Race with tailgate up or down or removed, Tonneau cover on or off? Answer inside
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10-07-2004, 09:31 PM
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Race with tailgate up or down or removed, Tonneau cover on or off? Answer inside
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Ever wonder what the aerodynamics are of removing the tailgate or the tonneau cover? Leaving them on is better? others say removing it.
What is the answer?
well I found this intersting article Quite interesting.
Link to entire article
Ever wonder what the aerodynamics are of removing the tailgate or the tonneau cover? Leaving them on is better? others say removing it.
What is the answer?
well I found this intersting article Quite interesting.
"Recently, Kevin Cooper of the National Research Council of Canada published a paper through the SAE which proved that removing the tailgate from a pickup truck not only doesn't help gas mileage, it actually makes it worse... Removing the tailgate looks like it should re-duce drag, but a number of processes, including wind tunnel testing and computer modeling, proved it doesn't."
"Several methods-including CFD flow analysis-were used to reach the conclusions presented in Kevin Cooper's SAE paper. Using a variety of popular make full-size trucks and a 75-mph wind speed, the vehicles were tested in a wind tunnel with the tailgate up, down and removed. One had a mesh gate made of duct tape. One had an adjustable tonneau cover that could cover various portions of the truck bed. The wind tunnel balance-measured all six components of aerodynamic force and moment. Drag coefficients (Cd) for the trucks were normalized so the focus could be kept on box aerodynamics. All the measurements showed the same basic results - a small increase in drag with the tailgate down and a larger increase with the tailgate off. These measurements were made with the vehicle directly aligned with the stream of air.
Another interesting result was that lowering or removing the tailgate caused a larger increase in drag on 61/2-ft. boxes than on 8-ft. boxes. Installing the mesh gate was shown to yield the worst results of all. In one example, the Cd increased from .48 to .53 with the mesh gate in place of the solid tailgate.
What does work is a tonneau cover. Interestingly, a partial 20-in. cover placed nearest to the tailgate did 88% as well as a full tonneau cover. On an 8-ft. box, the estimate is that the improvement in fuel economy with a full tonneau could be 1.35 mpg, or a saving of 243 gallons over 100,000 miles of driving. Conversely, the same vehicle without the cover and with a mesh tailgate got 1.28 mpg worse mileage than a vehicle with the tailgate up and no cover."
"Several methods-including CFD flow analysis-were used to reach the conclusions presented in Kevin Cooper's SAE paper. Using a variety of popular make full-size trucks and a 75-mph wind speed, the vehicles were tested in a wind tunnel with the tailgate up, down and removed. One had a mesh gate made of duct tape. One had an adjustable tonneau cover that could cover various portions of the truck bed. The wind tunnel balance-measured all six components of aerodynamic force and moment. Drag coefficients (Cd) for the trucks were normalized so the focus could be kept on box aerodynamics. All the measurements showed the same basic results - a small increase in drag with the tailgate down and a larger increase with the tailgate off. These measurements were made with the vehicle directly aligned with the stream of air.
Another interesting result was that lowering or removing the tailgate caused a larger increase in drag on 61/2-ft. boxes than on 8-ft. boxes. Installing the mesh gate was shown to yield the worst results of all. In one example, the Cd increased from .48 to .53 with the mesh gate in place of the solid tailgate.
What does work is a tonneau cover. Interestingly, a partial 20-in. cover placed nearest to the tailgate did 88% as well as a full tonneau cover. On an 8-ft. box, the estimate is that the improvement in fuel economy with a full tonneau could be 1.35 mpg, or a saving of 243 gallons over 100,000 miles of driving. Conversely, the same vehicle without the cover and with a mesh tailgate got 1.28 mpg worse mileage than a vehicle with the tailgate up and no cover."
Link to entire article
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10-07-2004, 09:43 PM
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Stan
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10-07-2004, 09:45 PM
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10-07-2004, 09:47 PM
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10-07-2004, 09:50 PM
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10-07-2004, 10:12 PM
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Originally posted by Ruslow
forgot to add that those of you who run with yourcover on and the tailgate down or off are worse yet!
forgot to add that those of you who run with yourcover on and the tailgate down or off are worse yet!
But I have experimented some with leaving my soft tonneau on and removing my tailgate... I have picked up about 1mph (In the 1/4) pretty consistantly with doing that...
Just my experience...
-Dale
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10-07-2004, 10:21 PM
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You should of but was it due to the weight savings or the areo?Try it this way.Weigh the tailgate and what ever else you remove and add that weight back into the truck then tell me what happens.Stan
PS look at your time slips and see WHERE the mph was gained?at the beginning or middle or end?
PS look at your time slips and see WHERE the mph was gained?at the beginning or middle or end?
Last edited by Ruslow; 10-07-2004 at 10:33 PM.
#12
10-07-2004, 10:32 PM
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Yep, I see people make this mistake all the time. When you have a bed cover and tailgate, the air flows over the cab, and then over the back of the truck with minimal downforce. When you run with no bedcover and no tailgate (or tailgate down), the air comes over the cab, and instead of flowing over the bed, it gets sucked down and puts downforce on the bed floor. If you don't have a bedcover, it's best to just leave the tailgate up, because that creates a pocket of stagnent air in the bed that acts similar to a bedcover. As for the weight issue, I'd rather have a few extra pounds over the back of the axle to aid traction. That's why I always run with both my bedcover and tailgate in place.
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10-09-2004, 02:34 PM
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#15
10-09-2004, 04:14 PM
