# Masterbuilt 560 exhaust mod, anybody done it?



## Chasdev (Jan 6, 2021)

As soon as I saw the exhaust slot on my 560 I thought it was compromise design decision and probably works correctly at a narrow heat range, which means at higher and/or lower temp settings it's not optimal.
I use mine on a screen porch with a fan hung right next to the exhaust to blow the smoke through the screen and into the yard and while the hanging fan rig works great at keeping the smoke out of the house and off the porch, I think I may be sucking too much smoke and heat out of the cooker.
So, anyone have a report on the use of  a variable exhaust device?
For now, I'm going to try different opening levels with some gorilla tape to see what happens...


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## Aledavidov (Jan 6, 2021)

Very interested idea, let us know outcome 
Thx


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## rexster314 (Jan 6, 2021)

Several Facebook groups for the Gravity Feeds have adressed that problem with movable "slats" that are attached to the back of the smoker


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## Chasdev (Jan 6, 2021)

Saw that gizmo, wondering what effect it has or is it just another place to piss away dollars, so I would like to hear testimony.
Some of the other items are, IMHO, less that worthy of my frog pelts.


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## rexster314 (Jan 6, 2021)

Chasdev said:


> Saw that gizmo, wondering what effect it has or is it just another place to piss away dollars, so I would like to hear testimony.
> Some of the other items are, IMHO, less that worthy of my frog pelts.



The one with the sliding gate is the one I'd get if I were so inclined. Makes more sense than the swinging arm kind. Plus Nathan Kloter builds good stuff. I bought his firebox mod back in June when my 2 month old 1050 burned out it's firebox


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## Sudz (Feb 7, 2021)

I've been attempting to find some feedback on this subject without success.  There's a great deal of talk out there about the various ways to block off the vent but virtually nothing on how it actually works.  One guy said he liked it but nothing else.   It may be one of those ideas which looks good but doesn't bring much to the party.


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## Smokin Okie (Feb 7, 2021)

I've yet to see the need.   The only reason I would consider it,  is to have some way to cut off oxygen in case of a grease fire.

I don't want to restrict air flow through the cooker.


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## Smokin Okie (Feb 8, 2021)

I'm 68 yo.   I've not had a math course since I was in college in 1972.    But about this exhaust port on the MB 560,  I was wondering if replaced by a stack,  what diameter would the stack be ?

The port is roughly 1.25 inch wide and 17 inch long =  an area of 21.25 inches.

To find the area of a circle ,  that would be   Area =  Pie X  Radius squared .     So I work backwards to find the radius.

21.25 = 3.14 X r2

And very roughly I came up with a radius of 2.60,  which would be a rough diameter of 5" .

A 5" stack on this size cooker,   seems to be outsized.    But dayuum, that's a lot of air flow.   My Old Country Brazos stick burner has 4.5" exhaust port.

Anyone with better math skills than mine,  which would include a lot of people, are welcome to correct me,  cuz I could be wrong.


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## JLeonard (Feb 8, 2021)

daveomak
 can you help them out?


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## bill1 (Feb 8, 2021)

Stacks help natural  draft (airflow) over a range of temps in simple cookers.  The 560, like pellet machines, has its own auxiliary fan.  Hence, the air/smoke flow is engineered, it's not dominated by natural convection.  So a stack loses its appeal.  

Now if you're finding an unacceptable range of temps across the width of the grill, tweaking the resistance of the outlet flow from side-to-side _may _have some value.


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## Smokin Okie (Feb 8, 2021)

bill1 said:


> Stacks help natural  draft (airflow) over a range of temps in simple cookers.  The 560, like pellet machines, has its own auxiliary fan.  Hence, the air/smoke flow is engineered, it's not dominated by natural convection.  So a stack loses its appeal.
> 
> Now if you're finding an unacceptable range of temps across the width of the grill, tweaking the resistance of the outlet flow from side-to-side _may _have some value.



IMO, the 560 is still a bottom up cooker,  heat rises up through the cooker.    It does not use the fan strictly for convection, it uses the fan to stoke the fire.    It just gives the fire more or less air.

My only purpose for comparing to a 5" diameter stack, was illustrating how much air moves through the cook chamber.   And its a lot for a cook chamber as small as the 560 has.    Gravity feeds like Assassin,  Stumps, et al,  have about that same size exhaust for a lot larger cook chamber.


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