Consequence of an oversized firebox

[ThinBlue]

I'm curious, and I apologize if this should be assumed as common knowledge, but what is the consequence of having a firebox that is larger than what Feldon's calculator recommends? I've seen people talk about their professionally manufactured custom builds having a larger firebox, and after doing the math it appears that it might be around 140% of the calculator recommendation. I've also seen folks recommend going no larger than 105% of the calculator recommendation. What is not clear to me is why 105% is the typical cutoff for an oversized fb and if it is based on science why would some folks go above that and rave about it as a positive?

[Pete Mazz]

Besides needing a bit more work, material and fuel no real reason. The 105% is simply the smallest FB to get the best performance.

[Dirtytires]

I can see absolutely no benefit to building a firebox at 140% size. I would expect such a pit to burn a lot of fuel, have a bigger hot spot on the cooking chamber and be much more difficult to keep cooking chamber temps down in the 250 range. The excess volume in the firebox would just allow more heated air and thus make temps harder to control.

Search thru some of the old threads as this has been a topic that keeps popping up. We have had guys rebuild their fireboxes completely or have added false bottoms and/or bricks to decrease the volume. Almost all report better results from a properly sized firebox.

[EverydayDiesel]

In my limited research I have found that competition guys will use a bigger firebox, not to run a bigger fire but to give them the option to move the smaller fire around to different parts of the cooking chamber depending on what is needed. Because of this I settled at 125% but I full plan to place firebricks to make up the 20% if it is a problem.

[tinspark]

In my limited research I have found that competition guys will use a bigger firebox, not to run a bigger fire but to give them the option to move the smaller fire around to different parts of the cooking chamber depending on what is needed. Because of this I settled at 125% but I full plan to place firebricks to make up the 20% if it is a problem.

You mention moving the fire around the "cooking chamber" Are you referring to the Fire box, or are you actually talking about a chargrill where the fire goes into the cook chamber. No firebox needed for a chargrill. I am not sure why you would want to move the fire around a traditional firebox.

[EverydayDiesel]

You mention moving the fire around the "cooking chamber" Are you referring to the Fire box, or are you actually talking about a chargrill where the fire goes into the cook chamber. No firebox needed for a chargrill. I am not sure why you would want to move the fire around a traditional firebox.

i said cook chamber but i ment fire box. I need more sleep

According to some of the comp guys I was talking to, they move the fire around in the fb to lower the temp without limiting the smoke. I have no real experience so I cant say this is true. In a few more weeks I should be actually using my smoker.

[Dirtytires]

Everybody has their own little tricks and techniques that they use. Personally, I make a fire in the center of my firebox and have a "V" shaped basket to keep it there. Not really sure how practical it would be for me to try to move a fire during a cook or why I would want to so I just leave it in the center.

[hogaboomer]

I tried moving the fire around once, didn't do anything.