I would like to update this. A few months ago i loaded my smoker up with 5 butts totaling roughly 38lbs. Though this method above seemed effective running dry i discovered its not as effective running loaded with meat. i struggled to get temps above 200 so i pulled this plate out and installed the diverter back in. I believe the more meat you put in it the closer the temps seem to get from end to end. Nothing burned, everything cooked at the exact same rate, & everything got the exact same color. Pretty impressed with it. There is only one thing that i have now changed since this cook and thats the exhaust. where it connects to the cook chamber there is a noticable lip. i cut that out so the exhaust opening was the full 5" and the air flow is unbelievably better, not only that during a dry run the temps got even closer.
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This diagram is how it ran for me loaded with butts with no mods. Cutting the lip out on the exhaust flattend that curve of heat. I was able to determine this diagram by moving probes around. I was getting so caught up on temps at the grate that i wasnt thinking about whats flowing around the meat. I only rotated the butt in the middle all the other ones stayed the same.
That's interesting. My Brazos has the same exhaust port opening as the Pecos, but my stack is 6" . I've thought about trying to cut that " lip " out also. IDK why Old Country would put a 6" stack on the cooker and then restrict the exhaust. Maybe there's more to the air flow dynamics there, than meets the eye.
And I agree with your diagram about air flow inside the cook chamber. I was trying to regulate end to end by using the FB door. That increased air flow which threw heat to the stack end .......... but it caused the heat to be bottom up on the stack half of the cooking grate. I had a couple cooks with some bad bottom burn, ribs and pork butt. The ribs weren't anywhere near done, but the bottom of the rack was burned badly. And I think the heat was more direct heat , than radiant convective heat.
I finally gave up on running it with the FB door partly open. Just run it as Old Country designed it to run.