Without knowing the exact setup scenario I can’t say for sure. However, 50 deg temp differences MAY be seen between the outside temp and IAT2 if the intake air (IAT1) was already heated by the truck sitting stopped in traffic or shut off while gassing up or otherwise, and then driving a short distance only. The air temps are not reliable for comparisons unless the throttle is open more than slightly and the truck moving > ~50 mph for >~ 15 minutes. You just can’t take anyone’s word on their temps and compare to any others without knowing the exact conditions.
---------- Post added at 02:38 PM ---------- Previous post was at 02:12 PM ----------
Also now this makes a little more sense that Masimoto only advertises a 10 degree drop in temps with their IC.
I'm sure the 170 t-stat would have to have at least a small impact on IAT2 temps since it's in the manifold, right? That's 40-50 degrees cooler than the stock t-stat. I'm just not sure that running with engine temps that cool is the right thing. I'm considering maybe a 190 but want to see if I can find any info regarding what temps are safe or ideal for these motors.
The Mishimoto FMIC is what I have on the shelf and it fits in the stock location, so it increases cooling from the simple efficiency of the internal design and very small increase in core size. The much larger aftermarket FMICs that require cutting and cover the actual radiator area will likely have better cooling simply from surface area. That surface area causes increased drag and loss of actual cooling efficiency, but works because they are so big.
As for the T-stat issue, I can tell you from decades of experience that you want to keep it at 180 or more to maintain efficient combustion. The engine temperature must remain high to get the most from the fuel and tuning. The cold (relatively) T-stats come from the dark ages when we were trying everything we could to increase power/timing. The colder we could get the engine while keeping the carb and manifold warm enough to prevent icing the more timing you could add which equates to more power. We used a whole lot of gas, but who cared, it was 25 cents a gallon and plentiful.
The advent of EFI and the latest ECU/sensor hardware has made those ancient methods largely irrelevant unless you're drag racing in a carb-only class with no forced induction.
The optimum temp for the engine is right around 190-200 deg cylinder head/combustion temps, so the coolant running at ~200 is just right. Most modern engines are tuned to run best at the 200 deg mark with T-stats usually cracking open at around 192-195 deg and fully open by 210 or so. I've long abandoned the cold T-stat approach, but it keeps coming back, likely from old farts who haven't progressed their knowledge and the younger folks who take their old advice...
