This article will use some hands on testing to illustrate the lessons learned in the previous article, and in addition, go through cooking 2 pork butts to show what happens to the temperature in the cooking chamber.
We will use a temperature logging tool that is readily available to anyone, to run some simple tests and show how the gradient heat works in the Yoder Smokers pellet cookers, and how an aluminum pan, introduced into the cooking chamber, affects temperature performance.
We will use a Fireboard temperature logger to gather the data and chart the test results: https://www.atbbq.com/fireboard-fbx11-w ... ition.html
The photos and test results from this test are from a well used Yoder Smokers YS1500 that was built late in 2013. This cooker has cooked thousands of pounds of meat, burned through tons of pellets, and has been the guinea pig for engineering and programming changes. It is currently running B20 firmware and configured like the cookers currently leaving the factory, with the exception of a fixed chimney stack (not removable) and an original burn grate (not reinforced). The pellet fuel that is exclusively used is a 50/50 mix of BBQR's Delight pecan and cherry. In consideration of this, if the reader attempts to exactly duplicate the listed results, there will be differences and variations in the data, but the overall findings should be the same.
We will use 6 Fireboard temperature probes for this test. There will be 4 Fireboard meat temperature probes, one each on the lower and upper grates at 14" from the hopper wall, and one each on the lower and upper grates at 28" from the hopper wall. There will also be 2 fireboard ambient temperature probes mounted toward the mid point of each grate, one on the lower grate and one on the upper grate, mounted in Fireboard probe holders 1" above the grate surfaces. The goal is to simultaneously record 6 temperature locations over a 2 hour test period by following our Yoder Smokers factory temperature test (download/Best%20Practice%20and%20how%20to/Yoder%20Pellet%20Temperature%20Test%20v2.pdf), and then cooking 2 pork butts, one on the lower grate and one on the upper grate, illustrating the gradient temperature in the cooking chamber, from side to side and bottom to top, and the resultant effect on the Fireboard temperature readings without moving any of the temperature probes inside the cooking chamber after placing meat on the grates.
The YS1500 HMS plate damper was left fully closed (pushed in) and the YS1500 chimney damper was wide open from the start to the end of this test. Nothing was changed or modified during the test.
The temperature that was set on the controller for the entire test was 250 degrees.
Here are 3 pictures showing how the 6 Fireboard probes were arranged in the cooker. The 4 Fireboard meat temperature probes were placed per the instructions from the Yoder Smokers factory temperature test for a YS1500, and the 2 Fireboard ambient temperature probes were placed in a location common to owners communicating with us about temperature issues when cooking.
Lower Grate
Upper Grate
Combined
The next 2 pictures show the YS1500 door gauges 1 hour after pushing the START button to begin the test.
Upper left door gauge
Bottom right door gauge
The next 2 pictures how the 2 10 pound pork butts placed on the cooker, 1 on the lower grate and 1 on the upper grate.
Upper grate
Lower grate
The next 2 pictures show the YS1500 door gauges 1 hour after putting the 2 10 pound pork butts on to cook
Upper left door gauge
Lower right door gauge
The next 2 pictures show the pork butts after sealing in pans, and placed back in the cooker.
Here is the Fireboard session graph for the entire time the cooker was on, including the 2 hour temperature test and the cooking of the pork butts.
Here is the graph that I made showing the data through the entire time the cooker was running.
Let's take a look at what happened. To make the graph easier to read, I didn't place any analysis in the graph, but rather sectioned the graph and numbered the sections from left to right. The analysis for each section follows.
All of the data came from the captured data from the Fireboard session, with the exception of the controller display temperature, which was captured directly to a laptop using our internal proprietary testing tools (during this test, our testing tools recorded almost 150,000 temperature readings). The fireboard session data was downloaded at the highest resolution of data points, and then put into a spreadsheet to chart and calculate the results shown in the chart (over the test the Fireboard recorded almost 8,000 temperature readings).
The first thing to understand is that this YS1500 is consistently reading hotter than the set temperature. In our experience, the more a cooker is used and seasoned, coupled with proper maintenance and cleaning, the better they perform, and the better they hold heat. We have numerous employees, and many YS1500 owners that have experienced the same results as documented here.
Section 1 - As stated in Part 2, this is the normal 30 minute warm up time.
Section 2 - This is the next 1.5 hours of the cooker running the Yoder Smokers factory temperature test. The cooker lid has not been opened since it was closed during startup.
Average temperature readings over the 1.5 hour temperature test
Lower 14"308.3
Lower 28"295.8
Lower center above grate302
Upper 14"295.7
Upper 28"283.6
Upper center above grate288.1
Controller Display temp250.3
Section 3 - Opened the lid on the cooker and quickly placed two 10 pound pork butts, one on the lower grate and one on the upper grate, directly centered between the 14" and the 28" probes and directly in front of the ambient probes, in the center of the grates. The pork butts were both placed with the fat cap down toward the HMS, with the bone pointing toward the hopper end of the cooker. The meat was placed per the results of the temperature test in part 2, i.e., the fat cap and bone toward the highest temperature potentials. I did not outline a 30 minute recovery period after placing he pork butts in the cooker, because the process was done quickly and the heavy metal mass of the YS1500 cooker helped to immediately recover temperatures in the cooker.
If you compare the temperatures from Section 2 and Section 3 of the graph, you can see that the cooker is functioning properly and consistently above the desired set temperature of 250 degrees, but the placement of all of the Fireboard probes in proximity of the pork butts is skewing the Fireboard temperature readings and causing the waveform temperature swings. This deviation is caused by the cooler temperature of the meat and the "bubble" of evaporation surrounding the meat during the cooking process. This is all normal, and expected. We field a lot of questions about why the ambient probe in a cooker is up to 50 degrees cooler than what is being displayed on the controller; this is the explanation.
The red arrow is approximately 6 hours after placing the pork butts on the cooker, and where I opened the lid on the cooker to check the status of the pork butts to see if they were ready to wrap. They both had the color I was looking for and the bark was hard set, i.e., I couldn't remove the seasoning off the surface by gently using a fingernail to scratch across the surface. I removed the pork butts, placed them in a pan with some liquid and more seasoning, and used foil to seal the pan around the pork butts, placed them back into the cooker and closed the lid. The temperature probes were not moved from their locations. Unlike the YS640 test, where the cooker set temperature was raised to 325 after wrapping, the set temperature of 250 was not changed. Because of the heavy metal mass of the YS1500, the temperature recovery from having the lid opened while wrapping the pork butts was very quick, so unlike in the YS640 test(s), there was no need to chart a 30 minute transition for temperature normalization that required removal from the average temperature calculation.
Both pork butts were done, and removed from the cooker, at the same time. The internal temperature reading (taken with an instant read thermometer) were within 3 degrees of each other, with the pork butt on the bottom grate reading 3 degrees higher than the pork but on the upper grate.
Average temperature readings for the entire Section 3 of the chart
Lower 11"280.9
Lower 22"256.3
Lower center above grate271.1
Upper 11"284.4
Upper 22"256.5
Upper center above grate273.6
Controller Display temp250.2
Even though the focus and intention of this test is to document the effects on temperature by placing meat in the cooker too close to ambient temperature probes, I wanted to share the pictures of the final product after the test.
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