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Old 06-04-2008, 01:49 AM   #21
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OK...

Did you also put VG's on the side of the 2-box cars you have? The airtab car application (Gen'1 CR-V!) claims 10% saving but has 7 airtabs on each sides. Most other applications claim gains on guzzlers like 8MPG pickups or rigs... Not relevant.
http://www.airtab.com/Images/photoga...allery1.htm#AP

Why no visible gains?

Can we can assume the VGs create a longer tail at least on the top part of the car. The air will not wrap down the rear windshield down towards the undercarriage to increase turbulence.

To get a clean teardrop, maybe the air flow also has to be somewhat cleaned on the undercarriage and sides too.

The VGs should help getting a stable depression behind the car. It would help get the turbulent pressurized undercarriage air out, and generate less drag from trapped pressured air.
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Old 06-04-2008, 06:23 AM   #22
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Did you also put VG's on the side of the 2-box cars you have?
No, I did not. I installed the delta fins on the roof as recommended by the mfgr which concurs with the Mitsu PDF. "Vortekz" claims that the fins can be mounted on the sides, but stops short of saying exactly how/where to mount them. I've considered mounting Airtabs on the sides, but a secure mounting area for the larger tabs is limited on my Volvo.

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Why no visible gains?
Possibly because all three vehicles lack prime driving/testing conditions. Most of my daily commute is spent below 40mph. My Dad's commute is pretty much the same. Both of us have experienced moderate gains on long highway trips, but I find it difficult to attribute it to the VGs alone. And my friend with the Audi wagon is notorious for his lead foot and keeping his rear window clean was the only reason he wanted them in the first place.


And finally, green swift....where are those pics???
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Old 06-04-2008, 11:57 AM   #23
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I contacted a vendor of VGs, and the saying is gains should be around 10%, but can't guarantee because of test conditions.

Air Flow system:
http://www.prfprod.com

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Mileage is tough to determine for a single vehicle. So much depends on the driver, conditions, vehicle, etc...
In general we have seen on the average of 8 to 12 percent increase in fuel mileage, on passenger cars and trucks. You may see mileage increase up to approx 26 or 27 from 24mpg. Unfortunately I would be reluctant to guarantee anything.
On my motorhome I have seen about a 20% increase in fuel mileage at 60MPH, and still see about 12% at 75MPH. Typically I would see a reduction in fuel mileage at 75MPH of about 20%. Again, every driver is different. I typically do some drafting with trucks and larger vehicles when on the open road. The biggest improvement was the handling in a crosswind or turbulence coming off another vehicle. It just goes straight down the road.
...
The Vortex Generators that we manufacture are much easier to install than the ones you mentioned because they are on a single panel. We recommend them across the rear top most trailing edge of the vehicle. The most effective installations are if they are placed on the sides and bottom of the vehicle as well. I always recommend using the biggest ones that you
have sufficient mounting area. I have attached a pic of our 2, 3, and 4 inch Vortex Generator Strips that are 12 inches in length.
...
Mike Nish
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Old 06-04-2008, 01:16 PM   #24
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The way they are shaped makes me think they would act like little parachutes. Also I just would expect something with a pointed end with the air flowing around and along the surface of it rather than into it like a funnel.
No, they generate vortices. The inside of the airtab has higher pressure than the edges, and voila, a vortex is formed on either side! Anyways, no, they are not "little parachutes."

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Aside from the design; where would I put them on my Cavalier for best results?
The first place would be somewhere on the aft end of the roof, before the upper lip of the rear windshield. This would aid the reattachment of flow to the aft windshield.

Next, probably somewhere on the hood in an attempt to reattach the flow around the A pillar.

Last, somewhere on the leading edge of the underside of the car, to help "clean up" the underbody car airflow.
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Old 06-04-2008, 02:53 PM   #25
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Quote:
Originally Posted by dosco View Post
The first place would be somewhere on the aft end of the roof, before the upper lip of the rear windshield. This would aid the reattachment of flow to the aft windshield.

Next, probably somewhere on the hood in an attempt to reattach the flow around the A pillar.

Last, somewhere on the leading edge of the underside of the car, to help "clean up" the underbody car airflow.
I haven't seen anyone put them on the hood yet.I'm sure the leading edge of the underside is spoken for.
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Old 06-05-2008, 12:00 PM   #26
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I haven't seen anyone put them on the hood yet.I'm sure the leading edge of the underside is spoken for.
How is the LE of the underside "spoken for?" In your pic its a field of duct tape, but I don't see why you couldn't do it. Not sure I'd want to stick a VG on duct tape, but you could do it with some double-sided tape.

I've been thinking about the A-pillar vortex, best place to put a VG would be on the hood. The problem would be "aiming" the resulting vortex to maximize flow reattachment after the A-pillar. Furthermore, the VG might also help cleanup some of the disturbances casued by the windshield wipers.
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Old 06-05-2008, 12:12 PM   #27
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Aren't you talking to do what bug deflectors do with VGs? i thought the bug deflectors were detrimental to aerodynamics.
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Old 06-05-2008, 12:50 PM   #28
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Quote:
Originally Posted by dosco View Post
How is the LE of the underside "spoken for?" In your pic its a field of duct tape, but I don't see why you couldn't do it. Not sure I'd want to stick a VG on duct tape, but you could do it with some double-sided tape.

I've been thinking about the A-pillar vortex, best place to put a VG would be on the hood. The problem would be "aiming" the resulting vortex to maximize flow reattachment after the A-pillar. Furthermore, the VG might also help cleanup some of the disturbances casued by the windshield wipers.
To start with, I might be adding to the nose piece which means another inch or two forward and more tape stretched from the point toward the corner of the bumper. I'm almost there but not quite.
Second, the object is to clean up the air under the car. I don't think there is a lot of air going under the car and what does is getting somewhat of a vortex treatment from the bottom of the air dam. Notice the plastic tassel in the middle of the air dam. That is to create vortex as well( have more of those in several other places on the car.). The rest of the underside is screened with window screen to the back.
For the wipers I have this wavy plastic to shield the wipers. I made them wavy to create vortex and seems to be working from what I see when it's raining.

This vortex doesn't seem to be an exact science but I think there are a lot of ways to use it other than the official VG's you can buy.
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Old 06-05-2008, 06:50 PM   #29
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I threw together a couple for testing; the shark fin and the rat. They might be too big for the roof.

I was thinking make one more and do a string on the back window test with none on one side and the VGs on the other.
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Old 06-05-2008, 07:04 PM   #30
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Why don't you put used tennis balls instead? After all it's like reverse dimples and you get the fuzz action going. :-)
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