New electric fan solution with stock Scout II shroud

[Greg R]

I am a fan of electric fans Here are some reasons.

They really do save on the horsepower. Prop fans, like all fans, follow fan laws. For example, double the rpm you double the CFM and raise static pressure. However the power requirements increase drastically, the difference is cubed. It also follows when the air to the fan becomes positive, like positive suction pressure in a pump, the power consumption goes through the roof. Enter the fan clutch, it's a torque limiting deal that only allows the fan to draw so much Hp, usually they limit out above a certain roadspeed/ram air around 20 or 30 mph. This is neglecting the thermo actuated ones. What this comes down to is while a fan may only draw 3/4 to 2Hp at idle or light cruise, it could take a whopping 5 to 7 Hp at freeway speeds. If you don't think that's much because you have over a hundred at your disposal; try running a 5Hp electric pump from your house for a couple of days. The next month's bill could be astounding. Either way, it ain't a free lunch.
Past 25 or 30 mph, ram air is sufficient for cooling on the level.

Picking the right electric fan is a challenge because it is very hard to find the specs. Sometimes I wish the auto parts biz was more like the refrigeration industry in that at least with specs you can make a close match or replacement. Then again it's confusing enough with year to year and mid-year changes.

Jay is absolutely correct on fan placement, 2" or more spacing from the radiator with a shroud is the best. Not so much on the air density, but more on air mixing and flow straightening. A prop fan moves the most air about mid-section of the blade length. The center and tips tend to be zones of regurgitation or not much grab as the pitch of the blade is the least. Put that up real close to a radiator, and you get a donut effect through it with only a small percentage of the radiator area actually having air flow through it. The other areas, center of the fan, and some edges are zones of eddy currents and some patches of reverse flow. Move the fan away and you get a more even pattern of air flow across the radiator face, though there will still be areas of higher flow than others. I did a flow test on several rigs and radiators, and can honestly say I've seen it 1st hand. Put a sheet of paper on your radiator's inlet face, and you will see some areas that suck more and toward the corners you might see the paper wanting to blow the opposite way.

Before I would buy a fan, I would have to know the CFM and the electric current draw. I believe the Taurus fan on Hi draws in excess of 35 amps. A bigger alternator would be an answer, but the rest of the rig has to be protected from a meltdown 'cause now you have a way bigger power source. These things are systems and if you change one thing, you WILL affect another.

Last year I did some tests with my air flow meter. I checked a couple of Internationals, a Dodge Dart, and Ford truck. They all had 17" fan blades, most where 4 bladed, the Dodge had 6, and the Scout had 5. Whether they had 6 or 8 cylinder engines, they all moved close to the some volume of air. I would think for starters an electric fan for a Scout should have at minimum 1,200 CFM either fixed speed or a low speed if it was a 2 speed.

Here are some of my numbers with all engines measured at 1,000 RPM: 67 T'All with 265 I6 927cfm; 60 Ford F100 with 223 I6 1092cfm; 68 Scout with 266 V8 1180cfm; 65 Dodge Dart with 273 V8 1155cfm.

[76 xlc]

Originally Posted by ihscoutfanatic

If only we had those paper thangs with wurds in em to learn us stuff.

They're obsolete, there's the internet now. And I thought you were an "early adopter."

LOL!

[76 xlc]

Originally Posted by ihscoutfanatic

I give respect to those who give it back.

Ditto, kid.

[nightglide]

Guys with 67-72 chevy trucks do this exact mod with the same fan and it works awesome. The chevy truck fan shroud has a 19" opening just like the scout. I was planning on doing this and posting it but looks like ya beat me too it

[Patrick Morris]

I thought I'd point out, without mentioning who said it, that the stream/water analogy isn't accurate. You can't compare fluids and gasses in that way. Water's density never changes. It has the effect of being dense in turbulent situations like surf because it's momentarily mixed with tiny air bubbles. So for instance, a gallon of 'whitewater' from a river or a wave will weigh less than a gallon of still water.

But that's only because a heavy substance has mixed momentarily with a lighter substance. Air in turbulence may lose density, but not because it's mixing with something lighter. It'd be because of Bernoulli's Principle, which I won't describe here (you can google it if you want).

BTW, I really should look into getting a better alternator at some point, for all the usual reasons.

[orodos]

Graedin, did you ever get your project wired up? How does it work?

[Island time]

Great idea, gonna do it myself as soon as i find where i put that shroud...
How/where does the temp sensor get hooked up?

[R290]

Figured I would put out my 2 cents. I know most have your minds set.

I tested both fan setups mech vs electric , switching back and forth and different tests.

One test was going 15 miles on the freeway and then hit stop and go traffic. This is where the electric shines as it can run on high, when the engine RPM's are at idle.

But running an electric fan on a stock charging system is asking for trouble.
You want tank tough and proven just keep the fan belt.
I wrote a post on the IHON site called the top 10 ten things to check of overheating. link

[DHardy]

How did you attatch the fan to the stock shroud? Can you tell the difference between the stock fan and what you have now.
I have a Scout II with a 392 in it with AC here in Texas and the hot summers makes it impossible to drive. I saw your post and thought this might be a soloution to my problems. I see where that part is for a Grand Cherokee with either the 4.0 6 cyl.or the 3.7 v6 or the 4.7 V-8 None of them are hardly a monster like the 392 but like the Scout II both have a small engine compartment. I wish I knew before I undertook this adaptation that is would cure my ills. Let me know what the results are. Thanks

[DHardy]

I read all the pros and cons and debates over fixed fans vs electric fans. All I need to know is the basic principal. Does it work? Will it work with my stock alternator? If not what do I have to do to make it work? Bottom line principal! WILL IT WORK BETTER THAN WHAT I HAVE NOW.