From my experience, I bought a tri-fold soft roll, which can help me increase my MPG by about 10%.

 

I like towing with my canopy on. Seems to be less wind resistance and sway. I drive to Texas from Washington and it drove better. Now the canopy is off because it wont fit in my garage. the trailers seem to buffeet more going down the road.

 

Though this is an old thread, this is always a topic of interest.

Where both the linked Mythbusters and the SEMA tests fail is they cause people to incorrectly correlate that if it's true for one pickup, then it's the same for all pickups. Various pickup designs are aerodynamically different so these results are not comparable.

For instance, the quad cab mentioned earlier in the thread will have a different airflow pattern over the bed, as will fleetsides and stepsides. The SEMA article is especially flawed in that the pickup was tested with the side mirrors removed. These non-real world conditions provide irrelevant results since the airflow will be less turbulent and flow differently over the bed than a more disturbed airflow.

For reference, here's a link to Consumer Reports comparison test of tailgate up and down, and bed cover http://www.consumerreports.org/cro/news/2013/08/pickup-truck-tailgates-and-fuel-economy/index.htm

This testing is done under real world conditions so it's also inexact, but much closer to what we'll encounter. An aspect that's rarely mentioned in the highly vaunted wind tunnel test results is the effect of sidewinds, which are almost never tested. So while headwinds are the primary factor in driving, we must remember wind tunnels don't account for off-center and sidewinds, turbulence from other vehicles, and tailwinds.

In my experience, my best mileage is achieved with a bed top (camper top) despite the extra weight. I speculate this is due to it approximating a Kammback profile.

 

Though this is an old thread, this is always a topic of interest.

Where both the linked Mythbusters and the SEMA tests fail is they cause people to incorrectly correlate that if it's true for one pickup, then it's the same for all pickups. Various pickup designs are aerodynamically different so these results are not comparable.

For instance, the quad cab mentioned earlier in the thread will have a different airflow pattern over the bed, as will fleetsides and stepsides. The SEMA article is especially flawed in that the pickup was tested with the side mirrors removed. These non-real world conditions provide irrelevant results since the airflow will be less turbulent and flow differently over the bed than a more disturbed airflow.

For reference, here's a link to Consumer Reports comparison test of tailgate up and down, and bed cover http://www.consumerreports.org/cro/news/2013/08/pickup-truck-tailgates-and-fuel-economy/index.htm

This testing is done under real world conditions so it's also inexact, but much closer to what we'll encounter. An aspect that's rarely mentioned in the highly vaunted wind tunnel test results is the effect of sidewinds, which are almost never tested. So while headwinds are the primary factor in driving, we must remember wind tunnels don't account for off-center and sidewinds, turbulence from other vehicles, and tailwinds.

In my experience, my best mileage is achieved with a bed top (camper top) despite the extra weight. I speculate this is due to it approximating a Kammback profile.

 

I just read this study about tonneau covers. http://www2.sema.org/Main/SemaOrgHome.aspx?ID=52546. It's true that tonneau can help but there are several factors than affect fuel mileage.

 

I made a couple passes at the track a couple years ago with the tailgate off, absolutely no change other than looked like shit. I leave the tailgate on all the time, the weight is a good thing too, right where it needs to be.

 

personally, I think our little Dakota's look like crap without the tail gate....looks even worse with one of them bed nets on it

Bryan

 

They never tried a soft roll up one. I feel like that could make a difference compared to a fiberglass one cause its so much lighter.

 

There was a university that tested it to. They found the best design was a kind of half camper shell type thing that started level with the top of the cab and tapers back to even with the tailgate smoothing out the airflow. With the tailgate up, modern trucks are designed to create a low pressure area inside the bed which as far as the airflow is concerned is almost the same as a tonneau cover on the truck.

 

There was a university that tested it to. They found the best design was a kind of half camper shell type thing that started level with the top of the cab and tapers back to even with the tailgate smoothing out the airflow.

:banana2: >see photo<
I've racked up 540K miles on two Daks with a '93 Snugtop Cab-hi shell. I know its aero friendly because the truck is solid as a rock at highway speeds and in storms and crosswinds. Some credit may go to the Texas Tail wing, however. I get 20 mpg all the time.

 

Ah! So I'm good. No back window. Haha

Hey Brian, Happy Birthday!

 

I put a soft tonneau on mine after about a year. I did it mostly for looks, but I got about a 0.9 mpg increase in mostly highway driving. With 183,700 miles on it now, the lifetime average mpg is 19.6.

The trash coming through the back window effect is caused by a vacuum buildup behind the cab. A tonneau cuts that approximately in half, and also eliminates wind resistance against the closed tailgate.

 

IThe trash coming through the back window effect is caused by a vacuum buildup behind the cab. A tonneau cuts that approximately in half, and also eliminates wind resistance against the closed tailgate.

