fan clutch vs ele dual unit

[Grumman]

Hello all, I have a question to you all. I have a 6.5L 1995 MFI. My vehicle weights 11,000 pounds. I want to keep my temp needle right at 195 degrees. Would an electric dual fan from "Flex-a-lite" that is thermo controlled, and varible speed control from 60%-100%. Dyno tests show a 17 hp and a 20 ftlb gain. Or.. the Kennedy clutch and steel fan blade... I would like your options on both.

Thank you,

David

[NH2112]

Well, the short, simple answer is "no electric fan will move as much air as the stock fan will" with the caveat being you need a properly operating fan clutch. If the clutch is working, you'll know when it kicks in because your engine will stop sounding like a 6.5l and start sounding like a Pratt & Whitney Twin Wasp driving a 4-blade prop! Electrics are good for additional cooling with things like oil coolers, but I'd never use one as my main source for moving air.

Basically, you have to remember TANSTAAFL*. It takes a given amount of power to do a given amount of work (i.e., moving n cfm of air.) Whether the power comes directly from the crank or from the alternator doesn't matter. When a clutch fan kicks in, it draws power from the crank, and when an electric fan kicks in there's a vastly increased load on the alternator, which is driven off the crank via a belt. So it all comes back to the crank.

I'm planning on using a Duramax clutch and 9-blade fan on my 6.5l. I've read that this monster will move well over 10,000cfm when engaged. That sounds like it'll gain on ram-air cooling, even at 70mph! I don't think I've ever seen dual electrics rated over 5000cfm.


*There Ain't No Such Thing As A Free Lunch

[ 07-27-2005, 06:47 PM: Message edited by: NH2112 ]

[jcomp]

Personally, I avoid electric fans if I can. They can't match the airflow of a mechanical fan in this application.

The 17HP figure sounds (very) optimistic, especially on a low-rpm diesel engine.

[Grumman]

Thanks for the input.. I thought so.. but after you start to read more and more articles,, sometimes you get confused.

David

[DmaxMaverick]

Originally posted by Grumman:
Thanks for the input.. I thought so.. but after you start to read more and more articles,, sometimes you get confused.

David I depends on who is writing the articles. If I made my living selling electric fans, they would be more effective than anything else you could use (Hypothetically. I would not practice this). Of course, that's the pitch, regardless of the real world. Unfortunately these days, marketing and sales is everything. Actual performance is a distant second.

[Grumman]

Thanks for all the tips.. but is there a difference between 12"plastic vs 20 metal?

David