(2) 12" fans versus (1) 16" fan

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dcmilt

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Getting ready to order a new Champion 4 core radiator...I'm thinking having the redundancy of 2 fans would be a good idea, and that one 12" fan will likely maintain engine temp, while using the 2nd fan in traffic or after a hard run at the track. Has anyone studied this? A couple of notes: 12" fan is 870 cfm and 10 amp draw, 16" fan is 1600 cfm and 14 amp draw. Electrical won't be an issue as I am rewiring the car. I just like the idea of redundancy of 2 fans. Thoughts?
 
Lots of cars that have 2 have the 2nd incorporated to the air conditioning compressor circuit. I would always go for max CFM and minimum draw. But that’s me
 
Lots of cars that have 2 have the 2nd incorporated to the air conditioning compressor circuit. I would always go for max CFM and minimum draw. But that’s me

I dont know how much engine you got , but 2 12'' fans with more cfm than that wouldnt cool my 440/505 in a my 68 fastback. Depends on how ur engine is built and how much heat it produces --------
One 16'' wouldnt either !

If its adrag only car, u might get by with it ??
IMG_0470 (1).JPG
IMG_0469 (3).JPG
 
I used a Ford fan like this in my 71 Barracuda with a Champion radiator. Seems to work fine.
upload_2020-3-22_17-48-19.png
 
I dont know how much engine you got , but 2 12'' fans with more cfm than that wouldnt cool my 440/505 in a my 68 fastback. Depends on how ur engine is built and how much heat it produces --------
One 16'' wouldnt either !

If its adrag only car, u might get by with it ??View attachment 1715491892 View attachment 1715491894

Bob, it's a pretty livey 418, solid roller, 11:1...it will need a substantial cooling system. the 4 core radiator will help, but the more I study air flow requirements the more I see the need for more air moving across that radiator...
 
A while back some one posted about their engine running hot. They had 2 12" fans and a shroud. I did some calculations and the shroud blocked almost 50% of the airflow. Go mechanical and be done with it. If your going to do high RPM a lot, electric makes sense. But don't use a shroud, make an open frame to mount them
 
Getting ready to order a new Champion 4 core radiator...I'm thinking having the redundancy of 2 fans would be a good idea, and that one 12" fan will likely maintain engine temp, while using the 2nd fan in traffic or after a hard run at the track. Has anyone studied this? A couple of notes: 12" fan is 870 cfm and 10 amp draw, 16" fan is 1600 cfm and 14 amp draw. Electrical won't be an issue as I am rewiring the car. I just like the idea of redundancy of 2 fans. Thoughts?

I have several concerns. First, 1,600 CFM is no where near enough for a stand alone electric fan set up. If you aren't going to move at least 3,000 cfm you're not setting yourself up for success.

Second, the 4 core radiator. I won't get into 2 core vs 4 core or any of that crap as far as cooling, most of all that is gimmicks vs science anyway. But, A-bodies don't have a ton of space to work with, and if you make the radiator too thick you'll run out of clearance to the pulleys. A 4 core will be difficult to deal with for setting up the fans because of the thickness of the radiator.

I run a 26" 3 core Champion radiator with a '95-'00 Ford Contour dual electric fan set up on my Duster. It has a built in shroud, which is important because it means the the rated CFM for the fan is more likely to be reproduced for your application. With a non-shrouded fan it's almost impossible to tell how it's rated or if you'll actually see that CFM in your application. The CFM numbers are roughly 3,500 cfm on the low speed, with over 5,000 cfm on the high speed. It's pretty rare, but I have had the high speed kick on while I was in traffic in 100°+ degree weather. Which means, if I hadn't had it, I might have been on my way to overheating. You need more CFM than a lot of aftermarket fans are capable of to cool a moderate 418. The Contour set up is a very capable fan set up, Ford was nice enough to test the living crap out of it, and the reproduction fan assembly is made by Dorman and is cheaper than any of the aftermarket fans capable of moving enough CFM.

