Very interesting thread here on the Pecos. I've got the Brazos and I've noticed the consistent theme with airflow and temp consistency issues. I have also experienced the same and will highlight my thoughts, experiences, and theories here as well.
As others have noted, these cooker get almost too much airflow. If you try and run it like an open offset, the baffle and draw of the stack pull all the heat underneath your food and you get bad bottom burn. If you manage by temp at grate level and run at the temp you want to cook at, food takes a long time to cook through. If you close it down you get a dirty fire using the supplied coal grate. Not only that, with the stack wide open the stack pulls heat out of the cook chamber faster than the firebox can replace it.
I've noted that by using an alternate coal grate you start to move in the right direction. That gets heat a little closer to the cook chamber. A well designed open offset should create some backpressure in the cook chamber. I'm beginning to believe that is why Old Country left the oriface going to the stack at 4.5". They know that too much heat leaves the cook chamber too quickly. What I don't understand is why they haven't just fixed it completely.
I haven't done any math, but I would venture an educated guess that the stack should really be 3.5" to 4" in diameter, and should be 2 ft taller. I have tested this by running the FB with the door closed and using only the damper on the door, while closing down the stack damper to about the same relative ~ 3.5" size. This creates some backpressure in the CC and allows the temps to even out and still provides ample airflow for a clean fire. I can leave the FB door damper open and adjust my temps with the fire if needed. I prefer to cook in the 250 - 275F range most of the time. I'm toying with the idea of cutting out the heat deflector to run this way as well. It impedes the heat's ability to rise up in the CC quickly and then move across your food and out the stack. If we wanted heat under our food we would have all bought a reverse flow setup!
Of course, smaller offsets are harder to run than big offsets, but there is a significant price gap unless you build your own. The trade-off in running this way might mean running at 225 F to 250 F as the heat will be around the meat longer as the air will not be moving as quick.
I've done some dry testing this week and this so far seems to work well, but it will need more experimentation. In theory, it makes perfect sense and I think I'll see more improvements if I cut out the deflector when running the cooker this way. I'm half tempted to cut off the stack and build a new stack with a collector as well, as when you have back pressure you get a hot spot near the stack. I'm also half-tempted to just set out to build my own, but we shall see if that materializes. I have some friends that could make it happen, so one never knows.
I'll post my further findings here and hopefully it will help!
