Oversize Firebox and Exhaust Stack Size

[Cheese Burger]

Hello Everyone

In the process of building a 100 gallon straight-flow offset smoker, I was considering building an oversize firebox so that it'll give me flexibility for a higher grate and ease of building a larger fire, if required and allow me to move the fire closer of further away from the cooking chamber. I've heard that building a larger fire gives a better smoke flavour. I'm thinking of a 70% increase? The increase would be more in the length.

The cooking chamber is 24in in diameter and 51in in length. The firebox I'm intending to build will be 24in in height and width and 27in in length.

I've been through the old threads in regards to an oversize firebox and there's no discussion about increasing the size of the exhaust stack or firebox air inlet. If anyone had built an oversize firebox and have experienced with one, I would love to hear what their thoughts are.

Thank you in advance.

 

[mike243]

1 thing about a bigger fire box is you can build a bigger fire, not so with a smaller1, to my way of thinking a bigger will not affect the performance to the negative side, a box that's to small will require a lot more work to keep it at temps, nothing sez you have to have the whole box full of coals and wood and open flames, load it regulate the incoming air till you hit your target and add as needed to maintain, the larger the box the more heat it will lose due to surface area but its no worse than a smaller box, insulation there helps a lot to keep the heat in where its needed, that's like a leaking door loosing heat and smoke so why not add something to help out?

 

[Cheese Burger]

I'm actually contemplating on building an insulated firebox. But I've heard that with an insulated firebox, the fire burns so efficiently that you'll only need a small fire to maintain temperature and this results in little smoke in the cooking chamber, and therefore less smoke flavour in the meat? What are your thoughts on this?

 

[smokin peachey]

I have never heard of someone building a smoker with the thought of making it less efficient to produce smokier meat. You want the smoke and heat to flow through the cook chamber efficiently. If it doesn’t you will end up with nasty tasting meat. I would make the firebox no less then 1/3 the size of the cook chamber. Personally I think an insulated firebox is helpful but not a necessity. The nice thing about a bigger firebox is you can stagger your splits and get a longer burn time. I look forward to seeing your build thread. Another thing to think about is how many times have you heard of someone drinking liquid smoke yuck right. Well there is such a thing as to much smoke. You want clean smoke!

 

[mike243]

It takes a certain amount of heat to cook any thing, the amount of smoke flavor will depend on how much and what type of wood/charcoal you are using.

 

[Cheese Burger]

With a larger firebox would I need to increase the size of the CC/FB opening and increase the exhaust stack diameter to allow more airflow into the firebox, to fuel the fire? I'm just thinking that with a larger firebox, I would need to build a larger fire to get the same temperature in the cooking chamber?

 

[SmokinEdge]

One thing about a firebox oversized very far is you will burn a lot more wood to maintain temps. This is because you have to move the air from the fire to the CC. That extra volume in a bigger FB is also more air to heat up. This is why there is a calculation of FB to CC sizing. Big enough to heat the CC but small enough to be efficient. Nothing wrong with a bigger FB other than the loss of efficiency, meaning burning more wood To maintain same temp.
I wouldn’t mess with the opening to the CC or stack size. Then you would be moving more air through the CC than it needs and could dry out the meat.

 

[Cheese Burger]

1 thing about a bigger fire box is you can build a bigger fire, not so with a smaller1, to my way of thinking a bigger will not affect the performance to the negative side, a box that's to small will require a lot more work to keep it at temps, nothing sez you have to have the whole box full of coals and wood and open flames, load it regulate the incoming air till you hit your target and add as needed to maintain, the larger the box the more heat it will lose due to surface area but its no worse than a smaller box, insulation there helps a lot to keep the heat in where its needed, that's like a leaking door loosing heat and smoke so why not add something to help out?

Hello Mike243

Do you find with an insulated firebox that because you burn less wood to maintain the temperature, that you get less of a smokie flavour from your meat? I'm probably overthinking this. But it's on the back of my mind and I thought I'd ask.

Thank you.