First of all, let me say thank you for this site. I've been lurking here for a little while and have learned a lot by reading various threads.
I got my first smoker this spring, and have been having a blast. It's a Char-Griller Pro w/ SFB, and I've done about seven smokes in it, and talk about tasty.
This is a little long, but there's a question after all the background.
I've added a fire basket built out of expanded steel as big as I could make it and still fit it through the door. I've added two CharBroiler thermometers to the lid, one on each end. I've added the chimney extension down to the front left of the grates. I've also added a baffle in the firebox to limit the amount of air that can flow past the bottom of the fire basket and into the smoking chamber without either passing through or over the fire basket, and a baffle in the smoking chamber to eliminate "line-of-sight" to the fire. The smoking chamber baffle is 8" wide and long enough to extend from front to back of the chamber just above the firebox opening.
I have not built baffles through the entire chamber, nor have I added any gasket along the lid, or any other insulation.
I have tried using the main chamber charcoal tray as a baffle, but haven't done it that way the last few times I used the smoker.
I'm having a temperature issue I hope someone can help with. As I stated, I have two CharBroiler therms that I've added to the lid, one on each end, about 5" from each end. It still has the factory therm in the lid. I also have a Maverick ET-73, and a Taylor (don't recall which model) that I picked up from Lowe's. All have been tested in ice water and boiling water, and all (including the factory therm) read within 5 degrees of each other. Actually the ET-73 is the least accurate of the bunch. The food probe reads boiling water at 215. All the rest read boiling water at around 210 which is more accurate for my altitude.
OK. After all that background, here's the issue: The last smoke I did before I had the ET-73, was an 11.5# brisket. This only took 4 hours to get to an internal temp of 190 at a chamber temp of 225-240. This seemed way too fast, but there it is. After I got the ET-73, I lit it up again and had the Taylor probe stuck in a potato right next to the smoker probe for the ET-73, in the middle of the chamber. The two therms in the middle of the chamber were consistently reading about 100 degrees (no, that's not a typo, one hundred degrees) higher than the other therms.
Does that make a bit of sense? Can I really have that big a difference between the center and the edges? (Remember, I've tested all the therms.)
Since I have only had the ET-73 for the most recent smoke, I've been relying on the other therms for chamber temp, and the Taylor for food temp. I've struggled with keeping the temp up and in several cases the highest I could get was 200. I had initially chalked this up to choking the fire by adding too much charcoal, but now I'm not so sure. Even with the temp readings as low as they were, things have cooked successfully.
This would indicate that when I did the brisket, the temp at the center was really closer to 325 than 225. That would account for the short cook time.
As an aside, even cooking that fast, it was really tender with a very nice smoke ring. (Sorry, no Q-View, so I guess I didn't really do it. )