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post #1 of (permalink) Old 09-22-2001, 08:11 AM Thread Starter
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Why electric fans?

[img]/wwwthreads_images/icons/tongue.gif[/img] As you may have noticed, autos now use electric fans on the sideways-engine models. Obviously, the use of electric fans came because they could no longer include the fan in the accessory drive group on the crank pulley end of the engine. However, there IS another good reason to use an electric fan, DESPITE the fact that reliability is a questionmark, and current draw is fairly high. FUEL MILEAGE is improved by using an electric fan setup over clutch fans or direct-drive fans. Because the HORSEPOWER REQUIRED to drive a fan blade goes up as the CUBE OF THE DIFFERENCE IN SPEED....like when you double the RPM, the new HP required is 2 X 2 X 2 or EIGHT TIMES the original HP. When a clutch fan locks in on a grade at 3500 engine RPM, can you IMAGINE what the HP requirement is? The blade has to be such that it cools at 1500 RPM, so it has a lot of bite. At 3500 RPM, it is a HUGE power-robber. In industrial applications I have to add one gallon of diesel per hour if the engine has a direct-drive fan. However, we DO have the luxury in stationary applications of knowing exactly what the constant engine RPM will be and the fans are chosed specifically for that speed so no extra HP is consumed.....theoretically.....beyond what it takes to do the job. In the automotive world, consessions must be made to cover all possible conditions, so fans have to be made for the worst possible scenario, and that means BIG blades. Even though electric fans are actually driven by the alternator; and the alternator puts more drag on the engine because of it, you have the advantage of running the fans at constant, optimum RPM at all times, and no overspeeding has to occur to waste HP. So the overall HP input to the system is actually less with electric fans. One thing about it; when an elctric fan is OFF, it's off, no drag is present; and when it is on, it is immediately at optimum efficiency, regardless of engine RPM.[img]/wwwthreads_images/icons/tongue.gif[/img]


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post #2 of (permalink) Old 09-22-2001, 06:33 PM
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Re: Why electric fans?

your point being????

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post #3 of (permalink) Old 09-22-2001, 10:32 PM Thread Starter
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Re: Why electric fans?

[img]/wwwthreads_images/icons/blush.gif[/img] Well....er[img]/wwwthreads_images/icons/blush.gif[/img]....ah...only that there ARE some advantages to going with electric fans.[img]/wwwthreads_images/icons/crazy.gif[/img] It isn't for all applications, but a properly engineered electric fan system can have some measureable benefits.[img]/wwwthreads_images/icons/crazy.gif[/img]

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post #4 of (permalink) Old 09-22-2001, 11:09 PM
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Re: Why electric fans?

in some cross sectional engine.. thats about it.. lol

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post #5 of (permalink) Old 09-23-2001, 01:12 AM
 
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Re: Why electric fans?

I put an electric fan in my Wrangler (haven't wired it up yet though) for its underwater abilities. Namely, I can turn it off when I submerge the engine. Normally its not an issure, but after a big storm (or even a medium-sized one like Gabriel) there can be a few spots in town to put my headlights under....

Then there is off-road. Plenty of ponds, rivers, ditches, pools, and whatever else I can find that has fairly deep standing water. Moving water is better of course- washes the mud off my drivetrain.

'89 Comanche, '89 Wrangler, '74 Postal
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post #6 of (permalink) Old 09-23-2001, 09:26 AM
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Re: Why electric fans?

Well, as an ex: drag racer, hot rodder, mad scientist engine swapper; I love electric fans. They are a great tool. Like any other tool they cannot be used all the time, but they are very beneficial when you need 'em.

For one thing it takes less than 1/5 of 1 HP to generate enough electricity to spin the average electric fan. Engine driven fans can suck up anywhere from 4-10 hp. Swapping to an electric fan can sometimes mean maybe .03-.05 seconds off 1/4 mile time in your streeet macine/weekend racer. That may not mean s#it in a Jeep, but it does equate out in another area as well... fuel economy. That is the primary reason for clutch fans and electric fans being installed by manufacturers. Electric fans help the manufacturers meet federal CAFE standards. Swapping to an electric may be worth 1 MPG or more on the highway, less around town.

