Electric Fans....

[BlackoutSteve]

Re: Electric Fans....

Don't fix what ain't broken.

Your existing clutch fan will move more air than any electric fan can so you might expect some higher temps if you switch to an electric.
Also a clutch fan will disengage and use no power when it isn't needed.

Don't get the crazy idea that electric fans don't cost you power. They cause your alternator to load your crank pulley just like any mechanical fan does.

Personally, I believe the OE clutch with a 7 blade fan and shroud IS the superior setup.

[Lobucrod]

Re: Electric Fans....

With the current radiator set up in my coupe I dont have room for a mechanical fan even with the short water pump. In the past I never had a cooling problem with the mechanical fan and shroud. After going to the pusher fan (no room on the engine side) I have been experiencing some over heating problems in slow traffic in the 100 deg temps we have in west tex. ALso even with a high amp alt the voltage drops in slow traffic since the alternator cant keep up with the ac and the fan. OF course the ac condensor is adding heat to the mix too. Sitting at an idle with the ac off the fan has no problem keeping things cool and cycles on and of as designed. (designed my me that is since im using a generic 30 amp relay and temp switch of my own choice in the 'on at 190 and off at 180 range') If I had room I'd go back to a mechanical fan in a heartbeat. Sure you are still loading up the engine with the extra load on the alt instead of the mechanical fan drag but you are also using up the alternator in the process.

[TC]

Re: Electric Fans....

Don't fix what ain't broken.

Your existing clutch fan will move more air than any electric fan can so you might expect some higher temps if you switch to an electric.
Also a clutch fan will disengage and use no power when it isn't needed.

The problem with clutch fans is there is no way to test their cfm because it is dependant on engine speed. Where as an electric fan is constant. And yes clutch fans do rob HP from the motor. Here's a couple of quotes.

Why isn't there a C.F.M rating on your flex and clutch fans ?
C.F.M. ratings are based on constant variables, such as r.p.m and blade pitch angle. With direct drive fans neither of these variables are constant so a general C.F.M. rating is not assigned.

Here's the link.

http://www.flex-a-lite.com/auto/html/frequent-question.html

Q: Why convert from a belt driven fan to an electric fan?

A: At low vehicle speeds, when airflow through the radiator is crucial, the belt driven fan slows down with the engine RPM, decreasing airflow. Electric fans maintain their speed regardless of engine RPM, providing maximum airflow and better cooling than a belt driven fan. A belt driven fan takes horsepower from the engine to turn, resulting in less performance and lower gas mileage. Converting to an electric fan restores this power to the engine for better performance and increased fuel economy.


Q: How do I convert my engine from a belt driven fan to an electric fan?

A: First you need to determine your engine’s CFM (cubic feet per minute) requirements. Four cylinder engines need about 1,200 CFM; six cylinder engines need around 1,600 CFM; small block V-8s need 2200 CFM and big block V-8s require approximately 3400 CFM. These CFM requirements are based on gas powered passenger cars and light trucks, not used for towing, in regular driving conditions. Engines that have been modified, raising the operating temperature, will require more CFM than stock engines. Examples include raising the compression ratio, installing a turbocharger, supercharger, hot cam, etc. We have no way of determining what has been to each individual engine so, if you have modified your engine, you will have to estimate how much additional CFM is needed. Remember: When it comes to electric fans "the more CFMs the better."

Here's the link.

http://www.derale.com/faq.html

Now knowing this you can pretty much figure that a stock fan clutch for a small block chevy is only going to be pulling about 2200 cfm. Which is a far cry from the 5600 cfm that the two electric fans on my radiator pull. So saying that a clutch fan pulls more than an electric is purely misleading, as there are electric fans out there that do flow more CFM than clutch fans.

[hamrmech]

Re: Electric Fans....

i never believed in using electric fans until i got a fox body mustang, and the huge mechanical fan i wanted to use wouldnt fit.. now ive got a mark VIII fan, it works GREAT. it does pull alot of juice! you definately need a good alternator, i use a one wire 110 amp delco with a 1000 cranking amp deep cycle battery for my car, i dont have any electrical accessories beyond tail lights and ignition, id use an even bigger alt if i had a fancy radio and air conditioning.. i googled the CFM the mark VIII fan is worth..so far its 4000cfm plus is what im seeing... everybody has a google so ill leave it to everyone to believe what they want. when my fan is running with the hood open, itll lift my hat up on my head if im standing alongside the car. id rather run it then an aftermarket fan. also, the price is hard to beat. 15 dollars.. now ive converted a few buddies, they snatch those fans when they seem em in the yard..

[Eric68]

Re: Electric Fans....

Electric fans only cost you power when they are running. If you run yours with a switch you can just click the fan off when staging at the track. If you do it that way you will drop a little ET -- I did.

[PackardV8]

Re: Electric Fans....

Greetings,

I've tried most of the aftermarket fans with mixed results. Nowadays, it is only OEM fans for me. The one I like best these days is the Dodge Viper. I've used them on several different street applications. It is a two-speed fan designed to cool 600HP in a very tightly closed engine compartment. I keep a couple on the shelf for when an overheating street rod comes in the door. Mail me off-list at [email protected] if you want one.

thnx, jv.

[dieselgeek]

Re: Electric Fans....

I'm surprised by what I am NOT reading in this post, so I'll share some of our testing experience...


Electric fan performance is *entirely* based on the shroud, NOT the fan itself. You can get by with the cheapest actual fans (ever seen what's in the Lincoln and Taurus and SN95 mustang fan motors? tiny stuff! they don't draw that much amperage either - 15-20ish).


We did a test with a smoke bomb and were surprised what we saw. With no shroud, or with the "fan in shroud" that's a typical design, you basically get a donut of airflow around the outside edge of the fan. The low pressure are in front sucks air around the fan from the high pressure in the rear. You want to keep those separate as possible, even if that means a shroud that blocks a little of the radiator.

The reason people have such good luck with the Taurus, SN95, Lincoln etc. fans is because of the shroud. The best Spal fan with no shroud, is marginal efficiency at best. In my opinion, most of the aftermarket fans are OVERKILL on amperage draw in an attempt to make up for typical poor shrouding on the installation.

Eric68 makes a good point also, set up a WOT switch to disable the fan during a run and you will most definitely free up power. Do the smoke bomb test on your fan setup and see if you get the "donut" effect we observed. It was very enlightening.


-scott

[PackardV8]

Re: Electric Fans....

Hi, Scott,

Thanks for making it clear, it is about the shroud. The OEMs have done the engineering for us, so why not use it. I would never install a fan of any description, engine-driven or electric, without a full-radiator shroud. However, even with the best shroud, if you have a high-horse, high compression street motor, you are going to need a fan with some serious suction to keep it cool cruising Hot August Nights.

thnx, jack vines.