Pick up truck drag? - Fuelly Forums

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

Reply
 
Thread Tools Display Modes
 
Old 07-17-2008, 07:46 AM   #1
Registered Member
 
Join Date: Sep 2007
Posts: 6
Country: United States
Pick up truck drag?

will opening my back window on my T-100 truck increase drag? If so, how much?
__________________

chris Adamson is offline   Reply With Quote
Old 07-17-2008, 07:57 AM   #2
Registered Member
 
theholycow's Avatar
 
Join Date: Apr 2008
Posts: 6,624
Country: United States
Send a message via ICQ to theholycow Send a message via AIM to theholycow Send a message via MSN to theholycow Send a message via Yahoo to theholycow
Nobody responded in the other thread you started to ask this question. I was going to but lately I've taken a hit to my confidence on technical issues like this, as I've provided a few wrong answers...

Anyway, here's my thoughts:

- With the window closed there is a vortex directly behind the cab. Have you ever driven with dry dirt dust, leaves, dry dusty snow, or a plastic bag unsecured back there? The air apparently rolls forward and up until it hits the rear window; you can see dust rolling in circles back there, and snow gathers on the rear window when blow up out of the bed.

- Assuming your side windows are open, you probably get lots of air flowing through, pushing on that vortex and maybe breaking it up. Perhaps it would straighten it out and make it fall off the back of the truck. I have no clue how it would affect fuel economy.

- If your side windows aren't open, that vortex is going to push into the cab, which will act like a parachute. I think this will slow the vortex but not break it up. It probably won't have a measurable effect on fuel economy.
__________________

__________________
This sig may return, some day.
theholycow is offline   Reply With Quote
Old 07-17-2008, 08:34 AM   #3
Registered Member
 
GasSavers_BEEF's Avatar
 
Join Date: Apr 2008
Posts: 1,831
holycow- I have always thought highly of your advice and consider it a positive addition to the site. also, it is good to be wrong every once in a while, it keeps us in check and keeps us from getting cocky. also, there are different ways of looking at everything and almost impossible for one person to look at something in all the different angles.

I too agree that the back window will make you take a hit in FE. the question is by how much. I really don't think it would be by much. also, the comfort factor. you do want to be comfortable going down the road. I usually ride with windows down, as my A/C doesn't work, regardless of the FE hit I take for it because I wan't that level of comfort.
__________________
Be the change you wish to see in the world
--Mahatma Gandhi



GasSavers_BEEF is offline   Reply With Quote
Old 07-17-2008, 02:40 PM   #4
Registered Member
 
VetteOwner's Avatar
 
Join Date: Mar 2007
Posts: 1,546
Country: United States
exactly, when its 92 out with 75% humidity in bright sun, ya windows down all the way and vent on high...

i doubt havign the backwindow will have a real effect on it around town driving, interstate maybe but even then just crack it open.
VetteOwner is offline   Reply With Quote
Old 07-17-2008, 06:59 PM   #5
Registered Member
 
kamesama980's Avatar
 
Join Date: Nov 2007
Posts: 742
Country: United States
Location: Columbus, IN, USA
Send a message via AIM to kamesama980 Send a message via Yahoo to kamesama980
My old 96 ranger had a sliding rear window and with the side windows open, air would pour in the sides and out the back...the vortex is a definite low pressure zone no doubt. I guess the question is whether it's more drag to let the air in right after the windshield or force it to go in after the cab.

with the side windows closed I doubt it'll have any appreciable difference.

My S10 doesn't have a sliding rear window so it's a moot point.
__________________
-Russell
1991 Toyota Pickup 22R-E 2.4 I4/5 speed
1990 Toyota Cressida 7M-GE 3.0 I6/5-speed manual
mechanic, carpenter, stagehand, rigger, and know-it-all smartass
"You don't get to judge me for how I fix what you break"
kamesama980 is offline   Reply With Quote
Old 07-17-2008, 08:17 PM   #6
Registered Member
 
Join Date: Jun 2008
Posts: 123
Country: United States
it does on my 77 chevy
COMP is offline   Reply With Quote
Old 07-17-2008, 08:39 PM   #7
Registered Member
 
2000mc's Avatar
 
Join Date: Oct 2007
Posts: 72
Country: United States
Quote:
Originally Posted by chris Adamson View Post
will opening my back window on my T-100 truck increase drag? If so, how much?
my GUESS, also applies to windows down n such... how ever much air is swirling around in the passenger compartment, is wasted energy. what wattage fan would it take to create as much air movement if you were parked? 200watts, 1000, more? i think 746 watts = 1hp?
i have a 210w fan at work, i'd guess its moves air around about as much as windows down in my car at around 40mph
__________________
2000mc is offline   Reply With Quote
Old 07-18-2008, 07:58 AM   #8
Registered Member
 
Join Date: Sep 2007
Posts: 6
Country: United States
thanks for the response guys.
C
chris Adamson is offline   Reply With Quote
Old 07-18-2008, 01:31 PM   #9
Registered Member
 
Join Date: May 2008
Posts: 28
Country: United States
Location: Briggsdale, CO
theholycow - I know what you mean by taking a hit. Don't let those "tailgaters" put you in the corner in the fetal position whimpering! Opinionate away. Advise as you will. For every person that might say a bad thing, there are at least 10 that hang on to every word.

That's a GOOD question on your rear slider window. That's grounds for an experiment. Also, there could be a question of both passenger and driver windows down plus the rear slider window open. How would THAT affect wind resistance passing over the cab/bed? We could do the math in our heads on that, but it really needs real-world data.
__________________
99metro is offline   Reply With Quote
Old 07-18-2008, 01:50 PM   #10
Registered Member
 
Join Date: Jun 2008
Posts: 123
Country: United States
i used dry leafs in the bed test,,,,,,
__________________

COMP 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


Similar Threads
Thread Thread Starter Forum Replies Last Post
Fuelly Android App - eehokie Fuelly Web Support and Community News 2 07-14-2010 09:59 PM
Tire sizing odometer modifier? BDC Fuelly Web Support and Community News 10 07-25-2009 09:59 PM
drivetrain resistance bagpipe goatee General Fuel Topics 9 09-14-2008 10:04 PM
Experimental Engine Designs rh77 General Fuel Topics 8 08-30-2007 08:23 PM
Alternative Fuels blacktone Fuelly Web Support and Community News 2 05-21-2006 12:32 AM

Powered by vBadvanced CMPS v3.2.3


All times are GMT -8. The time now is 10:41 PM.


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