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  • #1

    Tonneau cover

    Been running my truck for years with the same setup mph has always been 115... For drag week I made a tonneau to keep thing cover up... and on drag week my mph was down 113 a every track... Get home and do some testing 113... Seem funny that it has ran 115 around 100 passes maybe more but a tonneau on and it slows down 2 mph... in the spring will test with it on than off same day see whats up... has anyone had experience with a tonneau
    Drag week 2009 Quickest street rod
    Drag week 2010 Quickest street rod
    Tags: None
  • #2
    Yes. Back in 2009-10 I ran the El Camino at the local dragstrip several times 'just for fun' (I'm by no means an accomplished or knowledgeable racer). With tonneau on best mph was consistent at 106-107.

    At the recommendation of one of the local hot shoes I removed the tonneau and ran with tailgate down. No other changes. Over half a dozen passes the car ran 2-3 mph quicker every time, but with minimal change in ET (prob due to crappy 2.0 sec 60 ft averages). I never thought to RAISE the tailgate and see what result that change might have had.

    I am sure anyone skilled in the science of aerodynamics could explain the improvement.
    Last edited by mlcraven; November 3, 2013, 12:20 PM.
    Michael from Hampton Roads

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    • #3
      Mythbusters did a thing on tailgates.. Up or down for mileage..they determined that with it open, the air off the roof pushed down on the opened gate, making worse MPG, with it closed, the air flowed over the top of the gate..thereby increasing MPG..
      If that applies to speed on the track or not.. I don't know..
      It would seem to me a tonneau SHOULD get better speeds as you don't have dirty air.. More streamlined..
      But the best way really is real world testing..

      Guess more guys need to chime in...

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      • #4
        Put a go-pro camera on the back window. Put some tassles on the tonneau cover. Colored yarn taped at intervals will work. Just don't take your wife's expensive cashmere yarn for this. They will tell you what the air is doing. Then do the same thing across the bed floor and tailgate with the tailgate up and down. Do it at the track when you can get up to 100 mph because the air will do different things at that speed than at 60 mph.
        BS'er formally known as Rebeldryver

        Resident Instigator

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        • #5
          I'm asking Santa for a basic Go-Pro package...and an Atomic Hot Rods deluxe 3-DVD set. End hi-jack.
          Michael from Hampton Roads

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          • #6
            Were you using a solid tonneau cover, or a fabric type?

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            • #7
              Don't confuse the vertex for air flow you need something heavier than yarn to check volume
              2007 SBN/A Drag Week Winner & First only SBN/A Car in the 9's Till 2012
              First to run in the .90s .80s and .70's in SBN/A
              2012 SSBN/A Drag Week Winner First in the 9.60's/ 9.67 @ 139 1.42 60'
              2013 SSBN/A Drag Week, Lets quit sand bagging, and let it rip!

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              • #8
                on all of the new trucks, you can see a lip over the end of the tailgate that sticks out roughly an inch or so. I think they are a vortex generator of sorts and help pull the air off the back of the gate into the airstream coming over the bed. I left about 2" of plywood on my redneck tonneau (2x4's and plywood). I never checked it without the lip over the tailgate, but I can say in general that I saw about 10% better fuel mileage so at some point, the cover is doing it's job. Your truck is way too pretty to start bolting junk like that onto it, but you might look at pulling the tailgate *and* putting an elevated ramp in it that starts at the front of the bed at the top of it and angles down to bottom of the end of the bed.

                I've been wanting to do that or a half a cone shape in the bed, but I've been working the truck pretty hard lately so there's been no real "control" driving. If it get's moved, it's full. Coming back on the same path isn't consistent for a wind load which might be a good test because a head wind impacts my mileage more than a load does.
                Flying south, with a flock of bird dogs.

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                • #9
                  I made the cover out of a 1x1 angle frame cover it with 1/8 plywood then convertable top material maybe is 20 pounds. will TNT in the spring. will be starting a new post going to change the shock location, converter this winter will be busy
                  Drag week 2009 Quickest street rod
                  Drag week 2010 Quickest street rod

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                  • #10
                    This experimental article explains it in detail: Tonneau Covers and Gas Savings

