68torino said:
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A good example would be a person working outside in the heat. They overheat and jump into a pool. If they move around just right(flow+time) they will cool down nicely. If they sit in one place(time, but no flow) they will slowly begin to overheat. If they move around and have extra coolant(pool water) flow (time+flow+flow) they will overcool and get chilled. If they are swimming around vigorously they could go into overheat(time+flow-excess work generating heat).
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OK... bolding mine... I came to this thread late, but if there's one thing I am an expert in, it's physics. Not necessarily all things Mustang, but Physics is definitely my bag. Hence, the bolding above is worth commenting on because it isn't exactly true. And here's why...
It's a fundamental law of physics that the rate of heat exchange between one medium and another is determined by the initial difference in temperature between those two mediums. In your example above, your assumption is that the pool water is initially quite high to begin with (which is not unfair seeing as how you did describe the day as being a hot one). However, consider the poor victims of the Titanic disaster who were thrown into the Atlantic after the ship sunk that night. The ambient water temperature that night was just 2C apparently, and as such, most of the victims died within 4 minutes - regardless of whether they tried to stay perfectly still. And the reason? The rate of heat exchange was incredibly great due to the permanent state of the ocean's temperature that night.
And my point? You can't have your cake and eat it too... if we agree that a thermostat restricts flow as an engine goes through it's warmup cycle, we can also agree that freeing up that restriction allows heat transfer to take place AFTER that restriction is removed. By extension, it's impossible to argue that freeing up that restriction EVEN MORE will somehow result in greater water temperatures once again. It isn't a parabolic graph with an ideal operating flow per minute area in the middle. Heat exchange is a function of exposure to cooler mediums - period. If there is a greater flowrate, greater amounts of coolant are being exposed to the radiator's cooler surfaces per given time frame. In short, radiator dwell time is an old wive's tale. An unimpeded coolant system exposes the ENTIRE coolant to an overall greater heat exchange, rather than just a PART of it.
The issues are maximum water pump flow rate, radiator efficiency, variable flow rate resistance, and most importantly, ambient air temperatures. The last two points are vitally important in the context of overheating. Essentially, in almost every American and European vehicle made since 1960, an unimpeded coolant system has almost always been capable of overcooling an engine unless the vehicle is driving around in Death Valley ambient temperatures. The assumption here is that the coolant system is perfectly healthy in all of it's parts. If that assumption is true, then the REAL role of a thermostat is actually to prevent overcooling, not overheating.
To that end, this is why modern Formula One cars overheat so quickly if they're sitting still on the grid for too long at the start of a race. The issue is not the thermostat, nor is it flow rate - rather, it's the fact that the still air in the radiator pods heats up to a point where vastly inefficient heat transfers are taking place.
If the coolant is hotter, then it's obviously removed more heat from the engine.
