Electric fan Vs. Mechanical fan (split from Chris' e-fan thread)

[blackhat620]

MOD NOTE- I split these posts from Chris' thread about changing the type of fan he was running per his request. This way we can keep the debate going here. Thanks guys. Tony

Do either of these fans (permacool, taurus fan, t-bird fan) move more CFM than the stock clutch fan + shroud combo?

Generally a stock clutch fan & shroud will move more air than an electric fan. The caveat to this is putting the largest electric fan made on a small car (ie Focus etc).

I've heard numbers tossed around for the tbird fan-- around 5000cfm. There's no telling just exactly how much air it's pulling. But Rick and I were talking about that and he said he heard the clutch fans are rated to pull in excess of 10k CFM when fully locked (and brand new from the factory). That's what scared him about the swap but he and I both found that the electric pulls MORE than enough.

Heavy duty cooling fans & systems used on full size trucks pull a large amount of air when fully locked, much more than any electric fan setup. If you research with the electric fan manufactures that are truthful, they will tell you that in heavy applications, towing, hauling, high ambient temperatures a OEM clutch fan assembly is the best choice.

Here are some quotes from the "Flex-a-Lite" catalog:
"Electric fans are not recommended for primary diesel engine cooling when the combined gross vehicle weight (CGVW) exceeds 18,000 pounds (truck, trailer and load)"
www.flex-a-lite.com/auto/html/universal.html

"What's the best type of fan to have on a vehicle that frequently tows ?
A good heavy duty clutch and clutch fan. This combination allows for the best air flow to fuel economy ratio."

"Do you have any electric fans you recommend for my motor home ?
We recommend that you keep a mechanical fan for your primary cooling needs. For additional cooling we offer several auxiliary fans listed in our catalog."
www.flex-a-lite.com/auto/html/frequent-question.html

Quote from the "Hayden" catalog:
"(3) Air volume requirements to large for electric fans.Use fan clutch. See fan clutch applications."
www.haydenauto.com/catalogs/hayden/2007-hayden-electric-fans.pdf

Electric fans have there place, such as race cars run on the strip; Off road specific vehicles (Mud bogger) that need to turn the fan off in deep water/mud; A supplement (pusher) to the factory fan clutch when the vehicle is used under heavy loads & high ambiant temperatures; mounted on auxillary coolers that cannot be mounted in the air stream.

Most cars that are designed with electric fans from the factory have larger radiators & cooling systems than there counterparts with the same size engine and a fan clutch. Electric fans on OEM cars came about do to the mounting of the engine tranversely on FWD cars. Under light loads and cool ambiant temperatures a large electric fan can be used to adequately cool in these conditions, but will be quickly overwhelmed in heavy load & high ambiant conditions.
Also when you are reading electric fan CFM ratings, this is for free air flow. The actual air flow through the radiator will drop 15-30% depending on the application and fan design. Also pusher fans are 15% less efficient than the same fan in a puller application. FYI if you retrofit your vehicle to an electric fan, make sure the fan is large enough to cover at least 70% of the radiator core and is fully shrouded. In addition most electric fan manufactures do not recommend using an electric fan on radiators that contain more than 3-cores.

 

[Skandocious]

Compelling arguments, Greg, but the numbers dont mean much to me. I've been using the taurus fan for over a year and never had overheating issues (yes, including some towing, as well as the snow trip which was REALLY rough on my trans). The performance of the fan speaks for itself-- I could care less how much CFM it's flowing. And keep in mind that I've been driving around with the taurus fan, which is FAR inferior to this Tbird fan.

Not to mention that all of those quotes are talking about heavy duty applications. "18,000# CGVW", motorhomes, etc... My truck will never even be in the BALLPARK of 18k-- it's hardly a "heavy duty" application. The very highest I'd ever see is 12-13k, tops.

 

[blackhat620]

Compelling arguments, Greg, but the numbers dont mean much to me. I've been using the taurus fan for over a year and never had overheating issues (yes, including some towing, as well as the snow trip which was REALLY rough on my trans). The performance of the fan speaks for itself-- I could care less how much CFM it's flowing. And keep in mind that I've been driving around with the taurus fan, which is FAR inferior to this Tbird fan.

Not to mention that all of those quotes are talking about heavy duty applications. "18,000# CGVW", motorhomes, etc... My truck will never even be in the BALLPARK of 18k-- it's hardly a "heavy duty" application. The very highest I'd ever see is 12-13k, tops.

You live in a cool climate and have a stock small block V8. Come and try that in the desert southwest daily from mid may to mid september, loaded with the ac blasting. Electric fans have there limited uses but they are not up to the task of heavy duty cooling.

