Clutch fan or electric?

[73jeep]

Lots of pros here for an electric fan...
There are also a few cons...

Theses fans consume a LARGE amount of power so electrical system upgrades may be required.

They are much noisier than their clutch fan counterparts.

Also any hp gains are offset by extra drag on the alternator.

Electric fans are also prone to failure.

 

[7D8CJ]

Lots of pros here for an electric fan...
There are also a few cons...

Theses fans consume a LARGE amount of power so electrical system upgrades may be required.

They are much noisier than their clutch fan counterparts.

Also any hp gains are offset by extra drag on the alternator.

Electric fans are also prone to failure.

That's what I'm screamin'

 

[tarry99]

I've read: Think the flex fans are flexible. When you hit / submerge partially into the water, the fan is now pushing water instead of air, the heavier water forces the fan to over flex towards the radiator, which puts it too close to the radiator...

~ JR[/QUOTE]

JR,

YEP!

 

[coldair]

Everything with moving parts is prone to failure. It just depends on what you do with your jeep. Some people can get away with a stock clutch fan some people can't. The way I look at it an electric fan will be cheaper in the long run because I won't be eating radiators up. Even if u have to buy a new alternator, fan, used electric fan that's still cheaper in the long run.

 

[73jeep]

Everything with moving parts is prone to failure. It just depends on what you do with your jeep. Some people can get away with a stock clutch fan some people can't. The way I look at it an electric fan will be cheaper in the long run because I won't be eating radiators up. Even if u have to buy a new alternator, fan, used electric fan that's still cheaper in the long run.

A mechanical fan just bolts to the waterpump. A electric fan has an alternator, wiring, relays, fan controls, and finally the fan. Which one is more reliable.

I have driven my CJ through plenty of water holes. The key is to keep a bow wave going to keep the water out of the engine compartment.

 

[coldair]

A mechanical fan just bolts to the waterpump. A electric fan has an alternator, wiring, relays, fan controls, and finally the fan. Which one is more reliable.

I have driven my CJ through plenty of water holes. The key is to keep a bow wave going to keep the water out of the engine compartment.

I never said the electric fan was more reliable then the mechanical fan I said that some people can get away with a mechanical fan and some can't get away with having one. Right now my motor will have a mechanical fan on it tell I can find a electric fan. Reason why Im going electric because I'm building my jeep/motor for the rocks/trails I like my jeep to stay cool when idling around. Don't gets wrong I've used both. The mechanical one does keep the motor cool idling around but the temp dose go up and down. I want something that will be constant.

 

[coldair]

Also I've had to replace clutch fans from the bearings going out which took my radiator out. I have never had a electric fan come apart and do that. Anyways like I said some people can get away with a clutch fan and some can't. To each thier own. Maybe the ticket is to run both electric pusher and mechanical.

 

[73jeep]

Typically a mechanical fan moves lot more air than a electric. I would estimate mechanical fan on a CJ will move around 4000-6000CFM.

 

[tarry99]

Typically a mechanical fan moves lot more air than a electric. I would estimate mechanical fan on a CJ will move around 4000-6000CFM.

The only way a mechanical fan will move 4000-6000 CFM would be at high engine speed & MPH................at exactly the time you need high CFM the very least. taking into account the clutch at that speed has since released the blade and the radiator is now enjoying the free air that is traveling through the grill.
Without getting into Laminar flows and aerodynamics which may have some bearing here the conversation regarding cooling fans in a off road vehicle normally comes up while Idling at low speed off road ( except perhaps when JR decide's to submarine racing LOL)
I believe the focus here should be more so on what will generate more air flow through the radiator at low engine and vehicle speeds.
Without any reservation there is no way a mechanical fan can generate comparible CFM at Idle compared to a single or dual shrouded electric fan.
Most of these later fans with improved blade design only draw 7-10 amps which is pretty good compared to the earlier units that were 15-20 amps.

 

[coldair]

Thank you for clearing things up for us tarry

 

[73jeep]

Without any reservation there is no way a mechanical fan can generate comparible CFM at Idle compared to a single or dual shrouded electric fan.

I'm not trying to be argumentive here, but I don't think kind of generalization always holds true.

My 2 12in fans couldn't hold a candle to the stock fixed blade fan at idle.

A mechanical fan and shroud will move a surprising amount of air.

Take a look under the hood of any hd pickup, mechanical shrouded fan.

I guess the point I'm trying to make here is that there is no need to reinvent the wheel, and a factory style cooling system will work fine for most wheelers.

