1. Never run any engine long with water cooler than roughly 185*F
... because it accelerates engine wear everywhere not just the cylinder
2. Temperature reading MUST be confirmed:
A. use at least two different temp sensors
B. try to use two different locations on the engine (ex. 1 in head, 1 in the water outlet to rad)
C. Pay attention to where the temp sensor location is with respect to water temp,
i.e. water WARMS as it moves from one side of the engine to the other,
most engine have TWO different temp sensor locations (e.g. LS engine head location choice) and this will impact the reading!
-most engines flow from back to front- so take your reading near the front
3. The ideal temperature range for majority of daily drivers with turbochargers is near 190 to 195*F (195 to 200*F outlet temps). For "old" engines like sr20det a max of roughly 210*F is recommended when using gasoline and especially when climate temp ambient is 80*F ( hot outside like Florida)
However!
210 to 225*F is technically "safe" for engine oil and engine coolant temps.
It isn't good when using gasoline because the high temp upsets the fuel and that is NOT GOOD when using turbochargers to boost compression.
-> Also there is temp rise as the engine accelerates, so if the engine starting at 210*F then it will finish the run at 220 or 230*F is likely.
Thus, we should keep our turbo sr20det engines near 190*F perhaps 188*F as much as possible, then allow them to warm to near 210*F as they are heavily loaded / raced around.
Note / example
* an outlet temp of 195 to 200*F could put the temp inside the engine near ~182*F at some point