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APR GTC-200 angle of attack setup questions

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APR GTC-200 angle of attack setup questions

 
Old 04-19-2018, 05:28 PM
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Default APR GTC-200 angle of attack setup questions

Yes I realize the Singular wing is the way to go for a track car. However fell into a new GTC-200 and couldn't resist drilling some holes even though the real splitter is not on car yet, only running a small splitter.

Going to Sebring this weekend and would like to set wing to its lowest drag - zero down force setting which is tough as the 15 degree twist really messes with the AOA?

Setting center of wing at zero will still give a pretty large AOA based on perceived airflow. Almost looks like a negative 4 degrees or so would be the least draggy for places like Daytona.

Tried it with risers, however had to pull them off as I figured its more important to see my Corvette and race car buddies closing on me (stock HP) than the small gain in efficiency.

Would someone mind sharing their 2009 data, shouldn't be a big secret as its old news. emilio700 , Savington , ThePass , ect. all used to run this wing and would really appreciate your help.
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Old 04-20-2018, 02:54 PM
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I didn't run the GTC200 personally but we've done some real world observations, and there is some windtunnel info available as well.

Wind tunnel pic shows the angle can be quite significant. With this pic rotated to level, it's ~7° slope up high at roofline just above the rear bumper and ~12° lower and a bit further forward where a GTC200 would sit. Note this flow demonstration is at the centerline of the car, the angle is progressively less severe as you move outwards to the sides.



In real world observations we've seen a bit less angle, more like 3° up high and far back where our kit places the GT250. Chalk the different results up to different cars, different air speed, any other number of variables. Relevant to your question though, it's easy to see that down low the angle is pretty dramatic. You will definitely make some downforce and the least drag at negative angles. Exact AOA will need some testing.
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Last edited by ThePass; 04-20-2018 at 04:32 PM.
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Old 04-21-2018, 01:23 AM
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I hope you know thats a photoshop image.
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Old 04-23-2018, 03:02 PM
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Nope, if that's the case, didn't know that. If so, that's the answer to why our real-world observations differ from what that shows. I trust the real world data a little bit more than a pic from a google image anyways
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Last edited by ThePass; 04-27-2018 at 02:35 PM.
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Old 04-24-2018, 05:23 PM
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Played a bit with the wing at Sebring over the weekend, kind of surprised myself.

My thinking was I would loose a few MPH on the back straight & front straight while hopefully gaining it back in the fast corners 1 and 17? Wanted a baseline before adding power as I figured the stock power would show numbers better than after turbo, also wanted to see if the naysayers were correct in that "a wing will only slow down" a naturally aspirated tired 150K stock engine Miata.

Pulled off risers as the wing was right in the middle of my vision and in run group 4 & TT, I need all the mirror I can get.

Set the wing at -4.5* degrees to start measured at center top which is a laser line to the top of the rear window trim & still not fully trimmed out which would be closer to -6*. Imagine my surprise when I gained 3 mph on the back straight and dropped 2 seconds average?
Same tires 225 RS-4 , same pressures, same suspension Xida 900/500, big bars & delrin bushings, however 3 months apart so could be different mix gas, better air, rubbered in track ext. ext. ext?? Was defiantly gaining a bit on pre straight corner exit and maybe staying flat a bit longer due to better feel at corner entry & under braking?

Changed AOA to -0.5* then the skys opened up. Once dry car was noticeably more planted under braking but did loose 2 mph on back straight & did average .2 second slower even though car was super planted and balanced?

Trick is wing boots me into a much higher TT class where I would need about twice the HP and some more tire to be competitive.

Time for horsepower.

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Old 04-27-2018, 12:48 AM
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Your observations make sense compared to ThePass's and others' observations. To paraphrase from the aero thread, when you were running the negative AoA, you're probably in a very high efficiency region for the wing. Wings should get a very good lift to drag (or downforce to drag for a car wing), so the low AoA wing balanced the car well. Running the higher AoA pushed you into more drag setup, and if you can't utilize the extra grip (ie poor aero balance) or don't push the card harder with the extra grip, your lap times will suffer to due extra drag on the front straight. Sounds like a successful first track day with the wing!
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Old 04-27-2018, 07:03 PM
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Time for a splitter. That much wing is pointless without one IMO
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Originally Posted by codrus View Post
Basically I've come over to the camp of "If something is a reliability problem on the track, just ask Andrew and do what he says".
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Old 04-27-2018, 09:05 PM
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Originally Posted by Savington View Post
Time for a splitter. That much wing is pointless without one IMO
Big nice sheet of composite sitting on the shelf ready to go.

Pretty sure I will be calling you for a turbo setup soon.
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Old 04-27-2018, 11:47 PM
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That much wing still needs a splitter, but it becomes far less pointless with a turbo setup
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Originally Posted by codrus View Post
Basically I've come over to the camp of "If something is a reliability problem on the track, just ask Andrew and do what he says".
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Old 04-29-2018, 07:57 PM
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Ouch
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Old 04-30-2018, 09:30 AM
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Originally Posted by charliehayes22 View Post
I hope you know thats a photoshop image.
that is such a bummer. been looking at that photo for years and just now noticed the PS.
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Originally Posted by Mobius View Post
Hopefully so, but let's hope it's never necessary. Experiencing your safety gear in action is ... not optimal.
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Old 10-05-2018, 09:49 AM
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Originally Posted by OGRacing View Post
that is such a bummer. been looking at that photo for years and just now noticed the PS.
I think we all have.
The worst bit is its a bad photoshop job too. I used to doctor photos for a certain film festival guide as a side job and didn't spot it.
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