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Old 04-25-2010, 12:09 PM   #1
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Default Rear wing/spoiler

I am going to be setting up a wing on my car and was wondering if anyone actually knows how much down force that they are actually using at given speeds? for instance 60 lbs @ 80mph, 110 lbs @ 130mph ect. I know that different wings provide different amounts of force at different angles. I would like to make one that would be optimal for us track guys. Thanks
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Old 04-25-2010, 12:40 PM   #2
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downforce created is the square of speed.

different wing on different car on different mounts on different AoA driving at different speed will have different downforce.

what's the question ?
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Old 04-25-2010, 06:38 PM   #3
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I want to see what the average down forced used is on one of our cars, Im toying with a few different shapes and need to choose the one that will best suit a miata for the track.
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Old 04-25-2010, 08:57 PM   #4
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Wouldn't this change from track to track?
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Old 04-25-2010, 09:32 PM   #5
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If you change the angle of the wing from track to track, or the altitude or the barometric pressure or the temperature, what Im looking for is and average. I saw almost everyone at the last miata challenge in the unlimited group running a APR wing, they where all mounted about the same, some had the ends modified some not. Im just looking for a starting point for my project.
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Old 04-25-2010, 09:49 PM   #6
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Wheres penguin?
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Old 04-25-2010, 10:52 PM   #7
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No penguin just want to make an affordable wing for all. for example if you had a air foil with a 4' span and a 1' chord w/ a thick-%crd of 14 and no camber at 0 deg you would have no lift or down force. But if you introduced a -10 angle with out changing any of the other variables you would end up with 133 lbs of down force at 100mph. Since all of the variables are changeable and this model is based on a symmetrical air foil you can calculate the type of air foil you would need for a given down force at a given speed or you can calculate the down force you should have from an existing air foil.
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Old 04-26-2010, 12:57 PM   #8
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You can get the data for an existing (and popular) wing from the APR Performance site.

I have the GTC-200. It is mounted at 9.3 degrees relative to horizontal, but the downwash from the hard top increases the AOA to about 15 degrees. From that, and the wing data, you should be able to figure out what I am getting vs. speed. My setup is fairly typical.
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Old 04-26-2010, 01:46 PM   #9
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on my car, rear wing is limited by front downforce. there is no use for 1,000LB down force if the front is only making 200LB down force at same speed.

as radical as my front splitters are, I find GTC200 is at the limit of rear down force. I cranked up AoA all the way to 10 degree vs. horizontal. but I also have Gurney flap and fast back. that was barely enough, rear would still want to step out at certain corners.

I ran GTC300 at MRLS. ran it at zero AoA, car was neutral.

but for most who don't have the big front splitter, GTC200 is a much better match. don't forget APR numbers are in newton.
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Old 04-26-2010, 09:40 PM   #10
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cool I think I found what I am looking for on their web site, thanks for the heads up on their units of measurement, that would have thrown me for a loop for sure.
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Old 04-27-2010, 03:17 PM   #11
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Quote:
Originally Posted by bellwilliam View Post
on my car, rear wing is limited by front downforce. there is no use for 1,000LB down force if the front is only making 200LB down force at same speed.

as radical as my front splitters are, I find GTC200 is at the limit of rear down force. I cranked up AoA all the way to 10 degree vs. horizontal. but I also have Gurney flap and fast back. that was barely enough, rear would still want to step out at certain corners.

I ran GTC300 at MRLS. ran it at zero AoA, car was neutral.

but for most who don't have the big front splitter, GTC200 is a much better match. don't forget APR numbers are in newton.
I was running my GTC 200 at 10 degree with Gurney flap and a bit higher with doubled up risers probably getting close to free streem air. I also probably have a less effective front splitter than you. The faster I went the more I’t would push. My car seems to be set up well for putting down power off corners though even on my 10 year old revalved Koni sports.

