Tonneau Cover Range Improvement numbers

[Pitbull2o08]

"So, the theory is this: a tonneau cover lowers the Cd (coefficient of drag) of a pickup truck. That is almost universally true, for reasons that are probably intuitively obvious. The tailgate is an obvious apparent wind catcher. Try to carry a sheet plywood with the flat side facing the wind on a gusty day, and you will appreciate aerodynamic drag."


This is false because, well, physics. The tailgate does trap air, creating a high pressure environment inside the bed. The increase in velocity of air over the truck drops the pressure above the high pressure system, a la venturi effect. although this isn't a perfect system and some swirling can occur, there is no outlet for the high pressure other than to stay high pressure and confined within the space of the bed. Generally, the fast moving air flows over the roof and over the box and creates turbulent flow behind the tailgate.

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[ZeusDriver]

"So, the theory is this: a tonneau cover lowers the Cd (coefficient of drag) of a pickup truck. That is almost universally true, for reasons that are probably intuitively obvious. The tailgate is an obvious apparent wind catcher. Try to carry a sheet plywood with the flat side facing the wind on a gusty day, and you will appreciate aerodynamic drag."


This is false because, well, physics. The tailgate does trap air, creating a high pressure environment inside the bed. The increase in velocity of air over the truck drops the pressure above the high pressure system, a la venturi effect. although this isn't a perfect system and some swirling can occur, there is no outlet for the high pressure other than to stay high pressure and confined within the space of the bed. Generally, the fast moving air flows over the roof and over the box and creates turbulent flow behind the tailgate.

I assume you are just being belligerent for fun, but in fact, there is nothing in the paragraph you quoted that is false. And oddly, you go on to agree with my several points. Wierd.

The First Statement:
"So, the theory is this: a tonneau cover lowers the Cd (coefficient of drag) of a pickup truck."
That is entirely true and very well known by every aero guy or gal at all the manufacturers. Does the theory pan out in practice? That's another question. But the answer there is also well known, and Brad Richards of Ford (see the autoblog video) puts its well: "Tonneaeu covers are more efficient." He goes on to say that the tailgate top surface mimics the last 6 inches of a tonneau cover.
So the first statement 100% true. Anyone arguing otherwise, would have to know essentially nothing about the last 50 years of auto aerodynamics studies.

The Second Statement:
"That is almost universally true, for reasons that are probably intuitively obvious. " It is 100% true that the theory is universally recognized, by those with subject matter expertise. Granted, there are loads of people who know nothing about aerodymanics, but I think, in context, we can say that I am not treating their theories (whatever they may be) as a "theory". They are instead "hunches". For example, the hunch that lowering the tailgate would reduce drag is clearly not useful. The SEMA tests. long ago showed that not to be valid, as had tests elsewhere at manufacturer's wind tunnels decades ago.
So, again: 100% true.

The Third Statement:
"The tailgate is an obvious apparent wind catcher." No one but a fool would disagree with this, and even you agree: "The tailgate does trap air," you say.
100%, unambiguously, and simply true.
(The second part of your statement is not strictly true without further explanation, given that local velocities within the general bed bubble are actually substantially higher that the free stream velocity, and therefore of lower pressure. Bed blowing would help with your theory.

The fourth statement:
Try to carry a sheet plywood with the flat side facing the wind on a gusty day, and you will appreciate aerodynamic drag."
Even people with essentially no aerodynamic training or exposure to physics would agree with this statement, unless they have led very sheltered lives. I might have gone on to say "Hold the sheet at its trailing edge, and with an angle of attack of 10 degrees, and as it flips over on top of you, you may also gain an intuitive understanding of lift... and even aerodynamic center and moments" .
100% true and known to anyone who has given these issues any thought.

So, were you hallucinating, or perhaps responding to someone else's post?

Are you thinking the Brad Richards is a fraud? What do you think his motives for lying would be?

 

[ZeusDriver]

This subject is so tired that I remember reading a study back in the late 90s that tested tailgate up, tailgate down (because that was a thing back then), and then those weird tailgates that had holes in them and looked like snowmobile fencing (except not orange). It was stated even back then that the air kept in the bed with the tailgate up created pressure to keep the airflow over the whole vehicle. So even back in the 90s we knew putting your tailgate down or having those air tailgate things were useless. Still applies with a tonneau cover.

