Yes. Ambient temperature. All the time. Multiple systems all at ambient temperature doing things this way. Maze 4 waterblock, Black Ice radiator (much better than the heater cores from pintos I had to use back in 2000), reservoir up high and 350gph pump with 1/2" tubing compression fittings all around. Ambient temperature readings of CPU temps from the motherboard, even after overclocking. 0.00 C/W is possible with watercooling without having to use a peltier. which i've also done plenty of, but there's not much need unless doing extreme overclocking with high vmods. anyways, just wanna say it is possible. the compression fittings mainly work so well because of the increased flow at the waterblock and the pressure with which it's hitting the waterblock right above the core which makes for better thermal transfer between the copper into the water. it's sucking the heat away as quick as it can be made and staying at ambient temps. or i could be crazy and have been doing everything wrong and should never have had dangerden start manufacturing their radiators with threaded holes (it cracks me up that people then just put hose barbs back on). so do i need to be more technical and say 0.000001 C/W?