My install on my Duster is here
My "new" '74 Duster- or why I need a project like a hole in the head

And the set up looks like this. You can see there isn't a ton of clearance even with a 3 core, and the Contour fan set up is relatively thin for a standalone electric fan.
img_1558_zps3b79216a-jpg.jpg


img_1559_zpse3b2d10c-jpg.jpg


@goldduster318 did a very nice write up of his install of the Contour fan set up with the Dakota Digital controller, I basically followed his install when I did mine. The PDF he did should be attached at the bottom of my post...

A while back some one posted about their engine running hot. They had 2 12" fans and a shroud. I did some calculations and the shroud blocked almost 50% of the airflow. Go mechanical and be done with it. If your going to do high RPM a lot, electric makes sense. But don't use a shroud, make an open frame to mount them

This is bad advice. A well designed shroud adds to the capability of the fan. Without a shroud, the fan will only pull air across the part of the core that it covers. With a well designed shroud, it will pull air across the entire core. If you're not pulling air across the entire core you're losing a ton of cooling efficiency. Not only that, but fans are pretty much always tested with some kind of shroud. So without one you can pretty much guarantee you won't get the fans full rated CFM.

As for the "blocking air" thing- if the shroud is on the backside of the radiator, it's not blocking air. The air has already passed through the core at that point. If the fans are small and the shroud doesn't allow all the air to pass easily through it may reduce airflow through the engine compartment, which will also reduce cooling, but it doesn't reduce the airflow through the core unless it's out in front.
 

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I have several concerns. First, 1,600 CFM is no where near enough for a stand alone electric fan set up. If you aren't going to move at least 3,000 cfm you're not setting yourself up for success.

Second, the 4 core radiator. I won't get into 2 core vs 4 core or any of that crap as far as cooling, most of all that is gimmicks vs science anyway. But, A-bodies don't have a ton of space to work with, and if you make the radiator too thick you'll run out of clearance to the pulleys. A 4 core will be difficult to deal with for setting up the fans because of the thickness of the radiator.

I run a 26" 3 core Champion radiator with a '95-'00 Ford Contour dual electric fan set up on my Duster. It has a built in shroud, which is important because it means the the rated CFM for the fan is more likely to be reproduced for your application. With a non-shrouded fan it's almost impossible to tell how it's rated or if you'll actually see that CFM in your application. The CFM numbers are roughly 3,500 cfm on the low speed, with over 5,000 cfm on the high speed. It's pretty rare, but I have had the high speed kick on while I was in traffic in 100°+ degree weather. Which means, if I hadn't had it, I might have been on my way to overheating. You need more CFM than a lot of aftermarket fans are capable of to cool a moderate 418. The Contour set up is a very capable fan set up, Ford was nice enough to test the living crap out of it, and the reproduction fan assembly is made by Dorman and is cheaper than any of the aftermarket fans capable of moving enough CFM.

My install on my Duster is here
My "new" '74 Duster- or why I need a project like a hole in the head

And the set up looks like this. You can see there isn't a ton of clearance even with a 3 core, and the Contour fan set up is relatively thin for a standalone electric fan.
View attachment 1715492151

View attachment 1715492152

@goldduster318 did a very nice write up of his install of the Contour fan set up with the Dakota Digital controller, I basically followed his install when I did mine. The PDF he did should be attached at the bottom of my post...

A well designed shroud adds to the capability of the fan. Without a shroud, the fan will only pull air across the part of the core that it covers. With a well designed shroud, it will pull air across the entire core. If you're not pulling air across the entire core you're losing a ton of cooling efficiency. Not only that, but fans are pretty much always tested with some kind of shroud. So without one you can pretty much guarantee you won't get the fans full rated CFM.

