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electric fan

Posted by jl1371 
June 04, 2009 03:57PM
Has anyone set up an electric fan. I have a crown vic fan and most of the wires to set it up. I was reading Peters post about engine mounts and remembered that I have this fan and would like to take the power off the motor. But am I signing up for a huge job and should just leave well enough alone.

Jack
June 04, 2009 04:22PM
First thing to do is decide where the fan will fit if at all.
Then you need to wire it in properly. The fuse/relay box already has slots for the fan relays and fuses...use these if possible. If not, there is also an auxiliary relay holder by the main box which was intended for this type of add on.
Definitely power the fan through a relay and fuse.

Next, you need to decide if you want the fan to be automatic or manually operated. Personally, I would set it up for automatic operation with a manual override.
You can get a controller thermostatic switch that mounts in on of several places.
rkj
June 04, 2009 05:12PM
But then, after all's said and done you have another electrical device to go wrong.

Keep it simple, my thoughts B)
June 04, 2009 05:40PM
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rkj
But then, after all's said and done you have another electrical device to go wrong.

Keep it simple, my thoughts B)

Exactly, so rip out all the fans. Drive so fast you don't need them, and never stop! smiling smiley

Is the engine drag that much less? After all, another device that draws power is going to increase the resistance within the alternator.
I'd bet large money a belt driven fan still has more resistance, but is it all that much when it's all said and done? Anything halfway scientific concerning this out there?
rkj
June 04, 2009 08:41PM
The less scientific the better B)
June 04, 2009 09:02PM
I'm willing to bet the electric fan actually puts a greater load on the engine. It has an electric motor which has to be driven by the electrical system which gets it's power from the alternator(another belt).
Since the fan clutch is temperature controlled and there are no other systems to drive; it is most likely the most efficient system when in working order.

If you add up all the things require to run the mechanical fan vs the electric fan; the mechanical is simpler and by virtue of it's design has to suck less power from the engine.
June 04, 2009 09:31PM
Careful, Peter. I'm sure you remember, I got flamed for posting just such a comment on the old forum. smiling smiley

Tyler, I would take that bet. A properly adjusted V-belt can have an efficiency in the high 90's. How efficient is the electric motor you would use in that set-up? And you also have to account for the losses from converting the power from crank rotation to electric.

In either case, the exact same amount of energy is going to be needed to turn the fan. It's all in how efficiently you can get that energy to the fan.

Lucky for Rick that was all engineering. No science involved at all. smiling bouncing smiley

John
June 04, 2009 10:23PM
I'm not worried...it's all about collective losses.
With the mechanical fan, there is only the main loss in the clutch. With the electric fan there are losses in the fan motor, the wiring and the alternator.
The more pieces you put between the fan blade and the engine that ultimately turns it, the more losses there are.

I'll stand by my and your deductions thumbs up
June 04, 2009 10:32PM
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John Yust
Careful, Peter. I'm sure you remember, I got flamed for posting just such a comment on the old forum. smiling smiley
John

I totally agree with Peter. But can I flame him anyway, just for old times' sake??
hot smiley
rkj
June 04, 2009 11:08PM
I was only concerned about the actual reliability of the thing, the fan is such an important component, I think Bmw did a fair job working it out. I've always liked the idea of a second electrical fan in front of the condenser though, but I think we have one of those, right? B) but is yours working?

Rick
June 04, 2009 11:18PM
Thanks Simon,

Consider me appropriately flamed smileys with beer
June 04, 2009 11:20PM
The aux fan is only there with the A/C option.
Most of them don't work any more; either because the inline resistor is toast or; like mine; the motor is toast. sad smiley
June 05, 2009 11:51AM
There are three reasons I have heard for running an electric
1. they don't take power from the motor
2. they move more air
3. they are smaller making it easier to move around the engine bay

Mostly I want to do this because I have another daily, lots of time, and a good fan sitting in the garage.
I cant see how putting more strain on the alternator could be an issue. If the electric fan is a more efficient motor and the alternator puts out at a range of current depending on rpm as long as you collectively stay below the min out put of the alternator you should be able to add all the superfluous electronics you want with out putting more strain on the alternator. This is unless my understanding on the way an alternator works is completely wrong but engine rpm is the determining factor or alternator out put not load.