Just an fyi, your snow trip was not very hard on your transmission, if you were in alot deeper snow & cutting a fresh trail, or mud bogging or rock crawling then we will talk about increased transmission work. In your recent outing your transmission had it pretty easy. As far as caring less about how much CFM your cooling fan is drawing, this is a naive statement at best. All engines and load conditions require a certain amount of CFM in order to achieve proper cooling, ignoring this fact can lead to serious overheating.

Chris i am glad you are happy with your e-fan modification, but just because it has worked up to this point does not mean you will not have cooling issues in the future if you start spending alot of time in warmer climates or pulling heavier loads for extended periods. When the e-fan manufactures are telling you that the e-fan is not as good as a engine driven fan & fan clutch, that ought to be a clue as to which system cools better.

 

[Skandocious]

Cool climate? Summers here in the valley get as high as 110*F. I've been stuck in stop and go traffic on one of those days-- temp gauge never skipped a beat.

Can't argue too much about towing cuz I've only towed with this truck a handful of times-- and the only heavy load I pulled was 2 months before my efan swap.

 

[subford]

I know with the E-fan you would lose power and your fuel mileage would go down as you not getting anything for free with the losses from the alternator recharging the battery and running the E-fan.
It is scientifically impossible to get a one to one exchange and there will be a mechanical loss.

I know you can pick when you want the loss with a switch if you racing someone but over all the performance would suffer unless you charge a battery at night for the fan. Then there is the light bill.
But now with the added above information I think I will keep the stock set up.

Just thinking out loud.

Thanks for all the information you guys I really applicate it.

 

[Lost]

You live in a cool climate and have a stock small block V8. Come and try that in the desert southwest daily from mid may to mid september, loaded with the ac blasting. Electric fans have there limited uses but they are not up to the task of heavy duty cooling.

Just an fyi, your snow trip was not very hard on your transmission, if you were in alot deeper snow & cutting a fresh trail, or mud bogging or rock crawling then we will talk about increased transmission work. In your recent outing your transmission had it pretty easy. As far as caring less about how much CFM your cooling fan is drawing, this is a naive statement at best. All engines and load conditions require a certain amount of CFM in order to achieve proper cooling, ignoring this fact can lead to serious overheating.

Chris i am glad you are happy with your e-fan modification, but just because it has worked up to this point does not mean you will not have cooling issues in the future if you start spending alot of time in warmer climates or pulling heavier loads for extended periods. When the e-fan manufactures are telling you that the e-fan is not as good as a engine driven fan & fan clutch, that ought to be a clue as to which system cools better.

I hate to tell u I lived in Arizona and the electric conversion was very common and the less drag more than makes up . As for stock fans after 4-5 years the stocker is 505 as reliable as used to be.

 

[Lost]

I know with the E-fan you would lose power and your fuel mileage would go down as you not getting anything for free with the losses from the alternator recharging the battery and running the E-fan.
It is scientifically impossible to get a one to one exchange and there will be a mechanical loss.

I know you can pick when you want the loss with a switch if you racing someone but over all the performance would suffer unless you charge a battery at night for the fan. Then there is the light bill.
But now with the added above information I think I will keep the stock set up.

Just thinking out loud.

Thanks for all the information you guys I really applicate it.

Drag is drag .Once turning the drain on alt goes down allot . Everyone I talk to that does the conversion has slight increase MPG and you can tell slight diff in performance . I have driven them My self . As for the actually drag .

My Start /alt Rebuild shop tested my friends truck it showed no more drain than having head lights on plus set of large driving lights for the taurus setup once engaged . And the electric fans runs allot less.

 

[Skandocious]

I know with the E-fan you would lose power and your fuel mileage would go down as you not getting anything for free with the losses from the alternator recharging the battery and running the E-fan.
It is scientifically impossible to get a one to one exchange and there will be a mechanical loss.

I know you can pick when you want the loss with a switch if you racing someone but over all the performance would suffer unless you charge a battery at night for the fan. Then there is the light bill.
But now with the added above information I think I will keep the stock set up.

Just thinking out loud.

Thanks for all the information you guys I really applicate it.

This argument is 100% bogus. My fan SELDOM turns on. And by seldom I mean maybe once a month at MOST, and even then only for a couple minutes. Any speeds over ~30mph is fan-off territory. Trust me on this-- there is no DECREASE in mileage or performance-- only increases. If I had noticed losses I would have swapped back to a clutch fan by now. Like Larry said-- even when the fan is on, the draw isn't large enough to suck power. My truck feels to be at 100% when the fan is running on high speed. I ran the taurus fan on high speed all day during the snow trip to keep my transmission cool; no problems at all.