                    A light-weight soft cover can effectively increase MPG by 10%. But if you install a hard cover, the effect is not obvious as the weight increases.​
                    The Real Truth About Tonneau Covers and Gas Savings
                    https://mostplusauto.com
                    In the world of pickup truck enthusiasts, one of the most discussed potential benefits of a truck bed cover is its impact on fuel efficiency. From an aerodynamic perspective, a truck bed cover can reduce drag by streamlining airflow over the truck bed, potentially improving miles per gallon (MPG). But does it work that way in the real world? We often get questions from customers during the sales process: Can a truck bed cover help improve MPG? How much fuel efficiency can it help improve? To better answer our customers' questions, our team of experts conducted two experiments, one at highway speeds and the other in daily use. Let's take a look. Experiment 1: On the highway Initial Setup and Preparation We used our own pickup truck for this test. The test consisted of two parts: driving a specified distance on the highway without the tonneau cover installed and then repeating the same route with the tonneau cover installed, all done on the same day, with consistent driving conditions throughout. The first thing to do was to establish a baseline for the truck's fuel efficiency. Both experiments were conducted with a full tank of gas. We set the cruise control to a steady 70 mph to ensure a consistent speed throughout the drive. The route chosen was pure highway driving, minimizing any variables that could affect the results, such as stop-and-go traffic. At the start of the test, the odometer read 187,000 miles. The First Test After driving 163.5 miles on the highway, we arrived at a gas station to refuel and calculate the MPG. The truck consumed 11.6 gallons of fuel during the trip, so the MPG was about 14.06. While not impressive by today's standards, it provided a solid reference point for subsequent tests with the tonneau cover installed. The Second Test We installed a soft roll-up tonneau cover on the bed of the truck. The cover is designed to reduce drag by creating a smoother surface for air to flow over, theoretically reducing the amount of fuel needed to maintain a given speed. Aside from the tonneau cover, there were no additional items in the bed of the truck, which is unlikely to have any significant impact on the results. After securely fastening, I drove along the same highway, again using cruise control to maintain a steady 70 mph. Since we wanted to get the results as quickly as possible, we shortened the drive to only 109 miles, but the other driving conditions were the same. After completing the drive, we arrived at a gas station and refueled the truck, then calculated the MPG. This time, the truck consumed 7 gallons of fuel in 109 miles, resulting in an MPG of about 15.72. This represents an 11.82% improvement in fuel efficiency compared to the test without the tonneau cover. Results and Analysis Based on the results of this experiment, it seems that the tonneau cover can indeed help improve fuel efficiency, at least under the test conditions. The 11.82% increase in MPG observed in this experiment is consistent with claims from various manufacturers and online sources that indicate cargo covers can improve fuel efficiency by up to 10%. Experiment 2: Daily use Initial Setup and Preparation This was a real-world simulation. The experiment was simple, we drove for 20 days without a tonneau cover installed, and then another 20 days with the tonneau cover installed. In the previous experiment, our team calculated the MPG ourselves, which may have been inaccurate. This time we tracked the miles per gallon (MPG) using the on-board diagnostic (OBD) tool, which reads the data directly from the truck's computer. We believe that this will produce more accurate data. The First Test For the first 20 days, we drove our usual route without the tonneau cover. This route included driving to work, running errands, and picking up the kids, while maintaining a consistent driving style and speed. The OBD tool was set to automatic recording mode, recording data while the truck was driving. The results are as follows: Average MPG: 13.1 mpg Average speed: 39 mph The Second Test We installed our best-selling soft roll-up tonneau cover and ran another 20-day test. This cover is nothing special, just a common, practical option designed to protect the cargo compartment. We then repeated the same driving routine for another 20 days, recording MPG data as before. The results are as follows: Average MPG: 13.7 mpg Average speed: 38 mph Results and Analysis At first glance, the tonneau cover does improve fuel efficiency, by an average of 0.6 MPG. However, it is important to note that some variables could affect these results, as the two experiments lasted for a long period and were subject to uncertain weather temperatures, one in February and one in March, and the weather in March is generally warmer than in February. Warm weather may help improve fuel efficiency, as vehicles tend to run more efficiently in warm conditions. The small increase in MPG observed during the experiment may be attributed to these seasonal changes rather than the tonneau cover itself. In daily use, having a tonneau cover installed or not may not result in a noticeable increase in MPG. Should You Buy a Tonneau Cover for Fuel Efficiency? Based on the results of this experiment, while a tonneau cover may slightly improve fuel efficiency, especially when driving on the highway. It's unlikely that a tonneau cover will save you a ton of money at the gas station, but it can still help improve fuel economy over long distances. It will add up over time. However, in everyday use, it's hard to definitively say that a tonneau cover will significantly improve your truck's fuel efficiency. While there was a slight improvement in MPG over the 20 days of using the cover, other factors, such as temperature and driving conditions, make it difficult to single out the tonneau cover as the sole reason for the improved fuel efficiency. In summary, don't expect to see a big improvement in fuel efficiency simply by installing a tonneau cover. If you're considering buying a tonneau cover just to improve your MPG, you must weigh this potential benefit against other factors, such as cost, practicality, and the specific driving conditions you'll encounter. Our recommendations If you frequently drive long distances, consider getting a tonneau cover. Your wallet and your truck's gas gauge may thank you. One thing to keep in mind is that while all tonneau covers reduce drag if your tonneau cover is too heavy, it will also add considerable weight to your truck, offsetting any potential mileage improvements. That's why we strongly recommend that the most fuel-efficient tonneau covers are soft roll-up or soft folding bed covers, which are light enough to be very effective in helping you increase your MPG. If you have any questions about your tonneau cover, please contact our product experts.

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