electric fan question
Thread Starter
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Joined: Sep 2004
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From: Boston MA
electric fan question
Hello Everyone ,
Here is my question about electric fans. I have added an electric fan to my 1968 coupe and I was wondering if anyone could help me figure out the correct tempeture for it to turn on. Currently, the fan runs all the time (hardwired), but I heard this is bad for performance and for cold starts. So my question is what tempeture should the fan come on? After looking at the majority of the kits available, the tempetures range from 160 to 210.
My guess is that is depends on the thermostat. Right now I have a 160 thermostat in the vehicle.
Should the fan come on after the thermostat opens, before it opens, or the same tempeture that it opens at?
Is there a general rule of thumb, like 10 degrees higher than the thermostat tempeture? (In case I change my thermostat in the future)
Thanks for your advice, it really means alot to me!
Here is my question about electric fans. I have added an electric fan to my 1968 coupe and I was wondering if anyone could help me figure out the correct tempeture for it to turn on. Currently, the fan runs all the time (hardwired), but I heard this is bad for performance and for cold starts. So my question is what tempeture should the fan come on? After looking at the majority of the kits available, the tempetures range from 160 to 210.
My guess is that is depends on the thermostat. Right now I have a 160 thermostat in the vehicle.
Should the fan come on after the thermostat opens, before it opens, or the same tempeture that it opens at?
Is there a general rule of thumb, like 10 degrees higher than the thermostat tempeture? (In case I change my thermostat in the future)
Thanks for your advice, it really means alot to me!
Drifting
Joined: Sep 2001
Posts: 1,427
Likes: 1
From: Boxford Mass
I have a 180 thermostat and 190 fans.
Here was something I just found about engine oil temp...
"Some experts estimate that the wear on the rings of an internal combustion engine is as high as 0.001" per 1000 miles of operation when the oil temperature is below 170 degrees F. If the maximum allowable wear is 0.006", how long can you run your engine when the oil temperature is below 170 degrees before you wear it out?" (A 6-to-1 engine-to-wheel reduction ratio, an average running speed of 3000 rpm, and 14-inch wheels 28 inches in diameter are assumed.)
The point of this problem is to stress that by far the greatest amount of engine wear takes place before the oil is warmed up. The amount of wear that occurs afterward is insignificant by comparison.
It can be appreciated, therefore, that it is important to warm the oil, as well as the engine block. An engine that is kept warm with a circulating heater or with one that is plugged into the block can usually be started easily, but the oil is not heated and it provides very little lubrication at first. Consequently, the most engine wear occurs during the few minutes immediately after starting.
Here was something I just found about engine oil temp...
"Some experts estimate that the wear on the rings of an internal combustion engine is as high as 0.001" per 1000 miles of operation when the oil temperature is below 170 degrees F. If the maximum allowable wear is 0.006", how long can you run your engine when the oil temperature is below 170 degrees before you wear it out?" (A 6-to-1 engine-to-wheel reduction ratio, an average running speed of 3000 rpm, and 14-inch wheels 28 inches in diameter are assumed.)
The point of this problem is to stress that by far the greatest amount of engine wear takes place before the oil is warmed up. The amount of wear that occurs afterward is insignificant by comparison.
It can be appreciated, therefore, that it is important to warm the oil, as well as the engine block. An engine that is kept warm with a circulating heater or with one that is plugged into the block can usually be started easily, but the oil is not heated and it provides very little lubrication at first. Consequently, the most engine wear occurs during the few minutes immediately after starting.
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Joined: Sep 2004
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From: Boston MA
excellent point, Jack!!
I think I am going to switch to a 180 thermostat and have the fan come on at 190. Do you have any problems on hot days in traffic??
Fans?? do you have more than one?? what is the CFM??
Thanks
I think I am going to switch to a 180 thermostat and have the fan come on at 190. Do you have any problems on hot days in traffic??
Fans?? do you have more than one?? what is the CFM??
Thanks
Thread Starter
Pro
Joined: Sep 2004
Posts: 595
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From: Boston MA
does your engine temp ever go over 190?? or do the temps stay around that??
I have an alum. rad from Be Cool and a 16 electric fan from perma cool. The fan is rated at 2950 CFM. ( I have a sbc).
Thanks
I have an alum. rad from Be Cool and a 16 electric fan from perma cool. The fan is rated at 2950 CFM. ( I have a sbc).
Thanks
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Verdad Gallardo
Pro
Joined: Sep 2002
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From: San Antonio TX
My .02 on the issue.
