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Im one of those guys that rock an Eaton with lots of documented results
Running 17.5 CST set at 125°
Below 100°+ outside Arizona temps idling.
AC output at 41.7° pretty cool
feel free to link it.
set to open at 125° ? Is that when these clutches open when stock?
The blue fan clutch I thought should be mod'd to open at 95°F. Any reason for the Eaton to be different, or is that what works best for you when running either the blue fan clutch or eaton clutch?
Just curious how you came up with that combo (17.5 CST set at 125°).
It's probably in another thread.
OK, the long answer, I have posted this info before, probably in the huge thread and fragmented, so will attempt to better explain it here. This info is a collaboration of several local users who have worked to get the best setup/performance from the clutches. My rig has run with temp sensors (grill intake air, fan output, water and A/C vent), for ~ a year out of the last 4 years, to attempt to get a feel for what is happening.
The clutches are made with 3 ranges of “on”, (on some the center step is progressive, but will use the 3 step, easier to explain), these ranges match well with fan demand, depending on load. The clutch uses cooler output air temp to control fan speed/power, IMHO this is a great method, it accurately senses loads, A/C cycles, motor loads, ambient temp, etc. The clutch thermostat is very active and quickly acts to changing loads.
The steps are not linearly progressive, the first is pretty wimpy, second somewhat stronger and the third a big step. If I had to make a guess, based on optical tach and fan laws, it would look something like this; first step 1250cfm, second step 2500cfm and third 5000cfm. These numbers are guess, the real number will very depending on viscosity, flow restriction, etc, but the ratio among the steps is close.
There are 3 main fan load need ranges, it’s almost like someone designed the clutch to work with them!First light load cruising, a little fan is needed, but not much. Second, heavy load cruising, climbing hills, hot weather with heavy A/C loads, towing, wheeling, etc. Third is stopped, idling, this is by far the most demanding, especially when hot with A/C load. The rig is stopped, so no airflow over it and the motor is at idle, so low shaft speed, the third step is mostly reserved for this and is why it’s stronger than the rest. Without this strong step, under hood airflow drops, heat soak increases, A/C vent temp raises and possibly raises the A/C high side pressure enough to cycle it off in very hot weather.
If you adjust the valve down, say 25F and use close to stock viscosity fluid, you have basically moved each step down a range. The first step is wasted, the fan runs almost all of the time and before it’s needed. The second step runs in the temp range where the first step would normally run, you gain some performance due to the bigger valve opening. The third runs in the temp range where the second step would normally run, you also gain performance due to the much bigger valve opening. At idle your still running in the third step, so gain nothing, idle heat soak will be high and A/C performance low, will start thinking about band-aids like cutting holes in the hood, electric fans, etc. In my observation this is like changing to a cooler coolant thermostat, it starts cooling sooner than needed, but adds nothing to total cooling capacity.
Our observation is that no fan is needed below about the 120F range at cooler output/clutch thermostat and about this setting matches well with the third step working only at idle/rig stopped. By stepping up the fluid viscosity, clutch performance is increased at each step, they work at the intended temps and total cooling capacity is increased, depending on the fluid viscosity dramatically increased.
Locally we have done dozens of clutches, adjusted the valves both hotter and cooler, run fluid from 6K to now a couple running 30K, played with electric fans, hoods, etc. Have directly compared them on the highway and trail and found changing the viscosity and leaving the valve alone is the best setup for overall performance. Once we figured this out some of the electric fans are abandoned in place or in the case of mine sold. Again this is our observations from years of playing with them in desert climate, so your mileage may vary.
set to open at 125° ? Is that when these clutches open when stock?
The blue fan clutch I thought should be mod'd to open at 95°F. Any reason for the Eaton to be different, or is that what works best for you when running either the blue fan clutch or eaton clutch?
Just curious how you came up with that combo (17.5 CST set at 125°).
It's probably in another thread.
My guess would be if you set an Arizona clutch up at 95° it would be full on 24hr a day for several months as it 100° at midnight a lot here.
Im not a fan expert, Tools set mine up years ago and I rarely see over 200° anytime under any conditions.
I haven’t finished my truck yet so no results here. Since the truck came with it I chose to use it.
What radiator are you running?Im one of those guys that rock an Eaton with lots of documented results
Running 17.5 CST set at 125°
Below 100°+ outside Arizona temps idling.
AC output at 41.7° pretty cool
