Stampede RT-590 3RPM Auger Upgrade

[flippingeo]

Hello fellow RT friends. I know you are just sitting there, watching football and wishing you had some long winded post on the RTF to read. Well you're in luck! I just replaced the factory 2RPM auger motor with an aftermarket 3RPM motor in my RT-590. And here's my story.

Overview​

When I bought my RT-590, this was my first direct exposure to pellet cookers. I had an aging, mid-range gasser and a 22" WSM I'd use for slow cooks. The gasser was in need of replacement, and the WSM was always more effort than I was looking for. So with months of research I landed on the RecTeq 590. It seemed like it would be a great way to consolidate my cookers. When I got it I loved it. Slow cooks became so much more hands-off and the smoke flavor was nothing short of the WSM IMHO. But, I quickly discovered that it wasn't a great alternative to a gasser for the quick cooks, searing, etc. So then I began researching what I could do to rectify this situation.

Issues Identified:

• Slow heat-up times for anything above 300° (30 mins in some cases just to get to 350°). God forbid I wanted 400°. I'd have to start the thing at breakfast to grill for lunch or early dinner.
• Even with Grill Grates, searing was just not feasible, or at least ideal, even if I wanted to wait an hour for the thing to heat up.
• When my wife wants a hamburger she only gives me a 30 min notice, and I must deliver. My RT-590 just wouldn't allow me to satisfy her.
• Impromptu "grilling" just isn't feasible, every cook must be planned out in advance.

Solutions Explored:

1. Purchasing another cooker (Bullseye specifically), but I really didn't want another cooker.
2. Attaching CampChef, or equivalent, sear box (Still an option).
3. Modify the RT-590.

I know from traversing this forum that I'm not the only one with these issues/concerns. So I was just about to pull the trigger on the Bullseye and I came across this thread in the RT-700 Group. https://www.recteqforum.com/threads/bfg-auger-motor-in-the-rt-700-its-awesome.3823/. I dove in. Let's try it, If I can avoid another cooker, I feel like a winner. I'm not the first to try this on the RT-590, but I've spent a good deal of time testing and documenting this so I thought I'd share. So here goes...

The TL;DR Version​

• What did you do? - I replaced the factory 2RPM auger motor with a 3RPM aftermarket motor found at SmokeDaddyInc.com - https://smokedaddyinc.com/product/3rpm-auger-motor-made-in-the-usa/
• Should I also get the Aluminum Auger Motor Stabilizing Bracket? - No. There isn't enough clearance to fit. (See details below).
• Was it easy to do? - Yes it was. Simply follow the instructions here -
• Did it fit without modification? - Yes it did. The upgraded replacement motor from SmokeDaddyInc.com fit perfectly.
• Did it make a difference? - Yes it did. I was able to reach temperatures at breakneck speed relative to the factory motor. I gained over 60° (12%) in max temperature, and ~70% gains on durations to setpoints. Substantial differences. All the gory details below.
• Anything negative to report? - TBD with further testing. I did realize some larger swings with the pit open tests. While it recovered much faster than the factory motor, it did swing quite high on some tests at 225° which is not great. However, this wasn't consistent so I'd like to do some further testing. It also seems a bit less stable at typical smoke temp (225°) which I don't like, but I'm going to try some cooks and see what happens. The 2RPM motor would hold dead nuts 225° for hours on end so expectations are a bit high.
• Would you recommend it? - It depends. If you are not having issues with your RT-590, only do slow/lo cooks on it, I wouldn't recommend it. If you struggled like me and looking to try something before buying another cooker, then yes. I recommend it. Based on other's experience, I would also explore the 2.5RPM motor. I'm looking to do that as soon as the motors become available. Others have reported lesser swing ranges than with the 3RPM.

​

The Details​

OK. For the rest of you who like this stuff, and want to read on, here are the gory details of this project.

General Information​

• Model: RT-590
• Min Feed Rate: 6.5%
• Temperature Calibration (Pit probe offset): +11%
• Pellets: RecTeq Ultimate Blend

Testing Preparations​

Conducted a series of tests that could be used to compare the 2RPM and 3RPM motor.

