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Discussion Starter #1
I'm trying to figure out radiator fans. Bear with me - this will relate back to my Nova eventually:

Our daily driver cars are not very old and both use an electric fan. Once up to temp, these cars NEVER vary according to the temp gauge. Below freezing outside? Rock steady temp. 90+ outside, sitting in traffic with the A/C on? The temp needle doesn't budge. And, from inside the car you can't hear the fan running. Excellent.

We also have a '99 Suburban that we use to pull a trailer. It has a clutch fan. Same results - hot or cold outside, traffic + A/C, the temp gauge never rises. How is this possible? At an idle, the clutch fan pulls minimal CFM, right? How does it maintain a steady temp at idle with the A/C running?

Now to the Nova, and this is related to the truck and car situations above. I have an LS2 with aluminum radiator and Spal electric 1600 CFM fan. Currently, no A/C compressor installed. The temp gauge on this thing is constantly moving, depending on conditions. If I'm driving steady above 35 MPH, the car runs at it's coolest and doesn't vary much. If speed drops, or if I sit at a traffic light more than about 30 seconds, the temperature starts to rise. If the car sits for several minutes, the temperature goes well over 200, but it never actually overheats. Once the car is warmed up, the fan pretty much never shuts off, and it's LOUD - very noticeable inside the car. I know there's a lot of variables here, but my main question is why the Nova would see temperatures going up and down with such variance? I could understand maybe a 10 degree swing, depending on conditions, but I'm seeing 30 - 40 degrees variance. That just doesn't seem right. Is it just as simple as the fan doesn't pull enough CFM? Would a beefier fan hold a steady temp, or would I still expect some variance? Should an aftermarket fan be so loud - especially one that's only pulling 1600 CFM?

And back to the daily drivers, how do the factory electric-fan cars maintain such a rock-solid temperature? I mean, the gauges literaly don't budge a degree once they're warm.
 

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In the first two vehicles, the systems are engineered to do what you are seeing. The engines are tuned to perform trouble free in terms of fuel and cooling abilities. A manufacture can't afford to have a marginal cooling system. Aftermarket parts can work if the right combination is used. In your case with the Nova, I suspect the fan isn't up to the challenge. Is your LS engine stock and computer controlled? I read an article recently about cfm requirements and 1600 cfm is 4 cylinder sizing. Driving 35 mph means the electric fan shouldn't be on because there is enough air coming through the rad to maintain a temperature the thermostat is designated for. I'm running a LS (with Fitech efi) and am using a Griffen aluminum rad. I'm using a new dual electric fan for a Ford Contour. The fans have shroud to aid pulling air from more of the rad fin surface. Not sure what engine they use but I assume it's a V6. I've got AC and since there is no transmission cooler in the rad, I have a very large transmission cooler in front of the AC condenser. The air has to travel through three things for part of the rad opening and two things for the remainder of the rad. It works like a factory system. I have a digital readout of the engine temperature that reads in 1° increments. I've been stuck In hot weather with the AC blasting and only moved on car length in 40 minutes. The temperature never varied much. I have the Fitech control the off and on temperatures 5° higher than the normal engine temperature (197°) and turn off at 195°.

My 72 GMC also has a LS engine. I'm using the stock heavy duty 4 core 1972 rad(recored 15 years ago). The fan is the LS truck fan and the rad continues to use the stock shroud. The fan pulls a lot of air and since the shroud is in place, pulls it from a large fin area of the rad. Again, I can see the temperatures with the Fitech handheld screen. It has AC and the transmission is cooled through the rad then through a large cooler in front of the AC condenser. The temperatures are very stable to the point of never having to look at the factory temperature gauge.
https://www.chevyhardcore.com/news/spal-electric-fans-keeping-things-cool-with-different-blade-types/
 

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You need a higher output fan. I am running a 2800 cfm on both my Novas. One has a 400 sb and the other is an LS6. No cooling issues.....ever.
 

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Discussion Starter #4
I appreciate the input so far. I'm still curious how our Suburban with the stock 350 small block keeps cool at idle. It probably turns around 650 RPM at idle. How in the world does that keep everything cool?

BTW, I do have a shroud on my fan, but I'm getting the picture that 1600 CFM is not enough. Who knew? I thought that since it was a SPAL 16" fan, that's all that mattered. I'm still learning.
 

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Also, remember that a lot of newer cars the temp gauge is kind of a dummy gauge. Even though the temp is changing 10-15 degrees, the gauge doesn't move. Its so the normal consumer doesn't freak out that their car is "over heating". Also, if you have HP tuners, your fans are probably made to come on at full blast "HI" at 185ish. A lot of LS guys do that to help keep them cool. You could adjust the fan speed to come on LOW at 185 and HI at 195, so the fan isn't so loud.
 

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Don't forget that in the new vehicles the computer is doing more than just turning the fan on and off based on temp. It is also in full control of the fuel mixture and timing so the maps in it can make adjustments to assist in keeping the engine temp under control.
Myself I have a dual carb setup on a blown sbc, one of the reasons for thinking about going to fuel injection is the computer control of the mixture and timing, I need every bit of help in keeping it cooler.
 
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