Controlling rad fans with A/C

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Max Headroom

Master Mechanic
Sep 8, 2011
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389
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I don't understand something and would love an explanation. Why would you want the fans to come on at different temps and why the first one at or around 180f?

I don't understand why you would turn the fans on when the engine is passing through (as in going higher than) the temp you want to maintain. That immediately puts you behind the cooling curve. The fact that you would turn a second fan on at 195* just makes my point for me. By the time the second fan comes on, you are headed out of, or already out of, the optimum temperature range. If you are in the gas at all, you are gonna stay out there until you get off the throttle and let the cooling system catch up. Bad strategy, I think.

If I could get my engine to run at 160 - 170 degrees all the time I would consider it an accomplishment. As long as I was doing it through fan management instead of reducing combustion chamber heat (inside the chamber, not the head itself). In my opinion, the benefits of lower cooling system temperature far outweighs any downside.

This summer, when I swap my 383 into my 79 Malibu, I have a four core radiator that is over-sized for my application. I plan to have a pull through electric fan with a full radiator shroud that will come on at about 140* and just run till I turn the key off.

I don't do ecm management, so if there is a reason for why you do it your way, I would really like to understand.
 

Supercharged111

Comic Book Super Hero
Oct 25, 2019
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Colorado Springs, CO
My logic is that is keeps the fan from cycling so much. If you stop for a short duration and the temp creeps up 5-10 degrees, no use in bringing in the fan if the temp is just gonna drop the instant you get moving again. If that puts you problematically behind the cooling curve you have bigger issues. Fan settings can be subjective so YMMV.
 

Max Headroom

Master Mechanic
Sep 8, 2011
420
389
63
My logic is that is keeps the fan from cycling so much. If you stop for a short duration and the temp creeps up 5-10 degrees, no use in bringing in the fan if the temp is just gonna drop the instant you get moving again. If that puts you problematically behind the cooling curve you have bigger issues. Fan settings can be subjective so YMMV.

What is the problem with the fans running all the time and getting the temp as low as possible? Then cycling on and off is not an issue, plus the fans running while the engine is not under load would tend to cool the engine not make the heat creep up (providing you cooling system is matched to the engine.). Heat is what usually kills an engine. I would rather replace the fans than shorten the amount of time before a rebuild of the engine needs to be done.
 

Supercharged111

Comic Book Super Hero
Oct 25, 2019
4,924
7,702
113
Colorado Springs, CO
What is the problem with the fans running all the time and getting the temp as low as possible? Then cycling on and off is not an issue, plus the fans running while the engine is not under load would tend to cool the engine not make the heat creep up (providing you cooling system is matched to the engine.). Heat is what usually kills an engine. I would rather replace the fans than shorten the amount of time before a rebuild of the engine needs to be done.

195 is not going to hurt a thing though. You're talking like you're struggling to keep the thing from boiling over but that's just not the case here.
 

Jimmy girl

Apprentice
Oct 11, 2014
55
92
18
What is the problem with the fans running all the time and getting the temp as low as possible? Then cycling on and off is not an issue, plus the fans running while the engine is not under load would tend to cool the engine not make the heat creep up (providing you cooling system is matched to the engine.). Heat is what usually kills an engine. I would rather replace the fans than shorten the amount of time before a rebuild of the engine needs to be done.
Well I went with a PWM fan controller to avoid my car sounding like an airplane , and to manage voltage draw . My car is supercharged/ intercooled so I have 2 rads, 4 fans. Just the 2 main fans draw 70 amps if started at the same time . My car also has Ac another big draw. PWM keeps the temps perfectly even while not creating much of a draw . My main fans are 4000cfm . They don’t need to be full blast all the time . I barely hear them now , which is nice . And they soft start , so there is no big initial draw, and go up and down according to temp . You can also set them to shut off at highway speeds ( you set the speed}.
 

Jimmy girl

Apprentice
Oct 11, 2014
55
92
18
I don't understand something and would love an explanation. Why would you want the fans to come on at different temps and why the first one at or around 180f?

I don't understand why you would turn the fans on when the engine is passing through (as in going higher than) the temp you want to maintain. That immediately puts you behind the cooling curve. The fact that you would turn a second fan on at 195* just makes my point for me. By the time the second fan comes on, you are headed out of, or already out of, the optimum temperature range. If you are in the gas at all, you are gonna stay out there until you get off the throttle and let the cooling system catch up. Bad strategy, I think.

If I could get my engine to run at 160 - 170 degrees all the time I would consider it an accomplishment. As long as I was doing it through fan management instead of reducing combustion chamber heat (inside the chamber, not the head itself). In my opinion, the benefits of lower cooling system temperature far outweighs any downside.

This summer, when I swap my 383 into my 79 Malibu, I have a four core radiator that is over-sized for my application. I plan to have a pull through electric fan with a full radiator shroud that will come on at about 140* and just run till I turn the key off.

I don't do ecm management, so if there is a reason for why you do it your way, I would really like to understand.
I have a 160* thermostat and my car stays around 175-180 tops if your gonna go electric fan , spend the money on a good quality fan . The more cfm the better. There are a lot of oem fans that work great . Dodge intrepid is one that comes to mind. Lotta cheap fans on the market .
 
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