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

Reply  Post New Thread
 
Submit Tools LinkBack Thread Tools
Old 09-02-2020, 07:30 AM   #1 (permalink)
EcoModding Lurker
 
Join Date: May 2016
Location: Virginia
Posts: 27
Thanks: 0
Thanked 11 Times in 9 Posts
//// Level out car for better aero ? /////

Hi All,

I drive a 2003 Jetta wagon with TDI engine and got to thinking the other day that if I level out my car (the rear currently sits higher than the front) I actually may get better aerodynamics ( I say this because if you extend your arm out the window and make your hand into a "wing" then when it held flat it takes little effort to hold it but if you angle it up or down you have to use extra effort to hold it).

I realize it may not be much drag but thinking every bit helps... what do you think ? has anybody leveled out their car found found that it helps aero ? ( I realize lifting is generally viewed as hurting aero but in this case I think a neutral "wing" may offset any extra bits hanging in the wind ? .... I would only be increasing the front an inch or two with commercially available kits.

Thanks in advance for any and all help.

Andrew

__________________
2003 Jetta TDI Wagon, 5 sp, 210K miles, Stock.....for now!
  Reply With Quote
The Following 2 Users Say Thank You to Andyinchville1 For This Useful Post:
aerohead (09-04-2020), GreenTDI (09-03-2020)
Alt Today
Popular topics

Other popular topics in this forum...

   
Old 09-02-2020, 11:58 AM   #2 (permalink)
Somewhat crazed
 
Piotrsko's Avatar
 
Join Date: Sep 2013
Location: 1826 miles WSW of Normal
Posts: 1,381
Thanks: 131
Thanked 382 Times in 321 Posts
My thought: put $3.00 sandbags in the back until it's level and test to see if your coast down improves. Shouldn't take more than 3-4 to level it and weight isn't supposed to be known to affect steady state mileage.
  Reply With Quote
The Following User Says Thank You to Piotrsko For This Useful Post:
freebeard (09-03-2020)
Old 09-02-2020, 12:50 PM   #3 (permalink)
Ecomodding amateur
 
M_a_t_t's Avatar
 
Join Date: Nov 2015
Location: Indiana
Posts: 552

The Van - '95 Chevy Astro Cl V8 Swapped
Team Chevy
90 day: 11.25 mpg (US)

The new bike - '17 Kawasaki Versys X 300 abs
Motorcycle
90 day: 64.78 mpg (US)

The Mercury - '95 Mercury Tracer Trio
Team Ford
90 day: 35.72 mpg (US)
Thanks: 92
Thanked 189 Times in 141 Posts
In this paper:
https://www.sae.org/publications/tec.../2016-01-1613/
Evaluation of the Aerodynamics of Drag Reduction Technologies for Light-duty Vehicles: a Comprehensive Wind Tunnel Study 2016-01-1613

They tested a range of cars model year 2013-2015 and found a 2-3% reduction in drag by lowering the nose by 20mm and a 5-6% decrease with a 40mm front and rear drop.

Based on this I would say definitely test first. Sandbags or otherwise. If you ever load the car down the rear will sag and have a reverse rake if you level it out. If that is something you do often it would be something to consider as well.

Stock image of OP's car:
__________________
Věci získávají svou skutečnou krásu pouze ve vztahu k našemu životu
-Jiří Mucha (1915-1991), Publicist

My herd includes:
1973 Fiat 124 Special
1975 Honda Civic CVCC 4spd
1981 Kawasaki KZ750E
1981 Kawasaki KZ650 CSR
1983 Kawasaki KZ1100-A3
1986 Nissan 300zx Turbo 5 spd
1995 Chevy Astro RWD
1995 Mercury Tracer
2004 Chevy Astro AWD
2017 Kawasaki VersysX 300

https://www.youtube.com/channel/UC6s...LulDUQ8HMj5VKA
  Reply With Quote
Old 09-02-2020, 05:30 PM   #4 (permalink)
Master EcoModder
 
JulianEdgar's Avatar
 
Join Date: Nov 2017
Location: Australia
Posts: 1,115
Thanks: 69
Thanked 925 Times in 609 Posts
Quote:
Originally Posted by Piotrsko View Post
My thought: put $3.00 sandbags in the back until it's level and test to see if your coast down improves. Shouldn't take more than 3-4 to level it and weight isn't supposed to be known to affect steady state mileage.
I think road coast downs are a completely ineffectual way of testing drag. At minimum, first do a windows up / windows down coastdown comparison and ensure you can see a major difference in coastdown times.

