65m3/min is (2275 CFM) which should be enough for these 4 miners, but you know you can't exhaust more air than you intake, so even installing 2 or fans might not solve the problem, 400m tube is pretty small especially if the spacing between these miners isn't enough. So until you figure out a way to get rid of that heat, I would suggest you underclock all 4 gears, if it was S9s I would not even bother with 90c, but these 17 series are pretty sensitive to heat and they could die faster than you think if you keep running them this hot.
what would be normal temperatures for the 17 series? and is there any specific firmware you would recommend for the 17s and for s9s?