1. Clean the grill, scrape the drip pan
2. Calibrate meat probe using ice water calibration process
3. Set pit to 225° and place probe in center about 1" above grates
4. Let pit reach target and hold for 30 mins to stabilize
5. Adjust offset as needed for pit/probe alignment
6. Remove probe

Testing Process/Results​

This section describes the testing process and presents the results. I colocated the tests/results for easy comparison. I would have liked to have exported the Temperature History Charts, but unfortunately there is no way to do that in the app. I was going to grab screenshots and stitch them together for comparison, but honestly forgot. However these are the actual numbers realized at each phase of the tests.

Dates/Conditions

• 2RPM - Sunday, Oct 10, 2021
  • Environmental Conditions - Overcast/Cloudy; 65°; Winds 10 MPH/22 MPH Gust; RH 90%
• 3RPM - Saturday, Oct 16, 2021
  • Environmental Conditions - Overcast/Incoming cold front; 72°; Winds 16 MPH/26 MPH Gust; RH 76%

225° Startup Tests
Started the pit with a setpoint of 225°; Record time to setpoint.

• 2RPM
  • Start time - 10:45A; Time setpoint reached - 11:05A; 20 mins to setpoint from ambient.
• 3RPM
  • Start time - 1:00P; Time setpoint reached - 1:06P; 6 mins to setpoint from ambient.
    • Actually topped over at 227°. Blower fan was in constant intermittent mode. Blew for ~5 secs then paused for ~5 secs. Interestingly it does not really hold 225° like the 2RPM motor, it ranged +/-3°. Blower continued intermittent operation which is atypical of 2RPM.

Once reached, I held both tests for 30 mins to stabilize.

• 3RPM
  • At 30 mins, I lost fire (flameout). Dropped to 192° and never recovered. Pit eventually dropped to 130°. Stopped test to investigate. Firepit was empty, so I suspected auger jam or motor failure. I turned it back on to see if auger would run, it didn't I placed a handful of pellets in the pit and they ignited. Shortly thereafter the auger started operating. Hit 225° in about 5 mins. No more issues and seemed to be ok to move forward with tests.

225° Recovery Tests
Opening pit for defined times and recording max temperature drop/rise and time back to setpoint (stable). Once setpoint was reestablished, I held for >=15 mins before next test to stabilize. Reported below as (LOSS; RISE; TIME TO SETPOINT).

• 2RPM
  • Open 15 seconds: No loss; No rise; Stayed at setpoint
  • Open 30 seconds: 223°(-2°); 227°(+2°); Back to setpoint in 10.5 mins
  • Open 60 seconds: 188°(-37°); 228°(+3°); Back to setpoint in 22.5 mins
• 3RPM
  • Open 15 seconds: 198°(-27°); No rise; Back to setpoint in 2 mins
  • Open 30 seconds: 187°(-38°); 245°(+20°); Back to setpoint in 13 mins
  • Open 60 seconds: 215°(-20°); 228°(+3°); Back to setpoint in 13 mins

3RPM motor was definitely swinging wildly before it would stabilize at the setpoint. I can't really explain the loss/rise difference between 30/60 sec. More tests might be needed.

500° Ramp Up Tests
Adjusted setpoint to 500°; Record time to setpoint.

• 2RPM
  • 31 minsto setpoint from 225°
    • 350° at 6 mins; 400° at 9 mins; 450° at 14.5 mins;
• 3RPM
  • 9.5 minsto setpoint from 225°
    • 350° at 5 mins; 400° at 5:45 mins; 450° at 7 mins

500° Recovery Tests
Opening pit for defined times and recording max temperature drop/rise and time back to setpoint (stable). Once setpoint was reestablished, I held for >=15 mins before next test to stabilize. Reported below as - TEMP LOSS; TEMP RISE; TIME TO SETPOINT).

• 2RPM
  • Open 15 seconds: 476°(-24°); No rise; Back to setpoint in 4 mins
  • Open 30 seconds: 429°(-71°); No rise; Back to setpoint in 12.5 mins
  • Open 60 seconds: 394°(-106°); No rise; Back to setpoint in 12 mins
• 3RPM
  • Open 15 seconds: 492°(-8°); No rise; Back to setpoint in 2 mins
  • Open 30 seconds: 450°(-24°); 536°(+36°); Back to setpoint in 14.5 mins
  • Open 60 seconds: 357°(-143°); 541°(+36°); Back to setpoint at 15 mins

While the swings found with the 3RPM are much broader, I'm not sure how much it matters at this cooking temperature. At this point in the test, the weather had gotten a bit more rough. It was raining and much more breezy as the cold front was coming in. Overall recovery between the 2 motors are close in duration, but not temperature. On the 2RPM motor I was realizing no rise on the backside as I was with the 3RPM. Again, not sure it matters much at this cooking temperature, but noticeable difference. I do hope to do some more tests with this.

