Does a tonneau cover safe fuel





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  1. #1
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    Default Does a tonneau cover safe fuel

    A friend told me that has a ranger d/c that driving without a tonnue cover saves fuel. Who can confirm this?

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    Default Re: Does a tonneau cover safe fuel

    Makes no discernable difference.

    If you want to save fuel, brake less, drive slower. Its that simple

    https://youtu.be/r3aqHbD-O9E

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    Default Re: Does a tonneau cover safe fuel

    Quote Originally Posted by Philliplau View Post
    A friend told me that has a ranger d/c that driving without a tonnue cover saves fuel. Who can confirm this?
    Probably true, my Corsa sport 1400 ute delivers beter fuel consumption without a tonneua cover
    Last edited by Sebastiaan; 2020/04/05 at 08:49 PM.

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    Default Re: Does a tonneau cover safe fuel

    Actually feels a bit counter intuitive.

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  6. #5
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    Default Re: Does a tonneau cover safe fuel

    When I still had a bakkie I didn't find a measurable difference. But it was a single cab. You'll probably have to check airflow over the vehicle

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    Default Re: Does a tonneau cover safe fuel

    The theory is that the airflow over a vehicle's roof causes an anti-clockwise vortex movement of the air behind the vehicle. Therefore this vortex of air will be "trapped" in a bakkie's bak and cause extra drag. Whether this is true or not I have no idea.

    What does make sense to me is that the smoother the surface air has to travel over (like with a tonneau cover as opposed to without), the less resistance it encounters and therefore the less drag it causes?
    Last edited by EttiennedK; 2020/04/06 at 03:00 PM. Reason: spelling
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    Default Re: Does a tonneau cover safe fuel

    Different opinions on this.

    Tested it on my KB (single cab). 5 Tanks with and 5 without. I really could not see a difference.

    Saw real difference driving 110km/h vs 120km/h. Ask me I've tested all the different driving scenarios.

    I could even measure difference in consumption with tire pressure.

    Nothing worth while from my testing. But nothing stops you from also testing





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    Last edited by hbannink; 2020/06/04 at 08:38 PM.


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    Default Re: Does a tonneau cover safe fuel

    Yeah driving that 10km/h slower makes a HUGE difference. When taking the trip down to the coast a bunch of people driving along, the others always ask me "why do you drive so slow". Then we get down there and my CR-V clocks 17km/l at the pump, loaded, and suddenly they see why.

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    Default Re: Does a tonneau cover safe fuel

    No difference on my bakkie.

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    Default Re: Does a tonneau cover safe fuel

    Quote Originally Posted by Toxxyc View Post
    Yeah driving that 10km/h slower makes a HUGE difference. When taking the trip down to the coast a bunch of people driving along, the others always ask me "why do you drive so slow". Then we get down there and my CR-V clocks 17km/l at the pump, loaded, and suddenly they see why.
    yep

    and you need to drive a REALLY long way before you get a meaningful difference in driving time

    The Wrangler jumps from 11L/100 @ 110 to 14L/100 at 130..........so driving slower takes me 8 minutes more and saves me R50

    If I drive to Cape Town at the speed limit, it will take 10 hours. And I'll use around 156L.
    If I drive 10km/H slower, I'll get there in 11 hours and save 24L. That's almost R400.
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    Default Re: Does a tonneau cover safe fuel

    Not quite the same, but I remember Mythbusters doing a similar experiment.

    https://www.coloradofans.com/threads/mythbusters-tailgate-up-or-down-for-better-gas-mileage.99016/


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    Default Re: Does a tonneau cover safe fuel

    The big problem with bakkies particularly the larger modern bakkies is they have a much larger frontal area than a normal car.The drag coefficient has improved over the years on some vehicles but overall the values are still pretty bad.If you look at the drag equation (That is is you are really that interested.... or that bored you can google it!).you will see that the biggest factor in increasing drag is speed so just slow down as the other guys have been saying.
    As for if the cover reduces drag or not ,from my experience I could not see a difference myself on the bakkie I owned. (A single cab Nissan hardbody ... many years ago).

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    Default Re: Does a tonneau cover safe fuel

    Ieave the tailgate open

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    Default Re: Does a tonneau cover safe fuel

    Quote Originally Posted by desdrake View Post
    Ieave the tailgate open
    You mean ... leaf it open..
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    Default Re: Does a tonneau cover safe fuel

    Just my 2c worth, but what I found with my Nissan, a few years ago, was the top speed of the pickup increased considerably with a tonneau cover, OR a full load bed, (not necessarily heavy).
    Lets just say that I had the opportunity on empty good roads in excellent weather to experiment with a variety of loads, on the same road, in similar environmental conditions.

    I think speed has much more effect on your fuel consumption than aero, especially where you will be doing the vast majority of your driving, say at less than 80km/h.

    Hard acceleration and hard braking as well, will have a significant effect on your consumption.

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  20. #16
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    Default Re: Does a tonneau cover safe fuel

    My experience - Had work done on my canopy ( D Cab). Fitted tonneau cover. Economy improved nearly 1 km/L.

    Open tailgate will also give big improvement.

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    Default Re: Does a tonneau cover safe fuel

    From a video done by the myth busters awhile back the air moving over your cab gets trapped by the tailgate and forms a vortex. This then gives the following air something to "slip" over. Dropping your tailgate worsened the drag / fuel consumption.

    https://youtu.be/xocaC15WwA0 This video explains tailgate up principle nicely.

    https://youtu.be/r3aqHbD-O9E This is a Mythbuster episode where they do the three way test / tailgate down , mesh tailgate and hard cover etc
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    Default Re: Does a tonneau cover safe fuel

    Quote Originally Posted by desdrake View Post
    Ieave the tailgate open
    Many many moons ago in the days of the little 1200 cc Datsun bakkie - the little one with cab and loadbed being one unit, a publication did a test to get some answers on this same question.

    The best fuel consumption and highest top speed was obtained leaving the tailgate open.

    The explanation for this phenomenon was that the closed tailgate created a vacuun behind the bakkie's tailgate which created an air-brake effect.

    Incidentally, in 1964 Datsun sold a 1200 cc one ton bakkie with a ladder frame that was as tough as nails.
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    Default Re: Does a tonneau cover safe fuel

    Have actually tested this. Fuel runs at a constant speed of 100km/h with and without a cover, also with a tailgate down. Variance is 0.2L /100km. This effect is nothing is general running day to day.

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    Default Re: Does a tonneau cover safe fuel

    Tailgate closed is what CFD is showing us : http://xplrcreate.com/2019/08/08/aer...losed-vs-open/

    Interesting - effects of the fitment of a roof mounted LED bar (on this vehicle) : http://xplrcreate.com/2019/02/06/led...-aerodynamics/
    The results of the aero analysis with the LED bar turned out to be more drastic that expected. Although it didnít necessarily add any significant cross-sectional area, the light bar really messes up the smooth airflow over the roof of the truck, which increases the drag force to 853N. This is a 7% increase, and drops the fuel efficiency to 17.4mpg. Iím not saying that you shouldnít do it, but if you are going to install a light bar on a truck, you will see a roughly 1mpg drop in gas mileage.
    Also see PDF Effect from Accessories on Pickup Aerodynamics by Computational Fluid Dynamics
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    Last edited by PieterOos; 2020/04/07 at 10:31 AM.

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