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

Reply  Post New Thread
 
Submit Tools LinkBack Thread Tools
Old 06-11-2009, 01:20 PM   #1 (permalink)
Grasshopper
 
alohaspirit's Avatar
 
Join Date: Feb 2009
Location: Hawaii
Posts: 964

Makai - '01 Toyota Echo 4D Auto
90 day: 34.45 mpg (US)

New Galaxy - '07 Toyota Prius
90 day: 42.15 mpg (US)
Thanks: 25
Thanked 30 Times in 25 Posts
Smile Tire Wind Deflector Question

I think figure A is better since it deflects air away
from your underbody but Id like to hear your reasoning

Attached Thumbnails
Click image for larger version

Name:	Air.JPG
Views:	980
Size:	21.0 KB
ID:	3686  
__________________
Past Present Future?
  Reply With Quote
Alt Today
Popular topics

Other popular topics in this forum...

   
Old 06-11-2009, 01:36 PM   #2 (permalink)
Batman Junior
 
MetroMPG's Avatar
 
Join Date: Nov 2007
Location: 1000 Islands, Ontario, Canada
Posts: 21,672

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

MPGiata - '90 Mazda Miata
90 day: 53.78 mpg (US)

Winter beater Metro - '00 Chevrolet Metro
90 day: 61.98 mpg (US)

Fancy Metro - '14 Mitsubishi Mirage top spec
90 day: 58.72 mpg (US)

Even Fancier Metro - '14 Mitsubishi Mirage top spec
90 day: 66.29 mpg (US)
Thanks: 3,410
Thanked 6,217 Times in 3,222 Posts
The airflow near the front tires is rarely travelling straight towards them, so the design of successful tire deflectors may not be intuitive.

High pressure at the bumper may be forcing flow both down and outwards, which is one reason why OEM spats don't extend out to the edge of the tires (they'd be overkill if they did, pushing air further out than necessary).

Some OEM spats that are angled similar to your Figure B would be subject to perpendicular flow! (Of course, it depends on the vehicle.)

One Volvo study found that even very small changes in spat size / positioning can have a negative effect (increase drag). I'll see if I can dig it up...

This is a tough one to guess at!
__________________
Latest mods: 3-cylinder Mitsubishi Mirage. EcoMods now in progress...
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 06-11-2009, 01:41 PM   #3 (permalink)
Batman Junior
 
MetroMPG's Avatar
 
Join Date: Nov 2007
Location: 1000 Islands, Ontario, Canada
Posts: 21,672

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

MPGiata - '90 Mazda Miata
90 day: 53.78 mpg (US)

Winter beater Metro - '00 Chevrolet Metro
90 day: 61.98 mpg (US)

Fancy Metro - '14 Mitsubishi Mirage top spec
90 day: 58.72 mpg (US)

Even Fancier Metro - '14 Mitsubishi Mirage top spec
90 day: 66.29 mpg (US)
Thanks: 3,410
Thanked 6,217 Times in 3,222 Posts
Here it is. No surprise that Julian covered it at Autospeed!

Modifying under-car air flow part 2

The table on that page shows how in the case of tire spats/dams it's not a simple matter of slapping something on.
__________________
Latest mods: 3-cylinder Mitsubishi Mirage. EcoMods now in progress...
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 3 Users Say Thank You to MetroMPG For This Useful Post:
aerohead (03-24-2012), Geo Metropolis (12-17-2011), utemarksman (03-05-2011)
Old 06-11-2009, 03:17 PM   #4 (permalink)
Master EcoModder
 
Join Date: Jan 2009
Location: Maui, Hawaii
Posts: 813
Thanks: 5
Thanked 34 Times in 26 Posts
Why are some spats parallel to the front of the tire? Why not just let the air hit the tire? It's not like it's less aerodynamic than the spat.
  Reply With Quote
Old 06-11-2009, 04:08 PM   #5 (permalink)
Grasshopper
 
alohaspirit's Avatar
 
Join Date: Feb 2009
Location: Hawaii
Posts: 964

Makai - '01 Toyota Echo 4D Auto
90 day: 34.45 mpg (US)

New Galaxy - '07 Toyota Prius
90 day: 42.15 mpg (US)
Thanks: 25
Thanked 30 Times in 25 Posts
Quote:
Originally Posted by MetroMPG View Post
Here it is. No surprise that Julian covered it at Autospeed!

Modifying under-car air flow part 2

The table on that page shows how in the case of tire spats/dams it's not a simple matter of slapping something on.

Thanks. Thats a good link.

Almost all the defectors helped except for the biggest one.

