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Reverse flow exhaust baffle?

Discussion in 'Reverse Flow' started by yieldmap, Mar 11, 2018.

  1. yieldmap

    yieldmap Newbie

    Hey all,
    I've been smoking on an electric, and pellet grill for a few months and decided to jump into the stickburner world. I picked up a used custom build trailer unit from a friend. 120 gal CC, 24" cube firebox. Seems to be a nice unit.

    While firing it up for the first time, it seemed difficult to reach temp's. I also noticed that the CC was always jam-packed with smoke when I opened it up to inspect. I'm wondering if the exhaust baffle plate is too low under the exhaust stack. I've looked around the site and seen some with plates, and some without. Take a look at the pics. Is there a spec for the drop on an exhaust baffle?

    Thanks in advance!

    Attached Files:

  2. smokejumper

    smokejumper Smoking Fanatic

    There should not be a baffle plate in the exhaust at all.
    My advice would be to remove it entirely.
    Remy Bernabela likes this.
  3. darkshadow

    darkshadow Fire Starter

    Seems odd and low.

    Can you post all your sizes? Maybe some of the boys can see another flow issue you could improve?
    Cc size
    Fb is 12,977 assuming 1/4 wall
    Fb-cc size?
    End of RF plate opening
    Stack size?
  4. daveomak

    daveomak Epic Pitmaster OTBS Member SMF Premier Member

    Where does the exhaust enter the Cook Chamber ??? If that's a damper in the exhaust stack, jerk it out.....
  5. yieldmap

    yieldmap Newbie

    Thanks for the replies all, I'm wondering if the exhaust baffle is causing the extra smoke, and the lower airflow. Here's all the dimensions of the airflow path. What's your thoughts after looking at the numbers?


    Attached Files:

  6. daveomak

    daveomak Epic Pitmaster OTBS Member SMF Premier Member

    Actual dimensions of the CC and I could give you some good numbers...

    Yieldmap's smoker.jpeg
  7. weedeater

    weedeater Smoking Fanatic ★ Lifetime Premier ★

    I would remove the baffle for sure as a start and see where that put me before making any other changes.

  8. yieldmap

    yieldmap Newbie

    Sorry, I forgot! The propane tank is 24" in diameter and about 67" long. The straight sided cylinder is 57" long, which leaves about 5" of crown on each end. Of course, part of the CC is taken up by the firebox, which sticks in about 6" from the end, and up 6" from the floor. The reverse flow plate is about 6.5" up from the floor as well, but I believe that's still considered part of the CC?

  9. yieldmap

    yieldmap Newbie

    Quick question....what does the upper air vent do for me in the firebox? I was considering a guru setup, would I still need the upper air vent at that point?

    I agree with the removal of the baffle. Is there any reason to keep any part of it....3" or so to keep heat in? If not, I'll likely torch out all but the bit in the center for the bacon rack support.

  10. daveomak

    daveomak Epic Pitmaster OTBS Member SMF Premier Member

    The upper air inlet to the FB has proven to be a good addition... It allows for cold air to enter and move heated air to the CC.. burning creosote in the FB... also, it adds extra air flow through the CC for temperatures that are more even across the food grate.. It reduces fuel usage by moving the extra heat in the FB to the CC... Think of it as the fan on your home furnace... You have the heat generator and the air mover.. The upper inlet is the air mover... it allows for fine tuning of the heat generated by the lower air inlet...

    The FB/CC opening should be about 110 sq. in. for optimum air flow.. the rest of the numbers are "OK"... The RF plate should be about 7" above the bottom of the CC ... but... 6.5" is close enough...

    6" exhaust stack is good.. It would be better if it was 35" or so above the CC... not a big deal..

    If you make the above modifications, you won't need the Guru... "once you learn how to operate the smoker"...

    The small "ish" opening of the FB/CC... Will cause the FB to overheat consuming excess fuel, and not allow for enough air flow through the CC..
    These smokers are a natural draft system... Constriction points that effect the air flow really screw up the natural draft..
  11. yieldmap

    yieldmap Newbie

    Thanks for the feedback on the airflow calc's. I'll open up the Firebox/CC opening...the current bottom is flat, and needs to be cut to the lower CC curve for easier cleanout anyway! I'll also zip out the exhaust baffle. I may give it a test burn and see how the fire and smoke behave. I also like the idea of that upper airflow vent in the Firebox, maybe a slider or a circular vent.

    Definitely worth a shot before buying a guru. My hope with the guru was to be able to load up the firebox a bit more, and get some sleep! But I certainly understand the idea behind fixing the base airflow problems before I start adding on electronics and widgets.

    Thanks again.
  12. daveomak

    daveomak Epic Pitmaster OTBS Member SMF Premier Member

    FB air flow diagram 2.jpg .. Smoker Exh and Intakes 2.jpg

    Smoker exh and int 3 Ahumadora.jpg
  13. yieldmap

    yieldmap Newbie

    Got back from Spring Break with the fam, and had a chance to update the Angry Pig. I thought "first things first" and removed most of the baffle plate. I left a bit to hold the bacon rail, but most of it is gone. Huge difference in airflow. No more choking and white smoke, just clean burning exhaust.

    I also learned a bit about fire management, and intake air. I used the bottom vents to control temp, but left the door open a crack to allow fresh air to mix and flow through. This seemed to help keep the air moving, and much cleaner smoke.

    As for fuel usage, I'm not sure what to expect, but it seems like I am adding a log split every 30-45 minutes to maintain 275. I'm afraid to load it up more, not wanting too much heat or smoke. Is this fuel add about what I should expect?

    Thanks all. It was a great day learning, with some awesome ribs as a reward. Truly the best ribs I've ever made....and not just because they were my first.... IMG_0429.JPG IMG_0434.JPG
  14. darkshadow

    darkshadow Fire Starter

    That little bit of the baffle should be good similar to lowering your stack/plenum lower then the top.