New Egger - First Post (Kick Ash question)

TheRainMan · January 2016

I have learned a ton from reading the experts on this site - so appreciative. I traded up from my Weber smoker to an XL BGE and am experimenting with different settings.

My question: Those of you who are using a Kick Ash basket - do you burn with the coal grate in the egg, or remove it. My first cooks on low and slow without the steel grate seemed difficult to maintain a 225 degree heat. Could that be because there is too much air with using the basket alone?

Thanks for the help!

WeberWho · January 2016

I leave the fire grate in with the KAB

badinfluence · January 2016

^^^^^^+1

tfhanson · January 2016

Must people leave the grate out as I do. You are going to get both answers.

chadpsualum · January 2016

^^^^^^+1

TheRainMan · January 2016

well there you go...

nobody has noticed any correlation between increased airflow and higher temps?

WeberWho · January 2016

TheRainMan said:

well there you go...

nobody has noticed any correlation between increased airflow and higher temps?

I noticed the airflow increase with my vent settings. The reason why I keep the fire grate in my large. Anymore airflow without the grate would change around the vent settings I know

Terrebandit · January 2016

Mine flows considerably more air with both the fire grate and the basket in place. The only reason I would remove my grate is to do a hot sear.

Ozzie_Isaac · January 2016

XL = grate in
L = your choice
M and smaller = no grate

TheRainMan · January 2016

Ozzie_Isaac said:

XL = grate in
L = your choice
M and smaller = no grate

Ozzie, sounds like you have thought this out - what is your thinking behind this?

Bulitt · January 2016

I have a large and leave the grate out. Works great!

Doc_Eggerton · January 2016

So, the basket is in the fire box, and the lump is down there too. Not on top of the grate?

Botch · January 2016

Okay, it's time. Viewer discretion is advised:

Image: http://tibbs.unc.edu/wp-content/uploads/2015/05/stand-back-im-going-to-try-science.jpg

A single hole in the OEM grate for the Large is approximately 0.6" in diameter, or 0.3" radius (I'm using decimal inches because it makes the math simpler, and Because I Can!).
Area of a single hole = pi * r^2 = 3.1415 * 0.3^2 = 0.2827 sq. inches.

There are 34 holes drilled in the Large OEM grate:
0.2827 * 34 = 9.61 sq. inches of opening for air to flow through.

Now, I regulate my low-und-slow temps with the bottom vent. It's normally between a credit-card and 1/16" open, but last weekend when I smoked a brisket overnight at 13º F, I had to open it to 1/8", or 0.125"; that's worst-case so I'll use that. The vent in my Large has a screen, and a strip of metal dividing the upper and lower openings, which are 1" long each. So, the total area for air to flow through is:
1.0 * 0.125 * 2 = 0.25 sq. inches.

So, let's step back and look at this. It can be helpful to view airflow through the Egg like water through a hose:

Hose: water that flows out of the faucet, has to flow through the hose, and has to flow through the spray nozzle, at equal rates. You can restrict the flow by shutting the faucet, or kinking the hose, or closing down the nozzle; whichever has the smallest opening controls the flow.

Same thing with the Egg: air that flows through the bottom vent, also has to flow through the OEM grate, and then the KAB if you have one, and then finally through the Daisy Wheel; whichever has the smallest opening controls the flow.

The bottom vent on my Large has a 0.25 sq in area, while the OEM grate has 9.61 sq. in. of area, or 3,845% more area!! So, finally, my point is (the crowd roars!) I can't believe that having the OEM plate in, or out, makes a damn bit of difference; the bottom or top vent control the airflow, not the OEM grate. That's my final answer and I'm standing by it.