Max Temp Tests
Yup! It's now time to see how high this sucker can fly. Adjusted the setpoint to FUL and placed GrillGrates (GG) flat side up on right side. Observed and documented temps at defined milestones. GG measured with Thermoworks IR-GUN-S. Reported below as - PIT TEMP/GG SURFACE TEMP.

• 2RPM
  • At 15 mins: 498° / 533° - From 500°: +/-0° / +33°
  • At 30 mins: 519° / 548° - From prior: +21° / +15°
  • At 60 mins: 536° / 563° - From prior: +17° / +15°
• 3RPM
  • At 15 mins: 602° / 620° - From 500°: +102° / +120°
  • At 30 mins: 600° / 635° - From prior: -2° / +15°
  • At 60 mins: 600° / 645° - From prior: +/-0° / +10°

So with the 2RPM, I was unable to get beyond 536° even after an hour. IMO that is a tough temp to get a good sear. While yes the GGs were higher, still not high enough IMO. Not to mention I'm not willing to wait an hour to hit that temp. The 3RPM was able to jump up over 100° within the first 15 mins. As you can see, I topped off at ~600° so essentially it reached max temp within 15 mins from 500° start point. Impressive for sure, and with the GGs, I definitely feel comfortable this joker can give a good sear.

Supplemental FUL Test
Last night the cold front came through and cooled us off substantially. I wanted to do a cold start FUL test with the 3RPM. Here are the results:

• Environmental Conditions - Partly Sunny; 55°; Winds 15 MPH/26 MPH Gust
• 500° at 17 mins after start
• 600° at 25 mins after start
• Held at 600° for over an hour
• Recorded max GG temp just over the fire box at 657°

Replacement Notes​

Its easy. Just watch this video (

). Pretty sure it took me no more than 30 mins, and that includes time trying to figure out whether I could use the SmokeDaddy motor bracket. Some notes though:

While you're in there, go ahead and clean things up. Keyboard duster, Swiffer, whatever you have lying around. Bugs find it to be a safe place.

SmokeDaddy Motor bracket just didn't have enough clearance to use. As you can see from the photos, the factory motor is only supported by the auger shaft and a small plate under the motor. In the first picture you'll see the motor is crooked as there is play between the motor and the plate. I did end up putting a small piece of weatherstripping on the plate to reduce the twisting of the motor. Not sure how necessary it is though.

Comments/Issues​

Now, in addition to the temp swing issues with the 3RPM and the flameout I experience on the first test, there was something else I noticed that I want to mention. At this point, I still don't know if it is related to environmental conditions, or whether these new high heats are literally forcing the moisture out of the pellets, but on FUL I realized substantial condensation in my hopper. I'm diligent about how I store my pellets, and they are always dry. Now the pellets that were in the hopper likely grabbed some moisture from this recent Oct heat/humidity wave we've had, so that is certainly possible.

But either way, this is concerning. I will keep an eye on this in my next few cooks. I'm in MD, so we are almost always humid. Though I've never noticed moisture in the hopper before.

 

[C. Keeper]

Well done!
Thank you

 

[chadinsc]

excellent reporting. thats a fast grill now. should definitely be able to please the wife now with a burger anytime!

 

[Oldboy]

Great data!

 

[IPlayWithMeat]

Thank you for taking the time to post this. Great work!

 

[Waterboy]

Great write up. Did you run all of your tests with the minimum feed rate at 6.5? If so I wonder if you would get more stable temps at 225 if you tried setting the minimum feed rate to 3.5 or 4. Just a thought.

 

[flippingeo]

Great write up. Did you run all of your tests with the minimum feed rate at 6.5? If so I wonder if you would get more stable temps at 225 if you tried setting the minimum feed rate to 3.5 or 4. Just a thought.

I did not try it. Though certainly worth a try. I thought I read somewhere that MFR only relates/impacts to the Lo setpoint. (~180).

 

[Waterboy]

I believe it affects lower temps not just the Lo setting.

 

[Greg Jones]

I did not try it. Though certainly worth a try. I thought I read somewhere that MFR only relates/impacts to the Lo setpoint. (~180).

