Myths: Thermostat

[85_Olds_Ciera]

In this commentary here (60DegreeV6.com > Homepage > Thermostat), it is suggested that "Open loop operation does not care if you have a 160, 180, or 195 degree stat. Closed loop is based on exhaust temp (O2 sensor working properly), coolant isn't below freezing (i have to look up the exact temp again...its really low though), and the time the car has been running."

As noted, closed loop for GM vehicles is:

1." Oxygen sensor output voltage is varied, indicating that the sensor has warmed up to operating temperature.

2. The ECT shows an engine coolant temperature above a specified level.

3. The engine has been operating for a programmed amount of time."


But, the best I can find for engine coolant temperature is above 100 deg F for TUNED PORT INJECTION (TPI).

And best I can find for engine operational time parameter is measured in the second range for OBDII type systems.

Would 100 deg F be good for OBD-I systems, along with engine operational time parameter being in the seconds range?

[Superdave]

in $A1 i have 3 closed loop enable timers, cold, warm and hot

Cold is 180 sec
Warm is 110 sec
Hot is 40 sec

I believe those are stock values as well.

I also have:

Max coolant temp for Cold C/L timer as 14.75c
Min coolant temp for Hot C/L timer 70.25c
Min closed loop coolant temp is 39.5c which is 103.1F