to allow air come up for cooling not in. And No that is not what I mean by vacuum effect.

You are correct about the panel idea, it would help greatly. I am not sure if a VG would work without it. In theory yes, but in the real world...who knows. I study alot of AERODYNAMICS. Plus the vortex generator was researched, desighned and tested on the Mitsubishi Evolution 8...never intended for the Fiero, but I talked about it because it sounded useful and was found to be funtional on other vehicles. So I thought why not the fiero. I believe it would help with the problem of our back windows.

I don't assume you are talking out of your ass, but it seems that our terminology is different. For a nasa guy seems like you are rusty, time to start studying again. Do you still have "connections" at the tunnel? I only repeat what I read in the books.

Did You ever get a chance to put a Fiero in the tunnel?
What do you suggest needs to be done to the Fiero to increase its performance/downforce?
What about.....canards?...chin spoilers?.....ground effects?.....roof scoops?.....naca scoops?.....vortex generator? have you had any experience with these mods?

I am not critisizing you (anymore ). I would really like to see what you do know.

No, I've never put a Fiero in the tunnel, at $8K an hour with a minimum of two hours setup it was just a little out of my price range I have done cup cars, Grand Am series cars, and a couple of others.

2nd- I think we are both confused on an understanding of eachother. Theres drag air going over a surface, I think think this is what you mean by frontal area. I mean this by boundary area. No surface is perfectly smooth. Imagine rubbing your hand against sandpaper, theres friction. Theres still friction against any surface, and this creates drag as well.

The way it (air flow) departs, or the flow detachment as you stated is absolutely critical. This vaccum is a form of drag. You could have a semi with a long tapered front and rear, that has a large frontal area, then take a a minivan thats shaped like a brick. The Semi would have more of a surface drag, (or parasitic) drag but less lift induced drag. Overall, the semi would experience less overall drag.

Taking example of NASCAR, it is not absolutely necessary to add downforce to both ends of the car. Their spoilers create a lot of downforce and drag (mostly drag) yet they are not running a front spoiler.

Lift is either created by a wing, or high pressure underneath the car. (there are a couple of other variables that may induce lift, but their forces are negligable) If you can eliminate the pressure underneath (I.E. an airdam, or a hole in the hood as you suggested) the pressure decreases.

I have some books somewhere on all of this and am trying to find them...

[goatnipples2002]

Is this a break through?

You are right. Air does "stick" to all surfaces. Just rub your car down with baby oil

Why the hell does it cost so much for a damn tunnel with smoke. Is it any cheaper anywhere else? I assume nasa would charge a bunch.

Now the nascars have airdams aka chin spoilers on the front and theyare about an inch or less off the ground.

What's a cup car?

You just can't put a hole in the front and ride out.....you must have a scoop facing the windshield. Just in case anybody had any ideas of just cutting a hole in their hood. I believe it is called an extractor scoop when use it this way.

So you don't think the VG would work on our cars?

What about canards.....I know they work, but do you think they are worth it?

[RandomTask]

I forgot to mention that vaccum is also a force of lift. Sorry if you mentioned that earlier.... (I guess i really am rusty )

A cup car, NASCAR (Nextel Cup)
Its usually $8k an hour for planes and what not, and cars START at $2k an hour for testing.

As far as the hole, it helps marginally, it relieves the pressure buildup from underneath the radiator as air can only vacate that compartment at a certain rate.

No, I don't think a VG would work on our cars. Its too serious of an angle for it to compensate. Basically, in creating these vortex's it kicks the air down, (the downside of a vortex) in doing so, it re-directs the flow downward. We have too much an area for it to comenspate for. Canards could work but it would take a little to get them dialed in.

I think the biggest help on the fiero (and I am desperately trying to remember the name of this device) is to speed the air up underneath the car. In that sense, the biggest amount of downforce can be obtained.

[goatnipples2002]

Does the device you are talking about go on the front or the rear.

It sounds like an air dam or chin spoiler. From what many have said it is the best for the front end of the fiero for downforce.

The hole does only flow a certain amount of cfm but if there is an extractor scoop that will help the flow a tremendous amount. The bigger the holr the better, but the radiator compartment of the fiero is only a fraction of the actual hood. If you lift the hood you will see the actual area of the radiator. That is the biggest hole you could make for any improvement. I have future plans to widen the hole on mine as soon as I find a scoop that looks good to me.

How much was your 3800 swap? Was it a kit? Has anything broken or do you drive easy?

[RandomTask]

Originally Posted by goatnipples2002

Does the device you are talking about go on the front or the rear.

How much was your 3800 swap? Was it a kit? Has anything broken or do you drive easy?

They don't make kits for the 3800 like they do for SBC's. In a sense, I purchased custom motor mounts, most everything else is/was done by myself. As far as running driving it, when its done, I spent a little over 4k on the swap, I'm going to drive the piss out of it. If I wanted to drive around slow, I would have kept with the 2.5 .