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Old 01-23-2010, 05:36 PM
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Originally Posted by HoustonHemi View Post
As aerodynamic drag inreases eponentially as speed increases, (not linear) I think, at least for the guys with better results at higher speeds, perhaps they have the 3.21 or 3.55 gears and may be just getting the Hemi up into it's most efficient rpm range, or, at a RPM range that doesn't 'lug' the motor.

Originally Posted by HoustonHemi View Post
The 'cyclone effect' is interesting,,, but if it means I'll have to drive 80 mph,,, eh, well, 'no thanks'.

Now, as far as the Tonno helping or hurting, I can't absolutely confirm either, but,,, Beaumont trip 1 was without tonno, and all the rest were 'with Tonno'

(Also, please keep in mind the truck had >1,000 miles on it during 'Beaumont 1")
You shouldn't need to drive that fast to get that "cyclone effect". There was an episode of Mythbusters where they were testing pickup truck gas mileage, and they showed a pickup in a little wind tunnel to demonstrate what was going on in the bed. I'm not certain what speed they had it going in the wind tunnel, but I'm pretty sure it was slower than 80.

With tonneau covers, I think the size of your bed might dictate how much of an effect it will have on your gas mileage. My friend has an F-250 with an 8 foot bed, and when he had a soft tonneau cover on his truck, he saw a significant improvement in gas mileage (sry, can't remember the exact numbers). I've heard of others with less significant improvements after putting a tonneau cover on their trucks.
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