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Old 08-25-2008, 03:50 PM   #31
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Originally Posted by LoudAccord View Post
reducing drag and creating downforce makes no sense to me.
They you've never studied car aerodynamics as a whole. The car is a system, not just a single piece.

In a wind tunnel, a single plane device will not be able to create downforce without drag. You're very right in this sense.

But now picture a moving wall going down the highway. We'll say it's 2 feet tall by 5 feet wide. Behind it is a spoiler recieving zero airflow. But now let's say we rake the wall back 45 degrees, just exposing the spoiler behind it. Now we've reduced drag AND increased downforce.

The reason vortex generators create MORE downforce and REDUCE drag, is all in direct relation to the boundry later, and turbulence. Turbulent air causes drag, period. And the more air in the boundry layer, the more air you're carrying with you. Reducing both is a good thing.

To illistrate the effects of turbulence. Swing a 1/2" x 36" dowel in the air. Nice and easy right? Feels like a sword right? Now tie a 12" ribbon to the end. Hows that? Not too bad? Now tie a 24" ribbon to it? Getting hard yet?

As you add on ribbon, you're not adding weight, you're not adding frontal area. You're adding turbulence that's creating drag. The ribbon slaps around the air creating poor air flow patterns.

Adding vortex generators reduces the amount of air you're dragging behind the vehicle, and removes tons of turbulence.

This would also make the care LESS ideal to draft behind, because there's a smaller pocket of unmoving air behind it.

On a big rig most of the turbulence is created around the edges of the air behind it, while theres a huge area of bounry layer to draft in.
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Old 08-25-2008, 04:01 PM   #32
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Originally Posted by Gollum View Post
They you've never studied car aerodynamics as a whole. The car is a system, not just a single piece.

In a wind tunnel, a single plane device will not be able to create downforce without drag. You're very right in this sense.

But now picture a moving wall going down the highway. We'll say it's 2 feet tall by 5 feet wide. Behind it is a spoiler recieving zero airflow. But now let's say we rake the wall back 45 degrees, just exposing the spoiler behind it. Now we've reduced drag AND increased downforce.

The reason vortex generators create MORE downforce and REDUCE drag, is all in direct relation to the boundry later, and turbulence. Turbulent air causes drag, period. And the more air in the boundry layer, the more air you're carrying with you. Reducing both is a good thing.

To illistrate the effects of turbulence. Swing a 1/2" x 36" dowel in the air. Nice and easy right? Feels like a sword right? Now tie a 12" ribbon to the end. Hows that? Not too bad? Now tie a 24" ribbon to it? Getting hard yet?

As you add on ribbon, you're not adding weight, you're not adding frontal area. You're adding turbulence that's creating drag. The ribbon slaps around the air creating poor air flow patterns.

Adding vortex generators reduces the amount of air you're dragging behind the vehicle, and removes tons of turbulence.

This would also make the care LESS ideal to draft behind, because there's a smaller pocket of unmoving air behind it.

On a big rig most of the turbulence is created around the edges of the air behind it, while theres a huge area of bounry layer to draft in.
what about the guys that use drops of oil to see the path ???
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Old 08-26-2008, 11:28 AM   #33
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Quote:
Originally Posted by Gollum View Post
They you've never studied car aerodynamics as a whole.
R-E-S-P-E-C-T!

good explanation too.
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Old 10-01-2008, 05:42 AM   #34
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Nice tuft test! Very nice! I don't have a scangauge either, so I can feel you there. But you could do a coast down test. I suppose it doesn't help much if you didn't do one before, but if you can coast further (with the same Crr and same local conditions and same frontal area) then you have a reduced Cid.

It's clear that the flow is better and less turbulent, but just like a spoiler adds drag in the basic sense (it has to use air force to direct car down), these are adding drag as well, at 15 degrees it's not much, and any sideways force is canceled out since they're mirrored, but they are dragging a bit and using energy to change the direction of air flow.

I'm sure curious if this energy is less than the drag caused by the previous turbulence.

I need to find a good level for coast down tests, nothing good near me . I want to try coast down before grill block, with block, with kammback and maybe with airtabs on end of kammback.
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Old 10-01-2008, 09:07 AM   #35
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Lets just say that I dont know of anybody with a Mazda 6 getting 36mpg constantly (with my high being of 41mpg!).

Nobody.

And all i have done is very basic aerodynamic mods such as grill block and this.

So I truly beleive they worked in my application, I really do, until I find a Mazda6 that gets more than 36-37mph hwy consistantly and doesnt have vortex generators... then ill start doubting them.
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Old 10-06-2008, 07:39 AM   #36
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Every time I'm driving along and come to a nice flat section of road, I start looking at my scangauge.
After a while, I've come to the conclusion that I'm getting about 33 highway..

My latest experiment is Giant Zig-Zag tape..
It's new to me, but I think ZZ tape is a type of VG strip also called turbulator tape. Or, maybe it just works like dimples in a golf ball..



Got to take a few road trips this week to see if it's doing anything.
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Old 10-09-2008, 10:18 AM   #37
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I'd keep those things on. It seems you proved that you have smoothed the airflow coming down the back window. Anything that makes air move across the car with less resistance, is good in my book. Isn't that what reducing Cd is all about?

Folks are doing Kammbacks, boattails, front tire air deflectors, grille blocks, etc with proven results. Nothing wrong with those vortex generators.
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Old 10-09-2008, 11:35 AM   #38
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99metro,

looks like you're really in the top ten(gas cars) w/ most ahead of you owning honda civics. nice job w/ no major mods.
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Old 12-28-2008, 04:09 PM   #39
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I wonder which is better, these or the ones that look like they have little NACA ducts
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Old 12-28-2008, 05:08 PM   #40
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Anyone else have any new "before and after" mpg data?
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