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Old 02-07-2007, 04:36 AM
FieroSpeeder FieroSpeeder is offline
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electric vs mechanical fan

a shadetree person posted someones site explaining why mechanical is pretty much better.

http://www.aaroncake.net/rx-7/efanmyth.htm


anyone see any mistakes in his findings or thinks he is missing a few things?
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Old 02-07-2007, 07:49 PM
olddog olddog is offline
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The farther this guy got the dumber he became. He is obviously educated beyond his intellectual ability to comprehend how to apply the knowledge he has acquired. He also sufferers from an overconfidence problem. I will call it “intellectile disorder.”

When he tried to take the efficiency loss of the alternator and claim that that loss would cause the fan motor to draw more current, I had to grab the duct tape and wrap it around my head, before it exploded.

If he was my student, I would give him a D, but only because he made effort. His arguments rate an F.
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Old 02-07-2007, 09:26 PM
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justen justen is offline
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Even though this guy didn't understand himself what he was saying, I would say ya, mechanical fans are better then electric fans, I don't trust them, you get a dead battery, and you want to limp it home and you'll overheat. Mechanical fans have been tested by engineers and most of them are over 5000 cfm. Alternator does get more of a load on it, although I don't think it would be more then maybe 1/2 hp. I personally do not like putting more load on the battery and alternator then I have too. It's just more of a chance of it prematurely failer. Where a mechanical fan theres a few things that can go wrong, but is more unlikely. One thing he didn't get right is, a fan takes the same current all the time, theres either off or on. Theres no in between. The only way a fan can draw more current is by running a longer period of time then normal.
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Old 02-08-2007, 12:21 AM
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Quote:
Originally Posted by justen
One thing he didn't get right is, a fan takes the same current all the time, theres either off or on. Theres no in between. The only way a fan can draw more current is by running a longer period of time then normal.
with the exception of some fans that have more than one speed.
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Old 02-08-2007, 02:39 AM
Saltmine Saltmine is offline
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GAD! The guy is a little "drifty"....

First, when I worked for GM, we discovered, on a chassis dyno, that a mechanical fan can draw up to 26 horsepower. Usually something like a seven bladed fan on a clutch, that is...Once the clutch engaged, the hp dropped sometimes as much as 26 hp.

Now, nobody can tell me (or Olddog) that running an electric powered cooling fan is going to put a 26 hp load on the car's alternator...That would take a larger alternator than most cars have, pulling a dead short....

Even recharging a dead battery, with the cooling fan on, an alternator will seldom exceed one horsepower to keep it turning..... Our Sheriff's dept cruisers had 140 amp alternators and with everything in the car on, including the communications radio, they never drew more than 100 amps....Think about it.....100 amps at 12 volts...that's 1200 watts.....it takes 760 watts to equal one horsepower....that's nowhere near 26hp. BTW, 26hp would be 19760 watts...And to get that out of a 12 volt alternator it would be producing 1646.6 amps, continuiously.....See where this is going? Olddog is right...the guy is intellectually challenged....
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Old 02-08-2007, 12:08 PM
Gearhead52 Gearhead52 is offline
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This guy was going on a premis that most everyone that is converting to electric was having an overheating problem already. Or did it go over my head again.....

If so, I've never known a conversion to an eletric fan that worked. Usually its because the electric fans can't move as much air as most mechanical fans or there is another problem in the cooling system that doesn't care what kind of fan its using.

He totaly missed the fact that some people miss diagnose cooling problems and throw new parts at the problem.

Many new cars have electric fans on them and they work fine. Would I put one on my truck before pulling my car hauler ?....nope!

What's watts ??? Pass the duct tape.........
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Old 02-08-2007, 04:17 PM
Saltmine Saltmine is offline
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I've seen and done many electric cooling fan conversions. A lot of people I know are using them also. The trick is to get yourself a fan assembly that moves enough air to cool the engine properly. Most conversions end up with cheap low powered fan motors that can barely move enough air to even help a mechanical fan, and as a result, they experience overheating.

Stop and think about it. EVERY front-wheel-drive car on the road has an electric cooling fan...The Crown Victorias we had in the Sheriff's Dept also had electric fans, with no mechanical fan on the engine....they NEVER overheated.
Most of the trucks coming out of the showrooms today are all cooled by electric fans..Even the manufacturers know that a mechanical, engine driven fan to cool the engine is a waste of power and energy. Well, everybody except DCX.

