How to fix water temperature fluctuation causing stutter in SILENT HILL 2 Remake fog scenes?

Fog scenes caused CPU frequency instability and rendering stutter. I tried maxing pump speed, but the noise was too loud. I used the GamePP Fan Curve Panel to set dynamic pump speed: low RPM below 60℃, gradual increase above 75℃. AIDA64 confirmed fluctuation dropped from 10℃ to 3℃.