UDS question: How stable is stable?

junyo · Oct 10, 2012

...for temps?

This is my first, a classic UDS build; straight, no chaser. Seems fairly air tight. 14"x24" fire basket, caps and ball valve vents. Two 1" ID chimneys.

I can take the fire up or down at will, so air control doesn't seem to be the issue (I think). Doing the test burn, and my temp creeps up (maybe 1 deg every 5 mins) or down, can't seem to get it to lock in. 2 out of 3 vents closed, just working the ball valve, 70-60 deg ambient temp/60% humidity on the test day. I'm giving 20-30 minutes between adjustments.

So my question is what should I realistically expect as far as temp stability:

Dead nuts on the temp for hours, +/- a couple of degrees
The gradual delta I'm seeing?
An over/under fluctuation of 30/40 degrees? (I guess this is not mutually exclusive from the former condition)

Any guidance would be greatly appreciated.

Cliff H. · Oct 10, 2012

Mine will react to adjustments within a couple of minutes.

Once the temps come up to ( 270-280 ) and after the meat is on and the fat starts dripping In the fire and I shut my two intakes down to 1/4 and the weber lid daisy wheel is full open the UDS will find the temperature that it wants to run at for an extend amount of time.

Mine likes 265-275. It will ride between those temps for hours.

I have issues when I try to force lower temps, say in the 220 range.

colonel00 · Oct 10, 2012

Yeah, fluctuations every 5 minutes is to be expected. Just plan on cooking within a range. As Cliff H. mentioned, they tend to find ranges and sit within them.

Bludawg · Oct 10, 2012

Mine will not go lower than where I set it it my ride up as much as 10* then settle back. If it starts to fall usually around 20 hrs I know it is running out of fuel.

chicagokp · Oct 10, 2012

Mine will run between 250-275 without much tending. After 5-6 hours, temps will start to drop due to ash and a swift kick will get it going again. That being said, I use my IQ 110 now and set the temp and quit watching now.

Pappy · Oct 10, 2012

My UDS was hard to "set it & forget it", until I add a clay pot base for a diffuser. I also have the IQ-110.........so now I do "set it & forget it".

Daggs · Oct 10, 2012

What size are your intakes. I have 2, 3/4" intakes and a 2" exhaust. The highest spike I have seen was 312* after openi g the lid for much longer than I should have but is settles down to a +\- 10*. I cheat though I have ball valves on both intakes and the exhaust.

landarc · Oct 10, 2012

My UDS is very solid at 275F and up to 325F, all depending on where I set it. But, it does not have a large enough fire basket, so it burns out fast at 325F. Still, I am getting very good, controllable cooks at 300F and getting good cooks out of it.

Durzil · Oct 10, 2012

You'll see more fluctuations with no meat in it imo (lack of heat sink). I set mine at 275*ish by letting it get to 250*-260* and then closing my ball valve down some. Once it stabilizes (hopefully 270*-280*) I put my meat on (I always shut it all the way down (2-5 mins) prior to minimise spiking) I then put it back to my previous setting. Watch the temps for a bit. Make an adjustment as needed. 30-40 mins later, then let it ride from there normally. After 2 hours I'll use a stick to bang against the basket to clear ash and adjust as needed from there. I don't see constant swings but will see it change in longer periods of time as the fire moves around or ash starts to build up. Once you get to know your pit well it'll get predictable and repetitive. I'd smoke a nekid Fattie and then a pork butt to season and get to know your pit starting out as there forgiving to learn on.

Hook_Line_and_Sinker · Oct 11, 2012

I'm just thinking aloud here, but is two one inch exhausts = the area of eight 1/2 inch holes? I'm thinking you may need more exhaust area !

But in the 5 UDS I have built the temp stays +-8 of the seting once the meat is on. Until ash buildup or outside temp or wind changes a lot

Not that I think your exhaust is causing temp issues, I'm more concerned that it may not be as clean or blue as it should be.

martyleach · Oct 11, 2012

I find that at lower temps (230-250) it holds within +/- 15 degrees very solid. If you want higher temps that is a whole different deal as the drum will turn into a heat machine with its own mind and the temps become way more difficult to control.

GreenDrake · Oct 11, 2012

I agree with Marty, mine finds it's sweet spot right about 230 at the top grate. I use a simple heat deflector made from the lid of the original drum, just resting on top of my charcoal basket. So very happy with my cooker build, it's more fun than my other three pits to cook on.

willbird · Oct 11, 2012

For some reason mine on "manual" (I have an Auber too) is more consistent pulling intake air through a "plain" opening (I have street ells) than through the ball valve.

Bill

jmoney7269 · Oct 11, 2012

If it set mine on 225, 275,350 it stays there dead nut.
The BBQ guru is worth the $300 and paid for itself manytimes over in comps or me

junyo · Oct 11, 2012

Thanks for all the helpful replies. So I guess I shouldn't freak out, just need to give it some time to level set and to tune this drum in (already got the second one in the works, trying to run before i can walk :-D ).

Hook_Line_and_Sinker said:
I'm just thinking aloud here, but is two one inch exhausts = the area of eight 1/2 inch holes? I'm thinking you may need more exhaust area !

Might be, I didn't have a bung in the lid, so I guessed at the correct amount of exhaust. The pics are right after start though, and i assume that some of that was the grease and what not burning off; the smoke got cleaner quickly. Maybe I'll put in another chimney or two.

Durzil · Oct 11, 2012

I also notice that my smoke gets cleaner after I close the air down and let it level than when its ramping up, just a thought. While your learing just keeping trying and you'll work it out. I got better as I went and my pit got more predictable as it got a good seasoning. Best of luck!

Daggs · Oct 11, 2012

Hook_Line_and_Sinker said:
I'm just thinking aloud here, but is two one inch exhausts = the area of eight 1/2 inch holes? I'm thinking you may need more exhaust area !

But in the 5 UDS I have built the temp stays +-8 of the seting once the meat is on. Until ash buildup or outside temp or wind changes a lot

Not that I think your exhaust is causing temp issues, I'm more concerned that it may not be as clean or blue as it should be.

The surface area of 8, 1/2" holes is the same as 2, 1" holes (1.57) or(1.570796326794897) if you want to get specific.

Hook_Line_and_Sinker · Oct 11, 2012

Daggs said:
The surface area of 8, 1/2" holes is the same as 2, 1" holes (1.57) or(1.570796326794897) if you want to get specific.

That being said it looks like the exhaust is fine !

captndan · Oct 12, 2012

Don't forget about the fuel you're using. Different brands different heat etc. If you're looking for stability use only one high quality lump or briquets and stay with it. Also the ash buildup effects the heat. Another reason to use lump. It's your call.

jeffjenkins1 · Oct 12, 2012

I never have an issue with temps from 250 -290 it will rise up on its own at 300+.

I am not a big fan of perfect temp = good que though. I cook on all types of cookers, some with good controls and some without.

Usually the results are close to the same.

Jeff

UDS question: How stable is stable?

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