Great idea to test and get to know your grill. Thanks
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Good morning sports fans, turns out that the rain in today's forecast will arrive later than initially thought, not til nearly sundown, so I have time this morning to run this experiment.
SnS kettle with the insert, started the coals a while ago and will fill the water reservoir and add the chimney of unlit once it's good and going. Here is where I have the probes placed. If need be, after it's run for a while I might move #5 from smack in the middle out to the perimeter just to check the temp at the diametric oppositve of the insert - TBD.
I left the foil on the lower grate from yesterday's cook, because that's how I always run, no matter what I'm cooking I have that foil there to keep the drippings from fouling the inside of the kettle.
Updates as the morning proceeds. For SCIENCE.Last edited by DaveD; January 27, 2024, 09:32 AM.Comment
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Where is the lid vent located in this image? I always keep mine over the indirect side. 🔥🔥🐿️ -
MsTwiggy The vent on the SnS kettle is directly above the indirect side, yes indeed. Not at the tippy-top of the dome. They incorporated all the design tweaks that Weber users have done homebrew-style over the years, like pre-drilled port for temp probe wires below the rim, the smokehole, having the dome thermometer much lower down (reads within 20F of what I read on the grate routinely). Love this rig.
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Ignition sequence started. Guidance internal.
Houston, we have cleared the tower.
First dot is when I filled the water reservoir. Second dot is when I went to double check the probe numbering, because #3 is reading significantly higher than the others despite being furthest from the heat source. Third dot is where I dialed back the vents to hold temp, and fourth dot in the huge divot is where I TRIPLE checked the probe numbering, and it's a good thing I did because I had mis-recorded where #2 and #5 were placed - all good now.
Should be passing through Max Q shortly
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DaveD - Did you edit your original post to reflect the correct TC #'s?
Some of us be of addled wits and get confused easily.
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Smoker_Boy Sorry I missed this question - yes, I edited the diagram, and everything is now accurate in each post.
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It will be interesting to see your final results.
I ran a test yesterday and got a few results that were kinda puzzling.
I am waiting on FedEx to deliver my probe clips today so I can run another test and try to simulate a 8# pork butt.
I think the vertical temp difference is going to be surprising.
Or not.Comment
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DaveD - That was in a previous life. I got paid to destroy HVAC/R compressors.
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We have achieved stable orbit, and now I'll just let it run for the next several hours. Here's the latest:
The temps are starting to get closer together as the rig has stabilized. Will update again after lunch
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Update. Temps have continued to converge. I've made teeny tiny little adjustments to the top vent to try to keep things flat (three most recent dots), but even those have been enough to produce inflections. Probe #6 (located very near the SnS kettle's small probe-cable passthrough port) has jumped to the top spot. But the other five are the same to within about 15F at most, which is quite uniform.
Rain is still on track to get here around 5pm, so I will let this run another hour or so, then close all vents to get it to smother out so that it will cool enough to put the cover back on before it starts raining.Comment
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Final update. Four hours in, it is as Eric ecowper described in his comment on the post above. Significant differences at first, but by 90 minutes in things tighten up considerably. The outliers, showing temps noticeably higher than the rest, are probes 3 and 6 - both on the opposite side of the kettle from where the coals began burning, which is in the vicinity of probe 1. That's at least circumstantial evidence that perhaps some convection delivers hotter air directly opposite the hottest coals, but the difference is still no more than about 12-13F (about 6C diff at this temp range). But probes 1 thru 4 are basically identical.
Here's what the coal bed looked like about three hours in. Not even half have begun burning.
And just for completeness, here is how my vents were configured during this run. I closed the bottom vent completely and then slid it open just a tiny bit.
My takeaway from this experiment is that, at low & slow conditions, the potential for convection is a near-negligible effect. Provided one measures the temp far enough from the meat to avoid a "meat shadow", one should be plenty confident that the measured grate temp is reliably reflecting cooking temp.
jfmorris Jim, I'm happy to repeat this at the 350F/175C range without the water res next week to see if the behavior is any different. All for science, of course!
