STi Wing, Aftermarket Wing, or No Spoiler?

IGOTASTi

System Operator
Staff member
The voice of the people is divided on the huge 04-07 STi wing. Some hate it, some love it, some think it looks ugly. Some say it?s only for looks, and then some say that it?s very functional. Let?s see whether you need that wing in the back.
We see a lot of STi owners remove their stock factory wing and replace it with fancy aftermarket creations. And some remove it completely or replace it with the low WRX spoiler. Is there a sane reason to remove / replace the stock STi wing?
Hate the wing: Common Reasons They?ll Give You

  • STi rear spoiler is bulky and ugly;
  • it weighs too much;
  • it is not functional and for looks only;
  • it attracts attention;
  • wings are for ricers.
Love the wing: Common Reasons They?ll Give You
  • it is functional;
  • it makes the STi look like an STi;
  • it attracts attention.
Let?s speak to the functionality of the STi wing. We hate to disappoint some people, but it actually does work. Subaru spent hundreds of thousands of dollars to develop that particular wing and then spent many, many hours testing and tweaking the wing in wind tunnels.

The wing is specifically designed to provide a significant amount of downforce past 70 mph road speed. The wing reduces lift and increases the high speed stability. The STi aerodynamics were further enhanced in 2006, with the addition of a roof vane spoiler, which stabilizes the air flow to the rear wing.

The WRX spoiler does not come close to the STi wing in realized downforce. So replacing the STi wing with a WRX wing may not be such a good idea if you plan on racing or just going fast once in a while.

Removing the STi wing will significantly decrease the downforce at high speeds and yes, you can notice a difference at 120 mph, even more so at 150 mph. Do you modify your car for performance or for looks? Would you rather have stability at speed?

Replacing the STi wing with an aftermarket spoiler is an equally bad idea. Just think about it for a moment using common sense ? do you really believe that some aftermarket, low-production-run manufacturer will invest hundreds of thousands of dollars to design their wing? Will they then take their ?cool-looking? carbon fiber wing, put it on the STi and spend weeks in the wind tunnel tweaking it?

No manufacturer will go through that expense and you are getting a non-functional, poor excuse for a wing that only looks ?fast?. Prodrive did do some serious R&D for their WRC wings, further improving the STi wing. The real WRC wings are even more functional than a stock STi wing, and cost a whole lot more than a ?cool? aftermarket wing. We wonder why that is?

We see a lot of ?cool? aftermarket wings put on STi's and other cars. The coolest thing about them is that at speed, the droplets of water stay on most of those wings, meaning there is no air flow anywhere near the aftermarket wing. In fact, most aftermarket wings will hurt your car?s performance and high speed stability ? they don?t work as they should.

Even if you don?t like the looks of the factory wing on your 2004-2007 Subaru STi, it is probably a good idea to keep it there, it is an excellent performance part that does a wonderful job at keeping your car stable at high speeds.

Below is a gallery of actual wind tunnel testing of the STi wing and roof vane spoiler. Testing was done at around 70 mph. As you can see the airflow is perfect and the stock wing is very functional. Don?t remove or replace it, use common sense
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Taken from : rusubaru.com



 
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Grinder34

Track Monkey
Counterpoint:

There are a lot of aftermarket wings that fit into your generalization above and do NOT provide the same levels of downforce. However, there ARE many companies that produce wings that can offer significantly more downforce than the stock STI wing. Furthermore, many of these aftermarket wings are adjustable and can be tuned for faster and slower courses and to levels of front aerodynamics. These aftermarket wings are usually much lighter than the very heavy stock piece which lowers weight, polar moment of inertia, and center of gravity. However, the adjustable nature and large amounts of downforce can cause significantly unbalanced aerodynamics and make a car slower and even dangerous if not set up properly and balanced out in the front.

On a WRC car a lot of compromises are made, specifically to the front of the car, to allow for the car to take big hits and not come apart and/or compromize functionality. Consequently, the STI doesnt have much front downforce. If you add splitters, canards, etc you may put the car out of balance: having not-enough downforce in the front. Look at most track STIs, they will be running aftermarket wings along with significant front aerodynamic additions.

On a final note, the STI Spec C RA-R, which i believe is the ultimate factory track STI (it stands for something like "Record Attempt-Radical") uses no rear wing.
 
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IGOTASTi

System Operator
Staff member
Very good counterpoint. :tup:
 

Alin

Diehard Car Enthusiast!
I have read about this in the past. It definitely is interesting. I love the fact that you found pictures to show wind tunnel testing! That's awesome! :tup:
 

IGOTASTi

System Operator
Staff member
I only want correct information.
 

STimedic

New member
Things I'm considering to balance out being wingless:

-Do-Luck or replica whale-tail trunklid
-Rear under diffuser (HKS Kansai or APR)
-Custom flat undertray
-Front splitter
-Beatrush louvered front undertray
-OEM mid-wing with (I forget who makes it) vortex generator insert
-Roof-mounted vortex generator

Now to get the stuff and find someone with the programm that allows one to test theories without expensive wind tunnels. Might come down to the old tape and flap routine.....
 

