Flex fan

[Wageslave]

It can be anywhere between 25 and 65 amps depending on how many and how big the fans involved are. I have a set of dual fans out of a Plymouth Breeze in mine, and they are rock steady at 200 degrees with a 195 thermostat installed.

The big advantage of electric fans for me is when I am driving down the highway at speed they are normally switched off, as the air flowing across the radiator is plenty to keep the motor cool. That means there is zero parasitic losses when you are at highway speed. When you slow down, they will only switch on when necessary to keep the car cool.

Think about it as electric fans are designed to use the minimum amount of energy possible to keep the motor at their setpoint. Clutch fans work under the same principle, just not as efficiently as they will always be using some amount of energy because of the fluid coupling in the clutch. Flex fans are even less efficient since the only control they have is for the blades to change pitch a little to reduce flow at high RPM's. OK if you cannot keep your motor cool under any other circumstances, but if that is the case you would be better off with a bigger radiator or better shrouding.

Just a little hard learned experience I thought I would share.

 

[pontiacgp]

Does anybody ever consider the current draw from an E- fan introducing parasitic resistance to the alternator and belt drive(s)? An old school mechanic and good friend introduced that theory to me, yet I've never seen it measured. A fan is a motor, and can draw substantial amperage...

my electric fans do not come on when travelling on the highway and only come on when the temperature hits 210 and shuts down at 195. The blower fan on high and rear defrogger takes quite of bit of juice as well so if the alternator can handle those components then it should not have an issue with an electric cooling fan.

 

[SoFloG]

I was referring to the current draw as if it actually creates resistance on the drive belts like a clutch fan would. Can anybody answer if an alternator spinning at let's say 5k rpms with a 100 amp load on it creates more drag than if there was a 10 amp load? Or do alternators spin just as freely with a large current draw as they would without?

 

[Wageslave]

I was referring to the current draw as if it actually creates resistance on the drive belts like a clutch fan would. Can anybody answer if an alternator spinning at let's say 5k rpms with a 100 amp load on it creates more drag than if there was a 10 amp load? Or do alternators spin just as freely with a large current draw as they would without?

The relationship between load on the alternator and resistance to turning is pretty much linear. The more load on the charging system the harder the alternator is to turn. That is why you might get belt screech when you first start a vehicle or if something that causes a heavy load is turned on if your belts are worn.

 

[Wageslave]

To answer your question a little more clearly, a 100 amp alternator would be about 1400 watts output , or about 2hp, figure 50% efficiency that would suggest you need 4hp at maximum load to drive it.

 

[fleming442]

Y'all trying to split short n curlies at this point...
I prefer electric- looks cleaner when done right. My fog lights draw more than the fans.

 

[airboatgreg]

Y'all trying to split short n curlies at this point...
I prefer electric- looks cleaner when done right. My fog lights draw more than the fans.

If you are worried about the draw. Take the belt off. End of discussion.
FYI: A parasitic draw is an amperage draw that occurs when everything is off. It is for keep alive memory on digital stuff(Radio) and on board computer. Rule of thumb a 50 milliamp draw is ok

 

[565bbchevy]

To answer your question a little more clearly, a 100 amp alternator would be about 1400 watts output , or about 2hp, figure 50% efficiency that would suggest you need 4hp at maximum load to drive it.

Yet another reason to back up building a more powerful engine

 

[SoFloG]

If you are worried about the draw. Take the belt off. End of discussion.
FYI: A parasitic draw is an amperage draw that occurs when everything is off. It is for keep alive memory on digital stuff(Radio) and on board computer. Rule of thumb a 50 milliamp draw is ok

Im not worried about the draw. And I'm not talking about parasitic draw I mean parasitic drag on the pulley/belt system(s) I'm just trying to point out the fact that people who think they are reducing so much drag from their belt systems by switching to electric fans are still introducing drag through the alternator now. I run electric fans on almost everything.

 

[SoFloG]

If you need 4hp theoretically to run an electric fan, then how much do you need for a clutch or flex fan? That's all I'm saying. Who has done a side by side comparison?