Temperature Control

[McFlyfi]

I am new here, but not new to cooking or BBQ So Cal Style. I consider myself a more than competent backyard cook. I have however, decided try my hand at meats that I have not cooked before, several of which I have not even tasted before.

In November, I decided to add a SnS Grill with the SnS basket to my gear. Over the last 5-6 months, I have taken my tri tip from good to something I would put up against anyone’s. I’ve dialed in the temperature for these short cooks (230-ish for about an hour and 15 minutes), but am beginning to branch out into longer cooks. And here is the question:
When does a temperature "trend" (either up or down) become something that you must address?

Example:
I was setting up a long term cook for pork shoulder and was expecting a roughly 8 hour time frame. I had two pieces of pork shoulder (Boston butt), one at about 3.5 pounds and one at about 4.5 pounds. The meat went on the kettle at 9:00 am, I was shooting for a 260-280 temp range, as my lone previous experience with a small pork shoulder at 230 took way longer than I thought it should (8+hours).
At about 12:30, the temperature dropped 15 degrees in less than 10 minutes. I haven’t seen a drop like this in any of the dozens of short cooks, the one other long cook, and the two long test runs I have done. After 10 minutes, I decided this "trend" was worrying. I opened the kettle, there was plenty of fuel, so the fire wasn’t dying due to lack of fuel. I closed up the kettle and opened the lower vent for a few minutes, and right back to target temp. I had a few other variations that I made, including adding more fuel at the 6 hour mark.
If food wasn’t involved, I think I would have just let it go to see what would have happened. It would have been interesting to file away that info.
When I first got the SnS, I did a couple of test runs without meat, and on both tests, got very consistent temps over two separate 6 hour runs. The second run, the temp never varied by more than 3 or 4 degrees in either direction.
So where do you draw the line? Or is there one?
Obligatory pics attached.

[GolfGeezer]

I do have a Jumbo Joe with an SNS basket, but I have not used it for smoking or long cooks. I have a pellet pooper which holds whatever temp I've chosen pretty tightly. However, from what I have read from many, many posters here on The Pit, temp swings are not a huge concern unless it is really indicating that your heat source is failing or out of control. Swings from setpoint of +/- 25* are not a big deal. Running from 225* to 300* mainly impacts cooking time, not result.

So, if not an indication of heat source failing or out of control, I would say you are fine. Just keep monitoring the way you are with those temp probes.

[rickgregory]

Strongly agree with GolfGeezer - temps don't really matter to quality if they're 200-300. HOWEVAH... obviously the faster the cook, the less time for smoke. That won't really matter if you're doing long cooks - the difference in smoke between a 9 hour cook and a 14 hour cook is marginal at most. This is likely different for pellets, where you get much less smoke at hotter temps.

PS: "...I closed up the kettle and opened the lower vent for a few minutes, and right back to target temp. "

One thing to be aware of is that the kettle takes some time to adjust fully to changes. So you can get in a 'chasing the temp' loop where you open a vent to get it to go higher... then it overshoots 20 mins later so you close it and it drops... but undershoots.... aiiieee!

BTW - your regular oven doesn't tightly control temps. 50 degree swings around the set temperature aren't atypical.

[Panhead John]

Agreeing with both Rick and Golf Geezer. 15* temp swings are nothing to worry about. In fact, almost any charcoal cook you do is gonna vary in temps to some degree. As they also mentioned 25*-30* temp swings aren’t uncommon and will only affect your cook time, not quality. It’s my opinion you can’t really compare temp swings, or lack of, in a grill without meat in it, to one with meat in it. The meat sweating and moisture inside the grill might affect the temp inside the cooker.