Existential crisis-BBQ Guru, temperature probe/ Today's pulled pork

[BARDSLJR]

Folks, I am troubled of mind: the BBQ Guru- where to place the temperature sensor? Okay, for all intents and purposes, the BBQ Guru works pretty well and is a game-changer- excepting, of course, the buggy software, which regular drops its bluetooth connection with my phone, or the control screen goes blank and I have to reboot the entire Iphone to get it back- but that's not today's topic.

The BBQ Guru works great- a temperature probe sense the heat in the cooking chamber, the control unit pulses the fan off and on to maintain a relatively constant temperature (the real miracle of the BBQ Guru) ....but what IS that temperature? As I was ramping up the 32" KK this morning, I was noticing the difference- at points huge - between what the KK thermometer was reading and what the temperature probe was showing: and, moreover, it differed really, really widely depending on where I placed the probe. Center of the grill?- 280. Over by the side, near the handles of the grill top- 150. Towards the center, rear, 190. And so on and so on...So I am watching the temperature, trying to get it close to stablizing on 275 for my pork shoulder, as Franklin recommends, but what is "275*??? Is it the Kamado thermometer? The Guru probe in the middle? Or over by the side? Or in the center? I have resolved to go with the Kamado reading for consistency, and regulate the temperature relative to whatever the Guru reading says it is. So  my KK reading right now is right around 270*, and the Guru is reading 228* and keeping it there. Happily, pork shoulder is a very forgiving piece of meat and I can probably cook it anywhere between 230 and 330 and be just fine.

What do y'all do? If I were running one of those 1,000 gallon, 2-foot-long propane-tank offset smoker there would be some temperature variation closer to the heat source and at the far end of the smoker, but it would be relatively consistent across the middle 15 feet or so, and maybe a little cooler at the far end. But the KK has significant variation in temperature from over the heat source to the sides: so ultimately, I've decided that the KK thermometer will be my benchmark for establishing "275*" and the Guru will be my controller and I will use it to reach a given temp, and maintain it, but I won't rely on it.

[jonj]

You raise an interesting concept: what is the actual temperature at which we are cooking? I don't use a BBQ Guru, but the issue of probe location and temperature is universal. Is the probe exposed to any radiant heat (outside the boundary of whatever heat deflector you choose)? Is the probe on the same plane vertically as the meat? The KK dome thermometer will generally read higher than a probe on the main grate, and may or may not match that of a probe on the upper grate, depending upon its location front to back. I'll have to leave it to the engineers of the group to determine the temperature effects of any eddy currents within the KK body and dome.

All this you have already stated, so I'm not adding anything new except my practice. I locate the smoker probe (I use ThermoWorks) within an inch or two of the meat, isolated from any stray radiant heat from the fire below (Tony also insulates his probe from the conductivity of the metal grate but I don't bother). Once the KK temp is stable, I note the difference between the KK dome temp and the grate temp and, if they are within 25° degrees or so, call it good. I adjust the KK temperature according to the smoker probe, as it is nearest the meat. I am referring to a KK23, which is what I use for smoking. A KK32 or KK42, with their greater configuration variations in fire to meat location left to right, would likely be more complex. 

Incidentally, I suspect (and with no proof whatsoever) Franklin's pit temperature also varies as you note, left to right and upper to lower grates. One of the reasons I was initially interested in a Lang smoker (which @Tyrus has) is its design to have the smoke travel all the way to the non-fire side of the chamber before it comes back across the meat to the exhaust. I thought this was an excellent way to accomplish a number of positive things, one of which would be to stabilize the temperature.

 Since our high today is only 12°F, I wish I had some of your pork shoulder for the game later today.

[BARDSLJR]

I set up my 32" KK with two 8x12" disposable baking pans filled with water, on the first grate above the charcoal and wood, placed close to the center and about 3" apart. I used to use a larger single 18x12" water/drip pan, but I thought- and this is highly theoretical- that for purposes of good smoke turbulence throughout the cooking area where the meat is, I was better served to have a space between the two drip pans which also serve as heat diffusers, to allow some of the smoke and heat to come up directly from the center of the pit and some come up around the outside of the diffusing pans.

Consequently, I get very different temp readings as I move the probe around from the far perimeter, the area directly over the diffusing water pans (and immediately next to the meat) or to the dead center of the smoker, over direct heat. And all these readings differ from the Kamado's temp sensor.

By the way, I had 72" Lang hybrid before this- half for traditional smoking and roast and half for direct charcoal grilling. In retrospect, I wish I had just gotten a 72" all devoted to smoking/roasting- I think it would have had better air movement and been better for smoking and flavor. The false floor of the Lang design and reverse air flow works well, though, to eliminate obvious hot/cold spots in the working area of the smoker- very clever design and the construction quality was excellent. The reason I traded it out for the KK was a simple matter of labor and versatility. With the Lang, and I presume any other traditional offset firebox-style smoker, I think you are constantly adjusting fuel and airflow to try to maintain a near-constant temp. A good long 14 or 16 hour brisket cook is long, drawn-out chore- you really can't be away from the smoker for more than a maximum of 20 minutes or so. With KK, however, I can check about once an hour and the temp is very, very likely to be exactly what it was last hour, or so close it doesn't matter. AND I can ramp this sucker up to 800* or more to do high temp cooking, or use it for direct heat roasting and searing (like for steaks.) I really, really like my KK, especially now that I have learned a few tricks about ramping up and maintaining level temperatures. (And it is, objectively, a lot prettier than the Lang.....)

