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

[big5oh]

There are two types of fan clutches "Thermal & Non-Thermal". Non-Thermal fan clutches always spin at 60% of the water pump speed regardless of ambiant temperature. Thermal clutches spin anywhere from 20% - 90% of water pump speed depending on the ambiant temperature coming through the radiator.

There are three grades of Thermal clutches, Standard duty spin at 50-60% water pump speed when fully engaged; Heavy duty spin at 80-90% of water pump speed when fully engaged and have a fin surface area of approx 47 sq in; Severe duty spin at 80-90% of water pump speed when fully engaged and have a fin surface area of approx 65 sq in. The larger surface area allowes the fan clutch to operate more efficiently and have a longer life span in High heat & load applications.
www.haydenauto.com/installation/faqs.htm

All Thermal fan clutches still spin at approx 20% of water pump speed in cold ambiant temperatures (ie disengaged.
Non-Thermal fan clutches spin at 60% of water pump speed regardless of ambiant temperature.

I perused the link.

I don't see the 20% figure anywhere. There is no mention of how many turns per water pump turn with a thermal clutch that is not engaged. That being said, I will repeat myself....where did you get the 20% figure??

Going by feel, a thermal clutch (heavy duty) when not locked has about as much drag as a non thermal. Since they provide figures for the non thermal, I assumed that the unlocked thermal would be near the non thermal when unengaged. But, since the amount of drag would vary with temp, the 60% figure would just be an average. This is how I got the 60% figure fo the thermal clutch.

 

[radialarm]

My turn!

#1: Before changing over to an e-fan I did a considerable amount of research on the CFM requirements for various displacement engines. My current setup produces two times more CFM than my application requires(as a margine for error).

#2: As for performance increase, I have noticed a BIG increase in top end power, and throttle responce is smoother.

#3: Gas milage. I noticed only a very slight increase in gas mileage, but it is the gashog 4.9L. It would still get only 10mpg coasting down hill in neutral.

#4: I have noticed that if I am driving at least 25 mph that my e-fan does not run at all. It only runs while sitting still or moving at speeds below 25mph. It seems that the forward motion of the vehicle provides enough airflow to cool the engine.

#5: A/C operation. My A/C system functions more effeciently with my e-fan setup than it did with the engine driven fan. When my truck is sitting still it is just as cool inside as when in motion. Which is a pleasure to me because with the engine driven fan I would have to keep the RPM above 1000 to keep inside temps tolerable.

#6: Winter warm-up. My truck now reaches operating temp. faster.

 

[big5oh]

Friction, heat, slippage. Nothing is 100% efficient. Fluid couplings always have a slippage loss.

Friction and heat are very low in the fan clutch.

As long as the fan is not spinning at water pump speed then yes there is slippage. But, that has nothing to do with efficiency. If the fan spins at a lower rate than the water pump then the air flow goes down AS DOES the amount of drag on the crank pulley. If draw on the accessory belt goes down with the CFM, then efficiency stays the same. If CFM goes down and load on the belt stays the same or increases then efficiency drops. If load at the belt increases and CFM stays the same or drops, then efficiency drops. Slippage drops the CFM and the drag on the belt so the system remains equally efficient no matter how much slippage there is. It would also be true to say that is air flow increases and load at the belt stays the same or goes down then efficiency increases.....that might be tough to do though.

 

[Skandocious]

Big5oh-- you can defend your points all day long but without citing sources they mean nothing. You expect everyone to just trust what you say?

 

[big5oh]

Big5oh-- you can defend your points all day long but without citing sources they mean nothing. You expect everyone to just trust what you say?

What do you want me to do? Look around on google and post a link?

Think about it.....the SLOWER the fan spins relative to the water pump the less the fan adds to parasitic loss on the accessory belt.

If CFM (fan speed) decreases and load on the belt increases or stays the same the system becomes more inefficient.

If CFM (fan speed) decreases and the load on the belt becomes proportionally less, then the efficiency remains the same. This is what happens during slippage.

This is all very easy to understand. But if your age/experience is as low as some say it is then I can see why you might need more help. I am not saying it is.....if being the key word here, so don't take offense. I am just going off what has been said so far in this thread.

 

[surewhynot]

I split this thread off of Chris' original switch thread per request of the op.

 

[F 150Cobra]

how will a flex-a-lite fan do with a fan clutch?

 

[NeXtras]

big50h.. just an FYI.. CFM is NOT fanspeed.. CFM is Cubic Feet per Minute.. MEAING the amount of air the fam moves

and for the last time people AGE HAS NOTHING TO DO WITH KNOWLEDGE!!! if thats true, why do i know more about computers than my mother?? THINK BEFORE YOU SPEAK!

NO ONE has answered me as to what the CFM output of the engine driven fan is and whats required of the radiator, PLEASE answer that...

also, the fan skan has, came off a t-birb, most likely one with a 5.0.. and i dont belive those were HO 5.0's.. radiators will be similar.. truck will obviously be bigger, but not by much, so its pretty interchangeable with the 5.0 in the trucks, THUS being somewhat compatible with the 5.8 of course because the 5.0 and 5.8 are very interchangeable!

