8 lb pork butt.....14 hrs. Let it run on out to 25 hours before shutting down. This was done with my new air distribution manifold pipe in the bottom underneath the coals.
I played around with the tuning a little bit at first but basically you can see how little the blower actually runs... With the blower not set to come on till 20%, it basically runs 20 to 25% most of the time... Up to about 30% max. Does a great job. Only got a little wonky as it got very late with very little coals left.p
Several observations about this with the air distributor...... First is that the overall control is better.... But the instantaneous control is not as good as it can be with the air going in on the one damper hole in the side. With the air distributor pipe, it probably fluctuated by plus or minus 1.5°. without that I've run plus or minus 0.5° for extended time. the difference is that when more air is bypassing the coals, it tends to buffer the effect of the heat it produces. With the air being introduced under the coals it responds immediately which is good but you always get about a 1-1.5F temp kick as soon as the blower blows no matter how gentle it blows. And a temperature drop when it doesn't.
But like I said overall it's good because of the instantaneous response it gets a hold of minor upsets immediately.
For comparison there's a cook of a brisket as well a couple of months ago.... No air distributor just the blower on the damper hole. You can see how much more the blower ran on average then when it was introduced below the coals. This is because of how much air is bypassing, it's a lot less efficient.
So when the air is introduce below the coals it's much more efficient... You burn less colds because you're not heating as much air that's bypassing the coals also. In the pork butt cook I did I used about 80% of my capacity ran for 25 hours and still probably had several hours of coas left. Introducing the air through a damper hole I was maxed at about 24 hours capacity with a full load. So i estimate it's probably about 45 % more efficient to put the air beneath the coals.... And that now my maximum runtime would be something like 35 hours. Not that I would ever need to run that long but just saying it's going to use less charcoal. Picture of Ash in the bottom after 25-hour running at 270 as well.
I'm a bit jealous of the absolutely straight line the gravity smoker can draw.... But then again it weighs hundreds of pounds more than my little WSM 18. I have been toying with the idea of putting a heavy iron weight inside of mine to help maintain temperatures stability. You can get a 25 to 35 lb Olympic wt disk, sandblast the paint off of it, season it, and place inside. That will surely help to make temperatures more stable in a WSM. The WSM-22 could probably even take a 45 lb weight disk or 2. Not that it really needs it or anything but you know.
If only I could find a used Rusty one cheap... They're a bit pricey new today.