If you are saying that "useless" still applies to the use of a tonneau cover, then the subject is not tired -- you are proof that there are still people who have no understanding of the aero involved, but still pontificate about it online. Having spent a few years consulting with Ford, I can say that the people like Brad Richards (middle management) are generally straight shooters (and many of them are pretty smart). (C-level folks, maybe not so much). So what motive do you think he has for lying about the beneficial effects of a tonneau cover?

 

[FloridaMan655321]

If you are saying that "useless" still applies to the use of a tonneau cover, then the subject is not tired -- you are proof that there are still people who have no understanding of the aero involved, but still pontificate about it online. Having spent a few years consulting with Ford, I can say that the people like Brad Richards (middle management) are generally straight shooters (and many of them are pretty smart). (C-level folks, maybe not so much). So what motive do you think he has for lying about the beneficial effects of a tonneau cover?

My point is that people for decades keep thinking that because there is an empty bed in the back of a pickup truck, that the wind must perfectly go over the cab and blast right in the tailgate and impact MPG. I’m sure you could add a big wing on the back and it’s going to do something, but will it be noticeable?

I love tonneau covers and am actually in the process of buying one, but I understand that adding this will not be any noticeable MPG increase. This is more of a ‘do you need one for utility reasons’ question, and if you do, get one, if not, don’t think the price of one is going to offset the savings of energy.

 

[Firn]

I assume you are just being belligerent for fun, but in fact, there is nothing in the paragraph you quoted that is false. And oddly, you go on to agree with my several points. Wierd.

The First Statement:
"So, the theory is this: a tonneau cover lowers the Cd (coefficient of drag) of a pickup truck."
That is entirely true and very well known by every aero guy or gal at all the manufacturers. Does the theory pan out in practice? That's another question. But the answer there is also well known, and Brad Richards of Ford (see the autoblog video) puts its well: "Tonneaeu covers are more efficient." He goes on to say that the tailgate top surface mimics the last 6 inches of a tonneau cover.
So the first statement 100% true. Anyone arguing otherwise, would have to know essentially nothing about the last 50 years of auto aerodynamics studies.

The Second Statement:
"That is almost universally true, for reasons that are probably intuitively obvious. " It is 100% true that the theory is universally recognized, by those with subject matter expertise. Granted, there are loads of people who know nothing about aerodymanics, but I think, in context, we can say that I am not treating their theories (whatever they may be) as a "theory". They are instead "hunches". For example, the hunch that lowering the tailgate would reduce drag is clearly not useful. The SEMA tests. long ago showed that not to be valid, as had tests elsewhere at manufacturer's wind tunnels decades ago.
So, again: 100% true.

The Third Statement:
"The tailgate is an obvious apparent wind catcher." No one but a fool would disagree with this, and even you agree: "The tailgate does trap air," you say.
100%, unambiguously, and simply true.
(The second part of your statement is not strictly true without further explanation, given that local velocities within the general bed bubble are actually substantially higher that the free stream velocity, and therefore of lower pressure. Bed blowing would help with your theory.

The fourth statement:
Try to carry a sheet plywood with the flat side facing the wind on a gusty day, and you will appreciate aerodynamic drag."
Even people with essentially no aerodynamic training or exposure to physics would agree with this statement, unless they have led very sheltered lives. I might have gone on to say "Hold the sheet at its trailing edge, and with an angle of attack of 10 degrees, and as it flips over on top of you, you may also gain an intuitive understanding of lift... and even aerodynamic center and moments" .
100% true and known to anyone who has given these issues any thought.

So, were you hallucinating, or perhaps responding to someone else's post?

Are you thinking the Brad Richards is a fraud? What do you think his motives for lying would be?

There might ve some points in there if you weren't relying on grandstanding so much.

If you have to be that condescending to make a point your might be arguing from an emotional perspective rather than a logical one.

The simple fact of the matter is that on our trucks, trucks that are VERY sensitive to changes in efficiency, it has been reported over and over again that covers do NOT impact range. Now I have said my piece, but you seem to continue to treat them as singular objects when there are a large number of external factors that determine if a cover may or may not be effective.