 

[Skandocious]

how will a flex-a-lite fan do with a fan clutch?

Whatchu mean buddy? You talking about an efan or a belt driven fan?

 

[F 150Cobra]

an mechanical fans the flex ones i heard that they run them without a fan clutch becuase the flatten at high rpms.. but how will they do witha fan clutch

 

[big5oh]

big50h.. just an FYI.. CFM is NOT fanspeed.. CFM is Cubic Feet per Minute.. MEAING the amount of air the fam moves

I know that. But in the context, an increase in fan speed yielded an increase in the cubic feet per minute of air flow. I worded it the way I did for simplicity. Even though they are not synonymous, they are very closely related in this particular case. Just becuase I put one word after the other like I did does not mean that I think they are the same.

NO ONE has answered me as to what the CFM output of the engine driven fan is and whats required of the radiator, PLEASE answer that...

Chris answered one of those questions a while back. It's hard to say how accurate his numbers were, but he said above 10,000 CFM is what the stock fan is rated to pull. But then, at what RPM? Fully engaged? 90% engaged? And how would anyone measure this?

You also ask how many CFM is required by the radiator. This would obviously depend on a few variables such as ambient temp, load on the engine, how fast you are traveling, the tune of the engine etc.

There are no good solid answers to your questions and that is probably why no one has tried to answer them.

 

[70blue]

A clutch fan will work great in most situations and be plenty adequate and so will an E-fan. They both have pros and cons but they both simply work. Anything beyond this is basically just a contest.

As far as age and experience go they do not necessarily go hand in hand. All too often when I was a young man in industrial maintenance I had to hear about my youthful inexperience while I repaired what the older guys either could not repair or they actually messed up.

 

[NeXtras]

big5oh.. u harp on everyword, quite ridiculous.. when u measure a fan, you look at RMP and CFM.. CFM is not the same thing as the speed. YES a fan will have a larger cfm at a higher speed. BUT, CFM also corresponds to the pitch of the blade...

In essence, you can have a fan spin at 2000 RPM and another at 1000 RPM and the one spining at 1k will have a greater CFM...

Fans are typically rated at there Max RPM, which will give there max CFM...

Think BOATS.. whats one of the first things you do when your boat doesnt plane right, change the prop to one with a greater pitch!

i think your biting off more than you can chew.. your a new member as of THIS months, and have 25 posts.. dont know who your trying to impress.. regardless, you pulled a no no (in my book)... why do you feel you can come on here and bash on Skan (the top poster BTW) whos been here almost since day 1, when youve been here less that 12 days? VERY disrespectful.. if it were my forum, you would have been suspended already..

 

[TexasNomad]

 

[big5oh]

In essence, you can have a fan spin at 2000 RPM and another at 1000 RPM and the one spining at 1k will have a greater CFM...

With 2 different fans with different ratings maybe.

But we are talking about 1 fan, the stock fan for the rigs applicable to this forum to be exact. You would likely have to turn more RPMs than the motor would be able to safely spin to see the fan start to decline in CFM. These motors redline at what....5000 RPM? So, while what you say could be true in certain situations, it is irrelevant here.

 

[TexasNomad]

I love my E fan one of the best Mods I've ever done to my truck out of every thing I've done to it HEI dizzy LEDs ect ect, and until I see some real number and not just opinions on E fans Vs Mechanical fans I will all ways say E fans are far superior..

 

[NeXtras]

its relevant, they are pure facts! It doesnt take much to grasp the concept of a fan..

NOT TO MENTION if the stock fan outputs 10,000 CFM at say 5000 rpm (redline of a 5.8) and the perma-cool outputs 5900 CFM at 1800 RPM, the e fan is more efficient. Considering you very RARELY get your engine to 5000rpm, more like 2500(some shift points), its going to output around 6000 CFM... If you can get the same CFM from an e-fan thats spinning SLOWER, A) thats less strain on the engine which will give a slight power increse and Sight better gas mileage! and B) Thats a more efficient fan!

...i asked every mechanic in my shop today, EVERY one said e-fan..

and on a 5.0, there isnt a redline, you will tach it out before then.. safe to say 6k is your redline.. 5.8's redline at 5k i believe, at least the lightning does..

youve already said some bogus things in other threads, at this point it is a pissing contest.. which is stupid

 

[TexasNomad]

Don't get your little undies in a wad, if you don't like what I say boy, then ignore me..

 

[NeXtras]

Don't get your little undies in a wad, if you don't like what I say boy, then ignore me..

not you, big5oh lol

 

[big5oh]

its relevant, they are pure facts! It doesnt take much to grasp the concept of a fan..

Even though it is a "pure fact" it is still irrelevant.

It is a "pure fact" that the speakers in my home theater system are made by JBL back in the 1970s. Does that make it relevant? No. But it is a "pure fact". My point? You were talking about different fans flowing X amount of CFM at different RPMs, 1000 and 2000 to be exact. OK, fair enough. But the fans we are talking about don't peak in the useable RPM range of the motor, rather they continue to flow more as the RPM raises. Thus what you were saying is irrelevant, yet possibly true in some cases different from the discussion at hand.