FLDAVE said: 191 deg. is low. Most run around 230 and higher when hot. This is normal. Sounds like somebody tweeked the fans to come on sooner. Oh, and the later models like a 195 deg. stat. The 180 takes too long to heat up to normal temp. Worse milage and more emissions. Remember, a stat doesn't control the operating temperature of the engine. The radiator (and fans) do.
Let me clarify a few points you make, so others aren't confused. The thermostat does indeed "control the engine temperature". It's that the thermostat is not the
only parameter that affects operating temperature.
In a nutshell, the thermostat controls MINIMUM temperature. Cooling fan settings control MAXIMUM temperature.
There are many influences as to the temperature an engine runs at. You insinuate that 230º is 'normal' and 190
is not. Wrong. A C4
should not run at 230º at all times. And, it may well run at 190º for a
very long period of time, even with a 180º thermostat, once Delta-T
to the radiator has stabilized. While 230º is
possible, and it is common for a C4 to reach
those temps when
airflow (road speed) is low, 230º is not a
temperature that should be expected for prolonged periods. Once airflow
is reestablished, coolant temp should drop.
In an early C4, the cooling fans are commanded
off at 35MPH. Later 2 main-fan and 2-speed cooling fan C4's have a complex strategy for fan control, but for the most part they too are fans-off at highway speed (LT5 turns off the fans at 45MPH. I'm not sure where LT1 turns off). So fans have nothing to do with temperature control at highway speeds. The OP's 190º at highway speed is 10º above the thermostat minimum temp. Seems about right. Depends on other factors as to how high above the
minimum (thermostat setting) temperature it actually runs at.
A thermostat has nothing to do with "how long it takes to heat up to 'normal'". It does depend on how much heat is being rejected to the coolant. An engine idling doesn't reject much heat. Start it, and run it up a steep hill at WOT, and it will get to "normal" (thermostat setting) much quicker. A thermostat is fully-closed until it begins to open at the set temperature. How can the setting possibly affect warm-up time? It can't.
The comment regarding "mileage and emissions" is most pertinent to the Coolant Temperature Sensor correction applied to a cold engine. A cold engine has to run richer for drivability. The warmer it gets, the amount of correction required ("richness") is reduced. Think of how a carburetor choke functions. It's been a long time since I looked at a L98 .bin. I don't remember exactly where the warm-up correction to CTS ends. I believe at about 175ºF-ish. The correction is VERY small near the top of the table anyway, and isn't of much influence above 125º or so. A 180ºF thermostat is certainly above where the CTS correction goers to 0%. A 160ºF thermostat is not. The fueling would never leave warm up enrichment in weather cold enough to keep the temps "on the 'stat" with a 160º. I bring the 160º up because I frequently see misguided peeps on other forums advocate a 160º thermostat for "performance".
There's some input from somebody that has a very solid understanding of how automotive cooling system thermostats, and cooling system Delta-T in general behave. Thanks for reading, hopefully everybody learned something from my effort.
martone_1
CaledoniaBrian
FLDAVE
