Couple years ago I revamped my entire cooling system because I was running 220-260 all the time. Well now especially with cooler weather here I took a road trip the other day and barely ever got over 165. Is this ok. I know this will leave my system in open loop (or is it closed loop) either way that will basically richen the fuel mixture which could lead to O2 sensor and catalytic converter early failure. Any other problems this could cause. Should I be concerned and go back to a 190 thermostat? See SIG for current setup.

 

you pretty much answered your own questions.

just put in a 195 thermostat, should take about 10 minutes at the most.

 

Actually my question was what kind of problems can it cause or what should I be concerned with if it runs to cold. I know how to make it run hotter I just don't know if its necesary. After all we hear all the time a cooler running engine is better for performance but how cool is too cool?

 

At a temp of 165° the system should have no trouble getting into Closed Loop. It should be in Closed well before 165°. The only real effect the lower t-stat should have is the warm-up time when you first start the car in the A.M.

This is from the FAQ section and the info. comes straight from the GM/Helm repair manual:

Q: What is the difference between 'Open Loop' and 'Closed Loop'?

A: When the engine is first started, and rpm is above 400 rpm, the system goes into 'Open Loop' operation. In 'Open Loop', the ECM will ignore the signal from the Oxygen (O2) sensor and calculate the air/fuel ratio based on inputs from the coolant and MAF sensors, but mostly from a pre-programmed table in the memcal.

The system will stay in 'Open Loop' until the following conditions are met:

1. The O2 sensor has varying voltage output, showing that it is hot enough to operate properly. (This depends on temperature)
2. The coolant sensor is above a specified temperature about 40°C/104°F.
3. A specific amount of time has elapsed after starting the engine.

The specific values for the above conditions vary with different engines and are stored in the mem-cal. When these conditions are met, the system goes into 'Closed Loop' operation. In 'Closed Loop', the ECM will calculate the air/fuel ratio (injector on-time) based on the various sensors but mainly the O2 sensor. This allows the air/fuel ratio to stay very close to 14.7:1.

 

Thanks BretD that is closer to what I wanted to know. I was under the impression that the closed loop kicks in alot later. I read somewhere on these boards at some point that if you run the lower thermostats and stuff that our cars would always be in open loop run rich and burn up cats.

I read some other posts in the FAQ sections talking about temps and fuel economy and effeciancy which I am not to worried about, I just passed a smog with no problems here in Cali. so I should be running pretty clean.

So so far I do not see any reason to worry about running this cool. As far as I can tell it should be better for the motor, and everything else under the hood that can be damaged by to much heat.