Cooling Upgrades Techie Question

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This leads me to ask why people like to put 180F thermostats in their cooling systems? Since the radiator cools more effectively with a higher delta T, doesn't this prematurely rob the cooling system of it's optimum effeiciency, which, I'll assume was designed in by GM originally for the factory stock 195F (or is it 205F?) T-stats?

I realize that there are 2 deltas at play; engine -> coolant, and coolant -> air (through radiator), but given that cylinder wall temps will be as high as 400F or more, finding a spot closer to the mid-point between 400 and ambient (say 100F) would seem to be a better fit.

Or is 195F just better for emissions only and at the expense of better cooling that could be obtained with 180F?

180's will allow the engine to put more heat into the radiator a little sooner than it would with 195's. In turn, the fan-clutch will engage a little sooner. This could allow some stock calibration clutches to engage when they should (or at least soon enough to help prevent an overheating problem). Plus, a 15-degree lower average engine temperature should produce a positive benefit for the DS4 electronics.

To use the Duramax analogy again.... it uses a pair of t-stats with staggered temperature ratings. The lower is at 185 degrees.

See a related thread on this subject.

Jim