Jack
June 05, 2009 01:22PM
Well, they do take power from the engine and that power comes from the alternator. The net power used by an electric fan will be greater than by the mechanical one with the fan clutch...if both are in proper working condition and thermostatically controlled.

Whether they move more air is irrelevant...the engine only needs so much air to keep the radiator cooling enough that it doesn't get too hot for the thermostat to control it. That's why it's best to have it automatically controlled.

Placement is limited to in front or in back of the radiator...both places are limiting in the size of fan that can be mounted.
June 05, 2009 02:44PM
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jl1371
There are three reasons I have heard for running an electric
1. they don't take power from the motor
Of course they do. Where else would the power come from?

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jl1371
If the electric fan is a more efficient motor...
Yes, a simple electric motor is more "efficient" in converting energy to useful mechanical motion, compared to all the thermal losses inherent with a gasoline fed engine.

However, using a gasoline fed engine, to crank an alternator, to generate the electricity, that is either stored in a battery for later use or fed directly to the electric motor to turn a fan, is NEVER going to be more "efficient" than using the same gasoline fed engine to turn the same fan directly.
June 05, 2009 02:55PM
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jl1371
you should be able to add all the superfluous electronics you want without putting more strain on the alternator.
Not true.

The more electrical stuff you power with your alternator, the harder it becomes to crank the alternator.

You can feel that when the engine is idling happily with no load on it and then you turn on the headlights with full high beams. The revs drop momentarily as the alternator suddenly loads up trying hard to pump all those extra electrons into the circuit before the idle controller eventually notices the dropping revs and kicks in with more air/fuel to raise the idle speed back up where it belongs.
June 05, 2009 05:34PM
Sorry by power I meant the drop in power to run the mechanical fan vs the electric fan. So you have lost less hp to run the electric fan. I would think the added drag on the alternator to power the fan would be less then the added drag of running the mechanical fan. I agree it is a less "efficient" of a set up.
June 05, 2009 06:51PM
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jl1371
Sorry by power I meant the drop in power to run the mechanical fan vs the electric fan. So you have lost less hp to run the electric fan. I would think the added drag on the alternator to power the fan would be less then the added drag of running the mechanical fan. I agree it is a less "efficient" of a set up.
Would you agree that It takes a certain amount of effort to keep either fan turning in order to move the same amount of air? The required fan power to deliver the same amount of air should be the same in either case.

Whether that amount of required horsepower is provided directly via a belt mechanically driven off the engine, or whether that horsepower is provided indirectly by the engine via a belt driving an alternator to provide electricity to drive an electric motor to then mechanically spin the fan, the same of amount of horsepower will still be consumed at the tail end of the process by the fan itself.

But, because of the extra added steps involved in first transforming the engine horsepower into electrical power then reconverting it back to mechanical power via an electric motor, clearly the electric fan will ultimately consume more gasoline for a given airflow rate than would a simple mechanical fan driven directly by the engine.

I can see it making a difference if the mechanical fan is constantly driven, whereas the electrical fan can be switched on and off as needed. But the mechanical fan in the E30 is attached at the front of the engine to the constantly driven water pump via a viscous clutch which engages/disengages automatically as needed.

The only real advantage of electrically driven fans is in typical FWD vehicles where the engines sit sideways in the engine compartment, rather than conveniently longitudinal as in our RWD cars. It's much harder to rig a mechanically driven fan with the typical FWD layout, thus the requirement for the added complexity of an electric fan in those cars.
June 05, 2009 09:42PM
I always thought that all electrical components ran off the battery and the alternator just kept the battery charged up. If this is the case would not the drag on the motor be the same at all times as the alternator does not get harder to turn when there is a larger draw on the system. The voltage regulator is what determines how much actual power is reaching the battery to keep it charged. The alternator is capable of producing 90 amps at all times whether it is being used or not.
June 05, 2009 11:25PM
When the engine is not running; the electrical components are driven off the battery. When the engine is running, the electrical components are powered by the alternator with the battery acting as nothing more than a giant capacitor of filter.

with the engine running, any electrical component turned on will create additional drag(load) on the alternator. As Ferd points out, turning on the headlights will cause an initial drop in rpm do to the added load on the alternator.
The alternator may be capable of producing 90 Amps continuously but it really only produces what the load requires. If there is no load on it, there will be little power generated and conversely with a heavy load, more power will be generated.

