New Digiq DX - Overshoot issue


 
B

Ben Leyhew

TVWBB Member
I just received my Digiq DX and have hooked it up to my WSM 18.5. I also picked up the hole plugs mentioned in another post--thanks for that helpful tip. I loaded the charcoal ring with cowboy hardwood lump charcoal first, then put a layer of briquets, lit 7 briquets in the chimney starter, then put them on. Temp ramped up just fine, surprisingly my lid temp is reading exactly what the Digi shows. I am cooking an 8.5lb boston butt and have set the temp at 215. After 1.5 hours, the temp has steadily climbed to 270. All lower vents are closed per Digi's instructions. I closed the damper on my 10cfm fan from 100% open to about 25% and closed the top vent to about 50%. Is there anything else I should do to try and bring the temp down? I am assuming that with a full load of charcoal it is all just starting to heat up. Are there any other tricks or tips to keep the temp from overshooting? Thanks!
 
Sounds like you may have an air leak, plus I would start your cooker on much less lit fuel. You can get by with much less, and I am thinking you can start off with a quarter of a chimney, plus I would close the top vent even more. I usually just barely crack the top vent just to let the smoke out. I also think that you may have too much fan for that cooker. I use a 4 cfm fan on both the 18.5 and the 22.5 cooker and it works just fine. You may want to just set your damper at 25% to start with and leave it there throughout the cook.HTH
 
Update: I have closed the top lid vent completely. I think the higher temp was caused by too much fuel rather than an airleak. I only lit 7 briquets--I just put way too much charcoal in the ring. Also, I think the lump that I used is burning hotter than the kingsford I typically smoke with. I will definitely use less charcoal next go round. Live and learn. This is my first ATC assisted smoke and am excited to get to use my new toy. As for the fan, I went with what BBQ Guru recommended. I would rather have too much than not enough. I will leave the damper at 25% and let it kick on when needed.
 
I own a CyberQ II and have a few observations.

1. You can put all the unlit briquits or lump that you want and it hasn't ever caused a high temp on mine. For a long cook I've put as much as fifteen pounds in without a problem.

2. Seven coals is fine as a start. I've been known to start three spots in the ring with a tourch which I'm sure starts more than seven.

3. The fan is fine I have a 10cfm on mine. There is a setting that controls the fan called the pulse time, mine defaulted to 6 but you can raise it. This value determines how often the fan pulses to give the fire air. You could raise it from 6 to 10.

4. You don't mention where the top vents started. But with a power draft system you don't need them to be full open. Low and Slow cooking I have them open about 1/3 for a target pit temp of 225. If the vents were open 100% then you are most likely creating a passive draft where the fire is getting air from somewhere other than the fan. I leave my fan dampner wide open, but you could shut that down a little. Look for leaks around the door, or other vents.

How old is your Weber? Mine had a dozen or more smokes on it before I hooked up the CyberQ unit and it holds a temp really well.
 
My smoker is about a year old. I smoke something at least once per week, often times more. I would say that I have 75-85 smokes on this thing so far. My wife thinks I am insane. I initially left the top vent at 100%--I agree with your assessment and think that is probably another contributing factor to the higher temp. On traditional smokes, the weber holds the temp just fine. I deviated from my normal routine with so much charcoal and leaving the top vent open. I have had this pork shoulder on the smoker for approximately 12 hours. Another Update--I just did an experiment with the top vent--fully closed it is holding a temp of 200 (which I set on the DigiQ). Then I opened the top vent to 3/4, within 15-20 minutes the temp had climbed up to 240. I am positive this is the culprit to my higher temps. Initially, I was concerned leaving the top vent shut and potentially oversooting my food. I appreciate all of the insight and expertise from all you smoking gurus!
 
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Smoke Ring Full of Fuel
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Fan Hooked Up
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Boston Butt after 18 hour brine
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Butt Rubbed!
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Smoking After several hours
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After 15 hours and just slathered on some Sweet Baby Rays.
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DigiQ at 225.
 
I noticed how you have your Pit probe attached and have two suggestions that I think work well for me.

With the alligator clip connected to the grate I've been afraid that the temps might become skewed in one direction or the other since you are reading the tempature of the metal more than the air.

I use one bamboo skewer and by placing that in the center of your brisket you can attach the alligator clip a few inches directly above your meat.

I just like having the pit probe suspended in the air above the meat.

BBQ Guru sells a probe tree that does the same thing but it is inserted into the grate so it would have to be beside your meat not above it.

I would leave the vents barely open to 1/3 open on top but personally I would not shut them off completety.
 
I ordered the probe tree, it just hasn't arrived yet. I will see if that has an effect on the temp. Surprisingly, my DigiQ and the lid thermometer were reading the same temp.
 
Here is a pic of the finished product. I foiled it up and put it in a cooler for a couple of hours. I mixed up some of that finishing sauce: apple cider vinegar, apple juice, water, brown sugar, black pepper, red pepper flakes, and Rendezvous rub. I also used some Sweet Baby Ray's. It was outstanding.
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I just ordered the DigiQ DX, myself. I'm hoping it arrives tomorrow... but I doubt it will. Probably tuesday.

Anyway... I also got the 10cfm fan as the bbq guru recommended. Before reading this, I probably would have left the top vent 100% open.

I will also be sure to attach the alligator clip to a skewer and not the grate.
 
I firmly suggest the probe tree since I don't like the way metal to metal contact can influence readings. The pit probe slides into a silicon collar which eliminates metal contact. Be sure to place the probe tree away from the sides of the grate since heat rising can influence the readings. For this reason, I place my probe tree somewhat in the middle of the grate centered over the water pan. (I use a foiled clay saucer in my pan)
You may be surprised that wind breezes in your cooking area can travel into the viper fan and add more oxygen that you expect. If you have the fan's damper wide open, breezes can get to the coals even if the fan is not pulsing. 50% fan damper setting on your system should work.
I try to leave the top damper on my WSM open at least 50% or more. Closing down too much will trap smoke in the chamber and make your meat get coated with creosote produced by the smoke. Gives an acrid oversmoked and bitter taste.
Its all a learning experience but a fun one.
BTW...IMHO, lump charcoal is the root of all evil. This comment will draw controversy, but I have learned to stay well clear of lump for lo n slo cooks. After all....lump is advertised to give hot, rapid burns. Is this what you want in you lo n slo cooker?
Good cookin!
 
The probe tree works very well. It keeps the temp readings very consistent. You can see it next to the bird in my pic. I have cut way back on my charcoal usage since getting the DigiQ DX. I only fill the ring up about half way and only light about 5-10 briquets. I let the ATC bring it up to proper temps. I do notice much higher temps when leaving the top vent open, so I am only leaving it barely cracked now. I haven't noticed too much smoke or negative flavor as a result. I do use water in the pan so that may also play a part to keep the smoke levels down. I agree with the assessment on lump--I have had better results with kingsford (more stable temps).
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Hey Ben, Thanks for the good looking pics. On the probe tree, there are two silicon tips that look like large pencil erasers with holes in them. They slide up and down on the center rod on your probe tree. You can take the pit probe out of the alligator clip and push the probe thru the small hole in the silicon tip. It can be adjusted up and down to your liking. If you use two pit probes like I do (Maverick ET-73 and Guru pit probe) both of these tips can be used close together for consistent readings. By putting the probe tip directly into the silicon tip, you will eliminate any metal to metal cntact.
I bet that turkey was really good. It looked great Ben!
 
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