However, the main reason that I personally like electrics is their versatility and their ability to be squeezed into small spaces. I have performed or assisted in way more than my share of engine swaps. Among others, I have built a 440 six pack 1/2 ton '82 Dodge Ram; a 427 tunnel rammed '78 Camaro; a 307 Chevy powered, rear wheel drive VW Scirocco; and a tube framed, front engine, rear wheel drive 454 VW bug.

Ever try to stick a V-8 into an early CJ? Sure, starting in '72 they made it easy but that 3'' makes a huge difference. An electric fan makes it possible.

Electric fans may not be needed in every application, but they are worth their weight in gold when you need 'em.

Hell, my Cummins powered M-715 would not be possible (well OK, not as "easy") without an electric pusher in front of the radiator. Without the engine driven fan the Cummins fit perfectly, otherwise I would have had to modify the firewall to get the room. I overkilled it and put 2 1800 CFM pancake pushers up front, and it hasn't seen the other side of 180*.

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post #7 of (permalink) Old 09-23-2001, 09:40 AM Thread Starter
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Re: Why electric fans?

[img]/wwwthreads_images/icons/smile.gif[/img] Heh heh.....Tom, you JUST CAN'T leave well enough alone! Don't you know that when you do engine swaps it beats up on the self esteem of the guy who designed the vehicle with the STOCK engine?[img]/wwwthreads_images/icons/wink.gif[/img] THINK how many automotive engineers are on anti-depressants because of you.[img]/wwwthreads_images/icons/laugh.gif[/img]

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post #8 of (permalink) Old 09-23-2001, 07:44 PM
 
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Re: Why electric fans?

I installed an electric fan on Friday.
The main reason, I wanted to run an electric, was to eliminate the threat of putting my fan blades through the radiator. This is a very real threat, with some of the up coming events I will be running, as I am anticipating quite a few rollovers in the next couple of months.
I bought a Flex-a-lite Black Magic M150 through PartsAmerica.com, for $183.00, and went about installing it. I wired it with a cut off switch, and a manual activation switch, (both in the cockpit), it took about 2 1/2 hours to install with it including the electrical.
I ran it this weekend on the Rubicon, and I was hoping to be able to give the report of how great it is and how happy I am with the set up. But instead, I have to report that I just removed it and its getting cleaned up and returned.
It had a couple of performance downfalls.
1: It just couldnt keep the engine as cool as the stock Lincoln 18" clutch fan, that I was running. The M150, is a 15" fan with a cowling and they say it moves 2800 cfm. I mounted it right in the center of my aluminum radiator and set the T stat to 190 degrees while ideling, when I started climbing Ice House Road( the steep 20 mile pavement road up to the Con), it immediately jumped to 220 and even 230, with my stock fan it never went over 200 degrees.
Also it took much longer for a cool down period when I stopped to let it cool.
2: It draws quite a bit of power, I could watch my ammeter drop by a couple of volts every time it came on. We had to help out a guy who had gotten his van stuck, in the middle of the night, with lights on, winch running, and fan wanting to come on, it was a heel of a burden on my 140 amp alternator, so I shut it off while I was winching, but then the temp went high, and the high underhood temperature began making the alternator work under extremely ineficient conditions(to the point that it started whining, which it has never done before).Even my power steering pump started grinding and whirring because of the engine compartment temperatures. Durring daytime trail conditions (90 degrees, and no additional electrical draw from lighting), it maintained good temperatures.
All in all, it was a waist of my time for my 5.0 HO application. I have an old 18" flex fan that I am going to install this evening, just to compare it to thelincoln clutch fan, Ill post the results later this week.

Jeff
89 YJ
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post #9 of (permalink) Old 09-23-2001, 07:51 PM
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Re: Why electric fans?

"my ammeter drop by a couple of volts "

Huh?

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post #10 of (permalink) Old 09-23-2001, 07:58 PM
 
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Re: Why electric fans?

semantics Will!

ammeter=amps, voltmeter=volts

whats been up Will?


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