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

[Bob Ayers]

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.

Very true!!

 

[Skandocious]

Bob that has already been quoted here:

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

We're not speaking about cooling diesels NOR heavily loaded trucks. I think we both know my F150 is not nearly capable of having a CGVW that high; so it's a moot point.

 

[O'Rattlecan]

That, and I'm sure there's a way to develop a bigger meaner electric fan. I'm sure the stock fan on my 94 f150 also has a ceiling.

Ryan

 

[subford]

Why do you think that the clutch has cooling fins on it?

They are heating fins not cooling. The fins heat it up to let it engage.

 

[Skandocious]

They are heating fins not cooling. The fins heat it up to let it engage.

Heating fins... cooling fins... They're really the same thing. At the very root I guess you could call them "heat transfer" fins. When the engine is hot, the fins catch hot air from the rad to engage the clutch-- once it's down to operating temp they catch the colder air to cool back off and disengage.

Point is, heat is a biproduct of the clutches operation. There ain't now way you can spin a fluid clutch and not generate heat; otherwise my trans wouldn't need a dedicated ATF cooler.

 

[Bob Ayers]

Bob that has already been quoted here:



We're not speaking about cooling diesels NOR heavily loaded trucks. I think we both know my F150 is not nearly capable of having a CGVW that high; so it's a moot point.

Just making a point that e-fans don't have the cooling capacity a mechanical fan has.......

 

[Skandocious]

Just making a point that e-fans don't have the cooling capacity a mechanical fan has.......

Nobody is trying to make that point Bob. We're making the point that a proper efan has the cooling capacity to cool an medium duty, gas engine truck. You see any diesel guys with efans in here? No. Your point is moot.

 

[O'Rattlecan]

the effectiveness of my fan shows me that I estimate it would be able to cool even if it was pumping out huge amounts of horsepower, too. You should see how fast the temp guage drops when it kicks on. For a ~220 hp engine, these e-fans are more than adequate clear up to about 100*F at least here in Missouri.

Ryan

 

[subford]

By the way electric motors have slip and give off heat too. Electric motors are not very efficient.

 

[Skandocious]

By the way electric motors have slip and give off heat too. Electric motors are not very efficient.

I'm well aware of that. I'm not the one who was claiming 100% efficiency.

 

[big5oh]

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.

So lets assume that SOME of the mechanical transfer from the water pump pulley to the clutch mechanism to the fan does get wasted in the form of heat or whatever. It isn't going to be anywhere near as much as an alternator. Those fins are not there to dissipate heat that builds up within itself, they are there to heat up so that it will then engage. It does not CREATE heat like you said. If there is wasted energy going from the water pump pulley to the fan, it is virtually not possible to measure. Just for conversation sake, what about the mechanical fans that have no clutch, no flex baldes etc.. Where is the wasted energy there?

My whole point is that it takes more HP to move a given amount of air through a radiator with an e-fan than it does with a mechanical fan. Thus if the e-fan spends alot of time in the ON position then the mod was counter productive assuming that the mod was done for HP, MPG gains. If it was done because of space issues then thats different.

 

[O'Rattlecan]

So since we're tearing apart electric fans - does anyone know how much heat is produced by a 351W engine under typical load and how many CFM are needed to cool it at say... an ambient temperature of 0*F and 100*F?

The point is - it's not 10,000 CFM. That's where the energy is saved.

Ryan

 

[Skandocious]

My whole point is that it takes more HP to move a given amount of air through a radiator with an e-fan than it does with a mechanical fan.

I will humor you here and say that IF in fact the alternator is less efficient than the clutch in the fan (which I still dont believe is true), then yes you would be correct.

Thus if the e-fan spends alot of time in the ON position

Stop right there-- the fan will NOT spend a lot of time in the ON position... THATS THE POINT! Mine doesn't turn on but maybe once a month. This is where your argument falls apart. Follow along with me real quick...

Say my efan runs at 3% of the time that I'm operating the truck (which is probably pretty accurate), then following your numbers I've got lost 20% efficiency--2% of the time.

On the flip side-- say the mech. fan is in fact 100% efficient, that's fantastic for the 3% of the time that the engine actually needs cooling, but the other 97% of the time the mech fan should NOT be turning-- and yet it is. Granted, during that time the clutch tries to disengage but just try to tell me that even ONE time you've popped your hood, with the engine running, and found the mech. fan to be completely stationary. It doesn't happen. There is a certain amount of friction in the clutch mechanism that prevents it from freewheeling from the engine 100%. Turning this "pseudo-disengaged" clutch fan, which has non-zero rotational mass, creates drag on the water pump pulley; and thus a parasitic power draw from the engine. I'm gonna throw a random number out there and say that the fan in this particular state is exhibiting a 10% decrease in efficiency.