As for the "blocking air" thing- if the shroud is on the backside of the radiator, it's not blocking air. The air has already passed through the core at that point. If the fans are small and the shroud doesn't allow all the air to pass easily through it may reduce airflow through the engine compartment, which will also reduce cooling, but it doesn't reduce the airflow through the core unless it's out in front.

I may have asked this before, but how thick are the contour fans at the thickest point ?
 
I may have asked this before, but how thick are the contour fans at the thickest point ?

With my Contour fans installed, the fans stick out the most on the driver's side about 3.5" from the cooling fins. I have around 1.5" between the fans and the water pump pulley. Plenty of room. Rod
 
Side note: I do have two more fans on my setup they are on the heat exchanger for the intercoolers, so when all 6 are on think its around 8500cfm flow
 
I may have asked this before, but how thick are the contour fans at the thickest point ?

I know I've posted it before but I'll post it here to make it easy. It depends on where you measure, but right in the middle in front of the water pump pulley the shroud is just over 3" thick. It's about 3.5" thick at the back of the fan motors, but they don't line up with any of my pulleys so it's less of an issue. That's the thickest part of the assembly, to the backs of the motors. On mine the tightest clearance is to the front of the water pump pulley, I had to leave the cosmetic cover on my March water pump pulley off and I used button head allen bolts to increase the clearance there. I have a little more than a 1/2" of clearance to that pulley, although the aluminum pulleys are a little thicker than the stock steel ones there.

For those without a radiator or all the stuff yet, the back of the fans are about 6" from the radiator support where the radiator flange bolts on.

To the back of the shroud in the center
img_5433-jpg.1715208330


To the back of the fan motor
img_5431-jpg.1715208328


img_5432-jpg.1715208329


To the back of the fan motors from the radiator mount on the radiator support
img_5437-jpg.1715208331


Side note: I do have two more fans on my setup they are on the heat exchanger for the intercoolers, so when all 6 are on think its around 8500cfm flow

See to me that says you're losing efficiency. You shouldn't need that much CFM. The 4 fans on the radiator leave a large portion of the core uncovered, so when the fans are running they're only pulling air through the portions of the core they directly cover. Based on your picture you're probably not pulling air through almost 25% of your core when the car is stationary and the fans are running.

Typically more is better when it comes to airflow, but you do have to supply power for all of those fans. The more amps you pull the greater the HP loss.
 
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I have several concerns. First, 1,600 CFM is no where near enough for a stand alone electric fan set up. If you aren't going to move at least 3,000 cfm you're not setting yourself up for success.

Second, the 4 core radiator. I won't get into 2 core vs 4 core or any of that crap as far as cooling, most of all that is gimmicks vs science anyway. But, A-bodies don't have a ton of space to work with, and if you make the radiator too thick you'll run out of clearance to the pulleys. A 4 core will be difficult to deal with for setting up the fans because of the thickness of the radiator.

I run a 26" 3 core Champion radiator with a '95-'00 Ford Contour dual electric fan set up on my Duster. It has a built in shroud, which is important because it means the the rated CFM for the fan is more likely to be reproduced for your application. With a non-shrouded fan it's almost impossible to tell how it's rated or if you'll actually see that CFM in your application. The CFM numbers are roughly 3,500 cfm on the low speed, with over 5,000 cfm on the high speed. It's pretty rare, but I have had the high speed kick on while I was in traffic in 100°+ degree weather. Which means, if I hadn't had it, I might have been on my way to overheating. You need more CFM than a lot of aftermarket fans are capable of to cool a moderate 418. The Contour set up is a very capable fan set up, Ford was nice enough to test the living crap out of it, and the reproduction fan assembly is made by Dorman and is cheaper than any of the aftermarket fans capable of moving enough CFM.

My install on my Duster is here
My "new" '74 Duster- or why I need a project like a hole in the head

And the set up looks like this. You can see there isn't a ton of clearance even with a 3 core, and the Contour fan set up is relatively thin for a standalone electric fan.
View attachment 1715492151

View attachment 1715492152

@goldduster318 did a very nice write up of his install of the Contour fan set up with the Dakota Digital controller, I basically followed his install when I did mine. The PDF he did should be attached at the bottom of my post...



