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[Hank D Thoreau]

I think it was here that I read that two pork butts take just as long as one.

That certainly is not the case in the cook I am doing tonight.

The first was on the hot side of my grill and took 14:35. The second is now finishing 15 hours and is at 171.

It looks like it is going to be a long night, but at least there will be pulled pork sandwiches, street tacos and faux machaca and eggs tomorrow.

[bregent]

>I think it was here that I read that two pork butts take just as long as one.

I think you may be confusion things. What folks are saying is that putting two butts on the grill does not (substantially) increase the cooking time compared with having just one. That's not the same as saying they will cook the same. Every butt is different and is done when it's done. Also, most of the time when I buy a twin pack, one butt is larger than the other and will obviously take longer. Did you weigh each separately?

[Hank D Thoreau]

I understood the comment. Both pork butts are taking much longer than any single pork butt I have ever cooked.

That is why I mentioned the hot and cold side of my grill. I have to move my deflector a bit to help balance it. The hot side butt has almost completed an hour rest.

Pork butt number two is still going wrapped at 15:30 hours and is still at 175.

[Bar-B-Lew]

Did you put the larger cut on the hot side of the grill?

[pmillen]

Hmmm.  Did your pit maintain temperature?

I looked through my cook notes and cooking two butts has never taken appreciably longer than cooking one.  Although, I have more two-butt cooks than one-butts, so the data is weak.

Not taking significantly longer makes sense to me.  Here’s what happens inside the pit–

• The fire heats up the air inside the pit
• The meat is warmed, and the air is cooled (thermal equilibrium at work)
• If you have two butts to heat up, each will warm at the rate they would have had they been in the pit alone (governed by meat’s specific heat capacity)
• In total they’ll “absorb” more heat from the air in the pit
• The pit controller will “notice” the need for more heat, dump more pellets and attempt to maintain the set temperature
• If the pit can maintain temperature, each butt will cook at the same rate it would have had it been in the pit alone

So…from my experience and understanding of thermal dynamics, two butts should not take appreciably longer to cook than one if the pit can maintain the temperature setting and the air currents are not significantly disrupted.

You’ll burn more pellets, tho’.

[glitchy]

Prepping for my sons graduation, I cooked 4 at once on my 575 a week back, and pulled the first 2 after almost 16 hours and the second 2 at like 17 with the grill at close to 300 for the last couple hours. I've never had a shoulder take this long. So there might be something to this. I chalked it up to the temp issues with the new models, but my Fireboard read right where I wanted it the entire cook. The were packed in there pretty good though.

[Bar-B-Lew]

I think it also has something to do with the availability of space to circulate the hot air.  2 hunks of meat or 4 hunks of meat consume more space than one hunk that is getting all of the air circulating around it which I would think would cook it faster.

[Hank D Thoreau]

I am using a Daniel Boone wiki. I recently changed the controller because it stopped working. The new one has been doing fine.

The first butt took 14:35. The second took 18:30. The second was on the cool side ( I moved it over after I took the first out). I discovered the asymmetry last week when cooking chicken wings.

I also kept upping the temperature to speed up the second one since it was on course for a much longer cook.

I had not moved the deflector yet to try to balance the cooker.

My recollection is that my single butt cooks were taking between 10 and 11 hours.

I wish the DB wifi would capture the temperature profiles so you can see what is happening. That would be my one recommendation for a future enhancement.

I did not see anything out of the ordinary in the temperature, but then, it moves around a lot and you would have to do a comparison between short cook and long cook temperature charts.

The thermodynamics are unclear. Temperature is not energy, and it is risky making thermodynamic argument if you are not talking about energy. Temperature is not a state function and is not conserved. It is the temperature of the air in the smoker that you are measuring. You fill up the smoker and there is less air to heat. Also, the meat itself is a heat sink that helps maintain the temperature in the grill.