Grinder34

Track Monkey
Things I'm considering to balance out being wingless:

1 Do-Luck or replica whale-tail trunklid
2 Rear under diffuser (HKS Kansai or APR)
3 Custom flat undertray
4 Front splitter
5 Beatrush louvered front undertray
6 OEM mid-wing with (I forget who makes it) vortex generator insert
7 Roof-mounted vortex generator

Now to get the stuff and find someone with the programm that allows one to test theories without expensive wind tunnels. Might come down to the old tape and flap routine.....


(I numbered your options for easy reference).

1. May increase rear downforce, probably just decrease drag.
2. Increase rear downforce!
3. Increase front/rear downforce (rear especially combined with #1). Decreases drag
4. Increases FRONT downforce, decreases REAR downforce (cantilver around front axle)
5. May increase front downforce. Decreases drag.
6. ??? Not sure what that is
7. Decreases drag



As for methodology.... I have an idea. Do you have a gopro? If so:

step 1: tape a very fine increment measuring stick/ruler to the side of your car vertically, exending over the wheel well.
step 2: aim go-pro at wheel and ruler. As straight-on as possible, but truely orthogonal is not necessary.
step 3: if possible, repeat steps 1,2 for a wheel well at the other end of the car.
step 4: go for a calibration drive. At a few reference speeds 70, 100 (at the track of course)?
step 5: review video footage. Note at reference speeds where the edge of the rim/tire/whatever measures on your fine scale ruler.
Step 6: Perform aerodynamic change (adding wing, undertray, etc...)
Step 7: Repeat steps 4,5.
Step 8: compare #s. Clearly a "lower" car (body work closer to wheel) means you're getting more downforce. At this point, if you know spring rates, and the angle at which your camera was in comparison to the rim, you can get a rough approximation of how much downforce was added.

So i can see the above method totally not working, or not deflecting enough with high spring rates, to notice a difference. But in theory it should work.
 

finallymysti

New member
slightly off topic but, since understeer is created by front tires having less grip, and the rear wing improves rear grip, then would taking the wing off improve balence until you started adding a front splitter at which point you would need to improve aerodynamic balance with a rear wing. i do realise that our understeer isn't aerodynamic but it can still play a role
 

Grinder34

Track Monkey
slightly off topic but, since understeer is created by front tires having less grip, and the rear wing improves rear grip, then would taking the wing off improve balence until you started adding a front splitter at which point you would need to improve aerodynamic balance with a rear wing. i do realise that our understeer isn't aerodynamic but it can still play a role

High speed understeer may be mitigated by removing the rear wing. Low speed understeer would not be affected.
 

Alin

Diehard Car Enthusiast!
It's the 06-07 midwing, the one mounted just over the top of the rear window. I think it was Zerosports who made a vortex generator insert for it to replace the factory black blade.

Ooooh. Never seen one. Is it proven to be better??
 

Grinder34

Track Monkey
The more I think about the roof vane "mid wing," or whatever it's called...i really dont think it adds any downforce. If anything, I think it adds low quantities of lift.

It's purpose is to direct air down the raked rear windshield towards the STI wing. It likely uses an specifically designed airfoil for low lift but lots of deflection in the flow direction. Just a guess, as I have no literature or cfd or anything for the actual STI roof vane.

fig2.jpg
 

IGOTASTi

System Operator
Staff member
:bump:
 

Alin

Diehard Car Enthusiast!
After being wingless for two months, i will never do it again. Wing is going back on tomorrow and will stay there for the rest of my cars life.
 

IGOTASTi

System Operator
Staff member
After being wingless for two months, i will never do it again. Wing is going back on tomorrow and will stay there for the rest of my cars life.

Why?
 

Batmobile_Engage

Squirrel Meat Aficionado.
Staff member
Honestly, I like the handling of my STi without the wing installed ***provided that I'm not exceeding 80-90mph***.
I like the increased oversteer especially 50-70mph or so. That being said, I also have my suspension tuned to match
being wingless. Either way though, over 100mph and especially over 120mph, I feel a little floaty in the rear end.
When I go to a track where I expect to exceed 100mph, especially in turns, the wing is going back on for sure.
 

Alin

Diehard Car Enthusiast!
What bat said. Gets squirmy high end.
 

Alin

Diehard Car Enthusiast!
I've been looking for the past couple of days to see if there was a testing like this done with the WRX wing, but couldn't find anything. I've been 120 or so with the WRX wing and it doesn't feel anything like wingless, so that's a great plus. (Aside from the fact that I HATE how it looks. :lol: )

The WRX spoiler HAS to have a good impact as opposed to wingless, but I can't find any proven evidence. :(
 
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