Mechanical Fan VS Electric Fan

"Where do you get 50 or 60 amps from? 25 or 30 amps is more realistic. Also where does it say you need 8,000 CFM? If your radiator is properly sized for the engine and it's HP level you shouldn't need that much air. Of course there are variables such as rate of coolant flow and ambient temp."

First off, I think of the "street" all the time. Not sure what Plumcrazy's application is. I like to design systems that will last 50 - 100 K as I like to drive my rig anywhere w/o issue at any time of year for miles and miles, for ever. Of course a person will have issues, but I like to minimize them to the minimum.

My last big build was reliable to 50 k with no cooling issues, it was a 462 cube olds in an ss monte carlo with 10.25 to 1 and tall gears. Factory used clean radiator, used Clutch fan from the junk yard, no shroud. Eventually I blew the trans off the motor and into a million pieces and took a chunk out of the engine block at 150 on a back road in the country at 1 am, because of a U joint failure (I suppose). But it stayed cool. This was a car with .229 gears used for long road hauls out in the hills of the South.

I have always run a thermo clutch and they never let me down. I have seen a hand full of factory and aftermarket elec fans let people down and that sucks big time. Overheated and stranded because a fuse blew, a fan motor seized up, fan motor started smoking, thermo controller went out, relay melted.

Alot of compromise can be made when you dont plan to drive 1000 - 2000 miles in a week across route 66, up thru colorado and down thru california in the middle of summer with the AC blasting, hauling *** repeatedly for years.

Well, a pair of elec fans or one big one that will let you run up a mountain in 100 degree heat at 75 - 90 mph with a trunk full of beer and a car full of friends with the A/C on will eat serious amps. Those amperage numbers I pulled out of my butt.

I am just estimating on a factory cooling system which is designed to properly cool with the AC on and in any condition on a V8 VS. most aftermarket electrical fans where the cooling is quite relative to the price.

The factory designs their systems to be reliable for 100k. Its hard to beat that.

If a person can get by with an economical elec cooling fan setup then great. I would not do it on the street because I would not want the electrical draw on my system, relays and alternator. Additional complexity, additional failure points and expense of what would be required to have a guaranteed more than adequate haus of an elec fan setup (such as the one Howard 1784 posted).

In other words that fan setup of Howard's looks like something that would be a great replacement for a clutch fan. How much amperage does your setup use Howard? I mean that thing is awesome.

This is why you find big *** heavy duty electric fans or a thermo clutch on big autos. I was not saying you need 8000 cfm but rather that large thermo fans pull near that, such as on an f250. Old v8 Car clutch fans pull about 5000.

Here is a clutch fan scenerio : 40 - 60 bucks for new clutch, fan blade at junk yard, blasted and painted 20 - 40 bucks, use factory shroud. My car had a clutch fan and shroud on it (360) so, I reckon my fan situation will cost near nil.

Were talkin a done deal which will last near 25 yrs w/o fail and has zero additional requirements to maintain functionality. So, 100 dollars investment that fits w/o modification for a done deal. Simple, economical, reliable and uses minimal HP.

Now rotating mass. The fan is clutched by fluid coupling so its rotational inertia is not what you would perceive nearly as much as the drag in hp which is really only active during cooling necessity (similar to a thermo elec fan). The clutch weighs 5 pounds? I agree that if you are saving every last gram of rotating mass and HP draw, a clutch fan would be slightly more draw.

If I were to run an elec fan on the street, and by on the street I mean driving around any time of year to any place in the country w/o any cooling issue, it would have to be guaranteed to be a couple notches above good enough and last 10 years minimum. That sweet fan system on Howard's post looks like it would do the job well.


Here is a nice summary of a thermo clutch fan vs elec fan. The comparison is good, some of the rx7 info is not applicable.

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