The voltage regulator is in the circuit simply to regulate the voltage levels seen by the battery and the electrical components. Without the regulator, the alternator will produce varying voltage levels as the rpm rise and fall. If the voltages rise too high, they can damage the electrical and/or electronic components.

The battery is mainly in cars today so that we can operate the electric starter or listen to the radio when the engine is off. Early autos with no electric starters didn't have batteries; they had either generators or magnetos to operate the electrical components.

To summarize:

Electric fans will use more engine power than thermostatically controlled mechanical ones, given that they are to move the same volume of air.
Adding electrical components to the circuit will create a greater load on the alternator and thus the engine.

There is no free lunch sad smiley
June 06, 2009 12:51AM
So I'm abroad in Seattle and not replying because all I have is my ipod. But here it goes anyway, short and sweet.

I understand what had been said so far, and the logic is sound. but the one thing being left out, that I always thought was the biggest deal, is the loss of power to a belt driven system with a pully. There is resistance there which consumes power. If the fan is transfered to the pully driving the alternator, than that resistance is overcome already. In otherwords, if there was no loss of power in the transfer from mech-elec than an electric fan should be more efficient, right?
June 06, 2009 09:31AM
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Earendil
So I'm abroad in Seattle and not replying because all I have is my ipod. But here it goes anyway, short and sweet.

I understand what had been said so far, and the logic is sound. but the one thing being left out, that I always thought was the biggest deal, is the loss of power to a belt driven system with a pully. There is resistance there which consumes power. If the fan is transfered to the pully driving the alternator, than that resistance is overcome already. In otherwords, if there was no loss of power in the transfer from mech-elec than an electric fan should be more efficient, right?

That would be an incorrect assumption.
Also, the additional resistance of the alternator itself is added to the sum total.

If we could build an electric motor that had to be powered by the engine that produced no resistance and no losses, we would have created a perpetual motion machine...unfortunately the laws of conservation of energy don't allow that sad smiley
rkj
June 06, 2009 04:20PM
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Archeo-peteriX




If we could build an electric motor that had to be powered by the engine that produced no resistance and no losses, we would have created a perpetual motion machine...unfortunately the laws of conservation of energy don't allow that sad smiley

But peter, couldn't we work that out some way, even if it was not totally pure; something like the Chevy VOLT, but better! I think that thing runs on an electric motor that, after the batts wear down, keeps running on a small gas motor.

Seems like with all the new (and old) technology we could put an almost perpetual motion car together.

Maybe Cab could be in on it smiling smiley or anyone with ideas eye rolling smiley

Rick
June 06, 2009 04:31PM
If the auto industry was willing to tell the oil guys to take a hike, we would be light years ahead of where we are right now. Until then the oil guys will continue to poopoo al other forms of power with marketing and lies. Most people today don't realize that electric powered vehicles are more efficient than internal combustion engines and can produce more hp and way more torque for a given size. Don't buy into all the crap about producing electricity as being dirty. If the energy is collected from solar, wind, tide, wave or other natural sources, it is clean with no byproducts like coal fired generating planrts.

My impression of the Chevy Volt is that it is an electric car with a gasoline battery charger...not sure if the gas engine actually drives the car directly or not; most likely not.

Chances are we may never find out...once the GM executives have divied up and squandered the 50 Billion hand out, the company will be completely dead and gone with the stock holders owning 62% of a defunct company sad smiley



Edited 1 time(s). Last edit at 06/06/2009 04:34PM by Archeo-peteriX.
rkj
June 06, 2009 05:20PM
Quote
Archeo-peteriX
If the auto industry was willing to tell the oil guys to take a hike, we would be light years ahead of where we are right now. Until then the oil guys will continue to poopoo al other forms of power with marketing and lies. Most people today don't realize that electric powered vehicles are more efficient than internal combustion engines and can produce more hp and way more torque for a given size. Don't buy into all the crap about producing electricity as being dirty. If the energy is collected from solar, wind, tide, wave or other natural sources, it is clean with no byproducts like coal fired generating planrts.

My impression of the Chevy Volt is that it is an electric car with a gasoline battery charger...not sure if the gas engine actually drives the car directly or not; most likely not.

Chances are we may never find out...once the GM executives have divied up and squandered the 50 Billion hand out, the company will be completely dead and gone with the stock holders owning 62% of a defunct company sad smiley

I think you're right, its just a charger of sorts that keeps the car going, but hey, that's not so bad. Not until we figure out something better!

