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

Reply  Post New Thread
 
Submit Tools LinkBack Thread Tools
Old 11-18-2019, 12:46 AM   #1 (permalink)
Master EcoModder
 
Join Date: Aug 2018
Location: USA
Posts: 455

Jeep - '97 Jeep Cherokee Sport
90 day: 19.36 mpg (US)

Blueberry - '07 Toyota Camry SE
Thanks: 180
Thanked 101 Times in 77 Posts
What kind of MPGs would a brick wall get?

https://jalopnik.com/what-kind-of-fu...1839901794/amp

Despite some inaccuracies and bad comparisons I noticed in the article, it explains well that engine efficiency plays just an important part in fuel economy as coefficient of drag does. So some cars that are shaped like bricks (my Jeep) can still get good FE without making too many concessions to aerodynamics. Not something too many ecomodders consider as most cars here have small engines and have a fairly low cd already.

  Reply With Quote
The Following 2 Users Say Thank You to Taylor95 For This Useful Post:
aerohead (11-20-2019), Xist (11-19-2019)
Alt Today
Popular topics

Other popular topics in this forum...

   
Old 11-18-2019, 10:17 AM   #2 (permalink)
Somewhat crazed
 
Piotrsko's Avatar
 
Join Date: Sep 2013
Location: 1826 miles WSW of Normal
Posts: 4,043
Thanks: 462
Thanked 1,103 Times in 973 Posts
@ what speed? Near zero, brick wall aero isn't all that bad. Supersonic, it sucks.
__________________
casual notes from the underground:There are some "experts" out there that in reality don't have a clue as to what they are doing.
  Reply With Quote
The Following 4 Users Say Thank You to Piotrsko For This Useful Post:
aerohead (11-20-2019), Cd (12-03-2019), freebeard (11-18-2019), Xist (11-19-2019)
Old 11-18-2019, 11:47 AM   #3 (permalink)
Master EcoModder
 
freebeard's Avatar
 
Join Date: Aug 2012
Location: northwest of normal
Posts: 27,561
Thanks: 7,736
Thanked 8,554 Times in 7,041 Posts
Quote:
...engine efficiency plays just an important part in fuel economy as coefficient of drag does. So some cars that are shaped like bricks (my Jeep) can still get good FE without making too many concessions to aerodynamics.
Provided you handicap the more aerodynamic vehicle with a less efficient engine.

Consider a brick with radiused edges.
__________________
.
.
Without freedom of speech we wouldn't know who all the idiots are. -- anonymous poster

____________________
  Reply With Quote
The Following 2 Users Say Thank You to freebeard For This Useful Post:
aerohead (11-20-2019), Cd (12-03-2019)
Old 11-18-2019, 12:13 PM   #4 (permalink)
Master EcoModder
 
Join Date: Aug 2018
Location: USA
Posts: 455

Jeep - '97 Jeep Cherokee Sport
90 day: 19.36 mpg (US)

Blueberry - '07 Toyota Camry SE
Thanks: 180
Thanked 101 Times in 77 Posts
Quote:
Originally Posted by Piotrsko View Post
@ what speed? Near zero, brick wall aero isn't all that bad. Supersonic, it sucks.
The author of the article calculated that a brick wall with a Prius engine would still get 29 mpg at 50 mph.
  Reply With Quote
The Following 2 Users Say Thank You to Taylor95 For This Useful Post:
aerohead (11-20-2019), Xist (11-19-2019)
Old 11-18-2019, 01:18 PM   #5 (permalink)
Master EcoModder
 
freebeard's Avatar
 
Join Date: Aug 2012
Location: northwest of normal
Posts: 27,561
Thanks: 7,736
Thanked 8,554 Times in 7,041 Posts
So I went back and read the article. Instead of a brick,he is using a flat plate as analogous. A brick, on it's long axis would have better fineness ratio, like a truck van.

His starting point was imagining his lifted SUV as having little brick walls all over it. Not a bad article, except for
Quote:
Imagine a tiny little bus taking chickens to work in the city. Oh no, the bus is running late and Meryl Cheep is going to be late to the egg factory!
__________________
.
.
Without freedom of speech we wouldn't know who all the idiots are. -- anonymous poster

____________________
  Reply With Quote
The Following User Says Thank You to freebeard For This Useful Post:
aerohead (11-20-2019)
Old 11-18-2019, 03:00 PM   #6 (permalink)
Master EcoModder
 
Join Date: Feb 2014
Location: Missoula, MT
Posts: 2,652

Dark Egg - '12 VW Touraeg
Thanks: 300
Thanked 1,176 Times in 806 Posts
A wall is worse than a cube as well right? Basically holding up a sheet of plywood is worse. As pointed out it's all about speed. I can hold up that sheet and walk with it and not notice the aero drag but try an old it up in the back of a pickup on the highway and there will be an injury involved. I'm glad he mentioned the size as well because while I couldn't hold a sheet of plywood up at speed I could hold a playing card up which both have the same Cd.
  Reply With Quote
The Following 2 Users Say Thank You to Hersbird For This Useful Post:
aerohead (11-20-2019), freebeard (11-18-2019)
Old 11-18-2019, 03:35 PM   #7 (permalink)
Master EcoModder
 