EXTRA CREDIT: But wait, there's more! Above, I stated:
...whichever has the smallest opening controls the flow.
That isn't exactly true! Matter exists in three forms: solids, liquids, and gases (we'll ignore plasmas because physicists/astronomers are geeks). Liquids and gases are both fluids, with one important difference: liquids are incompressible fluids, while gases are compressible fluids. My above statement is absolutely true for liquids (smallest opening controls the flow) but gases can be tricked, compressed, and a bunch of more things happen, higher math than I can remember how to do (googlez "how a scramjet works" if you're interested).
At the tiny amounts of airflow to cook a briskie at 250, the above paragraph can probably be ignored.

THE FINAL ANSWER:
The whole idea of the Kick Ash Basket is to remove partially-burned lump, to both shake off the ash, and to clean out the bottom bowl easily; if the OEM grate is sitting there that gets in the way. Take it out!

(I promise I won't do this again, sorry!)

TheRainMan · January 2016

Wow @Botch - that was a lot of work - thanks! Helpful.

lousubcap · January 2016

@Botch- great post above...and not even considering the air holes in the fire box

@TheRainMan - welcome aboard and enjoy the journey. And the above can be expected for most answers to questions here-many ways to get to the promised land. Pick one and see how it goes-then adapt as you eggsperiment.

Jeepster47 · January 2016

@Botch ... terribly disappointed that you didn't cover the increase in volume of the incoming air as it heats up - about 20% increase per 100 degrees - and the additional gas as a result of combustion. That's the real secret to understanding how to adjusting both the top and the bottom vents ...

jtcBoynton · January 2016

@Botch Nice discussion. On the large BGE, the OEM fire grates are not all the same. Some of us have the older ceramic fire grates. They have the same size holes, but only half the number the cast iron ones have. So the air flow openings are less, but not enough to change your conclusion.

You demonstrate that the fire grate should not be the controlling the air flow, so removing it or leaving it in should not impact air flow. You conclude to remove it to aide in the cleaning functionality of the KAB. I reach a different decision - leave it in. I leave it in because:

Without the grate, small unburnt pieces of lump fall into the ash pit and never get burnt - a waste of potential BTUs and $.
The fire grate does radiate heat back up towards the food, making it more efficient.
The fire grate does radiate heat back up away from the bottom of the egg, resulting in less stress on the bottom shell of the egg (important to those of us without warranty protection for a cracked egg).

Ladeback69 · January 2016

I haven't gotten my KAB for my XL yet, but I have noticed that my Xl seems to get to temp and hold temp better with the SmokeWare Cap. I used New Years Eve and it got to temp faster and stabilized faster. Now I haven't used it again yet, so I am hoping that this continues. I am starting to rethink the KAB, but I am mostly getting it to help with cleaning out my XL.

What about the high Que Grate for the BGE, is it worth it in setting better air flow? Found this on Amazon. Kind of pricey.
http://www.amazon.com/Stainless-Charcoal-Grate-Upgrade-X-Large/dp/B00J95T6SO/ref=sr_1_fkmr3_1?ie=UTF8&qid=1452183746&sr=8-1-fkmr3&keywords=high+que+grate+bge+xl

jtcBoynton · January 2016

@Ladeback69 Go back to review @Botch discussion of airflow. Unless you are getting blocked air holes, the grate is not the controlling restriction. Putting a more open grate on the inside will not significantly change airflow. The bottom or top vents control. Using a KAB does help to reduce grate holes from getting blocked.

Caymanite · January 2016

I just used the KAB for the first time for a low and slow, with the fire grate removed, and I burned way more lump than I usually do. Wondering if this is because of the KAB or because I removed the fire grate. Will try the next cook with the grate in to see if makes a difference.

Sardonicus · January 2016

Caymanite said:

I just used the KAB for the first time for a low and slow, with the fire grate removed, and I burned way more lump than I usually do. Wondering if this is because of the KAB or because I removed the fire grate. Will try the next cook with the grate in to see if makes a difference.

First, note that the KAB sits apart from the inner wall a bit. Even though the amount of pre-burn lump may appear to be the same as usual, it probably isn't.
KAB users aren't beginning with the same amount of lump - if judging solely by vertical fill.
(Or, as @JohnInCarolina might put it, 'KAB users aren't cookin' with a full load'.)