Wonder if Cab has found new battery technology yet. That would help tremendously thumbs up

50 billion, just think what we could do with that money Peter, if nothing else we could send those money grubbing Arabs packing!
June 06, 2009 06:33PM
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Earendil
the one thing being left out, that I always thought was the biggest deal, is the loss of power to a belt driven system with a pulley. There is resistance there which consumes power.
True. One might think it would be better to bolt the fan directly to the end of the crankshaft thereby avoiding the power loss of a belt driven system.

However, the small parasitic loss of the drive belt is worth it because of the greater advantage of using a large pulley on the crankshaft and a small pulley at the fan, and connecting the two with a flexible belt, thereby making it possible to drive the fan (and water pump) at a higher rpm than the crankshaft speed in order to better pull air (and pump water) through the rad when the fan is needed most, i.e. when the engine is idling at low rpm with the car stopped in traffic.

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Earendil
If the fan is transfered to the pulley driving the alternator, then that resistance is overcome already. In other words, if there was no loss of power in the transfer from mech-elec then an electric fan should be more efficient, right?

No. If there was no loss in the extra steps required to convert from mechanical to electrical and then back to mechanical power, the best that could be said is that the electric fan is only as good as the mechanical fan.

It requires a certain amount of power to pull a given amount of air through the rad. The fan itself requires exactly the same amount of power, regardless of whether it is driven by an electric motor or driven by a gasoline motor.

You could drive the fan directly with the gasoline motor which will consume a certain amount of fuel. Or you could use that gasoline engine to drive a water pump, which would pump water uphill to fill a reservoir, from where the water would flow downhill by gravity through a turbine, which spins a shaft, which drives a generator, which generates electricity, which is pumped via a long extension cord from Niagara Falls all the way across the country to Oregon, where the cord is plugged into an electric motor, which then drives the same fan which will still require the exact same amount of power to pull air through the radiator.

In both cases, at the tail end of the process, the fan ultimately consumes the same amount of power. Only if there were no energy losses whatsoever involved in pumping the water, spinning the turbine, pumping electricity across the country through an extension cord, etc, etc, then you could say the gasoline motor powering the fan consumes exactly the same amount of fuel in either case, meaning the electric fan is only exactly as efficient as the mechanical fan driven directly by the gasoline engine.

But nothing is 100% efficient. Energy is lost at each extra step along the way. Obviously in this extreme example more gasoline would be consumed driving the electric fan than driving the mechanical fan directly. It's the same principle, only on a smaller scale, in your engine compartment.
June 06, 2009 11:01PM
What a great discussion! If I may wade in...

I had always thought that unless you were on a maniacal horsepower chase, there is no benefit in swapping to an electric fan. Basically because of what Ferd has pointed out: every time you add another component which converts energy, you get losses. So going mechanical (engine rotation) > belt > fan is always going to be more efficient than adding the extra conversions for an electric fan.

But here's something to think about: even if there is no electrical load, the alternator is always spinning, so it is always putting some drag on the engine (maybe only a very small amount though). Anyway, perhaps the INCREASE in drag of the alternator caused by the amps of the fan is less than the drag force of a mechanical fan driven through a clutch. I'm not saying it is, but just it's a possibility.

It's kinda similar to how we shouldn't pay for electricity we use in the middle of the night. The power stations need to keep running (it's a massive deal for them to shut down and restart) so they will be still using fuel regardless of whether we are using the power or not. Actually, that's a slightly different situtation, but I wanted to share the story anyway!!

Hey Jack, my understanding from basic electrical principles is that the maximum output current of an alternator is related to revs, but an alternator will cause more drag on an engine when it is charging the battery than when it isn't. So adding an electric fan might cause the alternator to be charging for an extra 5% of the time (I made that number up) and that's what you've got to compare against the extra drag of the mechanical fan. Perhaps we should write in to Mythbusters... or use your car as a test rig...
June 08, 2009 02:16PM
I am not telling anyone they are wrong, I'm just opening this up for further discussion because I love this stuff. Also, I didn't feel like I got my point across before using a little dinky iPod interface.

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Ferdinand
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Earendil
the one thing being left out, that I always thought was the biggest deal, is the loss of power to a belt driven system with a pulley. There is resistance there which consumes power.
True. One might think it would be better to bolt the fan directly to the end of the crankshaft thereby avoiding the power loss of a belt driven system.

