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Old 05-31-2011, 10:06 PM   #1
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Default Aero balance with trunk "lip" ... CSP style

I have a spare trunk that I'm willing to sacrifice to build a trunk lip CSP style until I can spare the change for an APR. Now my question is what would be a good hieght/angle in the rear to start with that would balance with a 3-4'' extrusion splitter? The splitter I'm building goes to the oil pan, mushroom shape style.

I read somewhere (although I forget) that 6'' 45* is a good place to start and build it with turn buckes to adjust if needed. Would it be better to go with a higher lip with less angle to reduce drag than making a shorter one with a more upright AOA?

edit: oh, and this is for track use. my local track is fairly low speed (straight about 110MPH) and fastest corner is maybe 75 on exit. The rest are 30-55. I will be doing portland/seattle this summer though which is quite a bit higher speed with more sweepers. Car makes 230whp right now and will make a but more soon.
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Old 05-31-2011, 10:13 PM   #2
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This is the track.

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Old 06-01-2011, 02:07 AM   #3
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Good question, I've been wondering the same in the back of my head.

I'm also wondering if this falls into the category for an aftermarket trunk lip spoiler for MC - and therefore only +.5 points - as long as it is less than 6" vertical height from lowest point on trunk to top of the spoiler...

Interested if anyone has used this style spoiler on the big tracks.
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Old 06-02-2011, 02:01 AM   #4
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Sorry aussie here, are we talking nascar style lip?

Dann
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Old 06-02-2011, 02:46 AM   #5
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Old 06-02-2011, 04:55 AM   #6
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Yeah thats the one. Anybody done some roll down tests to determine how horrid these are for aerodynamics?

Also, holy **** look at dem tyres !..

Damm




(yes that was intentional..)
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Old 06-02-2011, 09:31 AM   #7
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Yeah thats the one. Anybody done some roll down tests to determine how horrid these are for aerodynamics?

Also, holy **** look at dem tyres !..

Damm




(yes that was intentional..)
I know after driving a CSP with and without one, and the spoiler really improved the balance in transition. Though all the competitors in CSP run without a hardtop, so the aero effects on the track will be different.
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Old 06-02-2011, 10:51 PM   #8
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I think at high speeds you would only need 2-3'' of "lip" to be effective.
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Old 06-03-2011, 01:00 AM   #9
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Quote:
Originally Posted by falcon View Post
I think at high speeds you would only need 2-3'' of "lip" to be effective.
If that's the case I really wonder how effective one of these would be.




I've always been under the impression that they're more good for drag reduction than any kind of increase in downforce. With that said I'd imagine you'd still need some kind of downforce solution in the rear to help balance a front splitter. My best guess is to come up with a budget diffuser if you can't drop the coin for an APR just yet.
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Old 06-03-2011, 01:31 AM   #10
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Can't run a rear diffuser in my class. Only a front diffuser and wing.

The only downside to the one you posted is it is not adjustable.
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Old 06-03-2011, 04:00 AM   #11
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Quote:
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whattup g

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Old 06-03-2011, 04:27 AM   #12
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I feel like the other downside to the trunk lips like those as opposed to say, a stock trunk with a 3-4" CSP style lip on it is the width - and I bet the sides is where you get the most benefit.
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Old 06-06-2011, 06:24 PM   #13
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Make it as wide as you can to catch the "clean" air that isn't effect by cabin. If you have access to enough material, it would be interesting to test a few different size spoilers. Most of the competitive auto-x cars with spoilers run the spoiler the full width of the body (at the widest point). The problem how to keep the spoiler rigid outside the width of the trunk.

Working on a friends XP car and we are building a wicker-bill/spoiler to compliment his wing. We are going with a 3 piece design. The two ends will be permanently attached to the car and the 3rd piece (attached to the trunk) will sit in front of the end pieces.
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Old 08-04-2011, 03:55 AM   #14
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nice picture Falcon!

I am cheap. The ends are made from aluminum tubing from osh (orchard supply hardware). The back brackets are made from 3/4" wide aluminum strips bent and thats .090 ABS plastic. All high class stuff. I made it between the tour and pro in Packwood in 2007 or so? The car was left on site and I bought a trunk and made the spoiler, threw it in a friends trailer and attached it when I arrived Friday night! I have since tested a few other spoilers but have always gone back to the original!

see you in Lincoln or maybe Packwood,
Scott Fraser

OK back to looking up Megasquirt stuff for my street car
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Old 08-04-2011, 02:14 PM   #15
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can i ask why you want a lip opposed to a spoiler? The lip will actually get very little air and help nothing but cosmetics and additional weight lol

Last edited by v01canic; 08-04-2011 at 06:40 PM.
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Old 08-04-2011, 03:36 PM   #16
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Not opposed, just can't afford it right now. I'm unemployed and in school so the motto is going fast for as humanly cheap as possible. All my expendable income goes to brake pads and track day fees right now. I figure the spare trunk I have and a CSP style duck tail should be better than nothing until I can pick up a nice APR or something...
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Old 08-04-2011, 06:44 PM   #17
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check out some cheapo ebay ones and try to see if there is a way to extend and mount the brackets through the spare trunk and onto/near the rear shock towers. The only real benefit it the APR is sexy *** carbon fiber

on a side not, great job on focusing on school and good luck
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Old 08-04-2011, 07:08 PM   #18
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Quote:
Originally Posted by v01canic View Post
can i ask why you want a lip opposed to a spoiler? The lip will actually get very little air and help nothing but cosmetics and additional weight lol
This isn't really true
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Old 08-04-2011, 08:08 PM   #19
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if you have grassroots motorsports check out the may 2010 issue (page 43 to be exact)
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Old 08-04-2011, 09:15 PM   #20
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Is this worth having?
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