So I'm choosing the less of two evils in this case... (1) An efan which is -20% efficient, 3% of the time. Or (2) A mech. fan which is -10% efficient, 97% of the time.

You tell me which is better

 

[big5oh]

So since we're tearing apart electric fans - does anyone know how much heat is produced by a 351W engine under typical load and how many CFM are needed to cool it at say... an ambient temperature of 0*F and 100*F?

The point is - it's not 10,000 CFM. That's where the energy is saved.

I understand what you are getting at. No it's not likely to be near 10K CFM.

However, the mechanical fan won't be fully engaged under those conditions and won't be trying to pull 10K CFM. In my experiance, the clutch only begins to lock under extreem conditions.

 

[Blue Goose]

OK guys, I had electric fan on a built 302 in my '79 F150 4x4 and I used to tow my 5,000# 21' wooden boat all around the midwest without a-n-y issue. I'm talking 750 mile, August heat, air conditioner on, marathon runs, and it wasn't at any 55 m.p.h. either. I have no regrets for having my truck set up that way aaaand, it was a helluva lot quieter not having that fan roar.

 

[big5oh]

I will humor you here and say that IF in fact the alternator is less efficient than the clutch in the fan (which I still dont believe is true), then yes you would be correct.

Stop right there-- the fan will NOT spend a lot of time in the ON position... THATS THE POINT!

Chris, I have said at least once in this thread that if the fan does not run very often then the e-fan may be a good choice. That being said, if you think I am trying to blow away the entire e-fan idea you are wrong.

And trust me, alternators are not very efficient. Why do you think an alternator pulling 60 amps will create enough load to slip on a v-belt? Ever spent any time around an alternator bench tester? Alternators get HOT after being tested. This heat comes from the very nature that they are inefficient.

As far as how often the fans turn and how often you want them to turn, I see your point. Thats why I said that if the e-fans are used and they rarely need to run, then they are a good option. But if they run often, then thats another story. Not only because of the whole alternator issue, but here is another thought. An electric motor such as those used on an automotive electric fan has a service life of 2000 running hours.....thats flex-a-lite's claim anyways and they are arguably the industry leader.

 

[Skandocious]

...if the e-fans are used and they rarely need to run, then they are a good option.

I'm glad we're in agreement

 

[blackhat620]

CRAP!!!!! Did you guys ever get this off on the wrong tangent. Go back and read the original posts. There were two questions asked and answered
1) Will an e-fan work in some applications - YES IT WILL.

2) Will an e-fan cool as well (move as much air) as an engine driven clutch fan - NO IT WILL NOT!

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.

Chris, wether you like it or not your age and experience matters. You have little mechanical and practical experience and this is do to your age.

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.

Chris you may choose not to believe it but, the numbes DO MATTER. As i posted previously i am glad it is currently working for your truck and use. You may want to correct the part about driving your truck for a year with your current fan. You swapped your previously beloved fan for a new larger fan that in your own words is working much better than your original "all encompassing" e-fan.

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?

Chris again i did not say your current fan was not cooling your truck in the current conditions you are using it in. What i said and will repeat again since you have missed my point entirely, An e-fan does not provide as much cooling as a mechanical clutch controlled fan. In light duty applicatins e-fans will work, in heavy duty applications an e-fan does not have the ability to pull enough air through the radiator. In addition, if your fan clutch was worn out, then the e-fan or a new fan clutch should cool your truck better.

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.

With an e-fan you will see a slight ET drop and MPG gain, but at the expense of cooling capacity. In our drag cars we did not run a radiator or cooling fan. Again you have to know your application and what you need to accomplish. Yes ram air effect takes over at speeds above 55 mph, fans are needed for lower speeds and extreme loads & heat conditions.

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!

This gets back to my original point with Chris, that is e-fans do not provide the amount of air flow that a mechanical clutch controlled fan can provide. Yes i tow heavy in extremely hot conditions all the time so an e-fan set-up will not work for this application.

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.

Chris, i see your age and in-experience is showing through again. Tony changed so many parts on that build up, he cannot pinpoint why the system as installed works. As far as googling for answers, i am sorry that you find it offensive when the e-fan manufactures state, in their printed materials, that e-fans are not adequate in high heat & load applications.

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.

First off mechanical clutch fans are NOT 100% efficient and neither are e-fans. Heavy duty mechanical clutch fans are 90% efficient, and lighter duty clutch fans are 75-80% effiecient. That being said, e-fans are not 100% efficient either as i posted earlier. E-fans CFM rating drops 15-30% from the published data when the air is pulled through a radiator (pusher fans drop an additional 15%). This translates to e-fans being 70-85% efficient when used as a puller, and 55-70% when used as a pusher.