Join Date: Feb 2014
Location: Missoula, MT
Posts: 2,652

Dark Egg - '12 VW Touraeg
Thanks: 300
Thanked 1,176 Times in 806 Posts
Quote:
Originally Posted by Taylor95 View Post
https://jalopnik.com/what-kind-of-fu...1839901794/amp

Despite some inaccuracies and bad comparisons I noticed in the article, it explains well that engine efficiency plays just an important part in fuel economy as coefficient of drag does. So some cars that are shaped like bricks (my Jeep) can still get good FE without making too many concessions to aerodynamics. Not something too many ecomodders consider as most cars here have small engines and have a fairly low cd already.
They used .22 as an engine efficiency in the caculator while claiming a .4 engine efficiency in the article. 40% must be "peak" efficiency not seen at 50 mph.

I was going to try and see how reducing engine efficiency while leaving the aero good to see what effect that had compared to the aero. You have to take efficiency down to .105 to get 29 mpg. I don't know of any properly functioning ICE that is quite that bad. Take the speed up to 70 and run the same numbers and the aero is now a 40% worse penality than thermal efficiency.
  Reply With Quote
The Following User Says Thank You to Hersbird For This Useful Post:
Xist (11-19-2019)
Old 11-19-2019, 08:13 AM   #8 (permalink)
Banned
 
Join Date: Oct 2009
Location: Fort Worth, Texas
Posts: 2,442

2004 CTD - '04 DODGE RAM 2500 SLT
Team Cummins
90 day: 19.36 mpg (US)
Thanks: 1,422
Thanked 737 Times in 557 Posts
The efficient USE of a vehicle is second consideration. MPG is far down the list as to what matters

1). How many family members? Must fit all persons aboard (with luggage).

2). Distances for necessities. Not work or school.

Etcetera

Where one lives in relation to necessary re-supply is prime as to the convenience of personal transportation. Overrides all others, as it’s a desire NOT a necessity to own a car.

A 5-mpg motorhome gets “better” fuel economy than a Prius with a roof rack tent.

Be sure you’ve defined, what is mpg?

It’s work performed against an energy input. One or two people being transported ISN'T work, per se. Its waste. Where’s the income offset or addition? Every single trip.

As to shape, the volume that encloses the most space in the most compact form is the winner.

How much space is mostly a function of how many children in your family.

An unmarried man, like an unmarried woman, is pretty well a drone. Not necessary; limited usefulness before disadvantages outweighs other.

More to the point, again, FE not being central, aero should impose no penalty first (as above), second, it should maximize safe operation (crosswinds, etc).

A drivetrain that can maintain 60-mph in rolling terrain is adequate for a loaded vehicle (as empty operation is proscribed). Thus, it’s more about the transmission & drive ratio than engine size or fuel.

The small Ford Transit van with passenger outfit, is close enough.

.

Last edited by slowmover; 11-19-2019 at 08:29 AM..
  Reply With Quote
Old 11-19-2019, 12:56 PM   #9 (permalink)
Master EcoModder
 
freebeard's Avatar
 
Join Date: Aug 2012
Location: northwest of normal
Posts: 27,561
Thanks: 7,736
Thanked 8,554 Times in 7,041 Posts
Quote:
As to shape, the volume that encloses the most space in the most compact form is the winner.
The counterpoint is the external shape the volume must squeeze through. Generally 8.5x14x∞.
__________________
.
.
Without freedom of speech we wouldn't know who all the idiots are. -- anonymous poster

____________________
  Reply With Quote
The Following User Says Thank You to freebeard For This Useful Post:
slowmover (11-19-2019)
Old 11-19-2019, 02:38 PM   #10 (permalink)
Rat Racer
 
Fat Charlie's Avatar
 
Join Date: May 2011
Location: Route 16
Posts: 4,150

Al the Third, year four - '13 Honda Fit Base
Team Honda
90 day: 42.9 mpg (US)
Thanks: 1,784
Thanked 1,922 Times in 1,246 Posts
Quote:
Originally Posted by Taylor95 View Post
So some cars that are shaped like bricks (my Jeep) can still get good FE without making too many concessions to aerodynamics.
Within reason. Slapping an efficient engine in an SUV doesn't also add a more efficient drivetrain, lower weight or lower rolling resistance.

__________________

Quote:
Originally Posted by sheepdog44 View Post
Transmission type Efficiency
Manual neutral engine off.100% @MPG <----- Fun Fact.
Manual 1:1 gear ratio .......98%
CVT belt ............................88%
Automatic .........................86%

  Reply With Quote
The Following 2 Users Say Thank You to Fat Charlie For This Useful Post:
aerohead (11-20-2019), Xist (11-20-2019)
Reply  Post New Thread


Thread Tools




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