Underbody Aero Thread (splitters, panels, vortex generators) - Page 2 - Miata Turbo Forum - Boost cars, acquire cats.

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Old 02-10-2009, 04:58 PM   #21
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+1 for ABS. Easy to cut. Easy to form with a heat gun. Easy to glue with ABS pipe glue. Good stuff for the DIYer that doesn't have a great shop to work with metal. You can easily make your own inlet or outlet vents/louvers in the ABS to move air in or out to help with the cooling issues.
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Old 02-10-2009, 06:11 PM   #22
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Quote:
Originally Posted by the_man View Post
While it may get dented up, it's underneath a low-slung car, so I put aesthetics on the back burner.
yes, but dents are less aerodynamic than a smooth surface
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Old 02-10-2009, 06:17 PM   #23
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Quote:
Originally Posted by mazda/nissan View Post
yes, but dents are less aerodynamic than a smooth surface
Tell that to a golf ball

(couldn't find any Homer Simpson speed hole pictures... so you get this.)
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Old 02-10-2009, 07:22 PM   #24
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It's the car from Swordfish....is that John Travolta's very own?
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Old 02-11-2009, 01:04 AM   #25
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Quote:
Originally Posted by Splitime View Post
Tell that to a golf ball

(couldn't find any Homer Simpson speed hole pictures... so you get this.)
yup! I read about the aero of a golf ball a few years ago it was fascinating. I'm not going to pretend to be an expert or anything like that, but I seem to recall that inducing micro vortecies on the surface makes for a turbulant boundry layer. That boundry layer will consequently stay attached further around the trailing edge leaving a smaller wake and thus less drag.
very cool stuff.
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Old 02-11-2009, 02:37 PM   #26
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So who's got a hot car with a junker body on it? Ball peen that biotch everywhere. Let us know about the results!
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Old 02-11-2009, 05:08 PM   #27
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yes, but the space shuttles have flat surfaces, and they go really fast
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Old 02-11-2009, 07:12 PM   #28
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Maybe dimples only help golf ***** because they spin?
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Old 02-11-2009, 08:48 PM   #29
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Quote:
Originally Posted by johndoe View Post
Maybe dimples only help golf ***** because they spin?
I think you are correct, maybe the dimples help it grab the air. Kind of like stitches on a baseball.
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Old 02-11-2009, 11:26 PM   #30
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agian, not an expert. The stuff I read though implied that it was only benificial to keeping the boundry layer attached on a steeply dropping off trailing edge. it was also implied that the resulting smaller low pressure wake was the only reason that drag was reduced. so the increased drag on the leading edges was more than offset by the smaller wake produced.

I'm going to make an assumption here and it may be off base, but I'm pretty sure that it's correct. if you look at the MR? version of the evo 8 there are vortex generators along the top of the steeply sloped rear window. I believe these were put there to keep the boundry layer attached further down the window to adjust the wake in such a manner to make the rear wing more effective.
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Old 02-11-2009, 11:32 PM   #31
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Quote:
Originally Posted by dynokiller90 View Post
agian, not an expert. The stuff I read though implied that it was only benificial to keeping the boundry layer attached on a steeply dropping off trailing edge. it was also implied that the resulting smaller low pressure wake was the only reason that drag was reduced. so the increased drag on the leading edges was more than offset by the smaller wake produced.

I'm going to make an assumption here and it may be off base, but I'm pretty sure that it's correct. if you look at the MR? version of the evo 8 there are vortex generators along the top of the steeply sloped rear window. I believe these were put there to keep the boundry layer attached further down the window to adjust the wake in such a manner to make the rear wing more effective.
I saw a subaru today that looked like it had a small wing at the very edge of the roof-line, but it was parallel to the back glass, like it was trying to catch air coming over the car, push it down the back glass, and into the spoiler
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Old 02-12-2009, 12:29 AM   #32
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Quote:
Originally Posted by mazda/nissan View Post
I saw a subaru today that looked like it had a small wing at the very edge of the roof-line, but it was parallel to the back glass, like it was trying to catch air coming over the car, push it down the back glass, and into the spoiler
All the 05 or 06+ STis have that spoiler on the top of the rear window. I'm sure it's there for the same reason the Evo9s have the vortex generators on their back windows. To smooth the airflow out to get less choppy air behind the window and over the rear spoiler.
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Old 02-12-2009, 11:13 AM   #33
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laminar flow has a lot of shear in it. it's like a deck of cards being slid on a table--the top one moves over the next one and so on. turbulent flow (at high reynolds numbers) can actually work more like little vortex ball bearings and lower the flow drag of a body.

the stitches on a baseball are to hold it together. but! they are very tightly regulated on official *****. same number and spacing requirements... they do make a difference to pitchers, but they are a design consequence, not the other way around.

golf ***** do have dimples to reduce drag. but they also have them to induce lift... backspin creates a pressure differential from top to bottom and helps the ball maintain hangtime.

supersonic jets also have devices to create turbulence along the wing surface.

and check this out... even super efficient cars steal this technique.

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Old 02-12-2009, 11:19 AM   #34
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damn hippies and their carrots...

it is difficult to find pictures of the bottom of the LMP1 cars, I have a link at the house that I will put up where someone got pictures of the cars up in the air in the paddock, showing all its underbits
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Old 02-12-2009, 11:47 AM   #35
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hippies dont shop at costco...
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Old 02-12-2009, 02:08 PM   #36
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note that the dimples on that car are on the trailing edge of the fender only. very cool.
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Old 03-11-2009, 08:40 PM   #37
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I just bought an Elise mid body undertray and rear diffuser. Aluminum parts. The undertray has Naca ducts in it for transmission and exhaust cooling. Going to try to retrofit these to the Miata. The parts used were cheaper than buying aluminum sheet to fab myself! Here's a pic over at CR that shows what the diffuser looks like on a Miata.

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Old 03-11-2009, 09:19 PM   #38
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Quote:
Originally Posted by mazda/nissan View Post
yes, but dents are less aerodynamic than a smooth surface
You've never seen a fast honda? They normally look like golf *****..
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Old 03-12-2009, 11:04 PM   #39
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Quote:
Originally Posted by cueball1 View Post
I just bought an Elise mid body undertray and rear diffuser. Aluminum parts. The undertray has Naca ducts in it for transmission and exhaust cooling. Going to try to retrofit these to the Miata. The parts used were cheaper than buying aluminum sheet to fab myself! Here's a pic over at CR that shows what the diffuser looks like on a Miata.

Where'd you manage to find that? And how much ducket?
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Old 03-17-2009, 01:10 PM   #40
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^^ agreed.. How much for the lotus piece?

Lots of good info/links in here, subscribed.
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