As with all parts they wear out. I am sure you have seen fan clutches that are failing Chris. The fan clutch should be replaced when the water pump is replaced, but many people overlook this small fact. So they have a failing fan clutch, resulting in poor cooling performance, replacing a failing fan clutch with a new e-fan should result in better cooling, since the worn out part was replaced, but FYI if you just replace the fan clutch with a new one the cooling will be restored.

That, and I'm sure there's a way to develop a bigger meaner electric fan. I'm sure the stock fan on my 94 f150 also has a ceiling.Ryan

E-fans are limited to about 5-6k max "Free Air CFM" (actual CFM flow is 15-30% below this in use). This is do to the amount of space available to mount the fan and the electric draw of the fan motor. You can build a bigger fan but it will not fit your vehicle and the amp draw will be to high for most applications.

the effectiveness of my fan shows me that I estimate it would be able to cool even if it was pumping out huge amounts of horsepower, too. You should see how fast the temp guage drops when it kicks on. For a ~220 hp engine, these e-fans are more than adequate clear up to about 100*F at least here in Missouri. Ryan

E-fans work in the right applications, but in high HP applications, heavy loads and high heat the e-fans will reach there max capacity before a mechancial clutch fan. FYI 220 hp is not much.

 

[blackhat620]

There is a certain amount of friction in the clutch mechanism that prevents it from freewheeling from the engine 100%. Turning this "pseudo-disengaged" clutch fan, which has non-zero rotational mass, creates drag on the water pump pulley; and thus a parasitic power draw from the engine. I'm gonna throw a random number out there and say that the fan in this particular state is exhibiting a 10% decrease in efficiency.

So I'm choosing the less of two evils in this case... (1) An efan which is -20% efficient, 3% of the time. Or (2) A mech. fan which is -10% efficient, 97% of the time. You tell me which is better

Chris, you are correct, a mechanical fan clutch does not fully disengage, as there is always some drag, in fact it is about 20%. As i have posted before, there is no dispute that an e-fan will lower your ET & improve your mpg by a small percentage, the trade off is cooling capacity. Which is better??? the fan type that provides the cooling you need for your application and use. Light duty use or specialized use (ie racing etc) then e-fan will usually work. Heavy duty use then you need and mechanically driven clutch fan. Better ET's & MPG are great if i do not burn up the engine in the process.


I will state this again, you must know your required application, before you decide to run an e-fan or a mechanical fan clutch. E-fan designed cars use larger radiators than mechanical clutch fan equipped vehicles under the same conditions.
Can i build you a trophy truck to run the Baja 1000 using e-fans. Yes in fact most of them are built this way in order to relocate the radiators to a safer location on the vehicle. But the trick is to use very large radiators (larger than would be needed if they were mounted in the front & used mechanical fan clutch), along with large oil & transmission coolers. In addition air is ducted to the radiators for the ram air effect in place during the race since the vehicle will spend a large portion of the race at high speed. The fans are only needed for low speed driving.

Chris i applaud you for wanting to try new things on your truck and wanting to learn about vehicles But don't lose sight of the fact that when you change something, yes you may gain some positive aspects, but you will also lose some positive aspects. There is no free ride, all changes have negative consequences, along with the positives. It is always about tradeoffs and application needs.

BTW Chris i applaud you on finally losing your cherry... does Trista know?

 

[blackhat620]

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.

Tony,

You have multiple issues going on here, and without checking sizes, the F250 radiator you installed may have been the larger than needed for your engine application. In addtion, i will give you that 15k is heavy, but you live where you have relatively high humidity which aids in cooling. Bring your truck to the deserts of West TX, NM, AZ or Southern CA and you may find with the high ambiant temps and low humidity that your system is not up to the task. Without testing in these conditions we will not know for sure. Unfortunately i have seen e-fan setups not cool properly in the Desert Southwest, under high loads & ambient temperatures. There is a reason all the auto manufactures came to the AZ desert to build there proving grounds and test tracks.

On a side note AC systems for houses and buildings are switching to the new "greener" R-410 refrigerant. Well the draw back to R-410 is excessively high head pressures. These units work well everywhere but the desert southwest (this is a closely concealed fact by the HVAC industry). In the desert southwest the HVAC units with R-410 reach there high pressure limit switch rating on high temp days and cycle off to prevent the compressor from failing. The engineers are making strides to try and fix this "little" problem but so far if you want your HVAC to work on high heat days in the desert southwest you need to run units using the old reliable R-22. Hopefully by the time R-22 is no longer produced in 2020 they will have this problem fixed.

Bottom line of all this is that the Desert Southwest's high temperatures are extremely hard on equipment. Think of the polar opposite of Alaska in February.