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Re: BlueScooby's 06 STI - Looking around at rear wing options

So I talked with Ryan at Zebulon a bit through email and I think I'm going to have to hold off on the spiltter/rear wing thing for now. They really do need to be done at the same time, and I'm just not ready to put on a GT wing...
Yeah even the least downforce producing APR wing puts something like 8 batteries worth of downforce on the back of the car at typical strait-away speeds....Just imagine taking the next turn with that without 8 batteries on the front as well. HELLO UNDERSTEER. However you can do what the FWD guys do and set the car up to be very loose/twitchy without a wing. What this does is make your car very agile in the slow speed stuff but the downforce of the wing brings the car back to a neutral state the faster you go. You can always adjust the angle of attack to raise or lower the speed at which the car becomes neutral.

But he also gave me a couple pointers on the underbody that I'm going to see if I can work with. He reminded me that the skirting is illegal for any sanctioned race (which I already knew) but also that the skirts sort of open/close off the underbody at various spots which is probably hurting me a little.
Porsche found this out when Norbert Singer was developing the 962. It was the time when F1 had just found ground affects and they thought that it would translate onto a full bodied car. It didn't when they did it the way the F1 cars were doing it... i.e. skirts. Skirts actually made the car worse. They realized with full bodied cars you have to actually do it backwards compared to the theory behind skirts, you need that air coming in from the sides for the tunnels. Whence they fixed that the car made 2.5 times the down force compared to no ground affects at all. You only want to seal off the sides of the car via skirts or vortexes when you have a completely flat underbody and use the rake of the car as your pressure differential device. When you have a defuser or tunnels you want as much air going into them as possible to maximize their effect.

Also that with the rear diffuser sticking out that far, its really limiting (preventing) the rear wing from aiding in drawing air out from under the car...
You would need to overhang the rear wing quite a bit for the wing to interact with the diffuser. If you cut it short and made the diffuser to bumper transition smooth the air flow won't want to detach as soon and keep moving up a bit before it separates completely and will give the negative pressure area under the wing a better chance of interacting with it better. Cause lets face it, unless your wing is massive and it over hangs the trunk the negative pressure area under it is not going to reach down far enough to interact with the air exiting a diffuser on our cars....the distance is just far too great. Look at Nemo's EVO, Scorch Racing's S15, Tilton Interior's EVO, Andy Forrest's Impreza, and the RP968 and you'll notice 3 things: The unbelievable size of their rear wings, the amount of overhang off the rear of the car they sit at, and the height of the tunnels under the car are measured in feet, not inches.

SO, it sounds like I'm going to be revising it a bit. In general i think I'll feel much better about it after its no longer sticking out so far, but that also means I probably won't be able to deflect the exhaust up to prevent interference anymore...

I may still look into some of the rear wing options from above (possibly) since they shouldn't be a dramatic change in the airflow enough to change the car's balance.
IMO I would just go with the S7-S8 wing if you keep it long or stick with the OEM wing if you shorten it. It's still a street car and sometimes the simplest way is the best way.


That's just my $0.02
 

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Re: BlueScooby's 06 STI - Looking around at rear wing options

Thats definitely one of the most helpful posts I've ever had! lol

Seriously though, you make a lot of really good points. I didn't know that about the 962 development, but it makes sense the way you framed it. I will definitely be removing the skirts :tup:

I'm glad you talked about the rear wing aiding the diffuser, thats a great point. They do have massive aero setups on those cars. The way Ryan mentioned the diffuser length thing, it made me think "i'd done messed up"... I think I may still try to shorten it though. It does look a bit odd, and I would feel much better about parking and not having to worry about people hitting it by accident. ¯\_(ツ)_/¯
 

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Re: BlueScooby's 06 STI - Looking around at rear wing options

Here here, Nick! I love it when people invoke/reference the old days of motorsport, and in a helpful way to boot. That's a good point/lesson to bring up. The 962 and it's history and development is one of my favorite motorsports topics. I'm not really gonna add anything here because I'd be saying the same stuff....:)
 

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Re: BlueScooby's 06 STI - Looking around at rear wing options

Haha thanks! You definitely know the theory and from what I've read going back over your thread you're definitely a smart person, but this was probably a case of "well the theory says this" but "in practice it doesn't quite work that way". Which is a completely normal thing to encounter, I've had it happen to myself quite a few times lol (most of the stuff I know that isn't just theory is from learning the hard way haha). Ensuring a smooth transition from the diffuser to the rest of the bodywork will probably do you more good than the extra length you have going on since you aren't utilizing air moving on top of the diffuser to help draw the air out of it and keep it attached.

Baron, in full disclosure I got all of that from Chris Harris' video he did about the 962 lmao. The bit where Ryan said the skirts were probably hurting him a little reminded me of that interview and the 962 so I went and watched it again before I made that post. :rofl:
 

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Re: BlueScooby's 06 STI - Looking around at rear wing options

Thats exactly right! And now (after watching said Chirs Harris video on the 962) I did exactly the same thing as Norbert Singer. I thought, it worked in F1 back when, so it must work for a car... LOL. And now, like Norbert, I've realized the error of my ways. hahaha

Since I have no aero development experience, books/theory are my main source of information. So I'm now learning the application the hard/slow way :tup:

Understanding why the skirts are not a good thing, in this case, actually makes a lot of sense when compared against my analysis of the NACA duct in the undertray. I said removing airflow would reduce the acceleration of airflow through the diffuser, and conversely, adding airflow from the sides of the car apparently HELPS to accelerate the airflow through the diffuser. And now you're wondering why I couldn't figure this out on my own. lmao

Interestingly the diffuser already seems to be working somewhat (based on the amount of water carry behind the car), so I will be curious to see if I notice any difference after removing the skirts. Based on our discussion here, the effectiveness of the diffuser should go up, but that may not correlate directly with the amount of water carry behind the car. We shall see :D
 

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Re: BlueScooby's 06 STI - Looking around at rear wing options

At least you have the right attitude though and are willing to learn, which already removes like 50% of people. You even have books on the subject, which is more than I can say for myself :D

That /DRIVE video with Chris and the 962 is pure gold, must've watched it 10 times since it came out. He's one of my favorite journos.
 

