Your thoughts

Discussion in 'Pork' started by soslow, Apr 17, 2012.

  1. soslow

    soslow Fire Starter

    After smoking a butt last weekend, No peek n and I got in a discussion on what rack to use on my smoke vault.

    I used my middle rack and he said move it up to around 2/3rds of the way for more even heat . Any ideas from you all?

  2. roller

    roller Smoking Guru SMF Premier Member

     I agree !
  3. heyer5

    heyer5 Meat Mopper

    What smoker are you using?
  4. soslow

    soslow Fire Starter

    I am using the Smoke vault 22'', My thinking was its cooler as you move up maybe i am wrong.

    He explained you will get more even heat but cooler with out so much fluctuation

  5. forluvofsmoke

    forluvofsmoke Smoking Guru OTBS Member

    Didn't know they made a 22". It will depend on if you've done intake vent mods (to fully close them) and if you're using that mod. I have the 24" and had temp fluctuations between the corners mainly, and a bit hot towards the left rear up high and down low, while a bit more even on the 3rd and 4th grate up. It's actually hotter up high with a light load, and hotter below when loaded up, which is pretty common for vertical rigs. Any food down low, especially with a larger foot-print, acts like a baffle to the grates above it and will tend to deflect the heat out and around the outside near the cabinet more than normal. The baffling effect is very prominent if you place a fairly large pan below anything else, so keep that in mind.

  6. soslow

    soslow Fire Starter

    Interesting , Eric it may be the 24" its not the smaller one ! I have closed of the btm vents by plugging with tin foil! so maybe not the mod you are thinking of but closed off, also door shimmed for no loss. I will give this a try next smoke ,but seems I will need to turn the heat up and use more propane to me .

    this why i ask?

  7. forluvofsmoke

    forluvofsmoke Smoking Guru OTBS Member

    Actually, what I've found with my 24 after a few years is when the side intakes are closed it tends to even out temps a bit more, but at the expense of reduced convective efficiency. In other words, reduced flows also reduce the rate foods will cook at, so to compensate, I can run a bit higher chamber temps. If I would have normally smoked something at 225*, if I bump the chamber temp by 15-20* it will still cook at about the same rate. I have had up to 60 hours of smoke time in moderate weather conditions on a 20lb tank of LPG at these temps with relatively large pieces of meat 15lbs and up, sometimes two larger cuts at a time...crazy, right? You will burn slightly (if not significantly) less fuel even at higher temps to compensate for reduced convective efficiency, because you are not heating as much air that flows through the chamber.

    If you leave the side intakes open (at least partially), you are in essence, mixing cold air with air that has been heated while it passed through the burner housing. This takes place somewhere in the smoke chamber above the water pan. I ran extensive grate temp tests on mine with multiple oven rack therms when it was fairly new, along with playing with the side intake draft positions with the tab-bend mod. There appeared to be some turbulence created when the side intakes were open much at all, and this translated into larger grate temp variances. The idea behind the side intakes is to aid in temp control, which is a good idea when you want to drop temps just 15-20* and a burner control tweek may throw temps too low...yeah, happens on all gassers, I think.

    Here's what I did with that project...been awhile,so even I don't remember exactly how it all went...maybe I need to review it myself for a bit of a refresher, but it was a good discussion as well. OK, just found it and opened it, it's a product review (lots of actual specs on my rig) along with temp testing, etc, 34 posts, total. There's a photo of a spreadsheet part-way down the first page (right-click and open to a new tab) that explains the details of my temp tests pretty well and further discussion on that, among other things: (EDITED)

    Last edited: Apr 18, 2012
  8. soslow

    soslow Fire Starter


    Boy you are intense, Good read and thank you for your help. Got home read the link and said how could this be?

    Cranked up the Smoke vault, any old setting (about 50 % my normal setting) on the gas vavle.