[jonj]

23 minutes ago, BARDSLJR said:

And it is, objectively, a lot prettier than the Lang.....

No question about it! 

[tony b]

I won't bore ya'll with talk about turbulent airflow (eddy currents - not bad for a non-engineer, @jonj!) Let's just suffice it to say that there's a lot going on inside a KK - both heat transfer and airflow wise. To the central problem at hand - where to place the temperature probe for the Guru to get the best representation of the local temperature for the piece(s) of meat being cooked? As noted, I insulate the probe off the grate to get a better reading of the actual air temperature around the meat. YMMV  You want to place the probe fairly close to the meat, but not so close that the temperature of the meat itself influences the probe temperature reading - the meat is ALWAYS going to be colder than the cooking temperature. I typically shoot for a couple of inches gap. Next, if doing an indirect cook, place the probe where it is shielded from the direct heat of the fire. With larger or multiple cuts of meat, this can present a challenge, in and of itself, once the grate starts to get crowded. I also prefer to center the probe front to back relative to the meat, when possible. As noted, there's usually a difference between the temperature near the front and in the back. If you notice the shape of the KK, Dennis has intentionally designed it so the airflow is predominately in the rear of the KK. And, don't forget that the center of your heat source is going to move around during a long cook, as the charcoal burns unevenly (unavoidable phenomenon of nature - chaos wins everytime! (aka - the 2nd law of thermodynamics!) But, once the KK is heat soaked, this shouldn't matter too much, relative to where the temperature probe is placed. Last piece of advice, when using the Guru - ignore the dome temperature reading, it's extraneous data in this situation. You either trust the Guru or you don't?

[BARDSLJR]

I don't (trust the Guru temp probe). The KK is always in the same place and always measuring the temperature the same way, so it is going to be my standard. RIght now at this moment (I am in the last two hours of the cook, when you want to raise the cooking temp on the now-wrapped shoulders- to 300*. The KK temp probe is reading right at 300. The Guru probe, which is lying on top of the grill next to the meat, shielded from direct heat, is reading 360*. I am okay with that. The shoulder has just started out of the stall in the last hour and is now steadily climbing towards 203*.

I've also ordered a higher end, supposedly more accurate and large face (3") oven thermometer which I will use as a reference point in the future.

[BARDSLJR]

And today's cook: first, the two pork shoulders, dry marinated overnight with Dizzy Pig Dizzy Dust. Second, Happy 32" KK, ramping up.... and lastly, four hours in and looking good.

[jeffshoaf]

2 hours ago, BARDSLJR said:

I don't (trust the Guru temp probe). The KK is always in the same place and always measuring the temperature the same way, so it is going to be my standard. RIght now at this moment (I am in the last two hours of the cook, when you want to raise the cooking temp on the now-wrapped shoulders- to 300*. The KK temp probe is reading right at 300. The Guru probe, which is lying on top of the grill next to the meat, shielded from direct heat, is reading 360*. I am okay with that. The shoulder has just started out of the stall in the last hour and is now steadily climbing towards 203*.

I've also ordered a higher end, supposedly more accurate and large face (3") oven thermometer which I will use as a reference point in the future.

try clipping the guru prove to the dome thermometer and see what its reading. If they're reasonably close, then you'll have good evidence that the grate and come temps - which we already know...

[Tucker]

From your phot w/ the two butts, I always put the probe with the probe tree directly in the middle on the main grate just back over the drip pan or your heat deflector.

This gives me the pit temp at the top grate level, the level where the meat is sitting.

This method has always given me the temp I set the guru for. I do not pay attention to the dome thermometer, it is usually a few degrees higher than the guru setting

[tony b]

@BARDSLJR From your picture of the butts on the grill, I can see that you've put the temp probe right against the grate and it's close to the edge of the drip pan (almost direct), so I'm not surprised by the high temp reading relative to the dome. You're measuring the grate (metal) temperature, not the air temperature. If you don't want to buy/build a "tree" for the air probe, just clip the alligator clip to the meat probe wire, so it's off the grate. Just don't get too close to the meat. 

If you don't "trust" the Guru probe, do a quick test of both thermometers - standard calibration technique - put both into a boiling pot of water and see what they read. Or next cook, follow @jeffshoaf suggestion. 

[BARDSLJR]

Tony, Jeff- great suggestions. I will try that. I had not thought of clipping the temperature probe to the meat probe. Tucker, your suggestion would work if I using just one heat deflecting pan in the center of the KK, but I used two smaller ones directly under each butt with about a 3" gap between them in the center, for-presumably- better smoke circulation. Of note to all- there is also a somewhat significant temperature differential left-right on KK as you can see from the photo. I put the smaller butt on the left and the larger on the right, and was surprised when the smaller required an additional 15-20 minutes over the larger one to reach 203*.

[tony b]

Not surprised by the left-right difference. The 32 has an oblong charcoal basket along that axis. Charcoal burns in a fairly random pattern, so no predicting how it will fan out from the initial spot where you lit it? As I said, the oblong basket has more room to burn in that left/right direction than front/back.

[Tucker]

I suppose the point you can take from my approach is to ensure the temp probe is not over direct heat and it is suspended in the air.

I don't have a 32, so I cannot relate to the variation of temp.