Also, as others have mentioned, more non-ash debris makes it to the base when using the KAB sans OE grate. Maybe that adds to the impression that more is "burned".

If you accept the bottleneck theory as detailed by @Botch and others, then that is all that's left.

Or so it seems to me.

jtcBoynton · January 2016

@Caymanite Are sure it really was "way more lump than I usually do"? How much unburnt lump ended up in the ash pit? See @Sardonicus comment about appearance. Some more heat is lost through the bottom without the grate in place. It has been colder the past few days down here than it has been in a long time - it will require a larger fire to maintain temps. I'm guessing a combination of all things make it seem like 'a lot'.

Sardonicus · January 2016

jtcBoynton said:

@Caymanite . . .
Some more heat is lost through the bottom without the grate in place. . .

Hmmm . . .
This is not the first time that you (and others) have mentioned heat transfer through the base without the OE grate in place.
You have me wondering - Will use of this or other after market grates nullify the BGE warranty we paid for?

IF so, will BGE sacrifice the goodwill it has earned and use that as an out?

Not worried,
. . . necessarily.

Jupiter Jim · January 2016

Botch said:

Okay, it's time. Viewer discretion is advised:

A single hole in the OEM grate for the Large is approximately 0.6" in diameter, or 0.3" radius (I'm using decimal inches because it makes the math simpler, and Because I Can!).
Area of a single hole = pi * r^2 = 3.1415 * 0.3^2 = 0.2827 sq. inches.

There are 34 holes drilled in the Large OEM grate:
0.2827 * 34 = 9.61 sq. inches of opening for air to flow through.

Now, I regulate my low-und-slow temps with the bottom vent. It's normally between a credit-card and 1/16" open, but last weekend when I smoked a brisket overnight at 13º F, I had to open it to 1/8", or 0.125"; that's worst-case so I'll use that. The vent in my Large has a screen, and a strip of metal dividing the upper and lower openings, which are 1" long each. So, the total area for air to flow through is:
1.0 * 0.125 * 2 = 0.25 sq. inches.

So, let's step back and look at this. It can be helpful to view airflow through the Egg like water through a hose:

Hose: water that flows out of the faucet, has to flow through the hose, and has to flow through the spray nozzle, at equal rates. You can restrict the flow by shutting the faucet, or kinking the hose, or closing down the nozzle; whichever has the smallest opening controls the flow.

Same thing with the Egg: air that flows through the bottom vent, also has to flow through the OEM grate, and then the KAB if you have one, and then finally through the Daisy Wheel; whichever has the smallest opening controls the flow.

The bottom vent on my Large has a 0.25 sq in area, while the OEM grate has 9.61 sq. in. of area, or 3,845% more area!! So, finally, my point is (the crowd roars!) I can't believe that having the OEM plate in, or out, makes a damn bit of difference; the bottom or top vent control the airflow, not the OEM grate. That's my final answer and I'm standing by it.

EXTRA CREDIT: But wait, there's more! Above, I stated:
...whichever has the smallest opening controls the flow.
That isn't exactly true! Matter exists in three forms: solids, liquids, and gases (we'll ignore plasmas because physicists/astronomers are geeks). Liquids and gases are both fluids, with one important difference: liquids are incompressible fluids, while gases are compressible fluids. My above statement is absolutely true for liquids (smallest opening controls the flow) but gases can be tricked, compressed, and a bunch of more things happen, higher math than I can remember how to do (googlez "how a scramjet works" if you're interested).
At the tiny amounts of airflow to cook a briskie at 250, the above paragraph can probably be ignored.

THE FINAL ANSWER:
The whole idea of the Kick Ash Basket is to remove partially-burned lump, to both shake off the ash, and to clean out the bottom bowl easily; if the OEM grate is sitting there that gets in the way. Take it out!