But I say it again, if your argument relies so heavily on long winded missivs and demeaning comments you are not arguing from the perspective of logic, you are doing so from emotion.

 

[chl]

The SEMA tests were performed in a good wind tunnel, and I am inclined to believe their findings (of about a 5% improvement in Cd with a tonneau cover, and a 1% degradation with the tailgate down.) The latter is not enough to show up (in consumption) in even a well-controlled, correctly-instrumented track test on an oval track. The former could show up in a very good track test, (as a reduction of circa 2% in consumption) but I have not seen such a test yet.

My Zing, from 2010 or so, achieved slightly lower drag than the Aptera (of that time) I thought at the time. (We were both in the same contest, until I pulled out, in a huff, at rule changes that made it impossible to win with anything other than a pure electric car.) The Aptera Cd was probably lower, but my frontal area was substantially less, because the seating was tandem instead of side-by-side. (My weight was less than half of the Aptera's.) I think my Cd was on the order of .16 or .18. At the time, the Aptera had its suspension members hanging out in the breeze, which is problematic for good aero. (Three wheels are problematic for aero too, a minor problem we both had.)

Back then, reasonable people considered wells-to-wheels as being the valid measurement for "goodness" in high efficiency vehicles. The calculations are complicated, for sure, but only by going through with them can you determine if a Tesla or a Prius is the more benign vehicle in West Virginia (the Prius wins) vs New Hampshire (the Tesla wins). There were teams in the X Prize who had developed engines from scratch (burning biodiesel, ethanol, etc), which, after the rules went to plug-to-wheels, could not possibly win. Sad. Fabulous efforts. As I remember it, the rules shifted when Musk ended up on the advisory board for the X Prizes. I could be full of it, however. Many of the contestants were active in developing the rules, and then suddenly they went in a new direction.

Adding to the Irony: The GM EV1 could achieve 100mpge (which is what the metric went to instead of wells-to-wheel). The X Prize was about achieving a 100 mpg vehicle that could be marketed in significant numbers. GM had already done that, (a decade it turns out, if you view electricity as showing up at the outlet without any environmental consequence.

I remember thinking at the time: many people worry about the handful of watts difference between incandescent bulbs and LED's, but consider the hundreds of thousands of watts consumed by an EV as being benign.

Hrumfff.

But back to the point of the thread: No, you cannot measure the effect of either a tonneau cover or an active front air dam on the road. But both have an affect: the cover about 5% in Cd, the dam about 4% in Cd. Combined, maybe as much as 2% or 3% in consumption. Given that my consumptions varies from day to day by about an order of magnitude greater than that (in other words by 20% or 30% ) I am not able to say that it has a great affect on me personally, other than to say that over time, my $100 tonneau cover pays for itself. Woo Hoo!!

And.... AND.... this is where we should get weepy, cuz we are saving the world: the combined effect of those two features reduces CO2 production by some very large number of tons, across the Ford fleet.

Agreed.

I saw my electric bill go down noticeably when I switched to CFLs, and again to a small degree when I switched to LEDs from the CFLs.

The biggest drop was when I got a hybrid (heat pump) water heater - paid for itself in a little over a year in savings, not to mention the reduction in related CO2.

I expect there is some small benefit from a tonneau cover because of reduced drag. I probably won't really notice it because I do most of my driving at 25-35mph where weight/friction is the main drag so to speak (not literal drag) on efficiency, not aerodynamics.

Even so, preaching to the choir here, we are spending way less money per mile in the Lightning than a comparable ICE F-150, so rejoice and celebrate the Lightning.

 

[chl]

There might ve some points in there if you weren't relying on grandstanding so much.

If you have to be that condescending to make a point your might be arguing from an emotional perspective rather than a logical one.

The simple fact of the matter is that on our trucks, trucks that are VERY sensitive to changes in efficiency, it has been reported over and over again that covers do NOT impact range. Now I have said my piece, but you seem to continue to treat them as singular objects when there are a large number of external factors that determine if a cover may or may not be effective.

But I say it again, if your argument relies so heavily on long winded missivs and demeaning comments you are not arguing from the perspective of logic, you are doing so from emotion.

Who was doing the reporting?
And what was their method of making that determination?

My point is some things that are merely seat of the pants conclusions when tested scientifically turn out to be wrong - that is what about 1/2 of Mythbusters is about.

