Fuel Consumption on High Altitude - Page 2 - Fuelly Forums

Android Users - Coming Soon! - Migrating from aCar 4.8 to 5.0

Reply
 
Thread Tools Display Modes
 
Old 09-23-2011, 10:26 PM   #11
Senior Member
 
Join Date: Mar 2011
Posts: 329
Country: United Kingdom
The following MPG calculator is awesome, it includes the effect of air pressure, so you can experiment with different altitudes.

http://ecomodder.com/forum/tool-aero...resistance.php
__________________

MMUK is offline   Reply With Quote
Old 09-30-2011, 12:57 AM   #12
Junior Member
 
Join Date: Sep 2011
Posts: 3
Country: United States
Location: Windsor, NJ
Other effects to think about involve cooling efficiencies. The thinner air at high elevations can not cool the radiator as efficiently, so there will be more drag from heat transfer losses. This will be offset by less induced drag from the shape of the car through the air. I'm not sure what the net effect would be, and it probably depends on the car.

Also, while rolling resistance doesn't change with air pressure, it does change with temperature, and the tires and brakes will be hotter in the thinner air, especially at higher speeds, which will increase rolling resistance.

Just some thoughts...
__________________

rallyr is offline   Reply With Quote
Old 09-30-2011, 05:31 AM   #13
Out of Fuel
 
Join Date: Oct 2009
Posts: 216
Country: United States
Location: EUP Michigan
I would have to imagine these subtle changes are minute at best. Probably less than .10 MPG
DTMAce is offline   Reply With Quote
Old 09-30-2011, 06:52 AM   #14
Senior Member
 
Join Date: Mar 2011
Posts: 329
Country: United Kingdom
70mph

At sea level, 15c

MPH KM/H Aero (a) Rolling (b) Total % Aero % Rolling Watts HP HP Aero HP Rolling MPG(US) L/100km

70 113 377.36 65.14 442.51 85.28% 14.72% 13,847.24 18.57 15.84 2.73 35.45 6.63

At 3500 metres, 15c (rho 0.854)

MPH KM/H Aero (a) Rolling (b) Total % Aero % Rolling Watts HP HP Aero HP Rolling MPG(US) L/100km

70 113 264.15 65.14 329.30 80.22% 19.78% 10,304.63 13.82 11.09 2.73 47.64 4.94

The only difference in these two scenarios is the altitude. The ground level one gives 35mpg, and the one at 3500 metres is 47mpg. This is entirely due to the extra 4hp required to overcome aerodynamic resistance at sea level.
MMUK is offline   Reply With Quote
Old 09-30-2011, 09:49 AM   #15
Out of Fuel
 
Join Date: Oct 2009
Posts: 216
Country: United States
Location: EUP Michigan
According to the math.

But for the real life factor, living in high elevations also usually means more hills. So that will throw that math out the window... LOL

Math calc = perfect world. Unfortunately there is no such thing.
DTMAce is offline   Reply With Quote
Old 09-30-2011, 06:58 PM   #16
Senior Member
 
Join Date: Mar 2011
Posts: 329
Country: United Kingdom
>But for the real life factor, living in high elevations

>also usually means more hills. So that will throw that

>math out the window... LOL

The original poster (judacomadc) lives on a plateau. So no hills.

You have to isolate each factor and treat it separately. But then you have to combine everything back again to see the overall effect. You can't just hand-wave and say that there is only going to be a 0.1 MPG effect without any grounds to say that.
MMUK is offline   Reply With Quote
Old 09-30-2011, 07:06 PM   #17
Senior Member
 
Join Date: Mar 2011
Posts: 329
Country: United Kingdom
I should also point out that 3500 metres was just a simple example of the effect of altitude on MPG - it wasn't a specific example tailored for Bogotá. The only thing I changed between the sea level example and the 3500 metre example was the altitude, it did not include temperature, or any specific factors related to the OP's vehicle or engine. But all these things can be added to the calculator as needed.
MMUK is offline   Reply With Quote
Old 10-02-2011, 02:55 AM   #18
Registered Member
 
Join Date: Nov 2009
Posts: 5
Country: United States
Location: Kansas
If an engine is properly tuned for the higher altitude, there will be an increase in MPG. Less power is required to move a vehicle through less dense air. Simple.
CyberGuy is offline   Reply With Quote
Old 10-04-2011, 02:26 AM   #19
Junior Member
 
Join Date: Jul 2011
Posts: 3
Country: Colombia
Location: Bogotá, DC
Well gentlemen I´m adding more details:

Travelling in the city of Bogotá at highway speeds (70mph+) is something rare because if there's no traffic jams the speed limit inside the city is 80km/h

(about 50mph) and on highway it increases to 100 (62mph).

Anyways I'll keep reading these more comments, then I'll find a clear conclusion.

Thanks for your opinions, I'm amazed of the knowledge of Fuelly users!
__________________

judacomadc is offline   Reply With Quote
Reply

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Powered by vBadvanced CMPS v3.2.3


All times are GMT -8. The time now is 12:02 PM.


Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2017, vBulletin Solutions, Inc.