That is very interesting that they actually did a test that we can actually benefit from. Most of the time I don't bother to watch Myth Busters because they test stuff that I could give a rip about. I would like to know the results of the "tonneau cover" test; with & without wing on the back.
Mythbusters testing tail gate myth
- Thread starter Michael Lighthall
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David j
Active Member
I agree with Bpoche. There's no way two trucks get the exact gas mileage. They should have done the test as you said, switching trucks.
Shawn Hennessy
Active Member
4. With a canopy
John Mastrocco
Active Member
Teh tailgate down idea worked on much older model pickups - before aerodynamics and mpg became an issue. The same tests done on a 50's or 60's model PU would have the opposite results.
The bubble is a relatively new concept in PU design.
The bubble is a relatively new concept in PU design.
I think they should have conducted test.
Each vehicle should have been tested with the tailgate up and the tailgate down and the drivers should have been switched to eliminate any possible variations in the vehicles and drivers.
Osverall, I think the test were pretty fair and are representative of what the average pickup driver would get. But I am still curious if the length of the crew cab vs the length of the pickup bed has any bearing on the results?
...Rich
Each vehicle should have been tested with the tailgate up and the tailgate down and the drivers should have been switched to eliminate any possible variations in the vehicles and drivers.
Osverall, I think the test were pretty fair and are representative of what the average pickup driver would get. But I am still curious if the length of the crew cab vs the length of the pickup bed has any bearing on the results?
...Rich
Thomas Rogers
Well-Known Member
Why didn't they simply use one truck, one driver, filled to the brim twice with gas from the same station?
Oh, I know why...it wouldn't have been as dramatic watching the same thing twice as it is to watch two vehicles going head to head while one ultimately sputters out of gas and the other continues...once again drama vs science, and drama wins.
TJR
Oh, I know why...it wouldn't have been as dramatic watching the same thing twice as it is to watch two vehicles going head to head while one ultimately sputters out of gas and the other continues...once again drama vs science, and drama wins.
TJR
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Travis Munday
Well-Known Member
...or, considering the truck went nearly 500 miles on one tank of gas over two days worth, condensing the test down to a more workable time span is just easier for everyone.
Using one truck with one driver twice has just as many variables, if not more, then two trucks and two drivers. Two trucks driven at the same time are subjected to the same weather conditions, altitude, road delays/traffic, etc. One truck two times, even over the same roads over the course of four days, has the possibility for very drastic enviromental conditions. What if the last two days you've got really strong winds? Or rain? Or traffic? Your test is no longer valid.
Two trucks with two drivers you have the possibility of one driver driving drastically different then the other, or one truck having different mechanical wear and tear, etc. However, some of these variables would still be present with one truck twice. The oil on the second run isn't as good, the fuel filter is more clogged, the air filter is dirtier, etc, etc. You can try to minimize the variables with the two driver's driving style by having strict acceleration rules and driving styles, etc.
The point of scientific testing of a variable to remove, or minimize as much as possible, all other variables. One truck twice may sound better and more 'sound', but things aren't always as easy as they seem.
Using one truck with one driver twice has just as many variables, if not more, then two trucks and two drivers. Two trucks driven at the same time are subjected to the same weather conditions, altitude, road delays/traffic, etc. One truck two times, even over the same roads over the course of four days, has the possibility for very drastic enviromental conditions. What if the last two days you've got really strong winds? Or rain? Or traffic? Your test is no longer valid.
Two trucks with two drivers you have the possibility of one driver driving drastically different then the other, or one truck having different mechanical wear and tear, etc. However, some of these variables would still be present with one truck twice. The oil on the second run isn't as good, the fuel filter is more clogged, the air filter is dirtier, etc, etc. You can try to minimize the variables with the two driver's driving style by having strict acceleration rules and driving styles, etc.
The point of scientific testing of a variable to remove, or minimize as much as possible, all other variables. One truck twice may sound better and more 'sound', but things aren't always as easy as they seem.
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Thomas Rogers
Well-Known Member
Altitude, road delays and traffic were not an issue, I assume this was a closed track.
One truck, one track, one driver, one test drive after the other sounds like less variables than two trucks, two drivers, same track, same time, but I get your point.
TJR
One truck, one track, one driver, one test drive after the other sounds like less variables than two trucks, two drivers, same track, same time, but I get your point.
TJR
Travis Munday
Well-Known Member
No, the test was done on open roads, given a very realistic feel to the entire test.