This is bad advice. A well designed shroud adds to the capability of the fan. Without a shroud, the fan will only pull air across the part of the core that it covers. With a well designed shroud, it will pull air across the entire core. If you're not pulling air across the entire core you're losing a ton of cooling efficiency. Not only that, but fans are pretty much always tested with some kind of shroud. So without one you can pretty much guarantee you won't get the fans full rated CFM.

As for the "blocking air" thing- if the shroud is on the backside of the radiator, it's not blocking air. The air has already passed through the core at that point. If the fans are small and the shroud doesn't allow all the air to pass easily through it may reduce airflow through the engine compartment, which will also reduce cooling, but it doesn't reduce the airflow through the core unless it's out in front.

EXCELLENT INFORMATION !!! THANK YOU !!!!
 
As for the "blocking air" thing- if the shroud is on the backside of the radiator, it's not blocking air
I have to disagree. If you have a room that has air (from a fan or the wind) blowing into it, the room will pressurize and once it reaches equilibrem there will be no flow. If on the other hand you open a window on the other side of the room you will have some flow thru the room. The amount of flow will be decide by either the opening in the inlet or the outlet.

My point is that a lot of driving is done at a speed where the fans are not pulling more air than the airflow of driving is providing and a poorly designed shroud will block air flow.
 
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I have seen (sorry can't remember what car) a factory fan shroud that had 'flappers' on the 'blocking' parts of the shroud, so it would allow the fans to pull air across the whole core at slow speed and also not restrict airflow on the highway.
 
I have to disagree. If you have a room that has air (from a fan or the wind) blowing into it, the room will pressurize and once it reaches equilibrem there will be no flow. If on the other hand you open a window on the other side of the room you will have some flow thru the room. The amount of flow will be decide by either the opening in the inlet or the outlet.

My point is that a lot of driving is done at a speed where the fans are not pulling more air than the airflow of driving is providing and a poorly designed shroud will block air flow.


I think we are talking about 2 things... 1. focusing the air flow through the radiator to capture all the surface area of the cooling fins. 2. making sure adequate air volume is moving across the cooling fins to maintain temperature. And there is item 3. moving the coolant through the radiator with a flow rate that allows for adequate heat removal of the coolant. I appreciate everyone's input! All your help with this issue (and several others as I start the phase 2 upgrades) will save me trial and error!
 
I know I've posted it before but I'll post it here to make it easy. It depends on where you measure, but right in the middle in front of the water pump pulley the shroud is just over 3" thick. It's about 3.5" thick at the back of the fan motors, but they don't line up with any of my pulleys so it's less of an issue. That's the thickest part of the assembly, to the backs of the motors. On mine the tightest clearance is to the front of the water pump pulley, I had to leave the cosmetic cover on my March water pump pulley off and I used button head allen bolts to increase the clearance there. I have a little more than a 1/2" of clearance to that pulley, although the aluminum pulleys are a little thicker than the stock steel ones there.

For those without a radiator or all the stuff yet, the back of the fans are about 6" from the radiator support where the radiator flange bolts on.

To the back of the shroud in the center
img_5433-jpg.1715208330


To the back of the fan motor
img_5431-jpg.1715208328


img_5432-jpg.1715208329


To the back of the fan motors from the radiator mount on the radiator support
img_5437-jpg.1715208331




See to me that says you're losing efficiency. You shouldn't need that much CFM. The 4 fans on the radiator leave a large portion of the core uncovered, so when the fans are running they're only pulling air through the portions of the core they directly cover. Based on your picture you're probably not pulling air through almost 25% of your core when the car is stationary and the fans are running.

Typically more is better when it comes to airflow, but you do have to supply power for all of those fans. The more amps you pull the greater the HP loss.

