Flow problems with my custom build smoker

  • Some of the links on this forum allow SMF, at no cost to you, to earn a small commission when you click through and make a purchase. Let me know if you have any questions about this.
SMF is reader-supported. When you buy through links on our site, we may earn an affiliate commission.
Pics have me even more convinced the firebox is the problem.

Id cut a pie vent in the bottom of the box you have, then scab another section to the bottom to hold a ash pan,  Then drop your grate down low.  Or you could just cut a square hole out of the bottom and weld your grate right into that hole, then fab a 3 or 4 inch extention to add to the bottom with a front slide vent. . Either way, you wont have to make a new door .

Once again, you said blowing air through the vent got it going!!!

670a5e43_aaaaaa.png
 
Pics have me even more convinced the firebox is the problem.


Id cut a pie vent in the bottom of the box you have, then scab another section to the bottom to hold a ash pan,  Then drop your grate down low.  Or you could just cut a square hole out of the bottom and weld your grate right into that hole, then fab a 3 or 4 inch extention to add to the bottom with a front slide vent. . Either way, you wont have to make a new door .


Once again, you said blowing air through the vent got it going!!!


I am going to block off the top half of my intake hole and open up the drain I have underneath the fire box and run it that way. That should kind of simulate what you are talking about.
 
The drain hole is 1 1/2" diameter. I am going to block off the top half of this intake hole. That will get my intake pretty low and with the hole underneath the box. I figure the drain hole is probably a little small and the door intake is a little higher than you are discussing, but I figured it would somewhat simulate it and I could see if their was any improvement.

 
Here are some pictures of the fire. I have also made the opening between the fire box and cooking chamber larger like SQWIB recommended. I was able to get the pit up to 400 degrees before I started to back it down. That is huge improvement. I am heading in the right direction. Now that I have a little better flow I did notice some smoke coming out my cooking chamber door. I am going to have to try and seal that up a little better. I also need to come up with a deflector plate and or tuning plates to redirect some of the heat coming from the larger opening. I also opened up the drain on the bottom of the fire box while it was running and it made a noticeable jump in heat. I may have to change my intake setup to something like Ribwizard recommended. I jumped back and forth from a 3" stack to a 4" stack and did not see any change between the two. I blocked of the top half of my intake hole and it kept my temp down, so I opened it back up. I opened up my grease drain on the exhaust end and that didn't make a noticeable change either. So it looks like a larger cooking chamber to fire box opening, deflector plate or tuning plates, seal door better, and move intake as low as possible.

 
Wow. you certainly have had your share of problems and issues. Maybe these mod;s and changes will get it where it needs to be. Hope so.

Gary
 
I just wanted to tell everyone thank you for all the help over the last week. I have really learned a lot and happy to be headed in the right direction.
 
Here are some pictures of the fire. I have also made the opening between the fire box and cooking chamber larger like SQWIB recommended. I was able to get the pit up to 400 degrees before I started to back it down. That is huge improvement. I am heading in the right direction. Now that I have a little better flow I did notice some smoke coming out my cooking chamber door. I am going to have to try and seal that up a little better. I also need to come up with a deflector plate and or tuning plates to redirect some of the heat coming from the larger opening. I also opened up the drain on the bottom of the fire box while it was running and it made a noticeable jump in heat. I may have to change my intake setup to something like Ribwizard recommended. I jumped back and forth from a 3" stack to a 4" stack and did not see any change between the two. I blocked of the top half of my intake hole and it kept my temp down, so I opened it back up. I opened up my grease drain on the exhaust end and that didn't make a noticeable change either. So it looks like a larger cooking chamber to fire box opening, deflector plate or tuning plates, seal door better, and move intake as low as possible.


Just place the intakes below the grate level no need to go on the bottom of the firebox. I think you would have more control over vents on the side or the door as opposed to the bottom.
 
Just place the intakes below the grate level no need to go on the bottom of the firebox. I think you would have more control over vents on the side or the door as opposed to the bottom.

I just now saw your post after I had made a bunch of modification. My fault for not checking back, but I already cut the vents in the bottom of the fire box.
 
I ran the pit up to 465 degrees evenly across the pit for the first time. In one of the pictures you can actually see the flame being pulled into the cooking chamber. We have made huge progress. It is finally drafting correctly. The only thing I haven't done yet is seal the door better and make a handle to operate the new intake easier. The only problem I have now is when I close the intake to less than a quarter open. From a quarter open to full open it drafts awesome. Anything less then that and I lose all my heat at the exhaust end. The lowest I can get the pit to run evenly is about 300 degrees. If I dial down the intake any less than a quarter I loss about 75 degrees at the exhaust end almost instantly.
 
putting the pie vent directly under the center of your fire makes a huge difference. Where you will also see the advantage is on windy days, where as there will be less effect from the wind. Ive seen fireboxes with side vents actually have the wind stall the fire due to the draft it creates.
 
I ran the pit up to 465 degrees evenly across the pit for the first time. In one of the pictures you can actually see the flame being pulled into the cooking chamber. We have made huge progress. It is finally drafting correctly. The only thing I haven't done yet is seal the door better and make a handle to operate the new intake easier. The only problem I have now is when I close the intake to less than a quarter open. From a quarter open to full open it drafts awesome. Anything less then that and I lose all my heat at the exhaust end. The lowest I can get the pit to run evenly is about 300 degrees. If I dial down the intake any less than a quarter I loss about 75 degrees at the exhaust end almost instantly.
Now that's what I'm talking about

 
 
putting the pie vent directly under the center of your fire makes a huge difference. Where you will also see the advantage is on windy days, where as there will be less effect from the wind. Ive seen fireboxes with side vents actually have the wind stall the fire due to the draft it creates.
How does it work as a cleanout?, sounds like it may have a double bonus?

Piped inlets , reduce this effect dramatically adding valves helps even more.
 
Sorry to keep bothering everyone, but the only way I can keep my draw going is to have my inlet vent a third of the way open. At this point my fire gets way to hot and I can't keep the temp down in the cooking chamber. It runs above 375 degrees at this point. Closing the intake any further causes me to lose my draw and lose heat at the exhaust end. Any suggestions? I am guessing that I need to learn to build the right size fire with the intake open a third of the way to give me proper temperature. Just wanted to make sure I wasn't missing anything else that would cause a problem.
 
Last edited:
I understand that heat rises, but when I raise the exhaust end of my smoker I can get the heat to even out at lower temps. I am able to get down to 225-250 degrees across the pit when doing this. If I were to move my exhaust to the top of my pit would this improve my draft. I am not sure if raising the exhaust end is simulating moving my exhaust up. If I Iet the exhaust end back down I have to been around 325-350 degrees to get the heat even. If I have to move my exhaust I could always go reverse flow as well. I am not sure if either will make a difference, but I am running out of things to modify. The exhaust stack location is the only thing I haven changed.
 
I understand that heat rises, but when I raise the exhaust end of my smoker I can get the heat to even out at lower temps. I am able to get down to 225-250 degrees across the pit when doing this. If I were to move my exhaust to the top of my pit would this improve my draft. I am not sure if raising the exhaust end is simulating moving my exhaust up. If I Iet the exhaust end back down I have to been around 325-350 degrees to get the heat even. If I have to move my exhaust I could always go reverse flow as well. I am not sure if either will make a difference, but I am running out of things to modify. The exhaust stack location is the only thing I haven changed.
To be honest, I'm not sure what you want.

At the risk of sounding like a smart a$$ It's not an oven.
 
SmokingMeatForums.com is reader supported and as an Amazon Associate, we may earn commissions from qualifying purchases.

Latest posts

Hot Threads

Clicky