(I promise I won't do this again, sorry!)

Totally agree, I just don't understand why we over think this air in and out theory! It takes just a little air flow to keep 225-250.

Jupiter Jim · January 2016

Sardonicus said:

jtcBoynton said:

@Caymanite . . .
Some more heat is lost through the bottom without the grate in place. . .

Hmmm . . .
This is not the first time that you (and others) have mentioned heat transfer through the base without the OE grate in place.
You have me wondering - Will use of this or other after market grates nullify the BGE warranty we paid for?

IF so, will BGE sacrifice the goodwill it has earned and use that as an out?

Not worried,
. . . necessarily.

How would they know if you had a non OE grate? I have had several items replaced under warranty and all I have had to do is produce a picture of the cracked, fire box, fire ring and Mini base. I have never been asked if I had any non OE equipment. In 9 years of Egging I have never had any problems with warranty.........................

Sardonicus · January 2016

Okay, Jupiter_Jim
Thanks loads.

Botch · January 2016

Jeepster47 said:

@Botch ... terribly disappointed that you didn't cover the increase in volume of the incoming air as it heats up - about 20% increase per 100 degrees - and the additional gas as a result of combustion. That's the real secret to understanding how to adjusting both the top and the bottom vents ...

Hmmm. You're right.
I'll need to think about this overnight, but for now my defense is: most of the gas heating, and all of the combustion, happens within the lump, way upstream of the bottom vent, OEM plate, and KAB. Stay tuned.

Botch · January 2016

jtcBoynton said:

You conclude to remove it to aide in the cleaning functionality of the KAB. I reach a different decision - leave it in. I leave it in because:
Without the grate, small unburnt pieces of lump fall into the ash pit and never get burnt - a waste of potential BTUs and $.
The fire grate does radiate heat back up towards the food, making it more efficient.
The fire grate does radiate heat back up away from the bottom of the egg, resulting in less stress on the bottom shell of the egg (important to those of us without warranty protection for a cracked egg).

Point One: At medium or high temps, those small pieces DO burn, sitting on the bottom of the Egg; plus, after a long low-und-slow, I pull those small lumps out of the cold ash and throw them into the next burn. Tie.

Point Two: The metal OEM plate, yes, would reflect radiant heat back into the firebox. Boynton 1, Botch 0

Point Three: True, the OEM plate would keep the bottom of the Egg cooler from radiant heat, along with blocking some of the smaller lump from falling to the bottom (see Point One above). Boynton 1, Botch 0

Argh. I don't wanna play anymore.

YukonRon · January 2016

I have a KAB for the XL & MM. I removed the grate in both. Air flow is better, heats faster, use about the same amount of lump, low and slows are no problem, and it is easier to clean. Glad I bought them.
Having had a fire grate explode previously inside my XL egg, and doing damage to the dome, PS and internal pieces, I no longer use the grates. After the warranty replacement on the XL, I purchased the Basket for that reason. Whenever I buy a BGE, it gets a KAB prior to use. Grates are pulled. Been using the KAB for while, no issues on stress in the bottom of the BGE, whatsoever. When home, the eggs are used everyday. I have done over 100 cooks, easily, no problem. Wish I had the KAB since day one. Pull the grate.

B747crew · May 2017

That was a very interesting post... thanks.. Just for laughs Density Altitude must play in her someplace LOL

Photo Egg · May 2017

From the KAB site, XL.
They still recommend keeping the OEM grate in place on the XL.
I know some on this forum remove it with no issues.
I think it was mainly due to warping as the XL span is much larger than the Large Egg. But the newer KAB does use heavier gauge wire.

Extra-Large Big Green Egg Ceramic Grill and Smoker.
17" Bottom Dia., 18.8" Top Dia. and 3.88" Depth
Overall height is 5.38" including handles.
Now with larger gauge wire similar to the other baskets
We still recommend using with your grill's lower charcoal grate

New Egger - First Post (Kick Ash question)

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