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Thermostatic fan switch - 195 vs 185

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14K views 3 replies 3 participants last post by  kbuhagiar  
#1 ·
Hello Folks,

Today I completed the installation and testing of my Mattson's Custom Radiator cooling module. I am very happy with the product and the results, and although it was a bit spendy, I feel the quality and workmanship justified the cost.

My engine is a Blueprint 383 stroker (420HP/490T). The previous owner, who had a 'dragstrip' mentality, 'deleted' the thermostat, and my previous radiator/fan was set to come on somewhere 175 degrees, as my temp gauge never got above 180.

When I changed out the radiator I also installed a 180 degree thermostat. Mattson's provided me with a 195 degree fan sensor (the module came with a Spal fan controller with two options, 185 and 195 and it would appear that based on my setup Mattsons decided that the 195 was more appropriate, as they never asked if I had a preference). With the current setup my temp gauge will spike to around 195 before the fans come on, but will then drop quickly to about 180 before shutting off.

At first I was concerned but I have to admit the the engine is running great, no pre-ignition at all and I get the feeling that the engine is running more efficiently, as the exhaust fumes are less intense than before.

Question for the group...I'm thinking that my old setup was too cold, but I'm wondering if the 195 switch may be too warm; would a 185 switch be more appropriate for my setup?

Thanks in advance.
 
#3 ·
The fans will probably never shut off with a 185 switch. That's what I don't like about temp switches. There is too much difference between on and back off (usually 15 degrees). I like the Dakota fan controller because you can program the on/off temps as close as 3 degrees. As you noticed, with a temp switch, the temp is always swinging up and down between 195 and 180.
 
R
#2 ·
The answer is no unless you want to go to a 160° thermostat, which I wouldn't do if mine. Even a 195° "fan on" temperature may be too low.

Here's why. With a 180° thermostat, it starts to open at 180°. It won't be fully open until 190° or a bit more. With a 195° "fan on" temperature, the "fan off" temperature will be 185° or so. This will result in the fan running all the time, and the fan trying to cool the engine with the thermostat trying to heat it. I'd recommend a 205° "fan on" temperature with the 180° thermostat.

With that big Mattson radiator, anytime the fan does come on the coolant temperature will drop quickly and won't have to run long if you set it up as above.

Around here it's hot much of the year and this scheme works well with a big crossflow radiator. The fans run only in heavy traffic when vehicle speed is low. Temperature mostly stays in the 190° range except in cool/cold weather when it's a bit lower.
 
#4 ·
acardon said:
The fans will probably never shut off with a 185 switch. That's what I don't like about temp switches. There is too much difference between on and back off (usually 15 degrees). I like the Dakota fan controller because you can program the on/off temps as close as 3 degrees. As you noticed, with a temp switch, the temp is always swinging up and down between 195 and 180.
Click to expand...
Good information, thanks for the input. :flag6:

I feel a lot better now about the 195 degree switch (as opposed to 185).
And I'm good with the increased operating temperature.

I'm going to keep it this way for a while and see how it works out.

Thanks again for the information. :shakehands:
 
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