It was interesting that after driving Emilios 949 rental and comparing back to back with my car even with twice the power and my car feeling less hooked up overall in the corners with a less responsive turn in I could much more liberally apply power early coming off the corners without the rear end wanting to step out. Same spring rates 700/400 probably similar alignment but I did have ISC swaybars set Full stiff in the front and full soft in the rear and the 949 rental had no real aero.

The GTC 300 makes more down force at 0 AOA than the GTC 200 will make at any angle of attack a bit more drag too. It seems like further Aero work for me would be some underbody panneling and diffuser which would probably be biased toward even more rear downforce. Im thinking it would be very difficult for me to optimize the aero and suspension with the GTC 300 wing from where I'm at now.

For the lower speed autocross stuff I have been just cranking it to 15 deg.

Bob
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Old 08-05-2010, 10:42 PM   #12
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Bringing up a dead thread, but better than starting a new one as this is relative to the topic.

Heading to Road Atlanta this weekend for some hot track time. Last time I went I just had my GTC200 wing with no splitter. I didn't have an angle finder but made sure it was negative... well it was so much that half way down the back straight I could feel the *** hunker down and acted more like a parachute and the best top speed I saw was 128mph. I know having a wing is a compromise between cornering speed and straight-line speed, but I'd rather much have the corning speed than trying to stay with the GT2s and Vettes in the straights. Anyway, I also have a gurney flap and can't find if the angle is to be set at wing center from front to top of flap or base of flap... see pics below. ALSO, looking at my DIY splitter what angle on the wing do you guys think is a good starting point? The splitter comes out 4"... god I'm such a retard at this stuff... same with suspension setup....



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Last edited by GeneSplicer; 08-20-2010 at 04:47 PM.
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Old 08-20-2010, 03:52 PM   #13
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The angle measured should go through the center of the leading edge directly to the trailing edge. This will often be very different from laying a level across the top of a wing.
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Old 08-20-2010, 04:04 PM   #14
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Quote:
Originally Posted by rlogan View Post
The angle measured should go through the center of the leading edge directly to the trailing edge. This will often be very different from laying a level across the top of a wing.
Whut? Got some pics? Im stupid and dont understand.
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Old 08-20-2010, 04:28 PM   #15
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Either way of measuring it is fine. The only reason for measuring it is to get a starting point, or return to some setting that worked. Without a lot of smoke or tuft studies, you wouldn't know what the angle of the incoming air is anyway.

The reference AOA line for the data provided by APR is across the upper surface, probably because it is easy to measure. They sell a cheap level and embossed APR bar to bridge across the high points.

The Gurney flap will probably increase the effective AOA about 1 degree, based on what they do to other high-lift airfoils. I measure from the front of the wing to the Gurney bond surface (like the 2.4 degree example above).
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Old 08-20-2010, 04:59 PM   #16
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Yes, it's just a reference point...but here is an illustration of the difference.
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Rear wing/spoiler-wing_v4.jpg  
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Old 08-22-2010, 02:44 PM   #17
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Default AWR has a diffuser, wing and splitter you might like

AWR makes parts for Mazda Motorsports, include the MX-5 Cup cages. These are prototypes for the Super Spec Miata Series being contemplated by MM now. I believe AWR is looking for a few racers to test these items, so you might be able to actually get them now.
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Rear wing/spoiler-dsc04771.jpg   Rear wing/spoiler-dsc04768.jpg   Rear wing/spoiler-dsc00870.jpg   Rear wing/spoiler-dsc00868.jpg   Rear wing/spoiler-dsc01397.jpg  

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Old 08-22-2010, 03:51 PM   #18
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That is a serious diffuser. I like it.
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Old 08-22-2010, 06:03 PM   #19
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**** the diffuser, I want the splitter. Wait, scratch that. I want my miata upside down.
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Old 08-22-2010, 06:30 PM   #20
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I'll stick with my cheapo disposable plywood splitter.
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