Closed track resuslts are usually good for closed track situations. There was a similar test done by the Mythbusters, do windows down or running the A/C use more gas? The test was done on a closed corse. The result was odd, at 55mph A/C was more fuel efficient, at 45mph, windows down was more fuel efficent. It turns out the crossover point for fuel efficiency for these two variables is about 50mph.
Ideally, a test like this would take place with one vehicle over a long time frame over many driving conditions over open roads. That is more accurate and more representitive of the general population, but difficult (and expensive) to test for a show.
Closed track resuslts are usually good for closed track situations. There was a similar test done by the Mythbusters, do windows down or running the A/C use more gas? The test was done on a closed corse. The result was odd, at 55mph A/C was more fuel efficient, at 45mph, windows down was more fuel efficent. It turns out the crossover point for fuel efficiency for these two variables is about 50mph.
Ideally, a test like this would take place with one vehicle over a long time frame over many driving conditions over open roads. That is more accurate and more representitive of the general population, but difficult (and expensive) to test for a show.
Thomas Rogers
Well-Known Member
Oh, I didn't see the show, I just assumed a test track, like the competition on Junkyard Wars where they had to make the ultralight vehicles (one powered by a weed wacker) go the furthest distance.
But a question to you, Tiger, do you TOTALLY dismiss the results of the test, to the point that you think the tailgate down should get better gas mileage if all other variables are the same?
TJR
But a question to you, Tiger, do you TOTALLY dismiss the results of the test, to the point that you think the tailgate down should get better gas mileage if all other variables are the same?
TJR
Travis Munday
Well-Known Member
No, in fact, I found the test to be fairly accurate of real life driving. The trucks were about as similar as you could get, down to the weight of driver, passenger, camera crews, etc. I don't recall a mileage for them, but I suppose they were low and supposedly very similar to each other. There were strict driving rules in place on the drivers, how well they abided by them is debateable, but just about every attempt was made, within reason, so that the only variable being tested was the effect of the tailgate. The trucks were driven on mostly highways, usually beside each other, and with the cruise set to the speed limit, and once the cruise was set, all acceleration was done, according to the driving rules, by the cruise control.
While the test on the surface was a pretty good indicator of which truck would be the better MPG over real roads, of course, one test isn't good enough. I'd like to see multiple tests, maybe even over shorter distances, the see how the results break down. Not because I think the results would be any different, but because scientifically, one is not enough and isn't acceptable.
In my spare time I enjoy learning about aerodynamics, in particular automotive aero. Typically I learn mostly about race car aero, but the principals here are no different anywhere else. The reason why the tailgate up gives better results is perfectly sound and reasonable. Although I suspect that the reason WHY there is a bubble isn't so much the air hitting the tailgate then forming the bubble, but that the tailgate simply contains the bubble. With the 'gate up there are 5 sides to the bed containing the air, with the gate down you only have four sides, air is much harder to contain then. Try filling a container with 5 sides with water, easy, the water stays inside the box. Now remove one of those sides, doesn't matter which one, water flows freely out, nothing to keep it in. Air acts in a similar manner. In fact, hydrodynamic tanks can be used in place of wind tunnels to study 'aero' dynamics because both are fluids and both act very similarly.
While the test on the surface was a pretty good indicator of which truck would be the better MPG over real roads, of course, one test isn't good enough. I'd like to see multiple tests, maybe even over shorter distances, the see how the results break down. Not because I think the results would be any different, but because scientifically, one is not enough and isn't acceptable.
In my spare time I enjoy learning about aerodynamics, in particular automotive aero. Typically I learn mostly about race car aero, but the principals here are no different anywhere else. The reason why the tailgate up gives better results is perfectly sound and reasonable. Although I suspect that the reason WHY there is a bubble isn't so much the air hitting the tailgate then forming the bubble, but that the tailgate simply contains the bubble. With the 'gate up there are 5 sides to the bed containing the air, with the gate down you only have four sides, air is much harder to contain then. Try filling a container with 5 sides with water, easy, the water stays inside the box. Now remove one of those sides, doesn't matter which one, water flows freely out, nothing to keep it in. Air acts in a similar manner. In fact, hydrodynamic tanks can be used in place of wind tunnels to study 'aero' dynamics because both are fluids and both act very similarly.
Thomas Rogers
Well-Known Member
Tiger says:
Air cannot enter an area closed on all sides...and by that I mean all sides BUT the side where the air is trying to come in.
There is an old Mr Wizard experiment that I do for my Webelos Cub Scouts.
