Fan speed all over the place


 
D

DavidAsman

New member
Every cook I've got seems to yield similar results to those in the pic. I cooked without the RD3 attached and my temp seems to stay fairly consistent once dialed in. I feel like I'm flying through lump with these cooks too... Ideas?

Also, is there a way of downloading the PNG file directly? This is a screenshot:

Screenshot_2016_02_04_05_07_22.png


PS. Is there a seamless way of posting images to this board? I'm not allowed to post attachments per my permissions...only post image from URL. (Thus the edits to this post)
 
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Need more information.

What type/size smoker? PID settings? Fan/Servo settings (min/max etc)? Top damper settings?
 
Where do you have top damper when doing cooks manually? I'd suggest starting around that point or maybe a bit more open.

Your graph suggests the RD3 was trying extremely hard to shove air into the grill and the top was blocking the effort. You will find as you open the top damper the RD3 will start controlling airflow from the bottom. Eventually you will find the door is about 25-35% open with the fan off and can stop messing with the top damper for that temperature.
 
Also, where is your fan blowing? Is it blowing above the coals? if so, that's wasted air. Again I ask, What's your setup? What Rig, what settings, etc. We need more information.
 
Sorry sorry sorry, been dealing with a sick pup the last couple days and couldn't get back on to see the replies!

The primary rig is a Kamado Joe Big Joe (I've also used it on my KJmini, but only a couple times). The RD3 is connected to a port that I've put in place from a piece of galvanized roof flashing where the bottom damper is, so it should be blowing right in the same way. I have the daisy wheel pretty much positioned the same way I would for a low & slow. I've toyed around with it less open or more open, but not much more -- the flap is still closed, just the holes more or less closed off using the spinner. I felt like a read something saying the top damper should only be open enough to slide a toothpick through...that seemed too closed off so I've had it more open than that. I can increase the opening further.

P = 8, I = 0.0035, D = 6; Servo pulse duration 320-2100. Ralph was concerned that 320 is too low, but I couldn't get the unit closed fully with it higher.
 
On my KJ classic, I keep the 5 daisy wheel holes fully open on low-n-slow cooks when using a servo driven damper. It's not the RD3, but that doesn't really matter. I think you're restricting the air too much by keeping the holes almost closed up. When that happens, the fan is going to have a difficult time.

I think your P value is also quite high. I'd cut it in half from 8 to 4 or even 3.
 
Steve_M said:
On my KJ classic, I keep the 5 daisy wheel holes fully open on low-n-slow cooks when using a servo driven damper. It's not the RD3, but that doesn't really matter. I think you're restricting the air too much by keeping the holes almost closed up. When that happens, the fan is going to have a difficult time.

I think your P value is also quite high. I'd cut it in half from 8 to 4 or even 3.
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Thanks for the direction! I'll definitely give both a shot on the next cook!
 
Another question that should be asked is what % was your blower running at? Clearly it powered through your top vent being too small and you breezed through your fuel to maintain temp. Also, how'd the food taste from these cooks? I was never a fan of my kamado when I owned it because I couldn't achieve the flavor I wanted, did forcing the burn make it taste better or was it just too much?
 
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SteveCK said:
Another question that should be asked is what % was your blower running at? Clearly it powered through your top vent being too small and you breezed through your fuel to maintain temp. Also, how'd the food taste from these cooks? I was never a fan of my kamado when I owned it because I couldn't achieve the flavor I wanted, did forcing the burn make it taste better or was it just too much?
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The food was good, but some bites tasted a bit "fuely" --- almost as though there was a gasoline/lighter fluid type taste. This might account for why I was burning through so much lump also.
 
DavidAsman said:
The food was good, but some bites tasted a bit "fuely" --- almost as though there was a gasoline/lighter fluid type taste.
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Makes sense. Blower was just pushing way too much air through it. I thought perhaps it might be good since you're using pure hardwood lump. Apparently not the case. Perhaps you could get away with it on short cooks though.
 
I would suggest you run the top vent open wider and probably lower your blower MAX value (though I dont think you've said what your blower settings are?), and I prefer the blower on at max only for low and slow cooking in a kamado. The general rule is when cooking with the blower on all the time you need to clamp down the top vent more (perhaps down to just a crack as you describe), when running the blower at max only (having the servo damper controlling the cook for the most part) you can run the top vent open much wider.
The reason I do low and slow with the blower at "Max Only" is to cure two of the issues you describe. When the fan is blowing cold air is forced through the pit which increases fuel consumption, at the same time the top vent needs to be nearly closed which lets smoke hang around in the grill long enough to get stale and give your food that fuel taste. In damper only mode there is no cold air forced in the pit so fuel consumption is less, and it allows you to run the top vent wider open so smoke flows out of the grill more freely preventing it from getting stale and putting that bad smoke flavor in the meat.
 
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