But you cannot seriously be arguing with wind tunnel tests that show the opposite, are you? That show that a tonneau cover on a pickup truck reduces aerodynamic drag?
That's a controlled test with precise instruments, not an anecdotal observation based on imprecise data.

People used to think a cannon ball would fall faster than a pea, based on their intuition, their guts, a seat-of-the-pants conclusion, but Galileo showed that was wrong with a scientific experiment.

My yard may be flat, but the earth is round.

I can draw a circle with a compass for example, and think that I can measure the circumference with a tape measure, and measure the diameter with a ruler, and then know precisely what the ratio between them is. Alas, the ratio of the circumference to the diameter of a circle is an irrational number (pi) that has an infinite and non-repeating decimal pattern and it cannot be expressed as a simple fraction of two integers, even though I thought it could be.

Time is not absolute either, it changes based on gravity and speed.
Clocks run slower at sea level than in at high altitude because gravity is stronger at sea level.
And gravity is the curvature of space-time based on mass and energy.
The clock at sea level is deeper in the curve of space-time.

Not to pontificate too much but people can have their own opinions and they may and often do differ.

But we ought to accept scientifically obtained, precisely measured data even when it counters our preliminary opinion about something.

Unless we can find an error in the experiment, the equipment, the calculations, we ought to accept it as valid.

Us Lightning owners trucking down the road for thousands of miles at varying speeds and under varying conditions may not notice any difference between a tonneau covered and an uncovered bed on efficiency, but that is not a controlled experiment so no definitive conclusion should be drawn from it about aerodynamic quantitative effects.

 

[Firn]

Who was doing the reporting?
And what was their method of making that determination?

My point is some things that are merely seat of the pants conclusions when tested scientifically turn out to be wrong - that is what about 1/2 of Mythbusters is about.

But you cannot seriously be arguing with wind tunnel tests that show the opposite, are you? That show that a tonneau cover on a pickup truck reduces aerodynamic drag?
That's a controlled test with precise instruments, not an anecdotal observation based on imprecise data.

People used to think a cannon ball would fall faster than a pea, based on their intuition, their guts, a seat-of-the-pants conclusion, but Galileo showed that was wrong with a scientific experiment.

My yard may be flat, but the earth is round.

I can draw a circle with a compass for example, and think that I can measure the circumference with a tape measure, and measure the diameter with a ruler, and then know precisely what the ratio between them is. Alas, the ratio of the circumference to the diameter of a circle is an irrational number (pi) that has an infinite and non-repeating decimal pattern and it cannot be expressed as a simple fraction of two integers, even though I thought it could be.

Time is not absolute either, it changes based on gravity and speed.
Clocks run slower at sea level than in at high altitude because gravity is stronger at sea level.
And gravity is the curvature of space-time based on mass and energy.
The clock at sea level is deeper in the curve of space-time.

Not to pontificate too much but people can have their own opinions and they may and often do differ.

But we ought to accept scientifically obtained, precisely measured data even when it counters our preliminary opinion about something.

Unless we can find an error in the experiment, the equipment, the calculations, we ought to accept it as valid.

Us Lightning owners trucking down the road for thousands of miles at varying speeds and under varying conditions may not notice any difference between a tonneau covered and an uncovered bed on efficiency, but that is not a controlled experiment so no definitive conclusion should be drawn from it about aerodynamic quantitative effects.

Actually, US Lightning owners trucking down the road for thousands of miles and not noticing a difference IS what matters, that is the practical application, that is where it impacts us.

And details matter, a lab test of a super cab with a 6 or 8 foot bed at 55mpg may show results, but that doesnt mean a crew cab 5ft bed at 70mph will have the same results, in the lab or in the real world.

In the end the practical effect IS what we are interested in. Arguing the theoretical can be fun, but these threads are trying to answer the impact to US.

 

[GDN]

My theory is if a tonneau cover made that big a difference Ford would be installing them on every truck. I would think they could claim it improves their CAFE numbers - or whatever numbers they try to hit. In the massive numbers they buy/sell they'd get them for $$200 each and add $800 to the price of the truck. Why would they pass u that mileage for the govt and that kind of profit?

