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Old 06-14-2011, 01:57 AM   #1
Back Road Runner
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Default Seems like an odd question but... - How much effort has been put in to aero testing?

I know there has been work here and there for various bits. I'm sure there has. I mean there has to have been. However, aerodynamics is a subject so seldom discussed on Nasioc. This isn't just a "oh I tossed on a wing" or "I have this awesome new splitter." I'm inquiring about technical data, actual modeling, testing, results. Is there much? At best, I've seen small bits, like a downforce comparison of an older STI versus Evo, that kind of thing, but it just existed to show that the wing was functional and how it was functional. Beyond that, I've never really seen much of anything.

Sorry for the rambling. I just find it really curious if any data is out there that actually has specific flow data of the car, any add-on parts, pretty much anything. It seems like such a very odd exclusion to the Subaru community given how much detail we go into with other hardware for our cars.
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Old 06-14-2011, 02:11 AM   #2
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im not sure it really matters at the speeds they are mostly driven at? I thought aero really only came into play at 120mph +?
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Old 06-14-2011, 02:16 AM   #3
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i believe aerodynamics such as a wing or splitter don't do much until about 40mph. but as for actual effects and the measurements there of i haven't seen any info but i sure would like to.
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Old 06-14-2011, 03:05 AM   #4
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It just seems like a very under researched area of the Subaru community. Now this is expected given anything outside of basic mathematical estimations gets expensive. Wind tunnel testing is expensive. Fluid modeling software is expensive. Prototyping is expensive. There could certainly be small scale testing likely done at a reasonably affordable level, even a DIYer approach with a little home brew creativity could provide a mini wind tunnel that could fit in part of the garage or room. I know this is something that I would enjoy furthering in the future simply as a hobbyist.
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Old 06-14-2011, 06:08 AM   #5
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Certainly I'm interested in formal testing too but I'm not holding my breath. My seat of the pants testing tells me it makes much more of difference at street speeds than most give it credit for.
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Old 06-14-2011, 08:13 AM   #6
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I don't think a street car is going to undergo extensive aero testing outside of the factory to be honest... the only aero you'd get into would be if it was a track car. I'm race teams put their $ into some aero testing for competition but you'd be hard pressed to find data on like a stock STI vs EVO.
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Old 06-14-2011, 08:42 AM   #7
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For my own purposes, I've tried to go with individual aero parts that have been tested. For example, Kognition provides CFD data for all of their wings. I am also considering a trip to the Aerodyne 2 wind tunnel since it is very reasonably priced.
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Old 06-14-2011, 10:39 AM   #8
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I think what a lot of club level people do is follow basic aerodynamic principles and apply them to their car. Things like rear wings, front splitters, cannards, flat bottoms, diffusers, reducing drag etc. are all qualified improvements, if not quantified ones. There are ways to test aero that do not break the bank like the well known oil streak test, taping yarn to the car and observing how it moves with the air, and coast down tests to measure drag. I believe GRM did a feature on backyard aero a few issues back.
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Old 06-15-2011, 12:05 AM   #9
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Quote:
Originally Posted by PitwrkzZ1 View Post
I believe GRM did a feature on backyard aero a few issues back.
They sure did.

Even basic things like the Limited front lip spoiler should made a noticeable difference at AX speeds. IIRC, rear wings need to be at the roofline or higher to really have an effect.
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Old 06-15-2011, 10:07 AM   #10
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All the stuff I've seen is testing at events themselves. People would put wings and splitters on and calibrate to that track and their driving style. To much push, tweak the splitter. To much rotation, tweak the wing. Once you get what settings you want write them down. Run a few events and you'll start to get an idea of what is needed at what tracks and can adjust accordingly.

And wings/splitters do work under 40 mph
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Old 06-15-2011, 10:29 AM   #11
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Quote:
Originally Posted by SubieEngineer View Post
They sure did.

Even basic things like the Limited front lip spoiler should made a noticeable difference at AX speeds. IIRC, rear wings need to be at the roofline or higher to really have an effect.
Clean air! :3
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Old 06-15-2011, 10:30 AM   #12
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A few years ago one of the local guys with an 04 wagon fabbed up a plywood/fiberglass front splitter and rear wing for the local time attack series. There wasn't much testing done, it was basically throw it on during a live event and see how the times compare to a known baseline time at the same track.

