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

Now available from EcoModder: ScanGauge II fuel economy gauge.  Click for details.  

Reply  Post New Thread
Submit Tools LinkBack Thread Tools
Old 09-06-2011, 07:19 PM   #11 (permalink)
dcb
needs more cowbell
 
dcb's Avatar
 
Join Date: Feb 2008
Location: ÿ
Posts: 5,032

pimp mobile - '81 gs 250 t
90 day: 96.29 mpg (US)

schnitzel - '01 Golf TDI
90 day: 53.56 mpg (US)
Thanks: 156
Thanked 259 Times in 203 Posts
Nobody has articulated the theory about how Vortex generators are supposed to help, and under what circumstances. Saying we just can't measure the difference is "logic" that can be applied to any unicorn. It really is a unicorn for all intents and purposes, and if someone comes up with a repeatable (not background noise) design/process that other ecomodders can validate, well I would reconsider it as a possible non-unicorn, but most of the time it is background noise (and a lot of hot air and wasted energy discussing it).

If the difference is that small, and requires such a large investment in design even then, then most folks here shouldn't be messing with them, better to label it a unicorn made of unobtanium until proven otherwise (no, claims about one race car is not conclusive "proof").


(Support Ecomodder.com & get rid of these annoying ads!)      
 
__________________
WINDMILLS DO NOT WORK THAT WAY!!!
  Reply With Quote
Old 09-06-2011, 07:22 PM   #12 (permalink)
Tenderfoot
 
ChazInMT's Avatar
 
Join Date: Jan 2010
Location: Bozeman Montana
Posts: 437

MagMetalCivic - '04 Civic EX
90 day: 37.18 mpg (US)
Thanks: 127
Thanked 169 Times in 88 Posts
I find it to be very difficult to believe that AirTabs & Vortex Generators do any good, except in very specific applications.

The reasons are these:

• If they create more thrust than the drag they produce, this would violate the laws of physics.

• The air being affected around a vehicle extends out several feet, it isn't all just within 1" of the skin. VG's seldom protrude more than 3/4" so the volume of air they have an effect on is very small compared to the huge volume that is in play, so it's doubtful that they could dramatically change the Cd.

• If they had measurable gains in fuel efficiency, we'd see them on production vehicles, you can't tell me that a cheap fix of adding these to a car or integrating them with the design of a car wouldn't be used if it could demonstrate 2-3 MPG's of difference. Car companies spend millions trying to figure out how to eek out that kind of FE gain.

• There is only 1 test I have ever see where they helped out a Mitsubishi Lancer, this took a team of engineers, a wind tunnel, and very specific placement to achieve a tiny gain in Cd. It is far beyond the reach of most people to figure out where & how to place these devices, and 95% of the vehicles made would receive no benefit from them no matter what number, where, or how they were applied anyway.

Show real reports by people other than the makers of these gimmicks showing an improvement in FE if you want to claim they work. My studied intuition says they're crap, they aren't in wide spread use commercially, and plenty of people have shown real results demonstrating they do nothing to help FE.

It is up to you to prove they do work, not up to those who are very skeptical to prove they don't. Show us real data, not hyped up marketing from someone who stands to make bucks selling these.

  Reply With Quote
The Following 2 Users Say Thank You to ChazInMT For This Useful Post:
Arragonis (09-07-2011), UFO (09-07-2011)
Old 09-06-2011, 10:23 PM   #13 (permalink)
Master EcoModder
 
Join Date: Oct 2009
Location: Corpus Christi, Texas
Posts: 897

2004 CTD - '04 RAM 2500 SLT
Team Cummins
90 day: 21.37 mpg (US)
Thanks: 259
Thanked 130 Times in 107 Posts
The reports of semi trailers having better handling characteristics keeps coming to mind. This is a consistent report when searched online. But FE is more of a problem. If but one truck fleet used them we'd have something to go on.
__________________
2004.0 7,360-lb DODGE Ram QC/LB 2500 2WD/6-speed Cummins 305/555 ISB. Stock, except LEER bed topper and twin muffler exhaust. 180,000 miles at 4,625-hrs @ 39 mph. 15-cpm solo, 25-cpm towing. (22-mpg avg past 37k)

Fuel Log
  Reply With Quote
Old 09-07-2011, 08:11 AM   #14 (permalink)
Eco-ventor
 
Join Date: Oct 2010
Location: sweden
Posts: 579

Princess - '92 MX-3 GS
House of Tudor
90 day: 33.52 mpg (US)
Thanks: 7
Thanked 113 Times in 79 Posts
Send a message via MSN to jakobnev
Isn't it "obvious" that for VGs to do any good, there has to be something down stream of them that can reap the benefits? (Like the trunk lid and wing on the Lancer for example)
__________________



Remember, even if you win the rat race - you're still a rat.

