Another Fan Question
- Thread starter Johnny
- Start date
Wild Mango
Member
Good opportunity for a discussion.
The electric fan is there to get cooling airflow through the radiator core when the incident airflow isn't enough, like when in traffic or stopped. A reliable measure of how well the radiator is coping is the temperature difference between the top inlet and the bottom outlet.("delta T") If we have a thermostat, we can know the water inlet temp. The closer the outlet temp gets to the inlet, the less cooling effect the radiator is having.
A good electric fan and shroud can really get a cooling air blast through the core, and it works quickly.
I have always used the outlet temp from the radiator as the process switch for the electric fan. While this is the logical place to sense the temperature, it is not popular because the setpoints require some experementation to establish inasmuch as every installation is different as far as temperature drop across the radiator goes. Here, our hobby shop equivalent of Radio Shack sells an adjustable temperature switch, and with an engine tstat of 180F I usually start by setting it to switch "on" at say 160degF , and "off" at 150degF. If the fan comes on in normal driving this suggests the cooling system is perhaps struggling for some reason that requires investigation. OR taking the "on" switch point up to 165F may fix it. (theory tells us, the hotter the water in the radiator, the greater the heat loss for a given atmospheric temperature)
Other traditional positions for the fan switch, like at the thermostat housing or in a cylinder head certainly work, but operate when an overheat condition already exists rather than intervening to prevent it. IMHO.
The electric fan is there to get cooling airflow through the radiator core when the incident airflow isn't enough, like when in traffic or stopped. A reliable measure of how well the radiator is coping is the temperature difference between the top inlet and the bottom outlet.("delta T") If we have a thermostat, we can know the water inlet temp. The closer the outlet temp gets to the inlet, the less cooling effect the radiator is having.
A good electric fan and shroud can really get a cooling air blast through the core, and it works quickly.
I have always used the outlet temp from the radiator as the process switch for the electric fan. While this is the logical place to sense the temperature, it is not popular because the setpoints require some experementation to establish inasmuch as every installation is different as far as temperature drop across the radiator goes. Here, our hobby shop equivalent of Radio Shack sells an adjustable temperature switch, and with an engine tstat of 180F I usually start by setting it to switch "on" at say 160degF , and "off" at 150degF. If the fan comes on in normal driving this suggests the cooling system is perhaps struggling for some reason that requires investigation. OR taking the "on" switch point up to 165F may fix it. (theory tells us, the hotter the water in the radiator, the greater the heat loss for a given atmospheric temperature)
Other traditional positions for the fan switch, like at the thermostat housing or in a cylinder head certainly work, but operate when an overheat condition already exists rather than intervening to prevent it. IMHO.
donsrods
Member
Too many variables to give one answer. Things like how large your radiator is, the cubic inches you are trying to cool, brand of motor (some motors just run cooler than others), modifications to the motor, etc, all factor in.
In my 27 I have a 331 stroker and am running no thermostat. It pops up to 170-180 and stays there. But my radiator is chopped 8 1/2 inches over stock and I am running a SPAL electric fan for traffic lights. My Son Don has basically the same motor, but 306 CI, a 160 degree thermostat, and a Walker radiator, his runs at 190 with the fan on all the time. My other Son Dan has a 468 Olds in his car with an aluminum radiator and SPAL fan. We are running a restrictor plate instead of a thermostat and that works best for his combination. When I had my 23 with a sbc in it a 160 thermostat would only bring it up to 150 and I had to go to a 192 to get it to 170 degrees. Evidently, sbc run cooler than sbf or some other engines.
Start out with a 160 degree and go from there and experiment. As for what switch, I assume you mean automatic switch. If so, I don't use them as we have had trouble with every brand out there. I run a 40 amp relay and a push pull Ancor marine switch to turn it on and off as needed. But that is just me.
Don
In my 27 I have a 331 stroker and am running no thermostat. It pops up to 170-180 and stays there. But my radiator is chopped 8 1/2 inches over stock and I am running a SPAL electric fan for traffic lights. My Son Don has basically the same motor, but 306 CI, a 160 degree thermostat, and a Walker radiator, his runs at 190 with the fan on all the time. My other Son Dan has a 468 Olds in his car with an aluminum radiator and SPAL fan. We are running a restrictor plate instead of a thermostat and that works best for his combination. When I had my 23 with a sbc in it a 160 thermostat would only bring it up to 150 and I had to go to a 192 to get it to 170 degrees. Evidently, sbc run cooler than sbf or some other engines.
Start out with a 160 degree and go from there and experiment. As for what switch, I assume you mean automatic switch. If so, I don't use them as we have had trouble with every brand out there. I run a 40 amp relay and a push pull Ancor marine switch to turn it on and off as needed. But that is just me.
Don
Why do you want/need an electric fan? Are you overheating now? When? There are lotsa options. I use the Dakota Digital controller for two fans, with separate on/off temps for each fan. Painless and SPAL have controllers that vary fan speed. And the simple on/off thermostatic switch works well for most folks. I set my fans to keep the temp 200-210F. I did a test with the fans off and the car sitting, to see at what temp it would boilover. It was 250F with a 23# cap, so I have plenty of headroom.
Read http://www.tbucketeers.com/threads/cooling-secrets.12176/ for more cooling info.
Read http://www.tbucketeers.com/threads/cooling-secrets.12176/ for more cooling info.
Buster
Member
I installed A electric fan from speedway, got relay controles from them also. I used a 195 deg thermostat and sensor was placed in right hand head, thought maybe this was going to cause problems with overheat. Radiator was from Speedway(Tbucket 3 flue or 3" radiator), had to make fan shroud so to get good fit and look nice. Finally got everything mounted and wired and fan shorted out. Speedway made good on warreinty and replaced fan(chromed one 16") but purchased another from KMJ. Finally reinstalled fan and had to tweek relay a little so fan would not come on until right before thermostat opens, does great job at keeping engine cool while sitting still. I let it run about 30mins in hot SC summer heat with no problems. Might be better if sensor was located in top of thermostat housing instead of block. Carb setup prevents me from using thermostat housing.
Rogers23T
Member
I would start with a 160 stat for the engine, and have the fan come on at 195 and off at 165 If you find this to be too cold where the engine will not heat up... Go to a 180 stat. and adjust the fan for on at 200 or 210 and off at 190. I think aanything over 220 in the out going water temp and you risk a possible head gasket or cracking the heads or block! Better safe than sorry IMO!!!
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