He had tons of track experience and was a good driver. His times had a definite improvement and his corner entry speed tended to be much higher than without. It looked absolutely ridiculous, but the timesheets stated that it was quite serious as he jumped up several places in the standings.

I'll see if I can find the pics for it.. because they did look rather outrageous.

edit:

http://www.ottawasubaru.com/forum/viewtopic.php?f=13&t=14520&hilit=ghetto+aero
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Old 06-15-2011, 02:31 PM   #13
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We've basically been on the trial and error method:

March last year:



August last year:



November last year



Now:





March of last year we went 1:25 around Big Willow, then 1:24 in August, then 1:23 a few weeks ago so it is helping, but power is also going up and I think there's more aero grip in the car. The big thing we've done is try to get more out of the front end and we seem to have made progress. Since we put that big Kognition wing on understeer has always been a problem and we're finally to the point where JC is really happy with the balance of the car. The annoying thing is that we have very good data logging capabilities and we just don't use them enough. At Subiefest when we went off we broke two of the suspension position sensors and haven't gotten around to replacing them yet. That would be a very good way to figure out exactly how much downforce we're making.

The next time attack project is going to have a much better aero package
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Old 06-15-2011, 03:06 PM   #14
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Better aero package? As in a blown diffuser?
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Old 06-15-2011, 03:36 PM   #15
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Quote:
Originally Posted by A-man07 View Post
Certainly I'm interested in formal testing too but I'm not holding my breath. My seat of the pants testing tells me it makes much more of difference at street speeds than most give it credit for.
I would agree. The aero has to have an effect at highway speeds and I have some anecdotal proof. I have a Thule bar on my wagon for my bikes and a 12ft jon boat. I can easily feel a huge difference on a windy day with the bars on the car sticking out up there. Also the sound is really loud at a mere 65 to 70 mph. In the winter with out the bars, I feel much less wind, especially cross winds.

So in my opinion aero makes a difference for highway driving. City driving probably not enough difference to merit checking.
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Old 06-15-2011, 03:53 PM   #16
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Quote:
Originally Posted by AQ Motorsports View Post
The next time attack project is going to have a much better aero package
Rado style front wing? Honestly, not as crazy as it sounds. All you would need is a custom mounting solution and a wing element.
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Old 06-15-2011, 04:17 PM   #17
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I'll be starting a project thread within a week or two for the car. For now I'll say that many hours of CFD went into the kit.
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Old 06-16-2011, 11:07 PM   #18
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Quote:
Originally Posted by AQ Motorsports View Post
November last year



Now:




Nice diffuser but those brake ducts in the fender are sweet! I love the look and the function of it.
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Old 06-17-2011, 06:29 AM   #19
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there is windtunnel testing of the APR GTC300 here:

http://forums.nasioc.com/forums/show...9&postcount=23

if you go to the thread there is also data of the 06 sti vs the evo 9.

the STI has a drag coefficient of 0.33 without lip, 0.32 with. the evo has around 0.38

unsure of the CDA though. google is your friend there.
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Old 06-17-2011, 06:39 AM   #20
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Quote:
Originally Posted by SubieEngineer View Post
They sure did.

Even basic things like the Limited front lip spoiler should made a noticeable difference at AX speeds. IIRC, rear wings need to be at the roofline or higher to really have an effect.
not true of the rear wing, but they're far less important than the front end.
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Old 06-17-2011, 04:52 PM   #21
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Quote:
Originally Posted by vicious_fishes View Post
there is windtunnel testing of the APR GTC300 here:
CFD doesn't stand for Wind Tunnel.

-Mike
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Old 06-20-2011, 12:55 AM   #22
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This thread hasn't been linked in here yet, so I'm adding it:

STi wing downforce at 120+ mph? and Auto Aerodynamics

Anecdotally, I live in an area where 20-30 mph headwinds are not uncommon. My car originally had no rear spoiler. I added a low/WRX style one due to the data in the above thread suggesting it actually worked. In headwinds on the highway (55-70mph road speed), I noticed the front end wanted to wander more with the rear spoiler added. This summer I added a replica v-limited lip, which removed that / balanced it out again.
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Old 06-20-2011, 02:15 AM   #23
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thanks for that link articwolf it was a interesting read
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