Should I crank up the vents?

Powak

Had my egg idling at 250° for about an hour, threw 8lbs of belly, walked away came back an hour later to 195° on the dome. Should I open up the vents or is the belly just keeping the heat from reaching the dome thermo?

Powak

ColbyLang

No surface of grill temp? I say open. Mine run about 12° difference in an XL

Powak

ColbyLang said:

No surface of grill temp? I say open. Mine run about 12° difference in an XL

Not this time. I used to always compensate when I open the dome and put the meats in but I started to figured if the egg was stable at one temp it would return to that after a while. Not today yet I guess.

PigBeanUs

If you put in a lot of anything cold, the heat will go into that instead of maintaining the overall “system” 

You can open the vents a little, sure

Powak

PigBeanUs said:

If you put in a lot of anything cold, the heat will go into that instead of maintaining the overall “system” 

You can open the vents a little, sure

That’s a good point. Like steppin on the gas a little to climb the hill.

Mark_B_Good

More fire = more temperature.
You are cooking at 195F now ... even with the energy going into the cook ... temperature is at 195F and it's at that temperature the energy goes into the cook.

As the cook get's hotter and hotter, the temperature difference between the dome and cook reduces ... that SLOWS the energy input into the cook ... you have less driving force.

So cooking at 195F simply takes longer .... much longer.

Open the vents, get oxygen in ... get to your target temperature ... dome is dome temperature ... period ... aim for 250F.  You're egg is capable of producing 700F or more if you want .... so open those vents up enough to hit your target dome temperature.

Powak

Mark_B_Good said:

More fire = more temperature.
You are cooking at 195F now ... even with the energy going into the cook ... temperature is at 195F and it's at that temperature the energy goes into the cook.

As the cook get's hotter and hotter, the temperature difference between the dome and cook reduces ... that SLOWS the energy input into the cook ... you have less driving force.

So cooking at 195F simply takes longer .... much longer.

Open the vents, get oxygen in ... get to your target temperature ... dome is dome temperature ... period ... aim for 250F.  You're egg is capable of producing 700F or more if you want .... so open those vents up enough to hit your target dome temperature.

Right on. Going back to treating it like a steam locomotive with more air to get up those steep grades.

Mark_B_Good

Yes, and of course, top vent is open enough only to keep a nice draft ... you don't need it wide open, you just don't want too much positive pressure building up in the dome by closing too much, which you will see when smoke is burping out of the bottom vent ... closing the top stack vent enough will help to maintain a more even temperature profile in the dome, and also prevent unnecessary heat loss (energy consumption = charcoal burning quickly = $$ per cook).

Foghorn

What's written above is not entirely true.  The dome temp is sitting near some cold meat and may be reading 195 even if much of the air in the egg is over 200 - as long as you are more than a couple of inches away from the meat where you measure it.  The belly pieces on the bottom rack may be seeing 250 degrees or more.  When you load an egg with a lot of meat - particularly if it is enough to restrict airflow (think multiple pork shoulders on multiple racks) - you can get a LOT of variation in temp between the grate and the dome.  As the meat warms and shrinks that variation reduces significantly.

In this setting, I wouldn't make much of a change.  If you make "a dome thermometer reading of 250" your immediate goal, you'll need to keep a very close eye on the belly pieces because it could be 300 degrees in some parts of the egg.

Canugghead

Mark_B_Good said:

Yes, and of course, top vent is open enough only to keep a nice draft ... you don't need it wide open, you just don't want too much positive pressure building up in the dome by closing too much, which you will see when smoke is burping out of the bottom vent ... closing the top stack vent enough will help to maintain a more even temperature profile in the dome, and also prevent unnecessary heat loss (energy consumption = charcoal burning quickly = $$ per cook).

That’s how Tip-top and Smobot operate.

Mark_B_Good

Foghorn said:

What's written above is not entirely true.  The dome temp is sitting near some cold meat and may be reading 195 even if much of the air in the egg is over 200 - as long as you are more than a couple of inches away from the meat where you measure it.  The belly pieces on the bottom rack may be seeing 250 degrees or more.  When you load an egg with a lot of meat - particularly if it is enough to restrict airflow (think multiple pork shoulders on multiple racks) - you can get a LOT of variation in temp between the grate and the dome.  As the meat warms and shrinks that variation reduces significantly.

In this setting, I wouldn't make much of a change.  If you make "a dome thermometer reading of 250" your immediate goal, you'll need to keep a very close eye on the belly pieces because it could be 300 degrees in some parts of the egg.

I agree there is a difference as you get closer to the meat ... I've measured it, comparing dome and grill ... and the difference can be about 40F at the beggining of the cook, less so at the end of the cook (maybe only 5F difference). Here's the thing, if you look at that picture down the stack, those pieces of meat are well into the cook, and the difference is probably not more than 10F or 15F.  

Second, what is the temperature on the lower grid?  It's a bit of a guess, unless you have a grill probe on that rack ... and besides, that meat is also cooking, so you will have cooling effect there too.

In the end, all my concern would be, if the dome read 195F that late in the cook, is it would take forever to finish ... for sure, you're never gonna hit an internal of 200F ... 

If you are at 250F dome at the beginning of the cook, you might be around 300F on the bottom grid, but that would only be at the very start, when everything is raw ... if you keep controlling to 250F, eventually a few hours into the cook, I wouldn't expect the bottom to be more than 270F to 275F ... which is well within the range of tolerance.  

Unless you're cooking a brisket ... I don't think you want your dome to be registering 195F, even in this case ... not unless you have lots of time on your hands.