Well at only 3amps on the smaller fans each isn't to much, I have that much cfm due to being twin turbo and twin air/water intercoolers, I do see your point on the center open areas, but with the 2 10" fans mounted in the middle in the heat exchanger should help keep that area cool as well. Plus in running a 200amp alt to carry the load of everything else for the engine and car.
 
Getting ready to order a new Champion 4 core radiator...I'm thinking having the redundancy of 2 fans would be a good idea, and that one 12" fan will likely maintain engine temp, while using the 2nd fan in traffic or after a hard run at the track. Has anyone studied this? A couple of notes: 12" fan is 870 cfm and 10 amp draw, 16" fan is 1600 cfm and 14 amp draw. Electrical won't be an issue as I am rewiring the car. I just like the idea of redundancy of 2 fans. Thoughts?

1600 CFM ain't jack diddly dangit. You need to be close to or over 4,000 CFM for any type of performance engine. Take a look at the Flex A Lite Black Magic fans. They MOVE some air. They ain't cheap, but neither is your engine.
 
I have to disagree. If you have a room that has air (from a fan or the wind) blowing into it, the room will pressurize and once it reaches equilibrem there will be no flow. If on the other hand you open a window on the other side of the room you will have some flow thru the room. The amount of flow will be decide by either the opening in the inlet or the outlet.

My point is that a lot of driving is done at a speed where the fans are not pulling more air than the airflow of driving is providing and a poorly designed shroud will block air flow.

I'm a firefighter by trade, so I have pretty extensive training on your example for positive pressure ventilation as it's how we clear smoke from houses. It's not a great comparison to begin with as there are a lot of differences between the examples that make the comparison fairly irrelevant. The air has to flow through and out of the engine compartment, for example, so the shroud isn't even close to the only thing that effects flow if you start considering the whole system. And it's not the biggest. The airflow out of the engine compartment would be a much larger factor for creating any kind of positive pressure and reducing flow through the radiator than even a fairly restrictive shroud. What you're talking about has more to do with the aerodynamics of the car as a whole than a fan shroud.

A few other issues- the fans shouldn't even be running if the car is moving at any kind of speed. If the radiator and the rest of the cooling system are operating properly the fans shouldn't even be on if the car is moving more than 25-30 mph, so all of the airflow at that point is from the speed of the vehicle which should be more than enough volume to be able to overcome a little extra resistance from the shroud. Meanwhile, when the car is moving slowly or not at all the shroud allows the fans to pull air across the entire core. The factory used shrouds for the stock mechanical fans, going without a shroud just reduces the efficiency of the fan regardless of whether it's mechanical or electric.

That's one of the reasons I used a factory electric fan set up. It has a shroud that was designed to work with the fans that it's equipped with over the surface area of that size radiator. Some of the aftermarket shrouds are a just a flat plate with holes for the fans- that's just a bad design. Same deal with fans that come without a shroud, you have no idea if you'll actually get the rated CFM because most likely the rated CFM was achieved using some kind of shroud for testing. If you don't replicate the testing parameters you won't get that kind of flow.

I have seen (sorry can't remember what car) a factory fan shroud that had 'flappers' on the 'blocking' parts of the shroud, so it would allow the fans to pull air across the whole core at slow speed and also not restrict airflow on the highway.

Yes, there are shrouds out there that have flappers and things that would be open when driving and closed when the fan is running. I personally think they're kind of gimmicky, the air flow through the shroud at speed has to be pretty darn restrictive before something like that is necessary or useful. Basically it's a band aid for a poorly designed shroud or undersized fan area.

I think we are talking about 2 things... 1. focusing the air flow through the radiator to capture all the surface area of the cooling fins. 2. making sure adequate air volume is moving across the cooling fins to maintain temperature. And there is item 3. moving the coolant through the radiator with a flow rate that allows for adequate heat removal of the coolant. I appreciate everyone's input! All your help with this issue (and several others as I start the phase 2 upgrades) will save me trial and error!