However, the small parasitic loss of the drive belt is worth it because of the greater advantage of using a large pulley on the crankshaft and a small pulley at the fan, and connecting the two with a flexible belt, thereby making it possible to drive the fan (and water pump) at a higher rpm than the crankshaft speed in order to better pull air (and pump water) through the rad when the fan is needed most, i.e. when the engine is idling at low rpm with the car stopped in traffic.

This same pulley system for increased fan speed could be implemented with an electric fan though, right? Or else crank the electric motor up. IN other words there isn't any great advantage to this gear system over using an electric fan, only compared to directly attaching the fan to the end of the crank shaft.
I was trying to relate what I said above, a loss of power due to a belt and pulley, to what I said below, about the total loss of energy.

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Ferdinand
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Earendil
If the fan is transferred to the pulley driving the alternator, then that resistance is overcome already. In other words, if there was no loss of power in the transfer from mech-elec then an electric fan should be more efficient, right?

No. If there was no loss in the extra steps required to convert from mechanical to electrical and then back to mechanical power, the best that could be said is that the electric fan is only as good as the mechanical fan.

It requires a certain amount of power to pull a given amount of air through the rad. The fan itself requires exactly the same amount of power, regardless of whether it is driven by an electric motor or driven by a gasoline motor

Okay, we agree that the fan, no mater how it is powered, requires the same amount of energy.
We also agree that all power in a running car initially comes from the mechanical turning of the engine.
The question is what path that energy takes, and where any loss (inefficiencies) there are in that path.

It seems to me that in a strictly mechanical situation (i.e. our stock cars), you have a loss of energy when
1. you use a mechanical belt, and two pulleys.

In a mechanical to electrical system you have loss
1. making that conversion
2. Any loss to the transfer of current through a wire
Since you are using a belt/pulley system that is already spinning regardless of the attachment of an electrical fan or not, the belt/pulley friction is already out of the equation.

It seems the entire ordeal rests and which one creates a greater loss of energy, two pulleys and a belt, or the transfer of mechanical to electrical. If what I have listed are the only differences in the two systems, than this is why I stated that I thought a system with no loss of energy due to a transfer, would result in a more efficient system than two pulleys and a belt.

I'm okay with being informed that one energy loss is far greater than the other. But let's not pretend that one system is the exact same as the other, with a few more losses in power. They appear to both have they own unique ways of losing energy in the system, thus we need to compare those inefficiencies in each particular system.

In either case, we're talking about mere fractions of a horsepower smileys with beer



Edited 2 time(s). Last edit at 06/08/2009 02:21PM by Earendil.
June 08, 2009 05:17PM
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Earendil
...

In either case, we're talking about mere fractions of a horsepower smileys with beer

I think you will find the losses in the alternator itself are greater than fractions of a hp. Under full load, the alternator could be consuming several hp just to build the magnetic field in it's coils.

There is no free lunch winking smiley
June 08, 2009 06:11PM
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Earendil
Since you are using a belt/pulley system that is already spinning regardless of the attachment of an electrical fan or not, the belt/pulley friction is already out of the equation.
Agreed. Whether you use the belt/pulley to drive a fan, or to drive an alternator to power an electric motor to spin the fan, the friction losses due to the belt itself should be very similar.

It seems that some people believe an alternator somehow provides free energy.

If there is no electrical load on the alternator, then yes it takes very little torque to keep it spinning. There will be some small energy loss due to the belt friction driving it, and some windage loss from the cooling fan on the alternator, but otherwise if it's not producing any current the alternator spins relatively effortlessly. But, the more electrical devices you try to power from the alternator, the harder it becomes to spin it and the more torque is required to force it to turn.

It takes work, horsepower, to generate the required electrical power.

The only way an electrically driven fan would use less fuel, compared to driving it mechanically directly from the engine, is if the electric fan is powered by a totally separate battery that has been charged by some external source, even ignoring the fact that the gasoline engine now has to schlep around the extra weight of this battery. But, if you are using the same gasoline engine to drive an alternator to charge the battery or directly run the electric motor that eventually powers the electric fan, then you've gained nothing whatsoever over simply powering the fan directly from the engine. In fact, it is significantly less efficient because of the extra steps involved, each one of which involves further losses.
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