Foghorn

Mark_B_Good said:

Foghorn said:

What's written above is not entirely true.  The dome temp is sitting near some cold meat and may be reading 195 even if much of the air in the egg is over 200 - as long as you are more than a couple of inches away from the meat where you measure it.  The belly pieces on the bottom rack may be seeing 250 degrees or more.  When you load an egg with a lot of meat - particularly if it is enough to restrict airflow (think multiple pork shoulders on multiple racks) - you can get a LOT of variation in temp between the grate and the dome.  As the meat warms and shrinks that variation reduces significantly.

In this setting, I wouldn't make much of a change.  If you make "a dome thermometer reading of 250" your immediate goal, you'll need to keep a very close eye on the belly pieces because it could be 300 degrees in some parts of the egg.

I agree there is a difference as you get closer to the meat ... I've measured it, comparing dome and grill ... and the difference can be about 40F at the beggining of the cook, less so at the end of the cook (maybe only 5F difference). Here's the thing, if you look at that picture down the stack, those pieces of meat are well into the cook, and the difference is probably not more than 10F or 15F.  

Second, what is the temperature on the lower grid?  It's a bit of a guess, unless you have a grill probe on that rack ... and besides, that meat is also cooking, so you will have cooling effect there too.

In the end, all my concern would be, if the dome read 195F that late in the cook, is it would take forever to finish ... for sure, you're never gonna hit an internal of 200F ... 

If you are at 250F dome at the beginning of the cook, you might be around 300F on the bottom grid, but that would only be at the very start, when everything is raw ... if you keep controlling to 250F, eventually a few hours into the cook, I wouldn't expect the bottom to be more than 270F to 275F ... which is well within the range of tolerance.  

Unless you're cooking a brisket ... I don't think you want your dome to be registering 195F, even in this case ... not unless you have lots of time on your hands.

Fair enough.  And points well taken.

Mattman3969

The OP stated he was stable at 250 for an hr then threw on 8lbs of meat and an hour later the temp was 195.  

IMHO the egg had not had time to recover from the 8lbs of cooler meat that was just starting to warm up. A hour is not enough time for the egg to recover on its own. Plus the upper grid was closer to the dome thermo and causing a touch of non accurate reading.  By increasing air flow you’re increasing the chance of chasing the fire. I don’t know what the OP did after the question was answered but I’m betting if left alone the egg would’ve been reading 250 again within 2 hrs.  

Powak

Mattman3969 said:

The OP stated he was stable at 250 for an hr then threw on 8lbs of meat and an hour later the temp was 195.  

IMHO the egg had not had time to recover from the 8lbs of cooler meat that was just starting to warm up. A hour is not enough time for the egg to recover on its own. Plus the upper grid was closer to the dome thermo and causing a touch of non accurate reading.  By increasing air flow you’re increasing the chance of chasing the fire. I don’t know what the OP did after the question was answered but I’m betting if left alone the egg would’ve been reading 250 again within 2 hrs.  

I started a little fire chase action 1 hour in. But pretty much just opened the vents till it hit 250, reset em to lock in which they did for the next 3.5 hours. I wound up going an extra 30 minutes on the smoke time thinking that the 195° hour would need me to go a little longer. The fat was perfect on my ends but the meat portions were a little hard. I don’t know if this was cause by too much smoke time or too much butter bath. 

Mark_B_Good

Mattman3969 said:

The OP stated he was stable at 250 for an hr then threw on 8lbs of meat and an hour later the temp was 195.  

IMHO the egg had not had time to recover from the 8lbs of cooler meat that was just starting to warm up. A hour is not enough time for the egg to recover on its own. Plus the upper grid was closer to the dome thermo and causing a touch of non accurate reading.  By increasing air flow you’re increasing the chance of chasing the fire. I don’t know what the OP did after the question was answered but I’m betting if left alone the egg would’ve been reading 250 again within 2 hrs.  

I guess the other side of that coin is, he added more meat, that cook sucks more energy. Where does that energy come from?  If you don't increase the burn rate, it's going to simply drop your temperature.  More meat = more charcoal burning ... has to be.

Mattman3969

Where does that new energy go once the meat starts warming up?

Langner91

I loved Thermodynamics in college.

Now, the closest I get is trying to figure out if I want one cube or two in my whisky.

Life's too short to worry about a few degrees.  Crank her up, shut her down, it all boils down to how long you want to cook.

Mark_B_Good

Mattman3969 said:

Where does that new energy go once the meat starts warming up?

Increased temperature ... so technically, if the cook isn't absorbing the energy, you'll need to close those vents a little more.

But here's what I think, most of the energy is going into evaporating moisture in the meet. That energy is 1000x the energy it takes to raise the meat a few degrees.  So the energy demand from the meat probably isn't changing all that much as the cook gets hotter ... which is why we don't see the dome temperature changing much.

nolaegghead

For the nerds out there, 1 btu is the amount of energy to raise one pound of water 1 degree F.  970 btu is the amount of energy to turn one pound of water at 212F to one pound of vapor at 212F  (latent heat of vaporization).

Also, a btu is approximately the heat energy created burning one typical match.  Also, the amount of energy it takes to lift one pound 778 feet against earth's gravity.

nolaegghead

....also 144 btu/lb to melt ice

Botch

nolaegghead said:
Also, the amount of energy it takes to lift one pound 778 feet against earth's gravity. 

Wat.  

Legume

“BTUs are BTUs” ended a lump size argument once.  Or made it worse, I can’t remember.