Sometimes I do things.
It sounds like something was changed somewhere in the settings.
In this case, I would recommend running a full uninstall and reinstall of MatterControl.
Before uninstalling, however, I would clear the cache as depicted in the photos below. Once you install a fresh copy from MatterControl.com, do not sign into your Mattercontrol account just yet. Set up everything as new to see if that resolves the issue. 
If you have printed with NylonX then the printing performance and warping will be very similar if not the same with the PRO series Nylon material.
The only major difference here is the Carbon Fiber in the NylonX.
@olivero said in PETG In elevated heat application for commercial use:
rinted a test peg out of ABS, PLA and now PETG as the material arrived and my main concern was the temperature, the water temperature in the machine gets upwards of 170-180*F so when I got the first Peg I put it through the machine and it actually survived really well, no flex or softening and no surface deform or layer split, it went through a
Heya!
Welcome to the world of 3D printing, glad you are here!
I am glad to hear the PETG worked for you to start out! I know it has a glass transition temperature of 80C ( about 176F) which it will start to get soft. That is kinda surprising but great news!
It is a bit hard to say how to resolve the cracking you are seeing.
PETG itself can be slightly flexible in some cases depending on your infil or walls.
If parts are cracking like that but now always, it might be the luck of the draw there.
What kind of settings are you using for infill and your walls?
Given the size of your part, I would say increase the walls vs infill since there wouldnt be much a benefit for strength.
That is a great question.
I would say try to open it up in MatterControl 2.0 which can be downloaded from mattercontrol.com.
MC 1.5 is extremely outdated and likely had a bug in the software which impeeded opening larger files.
In this instance, it looks like you may want to check your cooling fan. Making sure that it is on 100%for PLA.
I do not agree entirely with @mpirringer here. The reality is even a Nylon would not be good enough for something like this and the temperatures that can be reached in an engine bay. As I am sure you know, Engine bays can get to an excess of 280-300F
The material that comes to mind for something like this is Ultem material. Which, is not something that your machine can print and requires a highly specialized machine. Ultem material is actually designed for the automotive category and designed to be sufficient for high-temperature applications.
ABS or Nylon would likely not withstand these temperatures.
You can take a look at Ultem below:
https://www.matterhackers.com/store/l/3dxtech-thermax-pei-blend-175mm-05kg/sk/MXUMG8UX
I am not sure specifically which brush that is but that looks to be a regular brass brush you can get at a hardware store.
Though, I would advise caution in using something like this with the machine powered up. If the heater cartridge cable comes loose and the brass touches the exposed wires, it can cause damage to your machine. I would advise only using this brush while the machine is disconnected from power.
The first thing you will want to note here is you will need a hardened steel nozzle to properly print with abrasives like carbon fiber materials as the abrasive characteristic will hurt a brass nozzle over time.
That said, looking at the photo, it looks to be pretty wet. Depending on the material you will need to dry the material as most are hygroscopic.
I have included an article below that should help you out with wet material:
No such thing as a stupid question, you should be alright using the CR 20 Profile to get you up and goin.
Just note that you may need to do some fine-tuning in the slice settings as you print.