See also: http://ecomodder.com/forum/showthrea...fect-6381.html

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Here's the skinny on an A-B-A test @ 90 km/h on the end of the roof of a 2006 Toyota Corolla 4-door sedan automatic.

http://ecomodder.com/imgs/corolla-tu...vg-driveby.jpg

Results in mpg (US), averages of mulitple bi-directional runs:

A - 48.9 - no airtabs

B - 48.6 - airtabs

A - 48.5 - no airtabs

I'll post up the details later.

Update May 17/08:

Raw data:

Avg. of all A runs (7): 48.69 mpg (US)
Standard deviation of avg. of all A runs: 0.31 mpg (US)

Avg. of all B runs (4): 48.58 mpg (US)
Standard deviation of avg. of all B runs: 0.20 mpg (US)

The distribution of the data seems pretty tight. I have a good test route (next to no traffic) & had nearly ideal weather (next to no breeze).

Update - August 18/08

http://www.youtube.com/watch?v=We8LWkqjdX4

Metro, I don't know if you plan on including it... But the standard deviation for A and B would be awesome for something like this :)

Well, Tre, with results like these, I hope you made your VGs out of cheap plastic.

Tried them on you HPV streamliner yet?

Raw data:

Avg. of all A runs (7): 48.69 mpg (US)
Standard deviation of avg. of all A runs: 0.31 mpg (US)

Avg. of all B runs (4): 48.58 mpg (US)
Standard deviation of avg. of all B runs: 0.20 mpg (US)

The distribution of the data seems pretty tight. I have a good test route (next to no traffic) & had nearly ideal weather (next to no breeze).

I'm waiting (weather) for the opportunity to also tuft test the back window/trunk of this car with & without the VG's. Hopefully this weekend.

can you add pics ???

I'll get some when tuft testing.

cool ,,thanks

Hi Metro,

How about trying them at the front of the roof, about 6 inches back from the windshield, or even right at the top of the windshield? That is more in line with aircraft applications.

It looks like where you had them they were completely within the boundray layer and thus there was little impact.

Aerohead was saying that the flow is seperating there already. So, this makes sense. The idea at putting them forward, is that they may keep the cross section of the turbulent flow smaller.

On an 18 wheeler, my guess is that the flow is pretty laminar by the time it gets to the rear of the truck. That is, the turbulent effects have decayed, which then start up again behind the truck. I base this on driving next to trucks and watching my Prius mileage indicator. Cars are not long enough for these to have an effect on the roof above the C pillar, I do not think. Even though that is where the EVO uses them. The EVO has such a highly angled rear window, it may be pulling the bounadary layer on the roof down.

I found this link in an unrelated search, I hope it will help you guys on the subject .. Interesting stuff


http://www.mitsubishi-motors.com/cor...004/16E_03.pdf

Hi Donee -

The placement of the VG's was based on the PDF that trikkoncept linked. Have a look.

Flow typically separates at the trailing edge of the roof on 3-box vehicles, so that's where VG's would theoretically help most.

That said, also note that the Mistu engineers themselves managed only a 0.006 change in Cd in their application. So even if they were helping, I would have been surprised to see any significant change in the Corolla results.

Renault also used trailing roof edge VG's on their Michelin Challenge Bibendum Logan sedan: http://forum.ecomodder.com/showthrea...179.html?t=179

It's quite possible that the Corolla's rear glass angle is already close to optimal, so wouldn't benefit much anyway. Tuft testing will help figure that out.