Vortex generators - where's the solid data for hatchback/van benefits?

[newtonsfirstlaw]

Originally Posted by bryan

Unlike global climate change, evolution and reiki you should be able to prove this one pretty quickly... ie in about 2 tanks of gas.

I'm not sure I can prove anything in two tanks of gas. There are all sorts of confounding variables, the largest of which is driving style. Just a few big stops from high speed can really throw out your fuel economy.

I'd also like to know the theoretical basis behind vortex generators placed before abrupt ends of things, as MetroMPG says. I can understand how they'd work on something like a 20-40 degree slope, and Mitsubishi wrote a paper on it. But the back of a van? Color me skeptical.

[voxelman]

Originally Posted by trebuchet03

^^ Mitsu has a paper published too

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

worth a reduction of 6 points (.006) in cD

After reading the paper it looks like delta shaped VGs would help the aereodynamic characteristics of most notch back sedans. I think I'm going to try them on my 1991 Honda Accord 4D.

[MetroMPG]

I'm with Lazarus & Newton on this one - tank-to-tank testing doesn't generally produce reliable results.

And as a matter of fact - I have no "baseline" to go from. I don't commute with the car, so it doesn't see either typical or frequent use. Check my fuel log - it's all over the map.

I actually did stick the VG's on my car for a 200 km highway trip. Not surprisingly I couldn't conclude anything from the results - and I didn't really try. (Mostly I put them on to show the guy who lent them to me.)

Originally Posted by bryan

Unlike global climate change, evolution and reiki you should be able to prove this one pretty quickly...

The best way to test them is in a wind tunnel.

Following that, the best way to test them is with instrumentation & a series of back to back A-B-A runs on a deserted road using cruise control to remove the driver from the equation.

I had every intention of trying just that, but my play time in the past year was occupied with other stuff (ie. ForkenSwift). Maybe in '08 I'll add the "hatchback" VG test to Lazarus' sedan test.

[voxelman]

At the very least it looks like these things will help clear the snow (something we've been having a regretable amount of lately) off the rear window.

[MetroMPG]

True, but you'll have to "detail" the darned things on the roof after every snowfall too. I expect they'd fill in, at which point they're just hurting your Cd (and poss increasing A). And how long before you crack one or knock it off with the snow brush?

[voxelman]

You may be right but when the car gets snow covered or worse like two weeks ago ice covered (1/2 inch) I expect Cd and A get blown out pretty badly not to mention the added weight.

[bilgladstone]

Here is a row of VGs on the trailing edge of my 2005 smart car.

I have no empirical numbers to offer - I do so many mods to my car that I can never isolate the results of any one at a time!

The most interesting result is a noticable improvement in straight-line tracking at highway speed on this 8ft long car!



Cheers, all.

Bil

[SVOboy]

That's pretty nice looking, where'd you get them?

Welcome to the site!

[bilgladstone]

Thanks for the welcome - glad to be aboard!

The VGs are from Nish Motorsports Contact our buddy Mike Nish and tell him "Bil the smart car guy" sent you!

[SVOboy]

Thanks for the link! Perhaps we'll get some more testing on these things going...

Don't forget to make an intro thread,