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Wadak
GenIII
9/15/2006
16:00:55
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 Subject: Tailgate...up or down
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Message:
Everyone,
Here is an excellent and I mean excellent article on driving with the tailgate up or down on different pickups. It goes into all the mathematical calculations, shows wind tunnel simulations using visible trail marking smoke. It also show a chart with the coeffient of drap for tailgate up, down, off and using a tonneau cover. You will need Adobe Acrobe to read the article. The reader is free to down load. In this day of ever increasing gas prices, this article could help to be a real fuel saver. If you can't read it now download the file and read it offline. PLEASE READ IT IT COULD SAVE YOU MONEY AND POSSIBLY PREVENT AN ACCIDENT.
Here is the link:
http://ecow.engr.wisc.edu/cgi-bin/getbig/me/363/ghandhi1/pickup.pdf
Wadak
92 and 97 Daks both with many mods.
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roto
Dodge Dakota
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9/15/2006
19:33:03
| RE: Tailgate...up or down
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They did this on Mythbusters and reached the same conclusion.
Keep the gate UP for best gas milage.
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Josh
Dodge Dakota
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9/16/2006
00:56:26
| RE: Tailgate...up or down
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Message:
Yeah. I watched that episode, and they didn't account for a lot of things. They should have switched tailgate positions on the trucks and run it again to account for engine/drive train efficiency deviations due to manufacturing tolerances.
According to my Scangauge, (http://www.scangauge.com), my 2004 4.7L 4x4 545RFE 3.55 ratio Dakota gets better mileage with the tailgate down. Probably because there's a bed box.
With the windows up at 70 MPH, engaging the A/C drops MPG number by 1.5, and rolling the windows down with A/C off drops the MPG number by 1.2.
I think the Dakota (except for the butt-ugly version that came out in 2005) is a bit more aerodynamical than that brick of a Ford F150.
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stupid person
Dodge Dakota
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1/03/2007
13:38:43
| RE: Tailgate...up or down
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I hear that W/ tailgate up there is a locked vortice in the bed.. meaning (Mostly) the same air circulates around the bed... Meaning the tailgate up should have very little, if any, detrimental effect on mpg
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boomer
Dodge Dakota
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1/07/2007
07:28:00
| RE: Tailgate...up or down
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I agree with the stupid person. If you've ever had empty cans or anything like that in your truck bed when driving down the freeway you see that it just swirls around back there. eventually they get thrown out but most of the time they just bounce around off your back window. i dont usually have cans back there but before i got my tonneau cover it happened every now and then and i was surprised when I was doin 70+ mph they only floated around.
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GB2000
GenIII
1/07/2007
09:44:20
| RE: Tailgate...up or down
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Message:
Yeah...going off Boomer's reply...try getting a garbage bag's worth of popcorn out of your bed (friend worked at a movie theater...). You'll have more luck trying with the tailgate down since the airflows are all f'd up (causing the truck to be LESS aerodynamic), but even then most of it still swirls around behind the cab.
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Blakdak
Dodge Dakota
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1/09/2007
11:38:40
| RE: Tailgate...up or down
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I also saw the Mythbusters episode and agree with Josh that they should have changed settings between the trucks halfway through. Wasn't it an extended cab F-150 with short box (6 or 6.5')?
Even so, it's obvious that todays trucks have some different features that help the aerodynamics of the truck bed. All modern trucks have that little lips on the top and back of the cab and tailgate. Older trucks don't have this and running with the gate down probably did help some. Also a much greater percentage of trucks today run with shorter beds (6-6.5') and crew cabs (< 6'). A lot of the older trucks were regular cabs with 8 footers which would have a greater effect.
I sometimes drive with the gate down, but only with long loads. It negates the rear bumper and would likely be more dangerous in an accident.
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sneilan
Dodge Dakota
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1/09/2007
17:27:35
| RE: Tailgate...up or down
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i saw this episode of mythbusters too and all i have to say is that when i was commuting to school (63 miles each way) in my '95 S10 4.3L non-vortec, i got an extra day and nearly 75 miles out of a tank of gas with the tail gate removed from my truck. I just got a tonnaue cover for my '98 Dakota CC 5.2L and i haven't noticed a difference in mileage yet but i'm in stop n go a lot.
Sean
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Marv
Dodge Dakota
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1/09/2007
19:54:30
| RE: Tailgate...up or down
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What works for one model truck does not necessarily apply to another. Their first test was done with crew cab F150's, and was so lame it wasn't even credible. They should have repeated the test with swapped configurations. The second was done with a regular cab Dakota. Different trucks. Different aerodynamics. Different results.
The object of the test should have been solely about wind resistance (drag coefficient). The only way to know for sure is to use a wind tunnel and check for drag coefficient with various models in the different configurations and at different wind speeds. That would eliminate all the variables not associated with wind resistance.
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