 

[tarry99]

I'm not trying to be argumentive here, but I don't think kind of generalization always holds true.

My 2 12in fans couldn't hold a candle to the stock fixed blade fan at idle.

A mechanical fan and shroud will move a surprising amount of air.

Take a look under the hood of any hd pickup, mechanical shrouded fan.

I guess the point I'm trying to make here is that there is no need to reinvent the wheel, and a factory style cooling system will work fine for most wheelers.

73,

No problem everyone is welcome to an opinion............and the discussion was not meant to be an attack on a stock cooling system that does a good job within certain parameters. And regarding your twin 12" fans I can't speak for or against there efficiency's.

But since this forum is about Jeeps and there inherent normal slow crawling speed the fact remains that a comparable sized & equipped electric fan at Idling speeds as I stated above will outperform its factory counterpart simply based on RPM generated CFM.

Fact: In order to cool you have to move air through the Radiator core..... pure and simple its all about air flow and we know that most Jeeps suffer in that department at low speed.
Fact: Electric fans provide constant cooling regardless of engine RPM.

At say 1000 rpm's the factory 16" mechanical belt driven fan which are normally under driven as compared to crankshaft speed by 20-30% means the fan is at best turning 800 rpms versus a normal 16" electric fan that will turn at 2200 rpms.

The math simply proves the point in this low speed application.

 

[73jeep]

73,

No problem everyone is welcome to an opinion............and the discussion was not meant to be an attack on a stock cooling system that does a good job within certain parameters. And regarding your twin 12" fans I can't speak for or against there efficiency's.

But since this forum is about Jeeps and there inherent normal slow crawling speed the fact remains that a comparable sized & equipped electric fan at Idling speeds as I stated above will outperform its factory counterpart simply based on RPM generated CFM.

Fact: In order to cool you have to move air through the Radiator core..... pure and simple its all about air flow and we know that most Jeeps suffer in that department at low speed.
Fact: Electric fans provide constant cooling regardless of engine RPM.

At say 1000 rpm's the factory 16" mechanical belt driven fan which are normally under driven as compared to crankshaft speed by 20-30% means the fan is at best turning 800 rpms versus a normal 16" electric fan that will turn at 2200 rpms.

The math simply proves the point in this low speed application.

With everything being equal yes that would be true! There is more to fan cfm than rpm! Blade pitch, size and number of blades are all variables. This will be hard to prove without a fan performance curve.

I believe you will find that a cj with a heavy duty clutch fan and multi blade fan with shroud will move more air than a typical electric fan setup.

Also remember electric fans are rated without a radiator attached. Their airflow is greatly reduced when you install them in front of a radiator.

but we could argue this until we are blue in the face....I guess we will have to agree to disagree

 

[GatorBate]

Then there the Cherokee. It came with both the mechanical fan and an electric fan that kick in when the mechanical fan couldn't keep up.

Mmm a smaller flex fan on the water pump next to one or two electric fan in the same shroud? Dependability of the mechanical fan yet the air flow of the electric fan at low engine rpm.

 

[coldair]

Maybe the ticket is to run both electric pusher and mechanical.

Gatorbate I like the way you think sounds like what I said earlier.

 

[JR74CJ5]

( except perhaps when JR decide's to submarine racing LOL)

Yes my mechanical fan does great, even without my shroud on it, during idle and in 100 degree heat, I still havent had any problems with over heating. It moves a LOT of air, even at idle, but then again, the pitch is severe during idle because rpms aren't flattening it out like flex fans are designed to do.

Like Tarry's joke suggests... the problem is when I come to a mudd bog pit out at local OHV park, and can not tell myself no (because I am young and dumb! )

I have tried the keep a bow wave going tactic, but when the water is door jam high + and the hole is over 50 yards long, it tends to still come onto the engine compartment. Also on some smaller less deep ones it hits the thicker mud.

I simply liked the idea of a electric fan being able to be manually shut off during a crossing, inspected for mud and stuck "stuff" before re-initiating after the crossing, and a not having the fan throw water onto every component under the hood while also not flexing and hitting the radiator... (radiators are kinda expensive... )

To achieve the same exact thing with a mechanical fan / flex fan, I'd need 4 shorter bolts to remove fan and extension from front water pump pulley and re tighten pulley for use then on other side have to re install said components. I am lazy! And like the switch off / on better!

Now if I were to ever go with electric fan, my stock fan and extension would be packed away in the camp trail spares section, and if / when my electric fan did fail (which it would be more possible / prone to do than mechanical, as I believe 73Jeep pointed out & why perfectly) I'd be able to do a camp site swap, and get her home.

