SAE report: Pickup Truck tailgate aerodynamics... better up, down, or off?

[MetroMPG]

Posting this link because it addresses the age-old search query: will I get better fuel economy with my truck's tailgate up, down, or removed entirely?

It's also one of the better/most comprehensive studies I'm aware of.

Pickup Truck Aerodynamics – Keep Your Tailgate Up

http://ecow.engr.wisc.edu/cgi-bin/ge...hi1/pickup.pdf

The author concludes that, on average, it's best to tell all pickup owners to leave the tailgate up.

If you read the report, the most accurate answer to the question is: "it depends".

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[metroschultz]

Check with Discovery's Mythbusters, they did a story on the tailgate idea. Real world and wind tunnel testing showed that tailgate up was best for aerodynamics. Real world fuel consumption test showed tailgate up better (marginally) , and tailgate replaced with one of the woven (netting) types better still.

I watch a lot of Discovery, it is the only thing of interest at 2: am. S.

[Fuzzy]

Originally Posted by MetroMPG

It's also one of the better/most comprehensive studies I'm aware of.

The author concludes that, on average, it's best to tell all pickup owners to leave the tailgate up.

If you read the report, the most accurate answer to the question is: "it depends".

Color me "less than impressed." I wonder if they squeezed this into a free weekend (based on how much these guys nissan{from GS} did in a day ). It would have been real interesting to see the DeltaCd of an "triangular" and "curved" tonneau cover.

Reading through it only once, I'm a bit unsure about their weighting function. The 8ft bed average (Table 2 & 3) showed decreases in drag for tailgate down in comparison to the tailgate up. Whereas the data (figure 6) shows it's less for the 0-10 deg yaw area that composes the most probable conditions (figure 5) that I (skimming) conclude they are calculating the average from (55-65mph ~ 90% of likely conditions).

Also, figure "5f" which should actually be "6f" doesn't agree with the data shown in figure 8.

Anyone got the height from the bed to the top of the cab for an '01 F150 on hand?

[trebuchet03]

Originally Posted by metroschultz

Check with Discovery's Mythbusters, they did a story on the tailgate idea. Real world and wind tunnel testing showed that tailgate up was best for aerodynamics. Real world fuel consumption test showed tailgate up better (marginally) , and tailgate replaced with one of the woven (netting) types better still.

I watch a lot of Discovery, it is the only thing of interest at 2: am. S.

Alas, they only tested one style of pickup.... Changing the length (thus changing Reynolds number) can have a dramatic effect... I'm not saying down is better - just longer vehicles might have different results ...

[drcoopster]

The "Toyota Tacoma" sure looks like a Tundra to me ...