 

[blackhat620]

I hate to tell u I lived in Arizona and the electric conversion was very common and the less drag more than makes up.

It might be common in northern AZ but in the desert it is not a common practice if you work your vehicle alot everyday were we see 115+F for weeks on end and the night time lows do not drop below 105F. Have run to many fleets of trucks etc in the AZ desert and the desert SW for that matter for over 40 years, and the electric fans do not keep up with the demand when the trucks are worked. There is a reason the e-fan manufactures do not recommend electric fans for full size trucks and heavy loads. The OEM manufactures have figured this out as well after having major overheating problems in the 60's & early 70's, this is why they built testing grounds in the deserts of AZ.

 

[blackhat620]

This argument is 100% bogus. My fan SELDOM turns on. And by seldom I mean maybe once a month at MOST, and even then only for a couple minutes. Any speeds over ~30mph is fan-off territory. Trust me on this-- there is no DECREASE in mileage or performance-- only increases. If I had noticed losses I would have swapped back to a clutch fan by now. Like Larry said-- even when the fan is on, the draw isn't large enough to suck power. My truck feels to be at 100% when the fan is running on high speed. I ran the taurus fan on high speed all day during the snow trip to keep my transmission cool; no problems at all.

Chris,

That is funny right there! Oh to be a young shade tree mechanic and have all the engineers baffeled. If you study and learn about physics and thermodynamics, you will find there is no free ride. Is the electric fan slightly more efficient when turned OFF than an clutch fan that is in full freewheel, yes but it is only a very minor gain. If you are running the quarter mile and trying to shave a hundredth of a second off your time then fine run with the fan off for a better ET. Or just do what we do on our race cars and run no radiator or cooling fan at all. Do not need the extra weight in the 1/4. You may get a slight increase in ET but for that gain you give up cooling efficiency under high heat & load conditions.

Glad you live in a cool enough climate to not need a cooling fan once you reach 30 mph, but in warmer climates you will need a cooling fan for speeds this slow. Ram air effect does not reach full potential until you exceed 55 mph. There is a reason that the fan clutch assembly and factory e-fans are thermostatically controlled.

As far as not overheating when snow wheeling, well duh, did you look at the ambient temps when you where following the others down the road? Many people everyday plow through that much and more snow in the winter on there way to work. Sorry but, you were not working your truck very hard on that trip.

Remeber the manufactures design their vehicles to run properly when lightly loaded in Alaska during a blizzard in February and then heavily loaded in Death Valley in July when it is 120+F.

 

[big5oh]

Another thought....

The e-fan runs off of the alternator which is only about 80% efficient. This would mean that for every 1 HP used to turn the alternator, only about 0.8 HP goes towards usefull power for turning the fan (or whatever). The rest is wasted and jut turn into heat. The mechanical fan on the other hand is 100%efficient. So, every bit of every HP that gets used up on the mechanical fan is converted into usefull work at the fan.

The ratio of HP loss to usefull air flow for the e-fan is 0.8:1, for the mechanical fan it's 1:1. If the e-fan would have to be on all the time then it's not worth it, but if it is only on once per blue moon then maybe it is a better option.

 

[tomtoc]

Another thought....

The e-fan runs off of the alternator which is only about 80% efficient. This would mean that for every 1 HP used to turn the alternator, only about 0.8 HP goes towards usefull power for turning the fan (or whatever). The rest is wasted and jut turn into heat. The mechanical fan on the other hand is 100%efficient. So, every bit of every HP that gets used up on the mechanical fan is converted into usefull work at the fan.

The ratio of HP loss to usefull air flow for the e-fan is 0.8:1, for the mechanical fan it's 1:1. If the e-fan would have to be on all the time then it's not worth it, but if it is only on once per blue moon then maybe it is a better option.

valid points, but the draw is only happening when the fan is running. in skan's case, his only runs once every couple weeks. for him, seems like a great deal. if you live in the desert, might not be worth it

 

[O'Rattlecan]

Mine runs every time I'm in the truck so not to discount Chris but I don't see how his can be on so sparsely.

Ryan

 

[Skandocious]

Mine runs every time I'm in the truck so not to discount Chris but I don't see how his can be on so sparsely.

Ryan

You've got a whole different wiring scheme then Ryan. Mine is thermostatically controlled and will only come on when my engine start to climb past normal operating temperature. My temps seldom reach this high unless I'm doing a lot of stop-and-go driving, so my fan seldom comes on.

