Thermostat: Tuned car in the winter

[RodKnock]

So my sonic has been tuned this summer just after I bought it. It was done by a friend and I, and in the dead of summer never caused me any issues, coolant temp ran 90*C DEAD STABLE. I started noticing when the mornings got colder, I would see 100*C, but driving home from work, after the air warmed up and I left the heat off, temps back down to 90.

Has anyone else noticed anything like this? I remember reading that these thermostats meter water coming in rather than out, maybe it affects the heater coil when the radiator coolant is colder coming in?. I know the mechanical temp is 105, and it gets that high now that the temps are around freezing all day.

Any help is great, thanks.

 

[BigLee]

I have also noticed this, and was about to make a thread about it.
Remember, the 1.4s thermostat is on the INLET side of the engine, while the coolant temperature sensor is on the outlet side.

As such, its opening point is influenced some by return side coolant from the radiator temperature, and by the recirculation coolant from the heater core that's used to provide engine heated coolant across the thermostat's wax pellet.
Now in warm weather, the heater isnt used, so it doesnt loose any heat to interior airflow. In cooler weather, the heater core is used, and the coolant temp is reduced as it exits the heater, and returns to the thermostat housing. This cooler "sampling" coolant in turn postpones the thermostat's opening by several degrees, which in turn causes a slightly warmer coolant operating temp in cool weather.

So for these engines, this is a normal occurrence...

 

[BigLee]

Let me revise my wording a bit to be more clear from what I said above.
I said the cooler return flow coolant "postponed the thermostats opening by several degrees"
The thermostat is still opening at the same temperature as it always does, it just opens slightly later because the return coolant is cooled by the heater core, even though the coolant exting the engine is several degrees warmer than it would be in warm weather, when the heater isnt in use.

This Wednesday morning will definetly be the coldest temps I have seen last winter. I will try to remember to monitor the coolant temps then...
BTW: I'm using the Dorman 176 deg. Thermostat, so even though the threshold is about 40° lower than stock, this effect still happens...

 

[RodKnock]

BTW: I'm using the Dorman 176 deg. Thermostat, so even though the threshold is about 40° lower than stock, this effect still happens...

Have you noticed any issues running the cooler thermostat? I`m considering it, but not sure about performance issues, such as oil change intervals and fuel economy.

 

[BigLee]

I haven't.
In fact, my fuel economy is better than ever.
There MAY be a reduction in detonation threshold from the reduced coolant temps, that might partially explain the improved fuel economy.
Last summer, I was able to keep the DIC average fuel economy above ~40 mpg, if I avoid A/C use most of the time. In current cool/cold weather, I am currently averaging just over 36 mpg. Needless to say, I drive it pretty gently most of the time.
As far as oil changes, I change mine twice during the OLM recomended intervals, at 50% OLM I change the oil only, at 0% I change oil and oil filter.
I feel it's just cheap insurance for the turbocharger.
For those that say that's a waste of money, it's really not for me at least, as last year, I got in on a killer deal on closeout ACDelco synthetic 5W-30 and 0W-20 oil at $1/qt. From a local ACDelco distributor. I bought 12 cases.... BOOYAH...
and I also found a12pk. Of ACDelco oil filters on Ebay last year, ~$23 shipped...
So, even overly frequent oil changes are gonna be dirt cheap for me for a while...
But I havent seen any significant reduction in OLM distance.
I think it really only shortens the distance at even cooler temps.