[Hank D Thoreau]

I recently cooked a 15 pound brisket and it took way longer than I expected compared to smaller briskets I had cooked.

It makes me wonder what the pounds of meat versus cooking time plot looks like.

It may be non linear, with the slope increasing as you add weight.

We may need to have a little pellet smoker thermodynamics focus group to figure this out.

[pmillen]

We may need to have a little pellet smoker thermodynamics focus group to figure this out.

Yeah, there may be more to this than that which occurs to me.

Some experiments may be in order and may be fun.  I used damp cotton towels instead of meat when I was analyzing my pit's temperature swings at different pellet-drop rates.

On the other hand, we can just go with what our experiences have produced if they're consistent.

[pmillen]

The thermodynamics are unclear. Temperature is not energy, and it is risky making thermodynamic argument if you are not talking about energy. Temperature is not a state function and is not conserved. It is the temperature of the air in the smoker that you are measuring. You fill up the smoker and there is less air to heat. Also, the meat itself is a heat sink that helps maintain the temperature in the grill.

Temperature is the measurement of thermal energy.  As I see it, the only way to discuss what's happening to heat energy is to discuss the relevant temperature changes.  Is there a better way?

[Bar-B-Lew]

It all comes down the the old adage that I told my wife many years ago and she finally has come to an agreement...the BBQ is done when the BBQ is done.  When we had parties and she was making sides, it finally got to a point where she said, "I need XX time to make the side dish so LMK when you think the meat is about that far away from being done."  I would then start with an estimated time when the cook started and update as I measured the temp.  I would check based on my history of when I thought it would be done less the time she needed and reschedule plans from there.

I won't cook something that takes longer than 3-4 hours if I know I don't have the extra time to see it get finished.  I make sure my day and night is wide open if I am making shoulders or briskets or even chuck roasts for pulled beef.  Then there is less frustration that something took longer than I thought it would.

[bregent]

>I recently cooked a 15 pound brisket and it took way
>longer than I expected compared to smaller briskets I had cooked.

But that's a completely different scenario. Obviously, 2 smaller pieces will cook faster than one large one, as the energy needs to migrate into the meat - the thicker it is, the longer it will take.  You cannot conclude from a single cook that placing two butts on the grill caused the cook to take significantly longer.  It may increase it slightly because the extra mass and marginally reduced airflow, but it would not cause it to go from 10 to 18 hours, unless you are seriously overcrowding the meat or there is something wrong with the grill.

For me, a 9lb butt takes about 14 hours, whether I am cooking one or three. But I cooked a single butt last week that took almost 16.

[Hank D Thoreau]

The thermodynamics are unclear. Temperature is not energy, and it is risky making thermodynamic argument if you are not talking about energy. Temperature is not a state function and is not conserved. It is the temperature of the air in the smoker that you are measuring. You fill up the smoker and there is less air to heat. Also, the meat itself is a heat sink that helps maintain the temperature in the grill.

Temperature is the measurement of thermal energy.  As I see it, the only way to discuss what's happening to heat energy is to discuss the relevant temperature changes.  Is there a better way?

Temperature and heat are not the same thing. There are relationships between them. This is a very similar discussion I get into on archery forums where I have used my physics background to test bows. The archery community is focused on force (draw weight) rather than energy. Bow performance is based on the energy you store and the efficiency of turning that energy into translational kinetic energy. Temperature change is important, but you have to account for all the energy. Efficiency is also a factor when it comes to cooking. There may still be a few holes in the thought experiment.

[pmillen]

When you say, "Temperature change is important, but you have to account for all the energy" I'm assuming that you mean all of the heat energy since we're analyzing the transfer of heat energy from the air to the meat.  From my perspective, the only way to do that is to measure the meat's temperature. 

Accounting for "all of the energy" (heat energy) would involve analyzing–

• that which creates a change of state of the the meat's solids (fat) and fluids
• the pit's metal heating.

Perhaps even more.

Is that what you have in mind?