Quick question on WSM

Discussion in 'Charcoal Smokers' started by jp61, May 26, 2016.

  1. jp61

    jp61 Master of the Pit ★ Lifetime Premier ★

    Hey guys!

    I've had my 22.5" WSM for a few years now but I've never cooked on both racks.

    Anything I should be aware of? 

    I'll be smoking four butts, two on each rack, the two bigger ones on the bottom, minion method with water in the pan and probably no foil. I normally don't probe the products I smoke but will this time around on the lower rack along with monitoring the grate temp. Will also monitor the upper grate temp as usual so I'll find out the answer to my questions. But... I'm assuming there's a temp difference between the two racks with the lower rack being a bit cooler? I'm hoping the two butts on the top rack will win the race. What has your experience been with a smoke similar to this one?

    Thanks in advance for your advice!
  2. lancep

    lancep Master of the Pit

    Hey man, I have the 18.5 so I don't know if there's a difference there, but I've gone upper and lower a few times. Sometimes I rotate sometimes I don't but usually foil so that might be a factor. Personally, however, I haven't seen much of a difference. For whatever that's worth.
  3. jp61

    jp61 Master of the Pit ★ Lifetime Premier ★

    Thanks for the reply!

    I'm trying my best here to avoid playing musical cooking grates. Not a big deal though, if I must, then I will.

    I'm pretty sure I'll be just fine by placing the two bigger butts on the lower rack. 
  4. lancep

    lancep Master of the Pit

    I'm curious about what your probes tell you but I don't really think you'll need to. For me it's about ease of operation rather than differences in temp. Once the the top cuts are are foil I can just lift the top grate, grab the bottom cuts and pop them on a waiting piece of foil and toss the foiled cuts on the bottom grate. But if you think about it, the reason the bottom grate (which is closer to the fire) would be cooler, is the big ole pan of water right below it. Well what is the effect of having two big hunks of meat immediately below the top grate? I would venture to guess that even if an empty smoker registered a temp difference between upper and lower grates, once the meat goes on, it probably evens out to negligible differences. .......... But I'm not a physicist so what do I know. Like I said I'm curious. Keep me posted and I hope goes well.
  5. On my 18.5 WSM, the lower grate cooks faster than the upper grate. I rotate the butt from top to bottom approximately 1/2 through the smoke. If I don't, the butts on the lower rack finishes an hour or so ahead of the upper grate.

    FYI: I don't foil or use water in the drip pan.
  6. lancep

    lancep Master of the Pit

    Well see there in, from a thermo-physics point of view, lies the question. Even in the 18.5," the water pan is quite deep. When heat is applied, the water in the bottom of the pan begins to boil. As it boils, it raises to the surface. As a result, the water at the surface is displaced to the bottom where it is heated this continuing the cycle. Given a deep enough pan, this could go on indefinitely, but in my case goes for about 6-8 hours. This action provides a large mass of regulated temperature right around 212* which, I believe helps maintain temp. This makes sense, since everything I've read says that the lower grate runs a little cooler. Now if you put a thermal mass, say 20 lbs of pork butt on the lower grate, will it provide the same function as the water pan does for the top grate. I've cooked two shoulders, one up one down, on my WSM a few times and both have finished nearly identicle. Whether I rotated or not. Same with ribs and at all points of the cook, both top and bottom are similar for all practical purposes. Like I said, I'm really curious.
  7. smokinal

    smokinal Smoking Guru Staff Member Moderator OTBS Member ★ Lifetime Premier ★

    I always use the water pan with water in it and the bottom grate runs cooler than the top.

    I would think if you run the smoker with the water pan empty then the opposite would be true.

    magnus likes this.
  8. jp61

    jp61 Master of the Pit ★ Lifetime Premier ★

    Weather today was HOT & HUMID!!! 

    Butts are Cookin' and the TBS is Rollin'...

    For the first 60 minutes there's a temperature difference between the two cooking grates with the lower grate being on average 10°F lower.
  9. lancep

    lancep Master of the Pit

    Can't wait to see how it comes out
  10. wade

    wade Master of the Pit OTBS Member SMF Premier Member

    I use sand in my water pan as the heat buffer and have noticed that the bottom rack seems to cook hotter than the top. I never measured it though in the WSM and so it is circumstantial. I have a ProQ  Frontier 18.5" now (almost identical to the WSM) which I use for demonstration purposes and I will fire it up today with a temperature logger on each rack to record any difference. I will post the results later tooday.

    A lot of factors are going to affect the temperature - including the outside air temperature and any wind. The meat mass on the bottom shelf will probably affect the temperature distribution too - especially when it is cold.
  11. lemans

    lemans Master of the Pit OTBS Member SMF Premier Member

    I always run my 22 WSM without water and just foil the pan. I have found that the heat goes up around the sides of the water pan and because of the shape of the interior, it gathers at the top grate. So stating the obvious.. Heat Rises... So the top rack is about 20 degrees hotter.. but after about an hour as JP said , everything evens out.. The slight differences should not effect your cook..
    But I very rarely use the bottom rack for the meat,
    I place an aluminum pan on it to catch the dripping for au jui...
  12. jp61

    jp61 Master of the Pit ★ Lifetime Premier ★

    Into hour 14 and nothing much has changed. Still averaging 10°F lower on the lower rack. 
  13. lancep

    lancep Master of the Pit

    Is there a difference in the IT of the butts?
  14. jp61

    jp61 Master of the Pit ★ Lifetime Premier ★

    [​IMG]  Don't know, I only probed one on the lower rack,haven't touched the lid since they all went in. What I do know is that there wasn't a difference in the sleep pattern. I imagine the top two are a bit ahead. I will stick it with the thermopen when the lower is near 200°.
  15. jp61

    jp61 Master of the Pit ★ Lifetime Premier ★

    hmmm.... this is different. I used one full bag of KBB as usual for overnight smokes. Not much is left and the probed butt is sitting at 171°. Looks like I'll have to start a chimney. Haven't run out of fuel on any of my overnight smokes in the past. These butts aren't that big, each package (two per) weighed just over 15 lbs. Not sure what happened.... quality of the charcoal, the extra mass, humidity, topping off the pan at about the half way point or a combination of factors? Little while ago still had some water in the pan and had 9° difference between the racks. It must be all gone at this point with both grate temps reading 208°. Time to start the chimney, not adding anymore water.
  16. jp61

    jp61 Master of the Pit ★ Lifetime Premier ★

    Lance, about 5° difference in IT between the two butts measured one on each level and after 15 hrs.
  17. lancep

    lancep Master of the Pit

    Good to know. You get your fire rebuilt? I have to that for every overnight on the 18.5 so I just plan for it.
  18. jp61

    jp61 Master of the Pit ★ Lifetime Premier ★

    I added one chimney full so far. At this rate I will probably have to do it again..... IT at 180°.

    I have been smoking at a lower temp than I normally do, about 215° average. Hope I don't end up with pork dust lol.
  19. lancep

    lancep Master of the Pit

    Hopefully you got enough beer there devil. You probably still get some good nachos out of dust😉 How have they been on now?
  20. Pork dust, the next must have, secret rub ingredient... [​IMG]  

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