Water Pump and Thermostat

[epapp]

I didn't mean that the DME would run out of rope, I realize it has the ability to adjust fuel trims to many temperatures and altitudes. What I meant was that it would stay in some 'almost-warmed-up-fuel-trim state' by allowing the engine to cool to around 160 when on the freeway in low load conditions etc....because the DME expects 180 (186) minimum to be the steady 'warmed up' state on our cars.

Unless of course the DME doesn't think 186 is warmed up, but rather something lower. It depends on the fuel map vs. coolant temp. In a graph of those two, there is some temperature when the DME stops considering the car 'warming up' and changes its fuel trims accordingly. It very well could be below 160, in which case running the 160 thermostat would help in some circumstances to lower the coolant temp.

Which makes me think...why fit a 180 tstat at all? If running lower than 180 is better in some cases and doesn't affect the engine warmup fuel trims, why even put a tstat in the car from the factory that makes it run hotter? Also, why let the car heat up to 212 before turning on the fans?