I like to push conversations to the edge and will say that if you are worried about the amount of electric/gas savings from a tonneau cover and everything you need to carry can fit under it, you probably need to look at the bigger picture and dump the truck. Get you a smaller sedan and load it up, you'll still get better efficiency and now you're really saving. Bottom line to that however is that we aren't really all that concerned about saving electricity or gas, we just want to say we are doing the best we can to save a penny when we are driving the pound foolish thing down the road.

Don't get me wrong though, I don't care about the mileage as long as I have enough chargers along the route and I'm not giving my truck up either.

 

[Cbowe]

I can obsess about this stuff... but obviously if I were really concerned about vehicular efficiency, I'd be driving a Prius instead of a Lightning.

So, the theory is this: a tonneau cover lowers the Cd (coefficient of drag) of a pickup truck. That is almost universally true, for reasons that are probably intuitively obvious. The tailgate is an obvious apparent wind catcher. Try to carry a sheet plywood with the flat side facing the wind on a gusty day, and you will appreciate aerodynamic drag.

I've linked a study by SEMA that squares with my understanding of aerodynamics, and especially vehicular aerodynamics.
https://www.agricover.com/downloads/pdf/2007_windtunnel.pdf

Aerodynamic drag becomes increasingly dominant with increases in speed (going up at the square of speed, unlike rolling friction, which stays nearly constant). Power required, therefore, goes up with the cube of speed, (because you are both going faster and pushing harder). Power times time = energy usage. Range increases by the same factor as claimed fuel mileage increases.

If you do a lot of highway driving, (and charge at the robber barons' fast chargers) then a tonneau cover can justify its cost even if you have no other use for it. The range reduction you might imagine from the increase in weight is not measurable, because even the rigid covers are so light. (Do you stick your nose out the window and aim your sneezes backwards to give the truck a little boost?).

My range seemed to improve by about 10 miles (about 5%) after installing my ($100) fold up tonneau cover. However, I was driving fast on the day that I checked, and I don't bother to check on slow driving days, because I know there is no measurable difference. So read the article if you are so inclined, and figure in your style of driving. No "average" gain in range will likely apply to your use case... and my presumed gain won't apply either, unless you happen to drive exactly like me... on the same roads... at the same temperature... in the same wind conditions.

AC and heat have a significant effect on range, as does terrain and many other things. (That is why I used the word "seemed" above -- a definitive, reliable, repeatable test is quite difficult, if not darn near impossible.)

Related: My front air dam extension (the retractable part that extends at 40 to reduce aero drag) fell off a while ago, and I have not been able to detect any difference in range. I tend to drive at close to the speed limit. Maybe if I drove at 20 over all the time, I'd notice a difference.

I did a video on this did it on an off and it made no difference

 

[2sleep]

Have not read all of the posts so someone may have mentioned this before. These covers are not weightless. Neither is the stuff that I carry around in the frunk or cab that I rarely if ever use. Things like the 110/220 charge kit, trailer hitch, air mattress setup for the back seat, rear floor coverings, etc. If you are really obsessing over your mileage, go for the low hanging fruit first. Keep your speed at 55 MPH, don't run your heater or A/C or your stereo, dim your interior lights and put your big screen to sleep.
Or just enjoy your truck!

 

[Cbowe]

Have not read all of the posts so someone may have mentioned this before. These covers are not weightless. Neither is the stuff that I carry around in the frunk or cab that I rarely if ever use. Things like the 110/220 charge kit, trailer hitch, air mattress setup for the back seat, rear floor coverings, etc. If you are really obsessing over your mileage, go for the low hanging fruit first. Keep your speed at 55 MPH, don't run your heater or A/C or your stereo, dim your interior lights and put your big screen to sleep.
Or just enjoy your truck!

Weight has almost no impact on range as shown by the video that Aging Wheels did

 

[PJnc284]

I wouldn't quite say no impact on range. Really depends on speed. More stop and go and that weight will certainly matter. At interstate speeds, aero is the killer.

 

[2sleep]

So I could load the bed with sand and have virtually no effect on range!

 

[Cbowe]

So I could load the bed with sand and have virtually no effect on range!

If you stuck to the weight limits of the truck correct it would have very little impact as compared to aero for towing as an example or in this case the substantially less weight that is being talked about here with a bed cover. It would basically be within a statistical margin of error

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