Actually, modern truck designs have eliminated the "drag" caused by the tailgate. Which has been proven by more than just Mythbusters. When driving down the road a low pressure area is formed in the bed which basically causes the airflow to flow right over the tailgate with minimal effect on gas mileage. So little so that adding a bed cover is usually a neglibible difference. And lowering or removing the tailgate actually hurts mileage compared to leaving it up.

 

Figures. Though I suppose in the rain on the road, it comes in handy for naps and keeping stuff dry. So I won't complain about the down side.

 

They tested a camper shell, I think it was worse than nothing.

 

How about a camper shell though?

 

I used to have a flold a cover when I junked it gas mileage did not change I believe that all types of bed covers barely do anything modern pickups are designed towards mpgs put a paper plate in your bed it will swirl around or atleast swirl before it goes out the bed thats b/c they designed the cab shapes better so the bed is not a drag ive driven will my tailgate off really fast to see if i can feel reduced drag..barely only over 90mph but in my buddies 75 chevy with the tailgate off its a whole new world idk just mho

 

Good info here.

 

The only reason I have a soft cover is....

1st: It looks better and 2nd: it makes it harder for some dip to use my bed for his trash can...!!! :jester:

 

Here are some points:

First off those test where bogous, not same route temp wind dew etc.

next hard tonnaoh is lot heavier then without one, so obviously weight isn't considered.

Soft tonnoh was never tested, neither was a grandpa one- full lenght cap and some with the added ended cap.

Go all out or don't waste time. Mythbusters is full of shit half the time anyway, bunch of stupid ass acting!

 

Here are some points:

hard tonnaoh is lot heavier then without one, so obviously weight isn't considered.

While this fails scientific rigor in the sense that there are two free variables at play (weight and aero), it does reflect real world conditions. The test was how adding a cover affects gas mileage, so I think (in this case) lumping the two variables together is fairly valid, but means you can't generalize the results to all covers, just ones of similar construction. Generalizing all covers would require careful control of weight and design.

 

very interesting mythbusters.

 

My situation is a slightly different twist, since my Dak has a Snugtop cab-hi shell. It doesn't hurt or help the mpg. The shell itself weighs 160 pounds, which helps the traction considerably. It's aero-friendly enough (with the Texas Tail wing) that it rolls along on Interstate @70mph+ without a ripple. The Dak is absolutely rock solid when passing 18 wheelers or in cross winds. It's a work truck with an alter :woot: ego, anyway.

 

My Quad cab has the tailgate down most of the time and with my driving habits, gets better gas mileage vs. tailgate up. When it is up, I can feel the drag being created. Maybe the longer cab and shorter bed make a difference.
I'm curious as to what the Mythbusters findings would be with a Quad cab...

 

Did you watch the video? They were very angry over the feedback over their original test. I think if you asked they'd hunt you down in the middle of the night and kill you! :jester:

 

was alright result i guess. tests where still a :fail2:

 

I haven't noticed any change in MPG with my truck since I took the tonneau off, did make it quicker losing the ~150lbs it weighed though, big thick heavy SOB.

 

plus this is just what I think, it looks better without the tonneau and your bed is now useful

Ive always been into those folding or roll up soft covers though

 

Modern trucks are designed in wind tunnels to maximize aerodynamics. As mentioned, with an open bed, it creats a low pressure area which more or less causes the air to flow right over the bed with minimal restrictions. Mythbusters aren't the first to do this type of testing. I bought a tonneau cover to be able to secure stuff in my bed and for looks. MPG had nothing to do with it. And even if it did help, once you factor in the price of the tonneau, it would take longer than most people own thier truck to make up the cost of the tonneau in fuel savings.

 

Modern trucks are designed in wind tunnels to maximize aerodynamics. As mentioned, with an open bed, it creats a low pressure area which more or less causes the air to flow right over the bed with minimal restrictions. Mythbusters aren't the first to do this type of testing. I bought a tonneau cover to be able to secure stuff in my bed and for looks. MPG had nothing to do with it. And even if it did help, once you factor in the price of the tonneau, it would take longer than most people own thier truck to make up the cost of the tonneau in fuel savings.

That's because most people have Chevys, Fords, and import trucks instead of Dakotas. Of course they're going to sell their truck in a few years! Duh!

 

mesh is better becasue it traps SOME air, still creating a small pocket to help with drag, but it also allows the air to pass without stopping. so it's like gate down without the friction. kinda.

and i always knew the hardcover MPG improvements were BS. take any truck. put some micky d's wrappers in the bed and then open the back window at 60. THEY HIT YOU IN THE FACE. aerodynamics have some funny shit lol

 

put some micky d's wrappers in the bed and then open the back window at 60. THEY HIT YOU IN THE FACE. aerodynamics have some funny shit lol

put anything, paper, bags, disposable plates whatever you want

they float in the back, looks really funny, and if the back window is open it all flies in and hits you in the face just to teach you not to put trash in the bed to make it fly off behind you with the back window open...