Greg-- I'm not going to argue with you. You're now blaming my age? For your information I HAVE studied physics and thermodynamics, as well as relativity theory, differential equations, linear algebra, data structures and algorithm analysis... The list goes on. If you want to talk about education then we can-- but your big words don't scare me.

As I said before-- the numbers do not matter. You can google and post links all day long but the facts lie in the PERFORMANCE of this modification. I have been driving with this fan for a year with no issues of overheating, in a variety of temps and driving conditions. If you want to argue that it won't work for your application-- fine. But don't tell me it's not doing the job on MY truck because IT CLEARLY IS.

The day that my truck overheats, I will come back to this thread and give a formal apology. Until then actions speak louder than words. I have proof that it works. You do NOT have proof that it DOESN'T work.

If your numbers don't lie, why do the numbers on my temperature gauge show that the fan setup is working better than stock?

 

[Late Model Man]

I know with the E-fan you would lose power and your fuel mileage would go down as you not getting anything for free with the losses from the alternator recharging the battery and running the E-fan.
It is scientifically impossible to get a one to one exchange and there will be a mechanical loss.

Wrong. There are losses everywhere you go, the losses with the e-fan are significantly less than with a clutch fan, especially at cruising speeds. That explains the mileage increase.

The e-fan runs off of the alternator which is only about 80% efficient. This would mean that for every 1 HP used to turn the alternator, only about 0.8 HP goes towards usefull power for turning the fan (or whatever). The rest is wasted and jut turn into heat. The mechanical fan on the other hand is 100%efficient. So, every bit of every HP that gets used up on the mechanical fan is converted into usefull work at the fan.

The ratio of HP loss to usefull air flow for the e-fan is 0.8:1, for the mechanical fan it's 1:1. If the e-fan would have to be on all the time then it's not worth it, but if it is only on once per blue moon then maybe it is a better option.

Very wrong. The fan clutch is not at all like a car's clutch, is is a fluid coupling sort of like a torque converter. the lockup is nowhere near 1:1. The e-fan would NOT (and definitely does not) have to be on all the time.

Is the electric fan slightly more efficient when turned OFF than an clutch fan that is in full freewheel, yes but it is only a very minor gain.

When the truck is off and cold (clutch unlocked), go spin the mech fan, now go spin an e-fan, you'll get the idea on which one has more drag.


That being said...
-with a properly working radiator you don't need the fan at cruising speeds.
-at criusing speeds the e-fan being driven by air creates far less drag on the vehicle than the mech fan being driven by air.
-the rotating e-fan assembly is way lighter than the mech rotating assembly.
-everyone who does this mod that I know of has posted mileage gains and HP gains. I am getting better highway mileage now than when it was bone stock.


Bronco's and F-150s are relatively light in the truck world, I know I'll never tow a huge load through death valley on the hottest day of the year, I'm pretty sure Chris never will either. If you think you will, or you think your truck is too big, DON'T GET ONE!


rattlecan- Mine hardly ever goes on either, you must do more slow speed driving than chris and I.

 

[surewhynot]

This has always struck me as an odd disagreement every time it has come up. I have run an electric fan set up on a heavier truck before with no problems.

The truck was so cross bred, that it didn't even know what it was, lol. It was an Isuzu NPR cab over with a 20 ft. steel wedge flatbed for hauling my mud trucks. Empty the truck weighed just over 10K lbs and loaded would hit 15K depending on the load.

The engine was a 400 ford transplant with a c-6 automatic. The radiator came out of a mid 70's model F250. The electric fans were from a chrysler mini van. They had a built in shroud and fit just about how Chris' do. I had to go electric, it was the only way to make everything fit and work.

The engine had the stock temp. thermostat, 190*, and always stayed right in that range. Even in the heat of the summer down here in FL, it never went over 195*. 5* within the temp of the thermostat seems within reason to me.

It worked so well for me, that I never even thought that an electric fan setup wasn't enough to cool a truck. That is why I have a hard time understanding when these threads pop up. I have never seen a modern electric fan setup, that was done right, that has failed to keep an engine adequately cool.


EDIT:

This was the truck-

 

[Skandocious]

This has always struck me as an odd disagreement every time it has come up. I have run an electric fan set up on a heavier truck before with no problems.

The truck was so cross bred, that it didn't even know what it was, lol. It was an Isuzu NPR cab over with a 20 ft. steel wedge flatbed for hauling my mud trucks. Empty the truck weighed just over 10K lbs and loaded would hit 15K depending on the load.

