Thought I would update for anyone thinking about the noctua mod
I got the 328 and did the fan swap out right out of the box, so nothing to directly compare it to. I used the low noise adapters on these. This is with roughly only 55w draw atm. I used a push/pull config here just because of how the board layout was.
Current temps:
CPU Temperature 48
CBoard Temperature 35C
FAN1 2805 RPM
FAN2 2925 RPM
For the 354, it was ALWAYS loud. Sometimes louder than others when it would ramp up to 7500+ rpms for no reason. I posted before the temps/rpms at a random time I checked it, but here's the recap:CPU Temperature 56C
Board Temperature 46C
Fans all 6400ish RPM
After swapping out for the noctua's:
CPU Temperature 59C
Board Temperature 33C
FAN1 4170 RPM
FAN2 4185 RPM
FAN3 4590 RPM
I did not use the low noise adapter here just in case it needed those extra RPMs. It's a little odd that the board temp decreased pretty substantially but the cpu temp rose a tad. It could be that it's only been back up and running for about an hour and it'll eventually get near where it was?
With both, they are virtually silent. If I put my ear up to the 354, I can hear it, but a few feet away, I can't hear anything. With the 328, even if I put my ear up to it, I can barely hear it.
Very easy to do. The 328 took less than 10 minutes. The 354 has a bracket running down the center that made it take a little longer because 2 of the fans it was hard to get to the screws. I ended up just taking it off and putting it back after. Took maybe 20 minutes. Very happy with the results.
Fans used - https://www.amazon.com/dp/B071W93333
It's a 3800x, so nothing crazy. Also these Noctua fans (https://www.amazon.com/Noctua-NF-A4x20-PWM-Premium-Quality-Quiet/dp/B071W93333) are very quiet at 3500 RPM (5k max I believe)
Sure! I'm assuming you're running a fully stock hotend. If that is the case, then the only fan that will fit, without modification, in place of the existing hotend fan is the NF-A4x10, 12v. That fan is OK especially if you do not plan to change to an all-metal hotend, but some people have reported that the cooling capacity is sub-par compared to the stock fan.
The better option would be to run a NF-A4x20, 12v fan. That fan will not fit in the existing hotend shroud, but I thought about mounting it on the outside of the shroud, which MIGHT be possible, or you can look into completely replacing the existing shroud with one that would fit the bigger fan (print in PETG if you do!) This fan should be more than sufficient if you only ever plan to run the stock hotend, but when I upgraded to an all-metal hotend, using only this fan I lost the ability to print PLA and PETG due to excess heat-creep resultant from insufficient cooling.
TLDR:
For the stock hotend this will fit in the existing fan slot and provide decent cooling
For a non-stock/all-metal hotend run a better fan or (like me) a couple noctuas since the one 40mm noctua of any size doesn't seem to be enough
EDIT: if you go with the noctua, red and black go to the red and black wires (obviously), and you can just clip the yellow one it doesn't serve any purpose in this setup.