I don't have any 2500 info near me.And I don't know when the model change occurred.
The 2008 1500 2wd was rated at Cd 0.44 and 34.49 sq-ft frontal area.
The same year Quad Cab was rated at Cd 0.52.
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The 2013 RAM 1500 has a model with Cd 0.363.It's the lowest drag full-size half-ton.
It has:
*Active suspension which lowers truck for highway
*Active grille-shutters
*Factory tonneau cover
This would be a good pickup to find and inspect.You could investigate the grille area and consider between it and your truck.
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*Feysel Ahmed (SP?) did a masters thesis on a RAM pickup using Computational Fluid Dynamics and a cap as you've illustrated returned a 19% drag reduction.
*I used an old Chrysler racing hull to create a cap which is paying for itself
With some boat-tailing,you can see from the tufts that it is allowing the streamlines to come back together without separation
Your proposed tail is even more 'aggressive',so you ought to do a little better,and I'm pushing 40 mpg at a constant 60 mph on a good day without any tail.
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I would recommend you not take the air dam any lower than your lowest under-chassis components.Ahmed tested this and it raised drag.Some members report similar results.
Check out that new RAM.