The engine was a 400 ford transplant with a c-6 automatic. The radiator came out of a mid 70's model F250. The electric fans were from a chrysler mini van. They had a built in shroud and fit just about how Chris' do. I had to go electric, it was the only way to make everything fit and work.

The engine had the stock temp. thermostat, 190*, and always stayed right in that range. Even in the heat of the summer down here in FL, it never went over 195*. 5* within the temp of the thermostat seems within reason to me.

It worked so well for me, that I never even thought that an electric fan setup wasn't enough to cool a truck. That is why I have a hard time understanding when these threads pop up. I have never seen a modern electric fan setup, that was done right, that has failed to keep an engine adequately cool.

But Tony... Google says that it's not adaquate... So even though you THINK your setup worked fine-- it must have really been malfunctioning the whole time. Right Greg? Google doesn't put anything but factual links into it's search results.

 

[O'Rattlecan]

Late Model Man - I do about 90% highway driving usually 70 mph, sometimes 75 depending on the flow of traffic. The fan isn't infrequent. It's controlled by a probe in the radiator to determine water temp. It keeps my engine operating at the same temps as the stock setup, so it's not trying to maintain anything especially cool.

Ryan

 

[big5oh]

Very wrong. The fan clutch is not at all like a car's clutch, is is a fluid coupling sort of like a torque converter. the lockup is nowhere near 1:1. The e-fan would NOT (and definitely does not) have to be on all the time.

You did not understand what I said. I am not talking about lockup, I am talking about alternator efficiency versus mechanical drive efficiency and how it relates to HP loss and net CFM flow.

Since an alternator is 80% efficient, you get less air flow per HP spent. In other words it takes more of an HP loss at the alternator to move 2000 CFM with an e-fan than it does at the water pump pulley to move 2000 CFM with the stock fan + shroud. The 20% of HP that is lost at the alternator goes to heat build up. There is no loss (ie. wasted energy) at all with the stock fan and thus it is 100% efficient.....unless you consider the fan spinning when you don't need it to wasted energy, but thats a different matter.

If you convert this to ratios like I did earlier it would be 1:1 for the mechanical fan since it is 100% efficient and 0.8:1 for the e-fan since it is only 80% efficient.

As for lockup (what you were talking about), the clutch fan spins at 60% of water pump speed.....so 0.6:1.....thats 0.6 revolutions per water pump revolution (unless it begins to lock up due to heat).

 

[Skandocious]

You did not understand what I said. I am not talking about lockup, I am talking about alternator efficiency versus mechanical drive efficiency and how it relates to HP loss and net CFM flow.

Since an alternator is 80% efficient, you get less air flow per HP spent. In other words it takes more of an HP loss at the alternator to move 2000 CFM with an e-fan than it does at the water pump pulley to move 2000 CFM with the stock fan + shroud. The 20% of HP that is lost at the alternator goes to heat build up. There is no loss (ie. wasted energy) at all with the stock fan and thus it is 100% efficient.....unless you consider the fan spinning when you don't need it to wasted energy, but thats a different matter.

If you convert this to ratios like I did earlier it would be 1:1 for the mechanical fan since it is 100% efficient and 0.8:1 for the e-fan since it is only 80% efficient.

As for lockup (what you were talking about), the clutch fan spins at 60% of water pump speed.....so 0.6:1.....thats 0.6 revolutions per water pump revolution (unless it begins to lock up due to heat).

Okay... Some of these things you've said MIGHT be true, if the clutch fan was really 100% efficient-- but I can guarantee that it's not. First of all-- in an non-ideal world (such as the one we live in), 100% efficiency is impossible. This is the reason why we cannot create perpetual motion. Energy will transition readily between different states in any mechanical situation. That being said-- I can also assure you that the clutch fan on these trucks not even approaching 100% efficiency. As Rick said, it's a fluid clutch-- meaning that the ENTIRE mechanism is based on friction (or a lack thereof). And what do you get with friction? Heat. And what is heat? DISSIPATED ENERGY. Why do you think that the clutch has cooling fins on it?

It ain't styling-- this thing creates heat. And there's something else we've ignored this whole time: age. This 'supposed' efficiency rating which you've apparently read from a bogus website somewhere must be referring to a NEW fan clutch. But I think we all know that trucks this age often experience failing fan clutches. Either a full locked clutch which cools the engine too much, or a clutch that slips all the time and allows the engine to overheat. I've helped guys diagnose such problems on another site in the past. So I think it's safe to assume that the efficiency of the clutch degrades over time.

Just trying to keep all the facts straight here