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post #1 of (permalink) Old 09-03-2006, 07:17 PM Thread Starter
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OT pick up tailgate mpg

Hi there

So as I understand it...having the tailgate up is best for mileage with a pickup...something about cleaner aerodynamics...

Would anyone be willing to put together a short (25 slides or less) powerpoint explaining this...sticking with high school physics jargon, and emailing it to me?

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post #2 of (permalink) Old 09-03-2006, 07:51 PM
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Re: OT pick up tailgate mpg

Mythbusters Episode 43

Tailgate: Up or down?

Myth: Driving your pickup with the tailgate down gives you better fuel efficiency than with the tailgate up.
Test Setup

Adam and Jamie were each given identical, new model pickup trucks. They both had equal mileage, same tire pressure, and 30 gallons of gas. Jamie drove with the tailgate up and Adam the tailgate down.

The rules:

1. They have to maintain the speed limit
2. All acceleration must be done by cruise control
3. No drafting
4. Windows up, A/C must be exactly the same in both cars

The Test

After 300 miles there didn't appear to be much difference in the gas consumed, but after 500 miles Adam (tailgate down) ran out of gas. Jamie made it another 30 miles before he ran out of gas. This result was the exact opposite of the myth.
Water tunnel visualization

According to the experts, a circular pillow of air forms behidn the cab of the truck when the tailgate is up. This "separated bubble"/"locked vortex flow" keep the faster moving air from contacting the truck, and thus reduces drag. With the tailgate down, the bubble breaks down and is no longer able to keep the fast moving air out, increasing drag.

In their scale model with the water tunnel, they were able to see that the increased drag. With the tailgate down, the particles in the water were dropping down and hitting the tailgate.

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post #3 of (permalink) Old 09-04-2006, 07:26 AM
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Re: OT pick up tailgate mpg

That Mythbuster's episode was pretty hokey IMO. There were way too many variables that weren't factored out. The test should have been run at least four times to cover all combinations of driver, vehicle and tailgate position.

Or, for a real test, put a truck in a wind tunnel and measure the drag. Then you'd have a real answer for that truck . Put a bunch of trucks in the wind tunnel and you might be able to formulate an answer to the question about "a pickup truck."
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post #4 of (permalink) Old 09-04-2006, 08:27 AM
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Re: OT pick up tailgate mpg

We had this question asked in October, Click Here for the Thread....
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