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Old 06-18-2009, 10:38 PM   This thread is in the EcoModder Project Library | #1 (permalink)
Master EcoModder
Join Date: Apr 2008
Location: Michigan
Posts: 261

Bio Deezler (sold) - '03 Volkswagen Jetta GLS TDI
90 day: 50.78 mpg (US)

The Beast. - '03 GMC Sierra 2500HD SLT
90 day: 12.86 mpg (US)
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Tuft Testing - "Vortekz" vortex generators on 2003 Jetta Rear Window

I've seen a few people attempt to find fuel economy improvements using vortex generators. However most folks were using "Airtabs", which are a larger flow disturbance vs. a smaller delta-wing style VG. In addition many folks were also placing them at the very rear edges of their bluff body style vehicle, or at the trunk-lid edge of sedans/hatchbacks. That doesn't seem like the ideal application to me.

I went with the "Vortekz" delta-wing type: Welcome to

Their website is not too impressive to say the least.

Nevertheless, I bought some. The only other person I saw using these post on a forum such as this was a thread over on gassavers with a Mazda 6 sedan. I think he's getting the best documented mileage of anyone with this car. Otherwise, these VGs mimic the type used on Mitsu Lancer EVOs and Subaru WRX STIs to direct air down and around the rear spoiler. I don't think anyone could deny that they work in this context. If we can visualize them bending down the airflow, and accept the Mistu paper on drag reduction (with the spoiler), then it can't hurt to give this a try.

Those looking for measured fuel economy impact of my application will be disappointed here. Sorry. Too many mods going on, and 700 mile tanks just last to long to do them one at a time. In any case, I did what I could with some tuft testing.

The array:

Stock roof

So there is obviously detached flow in most of the center of the car. I was a little surprised with how well flow stayed attached down the sides. Or at least visually "attached". You can see one of the center trunklid tufts just dancing straight up into the air though. Other window glass tufts turn front to rear. But it appears to me that the flow definitely comes over the roof and partway down the rear glass before severely separating. This was a good find for my selected VG location.


Back onto the road for a quick test at speed:

The still image with the VGs looks a little blurrier as the sun was setting. Obvious flow attachment improvement down the rear glass and deck. Cool. Whether this saves me fuel or not may remain difficult to ascertain. I think I'll refill 'er with bio asap so I can try to asses them on the next tank vs the current one.

These things really don't add much in the way of frontal area. Technically none, but the if the airflow is attached when it hits them, there is obviously going to be an impact on drag.

View from interior:

I also threw some tufts onto my passenger side glass where I recently did a flush mirror delete. I'll post up the results of that vs. a small safety mirror over in my general build thread.

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