Which basically means "Bigger doesnt equal Better"

*insert joke here*



sadly what came stock on that prius is what i was thinking about making


__________________
Past Present Future?
  Reply With Quote
Old 06-11-2009, 04:20 PM   #6 (permalink)
Master EcoModder
 
doviatt's Avatar
 
Join Date: Mar 2009
Location: Utah
Posts: 388

Grey Goose (Retired) - '89 Geo Metro LSI 4 door hatch back
Last 3: 57.16 mpg (US)

Tweety - '91 Geo Metro Convertible -2 Door convertible LSI
Team Metro
90 day: 43.97 mpg (US)

Shadow - '02 Honda Shadow VT1100
90 day: 43.46 mpg (US)

Sonic - '07 Honda CBR1000RR
90 day: 42.69 mpg (US)

Filmore - '84 Volkswagen Vanagon
90 day: 20.9 mpg (US)
Thanks: 47
Thanked 44 Times in 31 Posts
Sounds like a good candidate for tuft testing. Though a difficult one to set up and observe. Tuft the raw car underneath front and note the flow directions then try with the spats placed according to preceding results.
  Reply With Quote
Old 06-11-2009, 08:38 PM   #7 (permalink)
Coasting Down the Peak
 
skyl4rk's Avatar
 
Join Date: Jun 2008
Location: M I C H I G A N
Posts: 514

Toyauto Pickup - '94 Toyota Pickup 2WD
90 day: 36.32 mpg (US)

Versa Base - '09 Versa Sedan 1.6 Base
Team Nissan
90 day: 41.69 mpg (US)
Thanks: 27
Thanked 41 Times in 34 Posts
The ideal shape for tire covers is a symmetric NACA foil. The rear of the tire is more important than the front.

The design of a symmetrical foil has been worked out in detail for design of boat rudders. You can use some of their tools and theory to make your tire covers.

NACA 4 Digits Series

Foil FAQ
__________________
Nissan Versa Aeromods
  Reply With Quote
The Following User Says Thank You to skyl4rk For This Useful Post:
aerohead (03-24-2012)
Old 06-11-2009, 11:24 PM   #8 (permalink)
Grasshopper
 
alohaspirit's Avatar
 
Join Date: Feb 2009
Location: Hawaii
Posts: 964

Makai - '01 Toyota Echo 4D Auto
90 day: 34.45 mpg (US)

New Galaxy - '07 Toyota Prius
90 day: 42.15 mpg (US)
Thanks: 25
Thanked 30 Times in 25 Posts
Aero Tire

something like this then?
Attached Thumbnails
Click image for larger version

Name:	Air1.JPG
Views:	638
Size:	10.8 KB
ID:	3687  
  Reply With Quote
Old 06-12-2009, 12:04 AM   #9 (permalink)
Master EcoModder
 
Join Date: Mar 2008
Location: USA
Posts: 560
Thanks: 1
Thanked 67 Times in 53 Posts
Hucho has a nice picture showing smoke flow from the front as it hits the tire. Turns out, the smoke trail deflects ~60 degrees from centerline parallel, outward. This would be due to bow wave where it impinges on the pavement.

You need elliptical deflectors, canted inward (pigeon-toed), as seen in one of the Julian Edger photos. The tire also needs fairings behind the tires, to smooth the turbulent air there. Prius made a weak attempt at this with their back wheels.
  Reply With Quote
Old 06-12-2009, 07:56 AM   #10 (permalink)
Coasting Down the Peak
 
skyl4rk's Avatar
 
Join Date: Jun 2008
Location: M I C H I G A N
Posts: 514

Toyauto Pickup - '94 Toyota Pickup 2WD
90 day: 36.32 mpg (US)

Versa Base - '09 Versa Sedan 1.6 Base
Team Nissan
90 day: 41.69 mpg (US)
Thanks: 27
Thanked 41 Times in 34 Posts
Behind the tire, make a long trailing edge that comes to a point. In front of the tire, either do nothing, or put a small rounded deflector that approximates the curve of a naca foil.

Between the front and rear tires, you can put in a catamaran which is a box between the wheels.

__________________
Nissan Versa Aeromods
  Reply With Quote
Reply  Post New Thread


Thread Tools


Similar Threads
Thread Thread Starter Forum Replies Last Post
Top 5 most fuel efficient tires (Lowest Rolling resistance: LRR) blackjackel General Efficiency Discussion 144 01-25-2016 11:39 PM
Discussion on tire efficiency Ernie Rogers General Efficiency Discussion 69 12-27-2014 01:17 PM
Bounce Test for Rolling Resistance? Ernie Rogers General Efficiency Discussion 14 05-25-2009 06:38 PM



Powered by vBulletin® Version 3.8.11
Copyright ©2000 - 2020, vBulletin Solutions Inc.
Content Relevant URLs by vBSEO 3.5.2
All content copyright EcoModder.com