MFR determines the minimum temp your grill will cook at, regardless of what the grill temp setting is. So hypothetically you could set your grill to LO and it could run at 225*. Set it to 200* and it is still going to run at 225*. That’s when it would be advisable to set a lower MFR in order to lower the actual minimum cooking temp. There is a limit to how low one can go, as at some point the grill is going to be starved for fuel and experience flameouts.

 

[flippingeo]

MFR determines the minimum temp your grill will cook at, regardless of what the grill temp setting is. So hypothetically you could set your grill to LO and it could run at 225*. Set it to 200* and it is still going to run at 225*. That’s when it would be advisable to set a lower MFR in order to lower the actual minimum cooking temp. There is a limit to how low one can go, as at some point the grill is going to be starved for fuel and experience flameouts.

So in your opinion, could adjusting this improve my stability at 225? It doesn’t seem like it.

 

[C. Keeper]

So in your opinion, could adjusting this improve my stability at 225? It doesn’t seem like it.

FYI-
I had the 3 RPM auger motor in my 700. I removed it because the temps were unstable at 200 degrees and required tinkering with MFR to prevent flame outs. YMMV

 

[Greg Jones]

So in your opinion, could adjusting this improve my stability at 225? It doesn’t seem like it.

I really have no idea - I was just adding more detail on how MFR impacts more than just the LO setting. I’ve not experimented with auger motor replacement as I’ve been happy with the factory performance on my grills. I would trust @Psycho opinion on this as he has a lot of experience with the higher RPM motors.

Just curious, and perhaps you mentioned it and I missed it-did you contact recteq about the poor performance of the grill with the stock motor? What you’ve experienced is not the norm for these grills.

 

[Mike]

Great info @flippingeo. I'm making this a sticky for sure!

 

[chadinsc]

on my 700 with a 3rpm i have noticed that to run stable at 180-225 it helps alot to clean the firepot before the cook. with a clean pot mine will run extremely stable. i don’t vacuum it, i just get as much as my fingers will get.

 

[IPlayWithMeat]

on my 700 with a 3rpm i have noticed that to run stable at 180-225 it helps alot to clean the firepot before the cook. with a clean pot mine will run extremely stable. i don’t vacuum it, i just get as much as my fingers will get.

100% in agreement with this.

 

[drm31078]

What is the 2.5 rpm option that is being talked about? I only see 2 and 3 on the link provided.

 

[Gpsman007]

When my wife wants a hamburger she only gives me a 30 min notice, and I must deliver.

( still smiling on that one) and you have shown the lengths to which you will deliver. Kudos! Now with that said buy the camp chef sidekick and as the commercial says…she’ll like it to

 

[flippingeo]

Hey all, Just wanted to update everyone on things...

I've ended up removing the 3RPM motor and putting the stock 2RPM motor back in. I did this just prior to Thanksgiving as I was having major fluctuations as temps less than 300.

While there are several benefits of the "upgrade", overall it presented several impedances that I just couldn't deal with. I'm now back to shopping for either a Bullseye, or modding the RT590 with the CampChef Sidekick (still trying to figure out the right path here).

So why did I go back.

1. +/- 20 degree swings when cooking below 300 degrees
   1. I tried adjusting the feed rate, with no improvement
2. I don't believe the RT590 was built for high temps, at least not for a long time
   1. Upon cleaning before Thanksgiving I noticed my heat shield was twisted, badly. I'm going to have to order a new one.
3. I'm in a often humid climate (mid-atlantic), and high heat cooks were forcing moisture out of the pellets and building up in the hopper, creating substantial condensation ruining the pellets.

So while it does get hot, and get there fast, I don't believe it is feasible that this auger replacement is the answer to getting the 590 to be both a smoker and a griller. I don't want another cooker if I can help it, but its looking like I'll need to, or mod the 590 further.

 

[coast smoke]

I found that just using my Blackstone for searing was the best option for me. I really did not want to mod. my 590 because it seems like it cause more problems than it was worth. might try the Camp Chef Sidekick and have everything tigether.

 

[DesertRat]

My 590 holds at 2:25, as yours did, with the original auger. But I’m not satisfied with using it as a grill either. I did read a substantial portion of your tome. Gave up and just decided to go with another gasser four steaks, as I have promised a bit failed to do on previous posts on this or similar forums.

However, in the interest of science I showed your post to my aerospace engineer sol. He urges you to put in an application at blue origin or that other guys company.