Top vent temp control.
- Thread starter Bruno
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Justin Hancock
TVWBB Member
The theory behind this is that if you restrict the exhaust the fire will not burn cleanly and give off a soot onto your meat.
However I do throttle with my top vent, but only as a last resort. If my temps are going wild and I can't seem to get it under control within 30-45 minutes, I'll throttle the top vent back to 1/2 at most. This coupled with the bottom vents being totally shut usually brings the temps down within a half hour.
However I do throttle with my top vent, but only as a last resort. If my temps are going wild and I can't seem to get it under control within 30-45 minutes, I'll throttle the top vent back to 1/2 at most. This coupled with the bottom vents being totally shut usually brings the temps down within a half hour.
Barry McCorkle
TVWBB Super Fan
Most of my heat control is done with the bottom vents, however, if the smoker gets too hot with the bottom vents closed, I will partially close the top vent. The only reason that you shouldn't close down the top vent is when a lot of white smoke is coming out of the WSM. Also, I rarely throttle the top vent for more than an hour. As to the amount of closing the vent, I have closed it as much as 1/2 to 2/3 closed with no problems. Typically, I close it about a 1/3 to get the heat down in the cooker.
Dwain Pannell
TVWBB Hall of Fame
I use the top vent in coordination with the lower vents. I always have the top vent opened more than the bottom vents. Even though the lower vents can be barely cracked open, I never close the top vent more than half way to ensure a positive chimney effect (the principle of the WSM is based on a chimney).
The combustion flue gases inside chimneys are much hotter than the ambient outside air and therefore less dense than the ambient air. That causes the bottom of the vertical column of hot flue gas to have a lower pressure than the pressure at the bottom of a corresponding column of outside air. That higher pressure outside the chimney is the driving force that moves the required combustion air into the combustion zone and also moves the flue gas up and out of the chimney. That movement or flow of combustion air and flue gas is called "natural draught/draft", "natural ventilation", "chimney effect", or "stack effect".
There can be cases of diminishing returns: if the airflow is restricted, the flue gases may cool before reaching the top of the chimney. This condition can result in poor drafting, and in the case of wood burning appliances, the cooling of the gases before emission can cause creosote to condense near the top of the chimney (or on your food).
The combustion flue gases inside chimneys are much hotter than the ambient outside air and therefore less dense than the ambient air. That causes the bottom of the vertical column of hot flue gas to have a lower pressure than the pressure at the bottom of a corresponding column of outside air. That higher pressure outside the chimney is the driving force that moves the required combustion air into the combustion zone and also moves the flue gas up and out of the chimney. That movement or flow of combustion air and flue gas is called "natural draught/draft", "natural ventilation", "chimney effect", or "stack effect".
There can be cases of diminishing returns: if the airflow is restricted, the flue gases may cool before reaching the top of the chimney. This condition can result in poor drafting, and in the case of wood burning appliances, the cooling of the gases before emission can cause creosote to condense near the top of the chimney (or on your food).
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Ray.S
TVWBB Super Fan
I posted this over on SMF after reading a newsletter from Harry Soo. I tried it yesterday and I did not notice any different color of sooty flavor.
Of the three components I mentioned: intake, fuel choice and amount, and the exhaust, the most effective component to maintain constant temperature is not the intake nor the fuel. It’s the exhaust. Many beginners I come across are not aware of that. All seasoned pitmasters know how to intuitively draft their pit using “clean” smoke to color and flavor their barbecue meats. The draft refers to the vacuum effect when you open or close the exhaust vent of your pit.
When you open the exhaust vent on the WSM, you allow hot air to leave the pit and this creates a vacuum suction to draw air in from the bottom intakes. Thus, by skillfully manipulating the top vent, you can control your WSM like a pro. Many beginners constantly fiddle with their intake dampers in hopes to maintain a constant temperature with less success than leaving the bottom vents untouched and fiddling with the top vent to control the draft within their WSM. In future articles, I’ll address the mechanics of damper control on the WSM (e.g., old school versus automated blower systems) and the science on dirty smoke, white smoke, clean smoke, blue smoke, sour smoke, etc. For now, just give my technique a try and see if it works for you.
Of the three components I mentioned: intake, fuel choice and amount, and the exhaust, the most effective component to maintain constant temperature is not the intake nor the fuel. It’s the exhaust. Many beginners I come across are not aware of that. All seasoned pitmasters know how to intuitively draft their pit using “clean” smoke to color and flavor their barbecue meats. The draft refers to the vacuum effect when you open or close the exhaust vent of your pit.
When you open the exhaust vent on the WSM, you allow hot air to leave the pit and this creates a vacuum suction to draw air in from the bottom intakes. Thus, by skillfully manipulating the top vent, you can control your WSM like a pro. Many beginners constantly fiddle with their intake dampers in hopes to maintain a constant temperature with less success than leaving the bottom vents untouched and fiddling with the top vent to control the draft within their WSM. In future articles, I’ll address the mechanics of damper control on the WSM (e.g., old school versus automated blower systems) and the science on dirty smoke, white smoke, clean smoke, blue smoke, sour smoke, etc. For now, just give my technique a try and see if it works for you.
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ChuckO
TVWBB 1-Star Olympian
I don't throttle my WSM from the top vent, but I do with my kettles. The downside to doing so, is the build up of smoke can "bitter" the cook. Chicken & Turkey can get "smoke-bitter" pretty easily. What I did discover, is that if you do bitter a cook, save it for the next day. The bitterness goes away after a day in the fridge
Bill French
TVWBB Fan
I would second the Harry Soo (not Woo) recommendation. He's the most successful WSM user that I know of.
WB Zipf
TVWBB Pro
In addition to the post from Harry Soo, I have also heard that he met with the Weber Engineering team and one of the topics of discussion was the throttling of the top vent for temperature control. From Harry's account, the engineers were skeptical, and his response was "don't take my word for it, try it for yourselves and see which offers better control." Now I don't know what the Weber engineers did after that conversation, but I do find it interesting that for the first time they have introduced a very finely calibrated exhaust vent on the new WSCG, and promote it as an effective tool in the effort to control temperatures.
Long and short, if both Harry Soo and Weber (in a reversal of previous advice) advocate the use of the exhaust vent to control temps, there must be something to it.
Long and short, if both Harry Soo and Weber (in a reversal of previous advice) advocate the use of the exhaust vent to control temps, there must be something to it.