    Dropped my temp sensor at about 1/4 inch off # 4 rack and gave it 30min  reading 234 . Ok put sensor at rack # 2 were i cook ! And 225 Wow 9 deg. cooler !  I  need to do a more intense study.

    I hope the pics load in order.[​IMG][​IMG][​IMG][​IMG]

    Eric you the Man.

     How did that smoke stack work out for you??

  9. forluvofsmoke

    forluvofsmoke Smoking Guru OTBS Member

    Soslow, you're most welcome-

    I did that SV-24 write-up so others could have a better idea what could really going on inside their vertical smokers, as I noticed some slight temp variances right out of the gate when she was new. It helped me to document it for my own future reference as well. The specs I wrote up on it were just a bonus for others to compare with other brands and models, as the SV-24 didn't have any spec sheets online that I could find at the time,which I thought was kinda weird, but I figured it would be useful to someone, eventually.

    The vent stack mod increased the flow through the chamber, which offsets the reduction of convective efficiencies due to closing-up the side intakes to some extent. I did notice that when I use the stack mod, I get a bit faster cooking with ribs (time it takes for a certain degree of pull-back from the bone ends) at the same chamber temps as I would without the stack, so it helped a lot to compensate for that minor but noticeable issue.

    BTW, what I used for a stack mod was just a metal stack for an outdoor fireplace or chimnea, resting on top of the Vault cabinet over the vent, so I didn't have to make any changes to the rig itself, just for testing...worked so well, I kept using it as a temporary mod ever since then. It's about 24" high, tapered design, about 6" diameter on the bottom and 4-1/2 to 5" on top, with a dome for keeping out the rain and a spark screen under the dome (which probably slows the overall flow rate just a tad), but using it does add a lot more draft through the cabinet. What seems to make it wall work so well together (the closed side intakes along with the vent stack) is that you get better draft, and all the air moving through the smoke chamber is preheated because it has to come in through the burner housing instead of mixing after it goes into the chamber. This reduces the grate temp fluctuations, or so it seems, by quite a bit.

    Also, I left the Vault's vent damper set at full open while using the stack most of the time, and rarely would choke it back unless my smoke wood seemed to be burning up a bit too quickly, indicating excessive draft...not often, though.

  10. no peek n

    no peek n Smoke Blower

    Hey Ya'll, been dormant for spell, It was my thoughts as well Eric, I mostly smoke the ribs, links, fatties and tri-tips, on the upper 2 racks in my MB-XL, I feel that it is cooler away from the heat source but it give the meat more of a "convection" affect and "swirl" that is not very more pronounced to fluctuate and stay more consistence, and with the TBS, it give the meat more of a coverage and stays in contact before it goes out the top back vent, And to add that is where it keep my probe as well, on the middle sweet spot on the rack that would give the most even reading for ALL of the things Im smoking, or for the largest cut ae. brisket, Butt, tri-tip or sirloin, that will take the longest to smoke and needs the most consist ant temp reading, and everbody else in the pool can just take a back seat to the main beast, and just stay slow & low..that was another reason I gave my 2 cents to SoSlow to completely block off the 2 lower side vents to stop the cross draft that was just cooling off and pushing the heat right out of the top vents and drive his Temp in a head spin.I think the area of the opening to the burner was just enough to bring in air and heat it up before it goes up and Out. that is one thing I love about my MBXL is just one top vent to the rear that allows the heat and smoke to stay just a little longer n the chamber , and doesn't give a draft up/down with the weather outside. Plus i did a Calc on the ammount of LPG  I went through on one bottle, with a brisket, Butt, sammie, Fattie, tri-tip, 3 BB ribs 1/2 a rack of SRibs,  and a whole 14lb Turkey,, I used only 3.25 gal of Jungle Juice....It cost me to fill up $8.25 at the station, WOW.! I would have gone through (4) 18lb bags of kingsford. On my upright, and my Char-broil Offset smoker.. 


Share This Page