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Re: BlueScooby's 06 STI - Looking around at rear wing options

I’m contemplating selling the SSRs and picking up a set of 18’s for daily duty...

Anyone got some suggestions? 18x9 +35 is the fitment I’m looking for.

I feel like theres lots of good options out there, but I always struggle to find what I’m looking for 🤣

Oh, and I need to sitdown and post up some picks of the revised diffuser location. Shortened it up about 4 inches. :tup:
 

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Re: BlueScooby's 06 STI - Rear Diffuser Revision Complete, looking into wheels

So I've been meaning to post an update on here for a couple weeks. I got laid off earlier this month and just started a new job this week (thankfully) so its been a crazy month. :eek:

But at the same time not working allowed me some time to work on the diffuser setup. I trimmed off about 4" upstream of the diffuser to reduce the rear overhang, while keeping the actual diffuser length itself. Cutting out new end-fences was the main thing I had to do to make it all work. :tup:

Hanging diffuser in new location (minus end fences)


Cutting out new end fences


First test drive to confirm fitment/clearnace


After a coat of paint and starting to patch some holes (painters tape)


Profile view


From above. Here you can see the actual overhang past the bumper is much smaller now :tup:


Finished Product. You will notice there are no more rubber skirts under here now either!
 

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Re: BlueScooby's 06 STI - Rear Diffuser Revision Complete, looking into wheels

Back to the 18" wheel idea. So far here are the wheels that I've found that I like that come in the size(s) I would consider. Basically, Ive looked through everything on the evasive motorsports website. I haven't really looked into rotas or xxr's because I don't want them, but I do have a Cosmis wheel on my list (which I suspect is basically an equivalent of those 2). CCW/Volk are just too expensive. Team Dynamics does not appear to do 18x9 wheels. I am open to other suggestions as well.

I do however need some input on which of these wheels will clear brembo's or need spacers however... Thats kind of a wild card here at the moment.



Let me know what yall think!
 

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Re: BlueScooby's 06 STI - Rear Diffuser Revision Complete, looking into wheels

Ah cripes, sorry to hear that; that happened to me last year as well...

Much better! That diffuser looks way more tame now, perfect actually.

Keep it simple and go with the TC105s; Kyle has those on his GD and they look great and fit Brembos without spacers - that's my vote. The NT03M is way more common IMO.Team Dynamics are great, but as I've tried to find for my ST, their sizes/offerings are finicky.
 

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Re: BlueScooby's 06 STI - Rear Diffuser Revision Complete, looking into wheels

Thanks! I love the wedsports as well, but my only reservation is that I already have a set... haha. Does Kyle have 17s or 18s? I know the 17s fit since i have a set ofcourse, but I haven’t confirmed the 18 fitment yet.
 

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Re: BlueScooby's 06 STI - Rear Diffuser Revision Complete, looking into wheels

Loving the diffuser! Super badass!
 

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Re: BlueScooby's 06 STI - Rear Diffuser Revision Complete, looking into wheels

All the wheels you've listed except the TC105N are heavy as hell.

Is weight a concern?
 

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Re: BlueScooby's 06 STI - Rear Diffuser Revision Complete, looking into wheels

All the wheels you've listed except the TC105N are heavy as hell.



Is weight a concern?


In this case, since these are specifically commuter wheels (no track duty), the weight isnt a big concern, but I do still like the light wheels :tup: The Weds are probably in the lead right now anyway lol
 

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Re: BlueScooby's 06 STI - Rear Diffuser Revision Complete, looking into wheels

Thought you'd be interested... Zebulon is about done with my aero. :)



Image Link


Oooo those are looking good! I’m really impressed with that splitter! He’s even curved the underside of the leading edge! I try to see how often folks actually do that with splitters, and I usually dont see them. So far I think Ive only seen that on IMSA/WEC cars and unlimited Time Attack cars with top level aero... I know its got to be elsewhere but its hard to find photos that show that small of a detail on the splitter. I know the Gobstopper2 had a curved splitter edge as well.

Im sure you already know about this since he’s building it for you, but in case the rest of you don’t all know what Im on about, this is a great example of the ideal “inlet angle” to the “venturi” under the car, that ideally terminates in a diffuser or “tunnels.”

This really solidified, for me, their ability to build an impressive aero package! Man I wish I was ready for this kind of kit!
 

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Re: BlueScooby's 06 STI - Rear Diffuser Revision Complete, looking into wheels

Updates look good! And yeah I'm in the TC105N camp as well, I'd be going with them for my new summer wheels if this motor build wasn't so expensive lol.
 

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Re: BlueScooby's 06 STI - Rear Diffuser Revision Complete, looking into wheels

I think I may just go with the TC105N after all... Those wheels are just plain beautiful! My current tires probably won't last too long, so I think I'm going to pull the trigger on these so i don't waste money on another set of tires...

Any of you interested in some SSR GTV02s? ;)
 

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Re: BlueScooby's 06 STI - Rear Diffuser Revision Complete, looking into wheels

I think I may just go with the TC105N after all... Those wheels are just plain beautiful! My current tires probably won't last too long, so I think I'm going to pull the trigger on these so i don't waste money on another set of tires...

Any of you interested in some SSR GTV02s? ;)
Yay! They will be awesome.

I totally would if I didn't have CE28Ns on the way :D
 
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