But I do agree that you should so some testing - I would suggest throttle stop (constant engine power) testing.
  Reply With Quote
Old 09-02-2020, 06:08 PM   #5 (permalink)
Master EcoModder
 
mpg_numbers_guy's Avatar
 
Join Date: Feb 2018
Location: Michigan/Virginia
Posts: 1,281

Insight - '06 Honda Insight MT
Team Honda
Gen-1 Insights
90 day: 88.27 mpg (US)
Thanks: 302
Thanked 429 Times in 329 Posts
Quote:
Originally Posted by Piotrsko View Post
My thought: put $3.00 sandbags in the back until it's level and test to see if your coast down improves. Shouldn't take more than 3-4 to level it and weight isn't supposed to be known to affect steady state mileage.
Adding weight to a car will almost always cause it to coast further, as more kinetic energy has to be put into the car to reach the same speed.
__________________
2006 New Formula Red Honda Insight MT, 272k: (Build thread)
  Reply With Quote
The Following 2 Users Say Thank You to mpg_numbers_guy For This Useful Post:
Gasoline Fumes (09-04-2020), JulianEdgar (09-02-2020)
Old 09-03-2020, 04:44 AM   #6 (permalink)
EcoModding Apprentice
 
GreenTDI's Avatar
 
Join Date: Apr 2020
Location: Belgium
Posts: 214

GreenTDI - '11 Skoda Fabia Estate R3 1.2 CRTDI
TEAM VW AUDI Group
Diesel
90 day: 66.24 mpg (US)
Thanks: 53
Thanked 76 Times in 61 Posts
Thank you for starting this thread, cause I was already thinking about this. I also start to notice that when I load the car (or just wife and kids, not that they are so heavy but still ) and make a long highway trip, that I'm roughly getting the same consumption figures than with an empty (and stripped) car. Difference is often +500 lbs, but also a 2 cm drop in the front and 6 cm or more in the rear.

That is to say, the roof line with an empty car is quite horizontal, but when it's loaded it gets that typical streamlined downward slope.

It will coast better due to the extra weight, but there might also be the improved air restistance thanks to a better shape. And it's not only the air that passes over the car, but also less under the car and in the wheel arches ...
__________________
Skoda Fabia Estate R3 1.2 CRTDI
See my thread: https://ecomodder.com/forum/showthre...mpg-38318.html
  Reply With Quote
Old 09-03-2020, 06:35 PM   #7 (permalink)
Master EcoModder
 
freebeard's Avatar
 
Join Date: Aug 2012
Location: northwest of normal
Posts: 17,572
Thanks: 4,743
Thanked 5,848 Times in 4,665 Posts

Put bigger tires on the back. (example is lower profile on the front, stock on the back)

I'd be concerned that raising the front would increase front lift. Generally, you want minimal air intrusion at the front tires with a central jet feeding a rear diffuser.

Nose-high increases frontal area and makes the underbody a converging duct, tail-high exposes the underbody to the wake.
__________________
.

Andrej Karpathy: If you bombard Earth with photons long enough eventually it will emit a Tesla.

_________________
  Reply With Quote
Old 09-04-2020, 01:16 PM   #8 (permalink)
Master EcoModder
 
aerohead's Avatar
 
Join Date: Jan 2008
Location: Sanger,Texas,U.S.A.
Posts: 11,786
Thanks: 18,992
Thanked 6,098 Times in 3,740 Posts
body inclination

Quote:
Originally Posted by Andyinchville1 View Post
Hi All,

I drive a 2003 Jetta wagon with TDI engine and got to thinking the other day that if I level out my car (the rear currently sits higher than the front) I actually may get better aerodynamics ( I say this because if you extend your arm out the window and make your hand into a "wing" then when it held flat it takes little effort to hold it but if you angle it up or down you have to use extra effort to hold it).

I realize it may not be much drag but thinking every bit helps... what do you think ? has anybody leveled out their car found found that it helps aero ? ( I realize lifting is generally viewed as hurting aero but in this case I think a neutral "wing" may offset any extra bits hanging in the wind ? .... I would only be increasing the front an inch or two with commercially available kits.

Thanks in advance for any and all help.

Andrew
Since Hucho ran VW's wind tunnel for a decade, and has published about drag sensitivity to body inclination, I'd be comfortable presuming that this aspect of your Jetta has already been addressed during development.

__________________
Photobucket album: http://s1271.photobucket.com/albums/jj622/aerohead2/
  Reply With Quote
Reply  Post New Thread


Thread Tools




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