Yes, you absolutely have to balance the entire system. All the components have to work together for the system to work the best. Sure, you can overcome some amount of undersized fan by running a larger radiator, or overcome a smaller radiator by using a much higher rated fan. Same goes for the water pump, pulley ratios, etc. But for best overall performance and efficiency everything has to work together. Run more fan than you have to and you're losing horsepower driving the fans. Run more radiator than you need and you'll lose space which may require running smaller fans, which could cause in traffic overheat issues when you're not moving enough air. Run too much water pump and again you're losing power driving the pump, plus you may lose cooling efficiency if the water isn't staying in the engine long enough to absorb heat.

Well at only 3amps on the smaller fans each isn't to much, I have that much cfm due to being twin turbo and twin air/water intercoolers, I do see your point on the center open areas, but with the 2 10" fans mounted in the middle in the heat exchanger should help keep that area cool as well. Plus in running a 200amp alt to carry the load of everything else for the engine and car.

If your system works that's great, it sounds like you have a fairly complicated set up with the twin turbos and intercoolers so going beyond the standard kind of set up and thinking may be totally necessary. A 200 amp alternator is something a lot of us don't have though, and something the stock wiring harness probably won't tolerate for very long. I was just pointing out that your CFM requirements, and therefore your amperage load to run the fans, would probably be lower with a well designed shroud. Of course, a poorly designed shroud may not help much at all.

1600 CFM ain't jack diddly dangit. You need to be close to or over 4,000 CFM for any type of performance engine. Take a look at the Flex A Lite Black Magic fans. They MOVE some air. They ain't cheap, but neither is your engine.

Yes the Black Magic fans have a great CFM rating, but they come without shrouds so there's no guarantee they'll flow that much on your car. Plus, you can get fans that flow more air for half the price and were tested to go over a 100,000 miles.
 
Yes the Black Magic fans have a great CFM rating, but they come without shrouds so there's no guarantee they'll flow that much on your car. Plus, you can get fans that flow more air for half the price and were tested to go over a 100,000 miles.

How about giving us some examples? Have you ever used or known someone who has used a Black Magic fan? I know a few people with them and none are dissatisfied. I do agree they don't come with shrouds, but then, since the application is going to be a custom one, that would be difficult. Shrouds are cheap and easily made.

BTW, thanks for what you do in your profession.
 
How about giving us some examples? Have you ever used or known someone who has used a Black Magic fan? I know a few people with them and none are dissatisfied. I do agree they don't come with shrouds, but then, since the application is going to be a custom one, that would be difficult. Shrouds are cheap and easily made.

BTW, thanks for what you do in your profession.

What kind of example are you looking for? The Ford Contour fans I run pull 3,500 cfm on the low speed, approximately 5,000 cfm on the high speed, and the Dorman reproduction set up is $131
Dorman Electric Fans 620-104

As for the flex-a-lite fans, I’ve never heard anything bad about them. They’re one of the few electric fans out there that flow the kind of cfm needed for a stand-alone electric fan set up. Their dual fan systems definitely move enough air, and most have some kind of shroud.

And actually, in looking at the black magic single fans now they do have shrouds. Maybe not ones designed to completely cover the radiator, but the are shrouded so they should perform as rated. As for the non-shrouded fans, if you’ve run a flow bench for cylinder heads it’s easy to see how even a few small changes in how you set up the bench can make a difference in the numbers that might not be relevant on the engine.

Only thing about the black magic fans is they start at like $250 for the single fans and get well into the $400 range for the dual fans. So the contour set up will flow more cfm for almost half the price in most cases. Although the Contour fans need a 26” radiator, so they’re not an option for everyone.

And thanks! As they say, if you love your job you never work a day in your life. Now, I wouldn’t say “never” as some of the days are pretty hard. But most days I do love my job, and the days that are hard, well, I’m pretty well compensated for. Times are a little strange right now, but someone has to do it.
 
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