It goes like this:
- Take an empty clean soda bottle, preferrably a glass Coca Cola bottle ideal for it's long neck, but any soda bottle glass or plastic should do.
- Crumble up a small piece of paper into a ball about the size of a green pea or a little bigger.
- Hold the bottle on its side with the opening facing you, and place the ball of paper JUST inside the opening.
- Try to BLOW the ball of paper into the bottle.
Man, those kids blow their hardest, but they can't do it.
The same for the wind whipping across the closed truck bed and trying to push down into the bed of the truck...it can't push down in, because all the air is trying to push down in on all areas of the top of the open bed (which is like the opening of the bottle) and there is no where for the air already there to go.
So, the air on the top drags across the air already in the bed.
And as other have surmised the air dragging across air provides less resistance than air dragging across metal.
And, I suspect, even worse, if the tailgate open causes the air to more forcefully push down on the truck bed because of the increased downward motion, then that only adds to the issue.
Just my thoughts.
TJR
Air cannot enter an area closed on all sides...and by that I mean all sides BUT the side where the air is trying to come in.
There is an old Mr Wizard experiment that I do for my Webelos Cub Scouts.
It goes like this:
- Take an empty clean soda bottle, preferrably a glass Coca Cola bottle ideal for it's long neck, but any soda bottle glass or plastic should do.
- Crumble up a small piece of paper into a ball about the size of a green pea or a little bigger.
- Hold the bottle on its side with the opening facing you, and place the ball of paper JUST inside the opening.
- Try to BLOW the ball of paper into the bottle.
Man, those kids blow their hardest, but they can't do it.
The same for the wind whipping across the closed truck bed and trying to push down into the bed of the truck...it can't push down in, because all the air is trying to push down in on all areas of the top of the open bed (which is like the opening of the bottle) and there is no where for the air already there to go.
So, the air on the top drags across the air already in the bed.
And as other have surmised the air dragging across air provides less resistance than air dragging across metal.
And, I suspect, even worse, if the tailgate open causes the air to more forcefully push down on the truck bed because of the increased downward motion, then that only adds to the issue.
Just my thoughts.
TJR
Travis Munday
Well-Known Member
Isn't that what I already said? A-5 sided contained will contain the fluid, a 4-sided will not. However, your assestment of "air will not enter a closed container" is not accurate. Air will still enter the container, but it must displace the air that is already there. The new air doesn't simply bypass the container. The reason why the ball of paper doesn't move is that the rate of displacement is equal to the amount of air trying to be forced in the container. Air is moving in, but air is also moving out, keeping the ball fairly static. Again, displacment is easy to see with water. have a clear container, say a 2L clear bottle filled with clear water. Pour blue dyed water into the container, the blue water doesn't simply run off the top of the clear water, it mixes and displaces the clear mater. In fact, most of the water that overflows to begin with will be clear, not blue.
The tailgate is just closing the container, any additional air trying to enter the bed will have to first dispalce the air that is there, so it creates a kind of displacement bubble. This bubble isn't like a soap bubble, it is rotating, counterclockwise when viewed from the passenger side. Some air will be displaced, but the majority will be forced above and around the bubble, bypassing the bed almost entirely. With out a tailgate, air has to content with the bed, making the distance the air travels greater, increasing drag, which decreses MPG. With the tailgate down, there is possibly more downforce over the rear wheels. Downforce is a direct result of drag, which decreases MPG. While there might be some amount of downforce being created, it is being created more from the impact of the air and not the influence of the air. Impacted downforce is the worst, all drag, little benefit. Influenced downforce is ideal, useable downforce, and minimal drag.
The tailgate is just closing the container, any additional air trying to enter the bed will have to first dispalce the air that is there, so it creates a kind of displacement bubble. This bubble isn't like a soap bubble, it is rotating, counterclockwise when viewed from the passenger side. Some air will be displaced, but the majority will be forced above and around the bubble, bypassing the bed almost entirely. With out a tailgate, air has to content with the bed, making the distance the air travels greater, increasing drag, which decreses MPG. With the tailgate down, there is possibly more downforce over the rear wheels. Downforce is a direct result of drag, which decreases MPG. While there might be some amount of downforce being created, it is being created more from the impact of the air and not the influence of the air. Impacted downforce is the worst, all drag, little benefit. Influenced downforce is ideal, useable downforce, and minimal drag.