If the thermostat is closed, there is no water circulating. If the fan is running, it cools the standing water in the radiator to a lower temperature than would be possible if it were circulating. The water in the block raises the temperature of the thermostat, causing it to open. When it does, the "cold" water from the radiator has a significantly lower temperature. It gushes in the block and shuts the thermostat down.
OK, seems to me that it would be better to have less fluctuation in water temperature. I think it would be better to have it synchronized, with the fan and thermostat working in harmony. This should even the temperature out, rather than causing rapid fluctuations of cold and hot water hitting the block and radiator.
If the thermostat is closed, there is no water circulating. If the fan is running, it cools the standing water in the radiator to a lower temperature than would be possible if it were circulating. The water in the block raises the temperature of the thermostat, causing it to open. When it does, the "cold" water from the radiator has a significantly lower temperature. It gushes in the block and shuts the thermostat down.
OK, seems to me that it would be better to have less fluctuation in water temperature. I think it would be better to have it synchronized, with the fan and thermostat working in harmony. This should even the temperature out, rather than causing rapid fluctuations of cold and hot water hitting the block and radiator.
you definitely don't want your fan and thermostat fighting each other. My running temp is around 190.
Thread Starter
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Joined: Sep 2004
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From: Boston MA
having a thermostat that is 180 and a fan that turns on at 180 would not fight each other right? What about a thermostat at 160 and a fan that turns on at 180? would they be fighting each other???
Thread Starter
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From: Boston MA
I see what you are saying. I am not sure what temp it shuts off. I assume it is the same as the temp it turns on. I do not disagree with what you said. I was just confused. Sorry. Now I get it though. THe fans should turn on and off while the thermostat is open. Right??
Thanks
Thanks
Thread Starter
Pro
Joined: Sep 2004
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From: Boston MA
I just called perma cool. the fan comes on at the desired temp and then shuts off when the temp reaches 8 degrees lower.
so my guess is that with a 180 thermostat, the fans should come on at 190 and shut off at 182. which is after thermostat is open.
Right??
Thanks!!
so my guess is that with a 180 thermostat, the fans should come on at 190 and shut off at 182. which is after thermostat is open.
Right??
Thanks!!
Melting Slicks
Joined: May 2002
Posts: 2,508
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From: Wisconsin
Just because your coolant temp is 180 degrees does not mean the oil temp is there. Oil temp is usually somewhere around 300 degrees at operating temp.
I have a 180 thermostat and 190 for the fan. Fan never kicks on and the temp never gets above 160. Damn no horsepower motor.
I have a 180 thermostat and 190 for the fan. Fan never kicks on and the temp never gets above 160. Damn no horsepower motor.
Le Mans Master
Joined: Feb 1999
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From: Hoosier
Cruise-In III Veteran
Speaking from hard experience 
I'm using the Spal fans with a 180 T-stat. My fans come on at 205 and off at 185.
If you use the garden variety type T-stat with a spring, those stats have an operating tolerance of +/- 10 degrees. Use a Robert Shaw type stat which operates at a much closer tolerance.
Next, the temp sensers have an operating tolerance of +/- 10 degrees also. This was told to me by Painless and Spal, both who provide sensers for electric fans.
So now you have the possibility of the fans and t-stat fighting each other.
I went through 4 sensers before I had one that would shut down the fans a few degrees before the t-stat would close.
When the fans are operating you want the t-stat open through the entire fans cycle.
Also, some of the aftermarket temp sensers for the fans are very finicky about surrounding temperatures. My headers were upsetting the senser when used in the head port. I found that using the intake manifold port is best. Some say there is a temperature differential between the head and the intake manifold. I believe it's negitable and a Car Craft cooling article once said that after two t-stat cycles they found the two temperatures equal.
I'm using the Spal fans with a 180 T-stat. My fans come on at 205 and off at 185.
If you use the garden variety type T-stat with a spring, those stats have an operating tolerance of +/- 10 degrees. Use a Robert Shaw type stat which operates at a much closer tolerance.
Next, the temp sensers have an operating tolerance of +/- 10 degrees also. This was told to me by Painless and Spal, both who provide sensers for electric fans.
So now you have the possibility of the fans and t-stat fighting each other.
I went through 4 sensers before I had one that would shut down the fans a few degrees before the t-stat would close.
When the fans are operating you want the t-stat open through the entire fans cycle.
Also, some of the aftermarket temp sensers for the fans are very finicky about surrounding temperatures. My headers were upsetting the senser when used in the head port. I found that using the intake manifold port is best. Some say there is a temperature differential between the head and the intake manifold. I believe it's negitable and a Car Craft cooling article once said that after two t-stat cycles they found the two temperatures equal.