Video: Fuel Economy Decrease with Opened Windows

[Cd]

That was interesting.
Are you sure that your Scanguage is working correctly ?

Imagine if that airflow coming in through the window could be channeled out the back of the car and used to reduce the wake
This would involve removing the hatch glass ( or the entire hatch ) , reclining the passenger seat and folding the rear seats down to make a smooth pathway for the wind.

It would not be pratical ( rain, wind noise, strange looks, family abandonment, loss of girlfriend / wife etc ... ) But it would be an interesting test though wouldn't it ?
And easy too !

[Cd]

Originally Posted by AndrewJ

I've noticed no significant difference in coastdown tests with windows up vs. down.

Kinda surprising, but you can't really argue with the numbers...

As in ... all the way down, or just cracked an inch or two ?

That's just weird !

[tasdrouille]

Fabrio posted a vid of a tufts test with back side windows open vs closed. The airflow over the back glass was so messed up it must have had a significant impact on drag.

[ankit]

Okay so open windows and air conditioner are bad, what about just running the fan and not the air conditioner?

Nice videos, I checked out a couple other ones on Youtube and I'm glad to see experimenting and testing for those of us without instrumentation.

[Peakster]

Probably just running the fan would be best. But it's not very sufficient on those hot days. At least with a Geo Metro, it seems that rolling down the windows isn't too detrimental at mediums speeds.

[MetroMPG]

Originally Posted by AndrewJ

I've noticed no significant difference in coastdown tests with windows up vs. down.

Kinda surprising, but you can't really argue with the numbers...

I saw a small difference when I did some coastdown tests in the Flea - both windows open/closed. Edit: not a rigorous test though.

[tasdrouille]

Originally Posted by ankit

Okay so open windows and air conditioner are bad, what about just running the fan and not the air conditioner?

Nice videos, I checked out a couple other ones on Youtube and I'm glad to see experimenting and testing for those of us without instrumentation.

On my Elantra the ventilation is just as bad as the A/C with only a 0.02 Gph difference between the two.

Cracking all 4 windows 2 inches or less did not make any noticeable difference up until 70 mph in the Elantra.

I am seriously thinking about getting one of those wood balls seat pad like metro mentionned in an other thread. They would probably help.

I use max A/C on deceleration fuel cutoff.

[Arminius]

Here's an article on this topic. Halfway down they mention Consumer Report's extensive testing on the issue.

http://www.bankrate.com/brm/news/auto/20050804a1.asp

[AndrewJ]

Originally Posted by .Cd

As in ... all the way down, or just cracked an inch or two ?

Both, all the way down and cracked about 3"

Both times I was coasting down my "calibrated" coastdown hill. No discernable difference between any of the three runs.

EDIT: oh, and speeds on my coastdown hill typically reach 65-71mph

[MetroMPG]

Originally Posted by Arminius

Here's an article on this topic. Halfway down they mention Consumer Report's extensive testing on the issue.

http://www.bankrate.com/brm/news/auto/20050804a1.asp

Interesting link, but the red flag went up on the "GasBuddy" guy's quote:

Drive at speeds over 55 mph with windows down and you'll decrease fuel economy by up to 20 percent or greater."

20% sounds exaggerated.