Dale Carlson
Active Member
Didn't somebody here post a link showing the testing that the University of Michigan (?) did on this very subject? If'n memory serves me correctly, what you guys are saying, disregarding your arguments in fluid dynamics, has already been demonstrated by scientifically valid tests - that the tailgate-down uses more gas than tailgate-up, that the tonneau cover had a neglible effect either way, and that, oh yeah, those ugly ass wings (like on the Avalanche and the Ridgeline), also cause the truck to use more fuel.
It could be something as simple as a slight tilt to the angle the gas tank was mounted, or a 1/4" difference in the height of the pickup tube in the gas tank. There are many variable in two identical vehicles because there are broader tolerances in the assembly line process to keep the line moving quickly. A slight tilt in the way the gas tank is mounted would not mean much to the average person but in a such a mileage test could make a big difference.
Had the vehicles and drivers been switched they may have noticed that one vehicle was consistantly getting slightly more or less mileage than the other. A better way would have been to mount a separate calibratged external gas tank in the bed and the tests could have been made more accurate. A small 5 gallon tank on an enclosed track would have allowed them to run more test switching drivers, and vehicles with the tailgate up and down.
I agree with their results, but I don't think a single head to head test proves or disproves the myth when there are so many other factors that were not considered.
...Rich
...Rich
Had the vehicles and drivers been switched they may have noticed that one vehicle was consistantly getting slightly more or less mileage than the other. A better way would have been to mount a separate calibratged external gas tank in the bed and the tests could have been made more accurate. A small 5 gallon tank on an enclosed track would have allowed them to run more test switching drivers, and vehicles with the tailgate up and down.
I agree with their results, but I don't think a single head to head test proves or disproves the myth when there are so many other factors that were not considered.
...Rich
...Rich
Kinda like Penn & teller testing the pheremones on one guy and the other without. The men were identical twins.
The first guy was not wearing any type of pheremones, the second guy was. They had ladies dance with the guys. All said the second guy was more attractive. The pheremones worked. They switched the guys. The second guy became the first. Again, the women chose the second guy.
It had nothing to do with the pheremones, but the women must have been aroused by the first guy and then seeing the second was the icing on the cake, so to speak.
There are little differences between two identical vehicles. As RichardL said, the fuel tank could have been tiped one way or another. The fuel pick-up might have been an 8th inch lower or higher. One might have had a better fuel ecomomy. No two tracs get identical mileage.
There are so many vairiables involved. The only true method would be in a wind tunnel on a dyno with the same truck. Tailgate up, tailgate down. Exact same temperature, humidity, barometric pressure, etc.
Tom
The first guy was not wearing any type of pheremones, the second guy was. They had ladies dance with the guys. All said the second guy was more attractive. The pheremones worked. They switched the guys. The second guy became the first. Again, the women chose the second guy.
It had nothing to do with the pheremones, but the women must have been aroused by the first guy and then seeing the second was the icing on the cake, so to speak.
There are little differences between two identical vehicles. As RichardL said, the fuel tank could have been tiped one way or another. The fuel pick-up might have been an 8th inch lower or higher. One might have had a better fuel ecomomy. No two tracs get identical mileage.
There are so many vairiables involved. The only true method would be in a wind tunnel on a dyno with the same truck. Tailgate up, tailgate down. Exact same temperature, humidity, barometric pressure, etc.
Tom
Rick Kent
Well-Known Member
Boys and girls,
Here is a write up on another study that shows using a tonneau cover is the most efficient way to tool around in a pick up truck.
They do throw in the caveat that different models, different bed sizes, etc... will yield different results.
Here is a write up on another study that shows using a tonneau cover is the most efficient way to tool around in a pick up truck.
They do throw in the caveat that different models, different bed sizes, etc... will yield different results.
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Jeff C
Well-Known Member
kefguy,
If I remember correctly, the wing actually decreases drag because it raises the height of the tailgate, thereby increasing the size of the bubble. And I think they look good on some trucks.
If I remember correctly, the wing actually decreases drag because it raises the height of the tailgate, thereby increasing the size of the bubble. And I think they look good on some trucks.
Dale Carlson
Active Member
I found that University of Michigan study (see link below)
Jeff C, this is what the study found out about what they call the sloped cab addition, but it might not be the wings I was thinking about (they don't show a different perspective of the test model):
And I remembered completely wrong about the tonneau covers. In their test, the cover decreased drag by 22%:
Jeff C, this is what the study found out about what they call the sloped cab addition, but it might not be the wings I was thinking about (they don't show a different perspective of the test model):
And I remembered completely wrong about the tonneau covers. In their test, the cover decreased drag by 22%:
