Go Back   EcoModder Forum > EcoModding > Aerodynamics
Register Now
 Register Now
 

Reply  Post New Thread
 
Submit Tools LinkBack Thread Tools
Old 11-28-2007, 09:36 AM   #1 (permalink)
Batman Junior
 
MetroMPG's Avatar
 
Join Date: Nov 2007
Location: 1000 Islands, Ontario, Canada
Posts: 22,513

Blackfly - '98 Geo Metro
Team Metro
Last 3: 70.09 mpg (US)

MPGiata - '90 Mazda Miata
90 day: 52.71 mpg (US)

Even Fancier Metro - '14 Mitsubishi Mirage top spec
90 day: 70.75 mpg (US)

Appliance car - '14 Mitsubishi Mirage ES (base)
90 day: 60.16 mpg (US)
Thanks: 4,058
Thanked 6,957 Times in 3,602 Posts
Vortex generators - where's the solid data for hatchback/van benefits?

Info given to me by Ron Davidson at Airtabs. (Posted with permission)
  • 3rd party tests showing utility of tractor/trailer "gap" VG application at MIRA (British Motor Industry Research Association) test track, by IRTE/BTAC (Institute of Road Transportation Engineers / Brewing Transport Advisory Committee), 1994.
    http://www.box.net/public/sbj6b0xsrk

  • Airtabs background info on the MIRA/IRTE/BTAC report.
    http://www.box.net/public/e192gezve1
AND most relevant to my situation:
  • Images showing wind tunnel results (base pressure reduction, ie. improvements to low pressure zone at the back of the car ) on a Civic hatchback model with VG's installed only on the sides. Click to zoom.





__________________
Project MPGiata! Mods for getting 50+ MPG from a 1990 Miata
Honda mods: Ecomodding my $800 Honda Fit 5-speed beater
Mitsu mods: 70 MPG in my ecomodded, dirt cheap, 3-cylinder Mirage.
Ecodriving test: Manual vs. automatic transmission MPG showdown



EcoModder
has launched a forum for the efficient new Mitsubishi Mirage
www.MetroMPG.com - fuel efficiency info for Geo Metro owners
www.ForkenSwift.com - electric car conversion on a beer budget
  Reply With Quote
The Following User Says Thank You to MetroMPG For This Useful Post:
aerohead (03-14-2012)
Alt Today
Popular topics

Other popular topics in this forum...

   
Old 11-28-2007, 09:38 AM   #2 (permalink)
Batman Junior
 
MetroMPG's Avatar
 
Join Date: Nov 2007
Location: 1000 Islands, Ontario, Canada
Posts: 22,513

Blackfly - '98 Geo Metro
Team Metro
Last 3: 70.09 mpg (US)

MPGiata - '90 Mazda Miata
90 day: 52.71 mpg (US)

Even Fancier Metro - '14 Mitsubishi Mirage top spec
90 day: 70.75 mpg (US)

Appliance car - '14 Mitsubishi Mirage ES (base)
90 day: 60.16 mpg (US)
Thanks: 4,058
Thanked 6,957 Times in 3,602 Posts
The Australian AutoSpeed web site recently ran a 4-part series on VG's. Some of the articles are open access, some require payment:

http://www.autospeed.com/cms/search/...vortex&x=0&y=0

The writers have done quite a few excellent articles on DIY aero mods before, and they're normally pretty rational and scientific in their approach (ie. decent methodology, healthy skepticism). I've paid the $5 to access a few of their articles in the past, and haven't been disappointed.

They claimed they "tested" VGs on the rear of an Insight and a 1st generation Prius in the last instalment of the 4-part series, so I bought access to one of the articles to read the results.

Save your money: there were no "results" because they didn't properly test them!

They did show a beneficial improvement in airflow down the rear window of the Prius via photographs of tuft tests, but they didn't quantify the results re fuel consumption changes.





For the Insight, they didn't even attempt to do controlled back-to-back testing - they just drove their regular commute over several weeks and then compared the results there to (apparently) a single commute with the VGs attached. That methodology sucks!

And it doubly sucks because this is the application I'm most interested in: ie do VG's have the ability to reduce wake / base pressure beyond the trailing edge of a hatchback-style vehicle?



Still, they somehow feel confident enough to conclude that:

Quote:
Quote:
On the basis of the scientific evidence that is available, and the results of this test, we very much doubt whether vortex generators fitted to the trailing edges of vehicles will reduce drag.
(emphasis added.)
__________________
Project MPGiata! Mods for getting 50+ MPG from a 1990 Miata
Honda mods: Ecomodding my $800 Honda Fit 5-speed beater
Mitsu mods: 70 MPG in my ecomodded, dirt cheap, 3-cylinder Mirage.
Ecodriving test: Manual vs. automatic transmission MPG showdown



EcoModder
has launched a forum for the efficient new Mitsubishi Mirage
www.MetroMPG.com - fuel efficiency info for Geo Metro owners
www.ForkenSwift.com - electric car conversion on a beer budget
  Reply With Quote
The Following User Says Thank You to MetroMPG For This Useful Post:
aerohead (03-14-2012)
Old 11-28-2007, 09:42 AM   #3 (permalink)
Batman Junior
 
MetroMPG's Avatar
 
Join Date: Nov 2007
Location: 1000 Islands, Ontario, Canada
Posts: 22,513

Blackfly - '98 Geo Metro
Team Metro
Last 3: 70.09 mpg (US)

MPGiata - '90 Mazda Miata
90 day: 52.71 mpg (US)

Even Fancier Metro - '14 Mitsubishi Mirage top spec
90 day: 70.75 mpg (US)

Appliance car - '14 Mitsubishi Mirage ES (base)
90 day: 60.16 mpg (US)
Thanks: 4,058
Thanked 6,957 Times in 3,602 Posts
I've had a box of airtabs for quite some time, but I refuse to just stick them on the car and pretend they work.

I've prepared to do a test: attached the airtabs on flexible/removable plastic sheets that I can remove in a jiffy at the road side.

I just need to make another couple of sheets to complete the sides, and double-check with the distributor that the placement is OK.

click/zoom...




Above: I increased the spacing between the tabs by 50% to compensate for the 45 degree angle on the rear window.

I may not be able to place an uninterrupted line of them down the side of the car due to contours that they won't stick to. But I'll add a few more at least.



Unfortunately, I've been too busy to actually DO the test yet.
__________________
Project MPGiata! Mods for getting 50+ MPG from a 1990 Miata
Honda mods: Ecomodding my $800 Honda Fit 5-speed beater
Mitsu mods: 70 MPG in my ecomodded, dirt cheap, 3-cylinder Mirage.
Ecodriving test: Manual vs. automatic transmission MPG showdown



EcoModder
has launched a forum for the efficient new Mitsubishi Mirage
www.MetroMPG.com - fuel efficiency info for Geo Metro owners
www.ForkenSwift.com - electric car conversion on a beer budget
  Reply With Quote
The Following User Says Thank You to MetroMPG For This Useful Post:
aerohead (03-14-2012)
Old 12-30-2007, 08:56 AM   #4 (permalink)
EcoModding Lurker
 
Join Date: Dec 2007
Location: Darwin
Posts: 6

Trakka - '95 Volkswagen T4 Transporter / EuroVan Trakka Camperization
Thanks: 0
Thanked 0 Times in 0 Posts
VG freeway stats

At last a site for milage OCD!

I drove from Vancouver to San Antonio and back in a 1995 VW Eurovan camper at the local posted speed limit. Gas auto otherwise unmodified typical 16 mpg. I would remove/install these VG's at fill ups and check mileage per tank. Considering the cost (2 yogurt containers & a meter of white electrical tape) the approx. 7% mileage increase (~$50 saved - $85 if I'd had them on the whole trip) was acceptable. Definitely a TLAR installation. Would be nice to do wind tunnel/tuft/rainy day video testing to optimize location.
A similar installation on a VERY heavy U-Haul trailer showed a 2% improvement.
Attached Thumbnails
Click image for larger version

Name:	3235 (2).JPG
Views:	329
Size:	77.5 KB
ID:	99   Click image for larger version

Name:	3236 (4).JPG
Views:	360
Size:	66.8 KB
ID:	100  

Last edited by bryan; 12-30-2007 at 09:05 AM.. Reason: photo issues
  Reply With Quote
Old 12-30-2007, 02:06 PM   #5 (permalink)
MechE
 
Join Date: Dec 2007
Location: Bay Area
Posts: 1,151

The Miata - '01 Mazda MX-5 Miata
Thanks: 0
Thanked 21 Times in 18 Posts
Quote:
Originally Posted by MetroMPG View Post
AND most relevant to my situation:
  • Images showing wind tunnel results (base pressure reduction, ie. improvements to low pressure zone at the back of the car ) on a Civic hatchback with VG's installed only on the sides. Click to zoom.




Damn, I was hoping to see the bit of info I've been after..... How far from the leading edge to place That variable will be one of the most important ones...
__________________
Cars have not created a new problem. They merely made more urgent the necessity to solve existing ones.
  Reply With Quote
Old 12-30-2007, 02:58 PM   #6 (permalink)
Batman Junior
 
MetroMPG's Avatar
 
Join Date: Nov 2007
Location: 1000 Islands, Ontario, Canada
Posts: 22,513

Blackfly - '98 Geo Metro
Team Metro
Last 3: 70.09 mpg (US)

MPGiata - '90 Mazda Miata
90 day: 52.71 mpg (US)

Even Fancier Metro - '14 Mitsubishi Mirage top spec
90 day: 70.75 mpg (US)

Appliance car - '14 Mitsubishi Mirage ES (base)
90 day: 60.16 mpg (US)
Thanks: 4,058
Thanked 6,957 Times in 3,602 Posts
Quote:
Originally Posted by bryan View Post
At last a site for milage OCD!
Hi bryan - welcome to EM!

Quote:
Definitely a TLAR installation.
OK, I have to say I don't know that one. What's TLAR??

Quote:
Would be nice to do wind tunnel/tuft/rainy day video testing to optimize location.
I agree. And good to hear from someone who gets the importance of data + testing.

That said... back to your anecdotal info... I'd be interested to hear more details about your experience with the things on your van & the trailer - E.G. how many on vs. off comparisons you made; whether the weather, road conditions & terrain were similar from tank to tank.

There's no shortage of customers claiming great things about airtabs in the company testimonials. But you have to take that with such a huge grain of salt, it's not really worth very much.

Again, not saying they don't work.

But I would like to see some more convincing data for my application. Either that or I need more warm months in the year to gather the info myself.
__________________
Project MPGiata! Mods for getting 50+ MPG from a 1990 Miata
Honda mods: Ecomodding my $800 Honda Fit 5-speed beater
Mitsu mods: 70 MPG in my ecomodded, dirt cheap, 3-cylinder Mirage.
Ecodriving test: Manual vs. automatic transmission MPG showdown



EcoModder
has launched a forum for the efficient new Mitsubishi Mirage
www.MetroMPG.com - fuel efficiency info for Geo Metro owners
www.ForkenSwift.com - electric car conversion on a beer budget
  Reply With Quote
Old 12-30-2007, 07:06 PM   #7 (permalink)
EcoModding Lurker
 
Join Date: Dec 2007
Location: Darwin
Posts: 6

Trakka - '95 Volkswagen T4 Transporter / EuroVan Trakka Camperization
Thanks: 0
Thanked 0 Times in 0 Posts
randomization

Considering that during this 15,000 km test the combined vehicle weight was 2500 to 5500 kg, speed limits vary from 45 to 130 km/h, altitudes from sea level to 10,000 ft and a prevailing westerly wind I just alternated on/off at each tank ~500 km. This then gave me, say, 500 km on and 500 km off at the Colorado Plateau, same at 80 mph Texas freeway speeds. Once I had convincing data I just left them on for the last 3000 km or so, since by then I was driving in heavy snow & mountain passes which gets a bit too variable.
TLAR: That Looks About Right . These are about the size & angle of attack of aircraft VG's (400 km/h) at half spacing, installed at about the location AirTabs recommends. I didn't do the reynold's number conversion to see if the size was appropriate. I will bet double density would help.

