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Originally Posted by IMADOGMAN
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What makes it obvious? Have you done any wind tunnel testing, or is it just that you think that the tailgate is a drag inducing item when it is up? I don't know if anyone has had their Titan in a wind tunnel, but all of the other trucks that I have seen tested in the past...had LESS drag with the tailgate up. The air inside the bed acts as a cushion, allowing the airflow to pass over the tailgate where it joins the air from the sides and bottom with less turbulence than with it down. Eyeball aerodynamics assumes that it has less drag, but tests have shown otherwise. Maybe someone who has access to a wind tunnel, or who has a friend in a college engineering class could have them do a wind tunnel test on a model Titan...any takers?
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I did exactly that in Senior Design back in college, around 13 years ago. Actually tested a 1/24 scale late-80's Nissan 4x4. With only tailgate, with bed cover, with a few different shaped toppers, and final test was to cut out the tailgate from the back. I don't recall all the numbers. Problem was with a 1/24 scale model, we were not able to simulate actual highway speeds in the 80 mph tunnel we had. We would have needed to run about 200-300 mph air to have an equivalent Reynolds number, due to the small size of the model. I also researched other full-sized tests too. The bottom line is that it depends on the size of the truck and the length of the bed. With a full-sized truck with very short bed, opening the tailgate hurts. With a long bed, it can help. Some of the truck mags have tested this before when the tailgate nets were popular. It depended on the truck as to whether it helped or hurt. Flat bed covers always help. Rectangular toppers hurt (bad). With toppers, the more sloped the rear is, the better. The absolute best setup was a triangular topper that was sloped from the top of the truck cab to the top of the tailgate. Much better than any other.