A watt is a specific measure of energy. As I said, it takes 760 watts to equal one horsepower. SAE (Society of Automotive Engineers) actually measures the power output of cars and trucks all over the world in "watts of energy" instead of horsepower.
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Old 02-08-2007, 06:28 PM
olddog olddog is offline
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Point 1) Say the radiator is 1 foot by 2 feet, which is 2 square feet of area. At 60 MPH or 1 mile/minute there is 5280 feet of air moving through the radiator times 2 feet of area, which is 10,560 CFM. You do not need a fan at 60 MPH. Usually not at 30 MPH.

Point 2) A mechanical fan attached to the engine that will pull enough air to cool the engine at idle (600 RPM) will indeed pull 10 times that much air at 6000 rpm and gobble up about 10 times more power than is needed. The mechanical fan (even with a clutch) will waste energy at higher motor rpm continuously.

point 3) At 60 mph mechanical fans were proven to actually be slowing the air down. Part of the idea of the clutch fan was to allow the fan to free wheel faster than engine speed to allow the air to flow through.

point 4) Flex blades that flatten out and clutches were designs to address these issue (point 2, 3, & 4).

point 5) The electric fan only turns on when the engine temp requires its use. Going down the road the electric fan never needs to turn on, thus it is not consuming energy at all. Zero, zilch, noda, nothing. The average speed in my Marqui is generally 30 to 35 mph for a tank of gasoline. Likely 80% of the time an electric fan would never turn on in the summer and less than 5% of the time in the winter.

No matter how you dice it, the electric fan always wins hands down on energy consumption. Granted it takes a very good electric fan to move enough air to cool a big engine under heavy load, but it is done all the time. I watched Shelby Cobra replica cars with 600 hp big blocks run hard at tracks, with nothing but electric fans in them. I never saw one boil over.
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Old 02-08-2007, 06:36 PM
chevy572 chevy572 is offline
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"Stop and think about it. EVERY front-wheel-drive car on the road has an electric cooling fan..."

Well my 85 Riviera has a mechanical fan and it's fwd

Last edited by chevy572; 02-08-2007 at 06:38 PM.
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Old 02-08-2007, 08:12 PM
danny danny is offline
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Quote:
Originally Posted by chevy572
"Stop and think about it. EVERY front-wheel-drive car on the road has an electric cooling fan..."

Well my 85 Riviera has a mechanical fan and it's fwd
i had an '81 eldorado that had fwd and mechanical fan
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Old 02-08-2007, 08:52 PM
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my wife monte carlo with the 5.3 has a mechanical fan.
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Old 02-09-2007, 01:33 AM
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Aaron had a few brain farts in the first diatribe as mentioned above, but his link to proper installation of an electric fan was pretty good. I had a partially seized viscous fan in my Diesel Dodge so put in an electric fan on a switch-and-relay; works OK for me 'cuz I'm "hyper-vigilant" about my truck gauges, sounds, smells and whatever. I'll take his lead and get a thermostat as he describes tho' so that I can obsess on other things, like maybe the engine noise and great fuel mileage ...
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Old 02-09-2007, 02:41 AM
FieroSpeeder FieroSpeeder is offline
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Quote:
Originally Posted by chevy572
"Stop and think about it. EVERY front-wheel-drive car on the road has an electric cooling fan..."

Well my 85 Riviera has a mechanical fan and it's fwd
but it isn't a 2007 riviera. Which is saltmines point. How many ,newer, cars actually have mechanical fans besides trucks.

Last edited by FieroSpeeder; 02-09-2007 at 07:10 AM.
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Old 02-10-2007, 03:24 PM
Saltmine Saltmine is offline
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I won't belabor the point. Most "MODERN" cars have electric cooling fans...As Olddog mentioned, quite thoroughly, a mechanical, engine-driven fan is horribly inefficient.
A mechanical fan would ONLY be practical on a "lateral" configuration engine layout. Since turning the rotation of the fan-drive 90 degrees would be impractical, inefficient, and, in some cases, noisy to boot. Even back in the "Old days" we knew driving a fan through a 90 degree turn was kinda stupid, but it was the only way to force cool air through the fins of an air-cooled Corvair.

Most cars today use transverse mounted engines, which would make for some really "monkey motion" to run a mechanical fan off of one.

Also, Olddog mentioned some fan blades "flattening out" at high RPM's...Yes, I once had a customer who complained of excessive noise and overheating on the highway..Turned out, his kid had installed a direct-drive fiberglass fan to replace the factory fan clutch on his truck. At 3000 RPM's the fiberglass blades flattened out, and effectively blocked or "walled off" the radiator, causing overheating. We replaced the fan with the right parts, and he had no more overheating or noise issues.
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Old 02-10-2007, 04:33 PM
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what are the "right parts" you mentioned in your post?
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