Quote:
Originally Posted by Concrete
I have considered that - but it shows up in the throttle position too
so it is driving a heavier load on the truck
I did get it adjusted from -2 mpg to zero loss 
the best I can figure is that the air is not rolling happily behind it |
Neat vid. I don't know what to think, so I'll just throw out some ideas:
- Maybe the shoulders want to be more rounded at the rear of the extension.
- Maybe the base of the extension should be flush with the side of the truck and twist upwards to meet the top.
- The extension changes the interaction with the tonneau and whatever "bubble" was created before. Maybe you accidentally added drag by removing a helpful section of the bubble.
I'd like to suggest trying a set of comparisons between cab extensions but without the tonneau, and maybe with a partial tonneau. I have a suspicion that the reason a partial tonneau can outperform a full tonneau is that a full tonneau eliminates the "box" that would otherwise support the stationary vortex, i.e. "bubble". Maybe messing with that bubble will get you the results that have mysteriously evaded you. Worth a try?