2010: 454.92L for 5313.90km => 8.56L/100km (27.5MPG US) (5 months)
2011: 606.11L for 7754.04km => 7.82L/100km (30.1MPG US) (Full year)
2012: 170.10L for 2405.00km => 7.07L/100km (33.3MPG US) (In progress)
  Reply With Quote
Old 09-07-2011, 08:50 AM   #15 (permalink)
dcb
needs more cowbell
 
dcb's Avatar
 
Join Date: Feb 2008
Location: ÿ
Posts: 5,032

pimp mobile - '81 gs 250 t
90 day: 96.29 mpg (US)

schnitzel - '01 Golf TDI
90 day: 53.56 mpg (US)
Thanks: 156
Thanked 259 Times in 203 Posts
Quote:
Originally Posted by jakobnev View Post
Isn't it "obvious" that for VGs to do any good, there has to be something down stream of them that can reap the benefits? (Like the trunk lid and wing on the Lancer for example)
No, it isn't obvious in the slightest. Half the vg enthusiasts stick them on the very back edge of their vans/boxes, and all of them "Want to believe". They want to believe they aren't chumps...

From the airtab site:
__________________
WINDMILLS DO NOT WORK THAT WAY!!!
  Reply With Quote
Old 09-07-2011, 10:28 AM   #16 (permalink)
Absent without leave.
 
Arragonis's Avatar
 
Join Date: Oct 2009
Location: Englishman living in Scotland
Posts: 3,365

George - '011 Aygo Go!
Team m8
90 day: 54.54 mpg (US)

Mildred - '011 Prius T-Spirit
90 day: 45.97 mpg (US)
Thanks: 168
Thanked 250 Times in 187 Posts
Aren't those ^ the wrong way round ?

EDIT - no apparently not.
__________________
No longer here. Bye, and good luck to all.
  Reply With Quote
Old 09-07-2011, 10:56 AM   #17 (permalink)
UFO
Master EcoModder
 
UFO's Avatar
 
Join Date: Sep 2010
Location: Denver, CO
Posts: 723

Beetle - '01 Beetle GLS
90 day: 42.61 mpg (US)

4x4 - '89 Pickup DLX
90 day: 30.36 mpg (US)
Thanks: 92
Thanked 60 Times in 42 Posts
Quote:
Originally Posted by dcb View Post
No, it isn't obvious in the slightest. Half the vg enthusiasts stick them on the very back edge of their vans/boxes, and all of them "Want to believe". They want to believe they aren't chumps...

From the airtab site:
LOL! That is hilarious!
__________________

"We think B20 is for suckers" N. Cowell, Denver B100
"Climate change denial is a conclusion in search of a rationalization" labman57
  Reply With Quote
Old 09-07-2011, 11:22 AM   #18 (permalink)
Master EcoModder
 
Phantom's Avatar
 
Join Date: Jan 2010
Location: Louisville, KY
Posts: 484

Bonnie - '98 Bonneville SSE
3800
90 day: 26.91 mpg (US)
Thanks: 65
Thanked 33 Times in 31 Posts
I really think they should be tested pointing the wrong way.
__________________
I move at the speed of awesome.
  Reply With Quote
Old 04-28-2012, 04:46 PM   #19 (permalink)
Master EcoModder
 
Join Date: Jan 2008
Location: Sanger,Texas,U.S.A.
Posts: 3,975
Thanks: 1,179
Thanked 807 Times in 469 Posts
Airtabs at PATE

While I was rummaging around the swap meet I ran across a HAULMARK trailer which sported Airtab brand VGs on its trailing edge.The owner was tracked down.he's a Texas Tech guy,has maintained 40-years of logbooks on his vehicles and reported that no savings were discernible with the Airtabs.
He has many friends who are career OTR truckers.None of them report savings from them.He told me that 'soft-sided' trailers were the only thing to 'show' at the Diesel pump.
  Reply With Quote
Old 04-28-2012, 06:33 PM   #20 (permalink)
Efficiency Aficionado
 
CigaR007's Avatar
 
Join Date: Jul 2010
Location: Province of Québec
Posts: 459

GreenTurtle - '01 Echo Sedan
90 day: 42.53 mpg (US)
Thanks: 107
Thanked 75 Times in 62 Posts
Renault seems to think that vortex generators can reduce drag in 3-box cars.



Search for the Renault Logan ECO2


(Support Ecomodder.com & get rid of these annoying ads!)      
 
  Reply With Quote
Reply  Post New Thread

Tags
air tabs, fixture, testing, van

Thread Tools





Powered by vBulletin® Version 3.8.7
Copyright ©2000 - 2012, vBulletin Solutions, Inc.
Content Relevant URLs by vBSEO 3.5.2
All content copyright EcoModder.com