My main focus was why is my fan hitting the radiator, and what should I do about it when I started this thread, my assumption of how clutch fans worked was off base though, and that was quickly dismissed as an option.

One day I will put the electrics in, just for the ease of shut off during crossings, but will in the mean-time be getting a smaller extension to move the fan further from the radiator.

I have already upgraded my electrical system for the DUI distributor (larger spark) and my Warn winch. I currently have a 55 AMP output alt. instead of the stock 37 AMP. I don't think the drag would effect me too much at this point, and also am not looking for high HP monster.


Now If only I learn to tell myself not to submarine race in the jeep until then, my radiator ought to last me a while yet...

All, very good info / discussion here. We all "good"!



~ JR

 

[tarry99]

With everything being equal yes that would be true!

73,

I think you need to stick to topic..........since no one can relate to all the variables hence why I stated "comparable sized and equipped at Idling speeds".

If your going to change topic then change it based on Fact and not assumptions as you are doing...........

All fans be it mechanical belt driven or electric are rated without obstructions or as commonly known as static pressure (mmH2-0) which will effect both in there overall performance.

The CFM math is quite simple 3.1416 x fan radius squared and therefore there is really no reason to question the bare calculations in a similar environment.

For me this is an educational type forum and although assumptions are welcome........ facts are what really are most important.

 

[73jeep]

The CFM math is quite simple 3.1416 x fan radius squared and therefore there is really no reason to question the bare calculations in a similar environment.

There is a little more to it than that!
Check out this tread were the equation is derived!

http://cr4.globalspec.com/thread/37227/Calculating-Air-Flow-for-Axial-Flow-Fans

Like I said we are missing some variables, so calculating it out is impossible.

 

[coldair]

There is a little more to it than that!
Check out this tread were the equation is derived!

CR4 - Thread: Calculating Air Flow for Axial Flow Fans

Like I said we are missing some variables, so calculating it out is impossible.

The fact is we are not building a rocket BOTH work end of discussion!!

 

[tarry99]

Yes my mechanical fan does great, even without my shroud on it, during idle and in 100 degree heat, I still havent had any problems with over heating. It moves a LOT of air, even at idle, but then again, the pitch is severe during idle because rpms aren't flattening it out like flex fans are designed to do.

Like Tarry's joke suggests... the problem is when I come to a mudd bog pit out at local OHV park, and can not tell myself no (because I am young and dumb! )

I have tried the keep a bow wave going tactic, but when the water is door jam high + and the hole is over 50 yards long, it tends to still come onto the engine compartment. Also on some smaller less deep ones it hits the thicker mud.

I simply liked the idea of a electric fan being able to be manually shut off during a crossing, inspected for mud and stuck "stuff" before re-initiating after the crossing, and a not having the fan throw water onto every component under the hood while also not flexing and hitting the radiator... (radiators are kinda expensive... )

To achieve the same exact thing with a mechanical fan / flex fan, I'd need 4 shorter bolts to remove fan and extension from front water pump pulley and re tighten pulley for use then on other side have to re install said components. I am lazy! And like the switch off / on better!

Now if I were to ever go with electric fan, my stock fan and extension would be packed away in the camp trail spares section, and if / when my electric fan did fail (which it would be more possible / prone to do than mechanical, as I believe 73Jeep pointed out & why perfectly) I'd be able to do a camp site swap, and get her home.

My main focus was why is my fan hitting the radiator, and what should I do about it when I started this thread, my assumption of how clutch fans worked was off base though, and that was quickly dismissed as an option.

One day I will put the electrics in, just for the ease of shut off during crossings, but will in the mean-time be getting a smaller extension to move the fan further from the radiator.

I have already upgraded my electrical system for the DUI distributor (larger spark) and my Warn winch. I currently have a 55 AMP output alt. instead of the stock 37 AMP. I don't think the drag would effect me too much at this point, and also am not looking for high HP monster.


Now If only I learn to tell myself not to submarine race in the jeep until then, my radiator ought to last me a while yet...

All, very good info / discussion here. We all "good"!



~ JR

Hey JR,

Sorry to get off point whereby the real question was why did your fan hit? Obviously you figured it out that your fan blades apparently flattened out when you hit the water and came into contact with the radiator. Your not the Lone Ranger on that one!
I've seen guys with the old school 4 or 5 blade rigid fans (there like 1/8" material) that will will not flex. Works good in water but probably is not as efficient as those flex style high pitch blade versions like you had..........
Want some advice?.............Stay out of the deep end of the pool!