Planning on adding additional bottom vents, anyone done it?


 
MKEvenson

MKEvenson

TVWBB Wizard
I have ordered 2 bottom vent damper kits from Weber. I cook a lot of HH and broke my door latch while doing so. Weber replaced the door but I want to try adding an additional vent or two and see if I can keep the doors original orientation. I read the description of adding a hood vent. What I am wondering is the best way to get the same high heat as I do by opening the door, should I put 2 new vents on the bottom, or 1 bottom and 1 top. Sounds fun, I love modifying my WSM. Have already added handles and tied the lower and upper cooking grates together. What next?

Mark
 
I wonder if adding just a top vent would do it? I have noticed that cracking the lid will get temps above 350 easily! hmmmmmmmmmm
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Timothy, thanks for the reference. I remember reading that a while ago and just couldn't remember where it was. I had not remembered the back pressure part of the equation. I think that one additional bottom vent would be ok with no additional top vent. I will see. Since I ordered 2 kits I may just do one xtra top and bottom.
Glenn, the reason I shy away from opening the hood to increase heat is loss of smoke. I like the amount of smoke I currently get with lid closed and top vent open.
Weber won't ship parts till after 9/20 so I have time to "think" about it all.

Mark
 
may i suggest doing the top one first ? you loose nothing if it does work. i'm of the school that it makes no differance in how much goes in it if it can't come out. auto performance and all that.
 
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by george curtis:
may i suggest doing the top one first ? you loose nothing if it does work. i'm of the school that it makes no differance in how much goes in it if it can't come out. auto performance and all that. </div></BLOCKQUOTE>

George, Maybe? I have been doing the math. Seems the original design was 3/1 (bottom to top) with all vents open. In actual use however for most of us the ration changes to 6/1 if bottom vents only 50% open and 12/1 if bottom vents 25% open. I usually run 1 bottom vent closed and the other two at maybe 10% for low heat. So the ratio is probably closer to 20/1 with that set up. Of course that is low heat BUT the in/out ratio is high. If I add one additional bottom vent and run all four 100% open I am at a 4/1 ratio. I am not sure how to measure for creosote but all is FOOD FOR THOUGHT.
 
Have you thought about the turning the door upside down and adding the long bolts to prop it open? (threads on bolts catch on opening allowing you to adjust how far you open it)
It has worked great for me if I need to get temps up.
 
Mk adding one top vent should do the trick, also cook with just a foiled water pan for higher heat.
 
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Craig M.:
Have you thought about the turning the door upside down and adding the long bolts to prop it open? (threads on bolts catch on opening allowing you to adjust how far you open it)
It has worked great for me if I need to get temps up. </div></BLOCKQUOTE>

Craig, yes, I have thought about it. At first after reading the posts on that mod I wondered how one would adjust the opening or close the door fully with the bolt in place. My second concern is that of the latch, mine has fallen apart and even tho I have received a replacement I anticipate it happening again. Don't know if having the door upside down had anything to do with it but it happened during a HH cook.

Mark
 
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Noe:
Mk adding one top vent should do the trick, also cook with just a foiled water pan for higher heat. </div></BLOCKQUOTE>

Noe, I do use only foil in the water pan during HH cooks. I have ordered 2 replacement vents so one option is to increase the top draft. My thinking in going on the bottom was that I would be adding draft closer to the fuel. I may do one on top and one on the bottom.

Mark
 
Mk, i would add the top vent 1st that will double ur air intake should raise temps easily, adding more vents on bottom and not having enough exhaust u have accomplished nothing, hope everything works out gl Mk
 
MK, I also added the bolts on the door to hold it open upside down in place. This adds additonal air to the coals and gets it hotter in a few minutes.

The temps rise despite havng the stock single vent system on top.

In convection principals, heat rises to colder areas. In the WSM that would seem to be that heat moves from top to bottom (coals to exhaust area).

With this in mind I can't see how adding another vent on top would help as much as adding more air down where the coals are located. I could be wrong but adding another vent on top could make it colder because more heat is escaping.

Also isn't this what the Guru devices accomplish, control air near the coals to control temps above.
 
J REYES, wish I had paid more attention in science class. The only explanation I can figure is, if there are more escape vents in the top, the air rushing out will pull more air into the bottom, like a vacuum effect, and the coals will in turn get hotter. I still think that I am going to try one on top and one on the bottom. Just cause I already purchased 2 new vent covers. If all else fails I will try the bolts in the door. Parts should arrive by Sat so I should be able to post pics and results early next week.

Mark
 
Reyes, the ratio is 3 to 1 intake over exhaust, u have 6.75 total intake and 2.25 total exhaust, match them up and u will have some heat, it really does not matter where u put the vent as long as it is above the heat source, that's why when u prop the door or crack the lid u get more heat, u can add 10 vents on bottom or below the heat source and if it can not exhaust back to square one. Remember when weber made the wsm it was meant for low and slow not high heat.
 
Noe, you seem to know about this heat exchange concept. Admittedly Weber designed the WSM for low heat. If one keeps the same relative ratio below the coals and above the coals will the cooker temp stay about the same? If you increase the vents above the coals, as you suggest, you disrupt the ratio low to high intake and exhaust. My goal is to be able to use the WSM for both HH 325-370 and low heat 225-250 on demand without upsetting the door. I really don't mind upending the door it's just that I suspect that may have been a contribting factor to my door latch falling apart. Of course it also could be the exposure to the higher than designed heat.

Mark
 
Mk, all i am saying is u have enough vents on the bottom already, u just need to pull more air thru the wsm to create more heat, if u add more vents on top u have the best of both worlds, want to cook low and slow just use one top vent want to cook high heat open up the second top vent, Mk when i cook i always have my top vent open 100% and adust my bottom vents to control temps, if i would have my bottom vents open 100% and try to use my top vent to control temps i would somther the coals not enough air flowing thru the the wsm to generate heat, its all about air flow. Mk my wsm gets up to 350-375 just with the single top vent open 100% and bottom vents open 100%
 
Noe, Thanks. Interesting that you can maintain heats in the 300-350 range with no additional air flow other than all stock vents open. Seems that most of us here have to either open the door or do other exotic things to get higher temps. I use my vents just as you describe, keeping top open 100% and adjusting bottom for heat control. Would be interesting to hear from other WSM users to see what kind of temps they normally achieve with al 4 vents open 100%. Another use for a poll. Wish we could create one. Hint!

Mark
 
Mk, when i do high heat cook i start with all lit charcoal and add unlit charcoal as needed gl bud.
 
" Would be interesting to hear from other WSM users to see what kind of temps they normally achieve with al 4 vents open 100%."

Right now I'm @ 325.Temps measured @ the top vent. Using lump with a Minion start, took about an hour to reach these temps. It's in the mid fifties, overcast with a decent breeze.

Tim
 
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