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Old 03-05-2012, 02:24 PM   #1
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Aerodynamics of tv-toad combos

After getting 7.5 mpg on my last pull I've wondered about improving the airflow over the trailer. Has anyone simulated, or seem a simulation of, wind tunnel testing of various combinations of open bed pickup, tonneau cover, low rise vs high rise camper shells? It would seem plausible that a "duck-tail" camper shell that directed airflow up over the top of the trailer would help improve mileage but I haven't yet found any data on the web. Air-tabs are reputed to help decrease drag by forming vortices on the trailing edge of the camper that smooth out the turbulence, but I've yet to see them on the highway or in a campground. My combo is a Ford F-150 Ecoboost short bed, 3.55 LS 4x4 and Tracer 230 with the Touring Edition cap.

Gary
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Old 03-05-2012, 02:52 PM   #2
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I would think that a high-rise camper shell with a ducktail would certainly help, but I seriously doubt anyone has studied the issue.
Why are you getting such terrible gas mileage?
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Old 03-05-2012, 03:42 PM   #3
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To be honest I don't believe the effort and cost to benefit the gains if any imo
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Old 03-05-2012, 03:52 PM   #4
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The camper shell should not only improve the fuel mileage somewhat, but also provides a secure and dry place to haul camping stuff. So the idea is not so easy to dismiss.
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Old 03-05-2012, 03:54 PM   #5
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Roamin Ovum, what speed are you pulling ??

I am not sure what can be done about the trailer airflow, but you might be on to something about the truck aerodynamics. On a trip last week, I noticed my soft tonneau cover really being whipped around.....I was carrying my canoe this trip. On trips without the canoe, it lays pretty still, so I contribute the cover being blown by the turbulent air of the canoe. Plus I had my bikes sitting over the bed, but I travel with them most times, and don't notice that kind of movement with the tonnaeu cover.

I have read several places that an open bed forms an air pocket, and doesn't affect the aerodynamics that much, but I prefer to think that a tonneau cover has to do a little in making the truck more aerodynamic. As far as a topper, I wonder if the more wind resistant stance would be countered by the extra weight.

This last trip, we decided to stay away from the interstate as much as possible. The slower speeds helped some with fuel mileage, but was countered some with some stop lights.

The 1st day we had 20 to 30 mpg sustained winds, with gusts to 50 mpg....there were all sorts of high wind warnings out. We were basically quartering into these winds (sometimes broadside, sometimes head-on) and my fuel mileage was 9.1 mpg that day....I think the canoe on top of my racks really hurt the mileage that day. The other fill-ups were much better, and I contribute that to the lower speeds using non-interstate speeds.
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Old 03-05-2012, 04:06 PM   #6
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I was towing at 62 - 68 mph into a head wind. I've gotten as high as 10 mpg on other trips. Tires were properly inflated - 42 front, 44 rear, and 50 in the trailer. There were quite a few stops this time, it seems all the lights were red. The trailer weighs 5000 lbs dry, maybe 5600 as loaded. The truck gets from 17 - 21 when not towing so no complaints there. The only factors affecting mileage are internal engine resistance (same towing or not) rolling resistance (much higher when towing - more weight, more tires) and wind resistance. Other than keeping the inflation pressures up to spec aero drag seems the only variable. I was hoping someone on the forum had taken a hit for the team and run the shell / no shell experiment
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Old 03-05-2012, 04:08 PM   #7
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"I was towing at 62 - 68 mph into a head wind."
==============================
That would explain it!
Without the Ecobeast, you probably would have been gong 50!
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Old 03-05-2012, 04:11 PM   #8
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The Eco-Boost is a super high efficient Engine and get great Gas Mileage. There has been some road tests of guys getting up to 32 MPG on the truck with a light foot and etc...

What has been a massive complaint is because of the twin turbo. It takes a massive amount of energy for the engine to "Spool" up heavy hauling or towing, which in turn consumes a far higher quantity of fuel. To the point at which getting significantly lower fuel economy then some large displacement motors.

What has also been a concern is the "rumor" of engine failures due to those people that are using the truck as a "work" truck, towing and hauling heavy loads on a regular basis. What the rumor is a lot of scorching going on in the motors due to the quite higher temps that the motor runs at when using turbos. Causing scorched cylinders and valve issues.

My buddy who is a Mechanical Engineer and works on heavy duty agricultural equipment said to me if you are towing or hauling nothing will ever beat displacement. Especially a low torque high horsepower engine like the Eco Boost.
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Old 03-05-2012, 04:14 PM   #9
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That headwind hurts. It has been speculation on how the Eco will do while towing. When you have 6 cyls. pulling just the truck without a load, then that engine is just purring along. Getting to the available torque when needed for trailer towing by making the turbos work is gonna dip into the gas tank some. I am also wondering if the 3.55 gears may be helping the non-trailer towing fuel mileage, but hurting the towing mileage.

Sounds like you are doing all of the right things. No excessive speeds and tires inflated. The aero end of the equation is about all that is left.
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Old 03-05-2012, 04:14 PM   #10
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Quote:
Originally Posted by crocus View Post
"I was towing at 62 - 68 mph into a head wind."
==============================
That would explain it!
Without the Ecobeast, you probably would have been gong 50!
agreed! don't know what you expected towing into a headwind.
we all get about the same gas mileage doing that. especially at those speeds.
you do know that you increase the wind resistance a lot, by driving that fast. and your tires are only rated to 65mph.
no wonder you got only 7mpg!

and i seriously doubt you'll see much of a gain in mpg, with a shell.
it'll take a lot of towing to recoup the money you'd spend for one.
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