Since then I also have tried premium gasoline which gives an 18% improvement (!) for a 10% cost increase. This is city driving and probably type-specific.

Per tank mileage variability was 9 to 25 l/100 km so the Signal to Noise Ratio here is pretty crappy. The fuel flow meter in the Saskatchewan Metro Videos would have speeded this up considerably.
  Reply With Quote
Old 12-30-2007, 07:34 PM   #8 (permalink)
EcoModding Apprentice
 
Join Date: Dec 2007
Location: Melbourne
Posts: 152

The Mighty Mira - '92 Daihatsu Mira
90 day: 61.32 mpg (US)
Thanks: 0
Thanked 7 Times in 7 Posts
I'd say if you don't have a sizeable 20-45 degree slope towards the center of the vehicle in the area after you place the air tabs, you'd be just as well off writing a check out to me as buying air tabs. But don't worry, I won't rip you off, you'll be getting the most premium magic beans sourced at great expense from exotic locations around the world.
__________________
"Every body perseveres in its state of being at rest or of moving uniformly straight forward, except insofar as it is compelled to change its state by force impressed." - Isaac Newton
  Reply With Quote
Old 12-30-2007, 09:04 PM   #9 (permalink)
MechE
 
Join Date: Dec 2007
Location: Bay Area
Posts: 1,151

The Miata - '01 Mazda MX-5 Miata
Thanks: 0
Thanked 21 Times in 18 Posts
I have some pictures, somewhere, of my buddy's rowing oars... He got them recently and have vortex generators on them (on leading edge)... I believe his immidiate comment on the first stroke was something like "These new oars are F'ing sweet" or something like that
__________________
Cars have not created a new problem. They merely made more urgent the necessity to solve existing ones.
  Reply With Quote
Old 12-31-2007, 12:24 AM   #10 (permalink)
Giant Moving Eco-Wall
 
DifferentPointofView's Avatar
 
Join Date: Dec 2007
Location: The Dale, IL (or A-Dale)
Posts: 1,120

The Jeep! - '95 Jeep Grand Cherokee ZJ Laredo
90 day: 23.75 mpg (US)

The Caliber - '07 Dodge Caliber R/T
90 day: 30.6 mpg (US)

The 'Scort - '98 Ford Escort LX
Thanks: 0
Thanked 7 Times in 6 Posts
The Mitsu Evo has similar fins on it.




__________________


Yea.. I drive a Jeep and I'm on a fuel economy site, but you just wouldn't understand... "It's a Jeep thing!" *Jeep Wave*

Did I Use Too Many Abbreviations? Here's The Abbreviations List
  Reply With Quote
Reply  Post New Thread


Thread Tools


Similar Threads
Thread Thread Starter Forum Replies Last Post
5th generation civic hatchback - improving aerodynamics AndrewJ Aerodynamics 396 06-13-2022 01:51 PM
Diesel- and Hybrid-Powered Vehicles Can Provide More Societal Benefits than Gas-Power SVOboy General Efficiency Discussion 12 04-29-2017 08:03 AM
Video: Illustrating the Vast Importance of Aerodynamics (open hatchback experiment) Peakster Aerodynamics 17 02-15-2012 06:29 PM
Found a coastdown hill! Mini comparo: windows vs skirts vs hatchback MetroMPG Aerodynamics 4 11-27-2007 11:40 PM



Powered by vBulletin® Version 3.8.11
Copyright ©2000 - 2024, vBulletin Solutions Inc.
Content Relevant URLs by vBSEO 3.5.2
All content copyright EcoModder.com