That would be Slow engine RPM from my understanding, and if you don't believe it watch your EGT when you press on the gas with low rpm vs high rpm

 

Because the data belongs to Ford, not me. I left it there when I quit, but since I don't own it I can't share it.

Forget I mentioned it. Enjoy.

 

Anyone ever thought of slapping one of these onto the intake?
betcha you'd spool alot faster

 

Thought about it but, couldn't find an intake opening big enough with the proper taper.

 

Farm69 I had a hard time putting the 16's in. They are already staggered one high and one low, and they still over lap the edge some, but maybe you can find a better way then I did. Anything is possible when you are fabricating

 

Basically because the electric fan beats the stock fan at idle. If you never need to fan for high load cooling, the electric is fine.

The fans are going to be comparable in efficiency - no, not the same, but one isn't twice as efficient as the other.

Some rough fan equations:

Power is proportional to the cube of rotational speed.

Airflow is proportional to the square of rotational speed.

Power is proportional to the square of airflow.

Some back of the envelope calcs for you:

The stock fan is 17 HP at 3300 RPM engine speed and moves 5500 CFM.

At 650 RPM idle the stock fan moves something around 200 CFM and uses 0.13 HP. Ever notice it doesn't really move air or make much noise at idle?

At 18A draw at 14V, those electrics are 0.34 HP. Now lets really go out on a limb - call the two fans equally efficient, and ignore the loss in the electric motor. They will move about 800 CFM through the radiator. Yes, that much drop is common between free airflow and system airflow on fans. But consider that the stock fan won't move that much air unless the engine is rolling over above 900 RPM.

Mind you, the numbers are a bit rough, but it's pretty reasonable to say that something anything around 800 to 1000 RPM is the crossover speed for the two fans. In low speed, the electric wins hands down. At high speed, the stock fan wins hands down.

It all comes down to what you do with your truck. Do you haul enough that when it comes to climbing passes, it means 100% throttle in drive? 100% in 2nd? If you do, you already know about the fan clutch loading up at 2700 RPM and just how much power it sucks and how much noise it makes.

If you don't, then most likely ram air is all you need at high speed. Put the electrics on and you'll never have a problem.

But if your stock fan regularly kicks in hard at high RPMs, when you're hauling in the summer, I'd pause real hard before considering the electric.

 

Sorry, that dog doesn't hunt. Spacing actually helps some, becuase it allows more of the area of the radiator to participate in the airflow, lowering resistance and increasing total airflow.

In a airflow design, the relevant questions are how tight the shroud is to the fan tips (that one is huge!) and how much air can leak back around. As long as there aren't big holes, spacing doesn't hurt, it helps.

 

Maybe this will help some of you guys contemplating electric fans.

http://www.flex-a-lite.com/auto/html...-question.html

http://www.perma-cool.com/faq/efans.html

And one nice install I found here

http://www.timskelton.com/lightning/...iator_fans.htm

I hope that helps

 

where do you get this information? why should i listen to you anymore than joe shmoe over in the corner? i'm not knocking you, i just want to make sure you a credible source. i dont want you to post all this information and then find out you got it from a friend of a friend!

i disagree... i think if the shroud is doing its job and covers about 70% of the radiator then the closer the fan is the more air it will pull through. it seems logical to me. if i am wrong i will happily admit it, however it doesnt sound to me like anyone can me prove me wrong.

i will be adding elec fans and i do regularly haul 18K lbs even in the seering, overly-humid GA summer! as soon as i get some other projects done (like everyone else) this is on my to do list.

-cutts-

 

Well I can honestly say I've never had my fan on at 3300 rpms (2k at most).

Hmmm... I'm gonna do it. I'll keep my stock fan and I'll that jazz. My clutch is shot anyways. Might as well try something new.

The idea about the shroud makes sense. I wonder if you could move the fans back a little bit and fit two 18's in there. It would take some fabbing up though.

 

One other great thing about electric fans is the space it opens up. I tran with no fan or shroud for a month or so until I put the snow plow on and had to change a CPS. Did it from the top with ease!! no laying in the dirt or breaking my arm to get it in there. just pop the hood and reach downt here. Electric fans are for me when the snow stops falling. The great things is that if you part hunt a bit and built the fans well. it will take 20 minutes to remvoe the electric fans and put the stock fan back on. No big deal! And very little money spent

 

Been reading this thread with interest. I lost my WP at about 73K a couple of years back. I was told the fan clutch went out and caused the premature failure of pump...I thought about going with electric fans to take load of stock steel fan off WP and reduce noise and fuel usage. I aked a friend who has worked at Ford for like 36 years as a enginer in the SVO/engine develpement area most of his years at Ford. His reply was :If you do a lot a trailer pulling with your truck,do not go with electric fans..Oh well...who was I to despute him?

I have been thinking about going to a later model (2000 up ?)SD lightweight plastic fan to replace the heavy stock 96 fan.. I am not sure they will interchange.Has anyone tried it ?? Might not help noise much but should help with fan clutch & WP life...and possibly some fuel savings too due to lighter rotating mass...I think in my situation I would feel better about a lighter fan...
What say you Mark K. ?? Can you still source a part # and if it will fit..

 

i have read this whole post with interest, and in no way am i putting anyone down, however, regardless of what this guy says or that guy says, the guys that have electric fans and are pulling loads and saying that they are not having a problem are the experts. is anyone on here going to call them a liar? not me, they have the experience using them day in and day out so why dispute it?

 

I've said all I have to say in this thread.

Since I don't work there anymore I do not have access to any part numbers.

 

I'll say I want to hear from someone who pulls a significant portion of their GCWR over mountain passes in the summer and doesn't have a problem using the electric fan.

If you don't do that, I firmly beleive the electric will do a better job. If you haul like that, I suspect you're going to overheat.