Hope this helps - it was a lot of fun to geek out on!
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DaveD EDIT: Never mind - I just saw you have a SNS kettle.
Also, do you think that having your bottom vent basically closed had anything to do with the temp spread?
(vent closed = very little convection)Comment
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I did the same thing as far as running my usual.
Hopefully I'll be able to present both sets of test data tomorrow. -
If you want to run low and slow, you literally HAVE to have either the top or bottom vent almost all the way closed. It really depends on how leaky your kettle is of course, but for those temps, airflow is fairly low. Especially on an efficient/insulated/sealed cooker like a kamado. -
jfmorris - I just get the idea that my bottom vents are open a little more than the SNS.
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DaveD and Smoker_Boy Thanks to you guys for your efforts!! Very interesting charts and results.Comment
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@DaveD - When cooking on your SNS grill, what location do you consider to be your "Control" temperature?Comment
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I usually leave my grate probe clipped at essentially location #4 as laid out in the above diagrams. In fact, if you look at the photos, you'll see it in that spot, just flipped around so that the tip of the probe is as close to the rim as I could get. If whatever I'm cooking has a shape and size that requires it, I'll shift it around, but that's its usual home.Originally posted by Smoker_Boy View Post
That said, I never did an experiment like this before, measuring at multiple locations on the grate, but now that I have, it's clear it's been fine at that spot. As I have said here many times, I am living proof that it's better to be lucky than good
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"I am living proof that it's better to be lucky than good." HA! I might have to steal that saying from you! -
Grillin Dad You'll be upholding a long, fine tradition... I stole it from someone too, and it goes back a long way...! Keep that lucky torch blazin'
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Thanks Dave, great info.Originally posted by DaveD View Post
I usually leave my grate probe clipped at essentially location #4 as laid out in the above diagrams. In fact, if you look at the photos, you'll see it in that spot, just flipped around so that the tip of the probe is as close to the rim as I could get. If whatever I'm cooking has a shape and size that requires it, I'll shift it around, but that's its usual home.
That said, I never did an experiment like this before, measuring at multiple locations on the grate, but now that I have, it's clear it's been fine at that spot. As I have said here many times, I am living proof that it's better to be lucky than goodComment
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I’m my experience the indirect zone is pretty consistent.Comment
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I would say my probe placement USUALLY is matching what would be #3 or #6 positions in the above diagram, but sometimes in the #5 position if doing a big brisket or something that needs the full width of the grate on the Performer. In those diagrams, I would always be lighting the coals in the top right corner of the SNS, just out of habit mostly, versus the top left corner, with the SNS at the "top" (back) of the grill. On the performer, if using the fan controller, I normally put the SNS in the back (away from me), with the table to the right of the grill. That is because my fan adapter is mounted on the front side, blowing towards the back. If not using the fan, I put it in the front, where it's easier to add coals and such.
Regardless, it is great to know that things stabilize and even out over the course of an hour. I've also over time looked at the vertical temp diff, and have seen it start about 100 degrees hotter at the top of the dome than at the grate level, by dangling a probe into the top vent. My old Performer has the analog thermometer in the very top as well. Over the course of a cook, the temp at the grate and top of the dome slowly converge, to maybe within 25 degrees of each other, but I only see this on long cooks like brisket or butts.
For ribs, if using a rib rack, which I do if cooking more than 2 slabs of them, I flip the ribs over halfway through the cook (about 2.5 hours in), due to the vertical gradient. I'll also swap the slabs of ribs that are farthest and closest to the SNS at that same time. Once I crammed 6 slabs of ribs into the kettle by laying #6 across the tops of the other 5 in the rib rack, and I rotated all ribs once an hour, through the positions in the rack and laying on top, and they all came out great after about a 6 hour cook.Comment
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