The Turing Pi 2 (v.2.4) has actually some secrets that just start to get uncovered. Looking closely at the board, you will find the red marked area with what seems to be an unpopulated 4-pin fan header (J16) and an unpopulated IC spot (U109).
These spots were, as found out by Sam Edwards (CFSworks) actually a place to install Molex 47053-1000 4-pin fan connector and a Microchip EMC2301 fan controller. It is not clear why they were left out of the production model, probably for cost savings, but without that the Turing Pi 2 lost a nice smooth fan controller. However, thanks to Sam Edwards work, the chip is now supported by the Turing Pi 2 BMC, so that after retrofitting, this will just work out of the box!
To do this little hack you just need to order an Microchip EMC2301 in its MSOP-8 / standard packaging. If you don't find the specific molex conenctor its also fine if you "just" use an male 2.54mm header pin. Yes, you will not have the locking feature of that connector and you will need to watch out for the correct orientation when plugging in fans - but it still works in a pinch.
When soldering I would advise to solder the EMC2301 first onto its spot, the orientation is as shown in the second picture. Afterwards you can solder the fan header.
Make sure the circle matches up as shown so that you got the chip in the correct orientation.
After the installation, update your Turing Pi 2 BMC to the latest firmware 2.0.5. Please make sure to read the comments on the repo, if you're updating from a BMC version < 2.0.0 you will need to make a first flash via a Micro SD card to get to version 2.0.0 and update further afterwards.
When everything is done and you log into your Turing Pi 2 BMC, you will see this nice slider to set the speed of your EMC2301 connected fan.
Currently there are still some things up for debate and configuration with the latest kernel release which changed naming of components but overall its already working and a nice and easy mod to get a better fan controller installed - instead of just the "on/off" as soon as one Turing node gets activated - or all deactivated.
Again, thanks a lot to Sam Edwards who had the idea and came towards with the PRs and implementation - thank you! 🙂