Gain power by converting to an e-fan?
 

Is there any truth in this? It seems logical since you wont have the regular fan connected to the eshaft so there would be a bit less loss going on...

but electrical power is drawn from the alternator thus creating the same resistence.
the more power being drawn form the alt, the more resistence is it has in order to spin it. so...



no.

This is covered in the FAQ.

I don't buy that, the alternator will spin the same amount of RPM, will have the same resistance and will put out the same amount of amps wether you are running an efan or not.

Read that link I posted, it will give you all information you need to buy it ;)

No need to...

As I said, nothing asides from pullies will affect the alternator RPMs, amps output, or resistance.

About the only thing you gain off of a stock clutch fan is room. If you want you can check out my project to see what I mean. You'll definatly put strain on the electrical system, but other than that you just gain room to work and the ability to run whatever you want through about 3 cubic feet or more.

What's not to buy? The stock fan is clutched, so it freewheels when cooling needs are low - typically when cruising, so that air is moving thru the rad - no advantage to an e-fan there. When the e-fan is on, in order to do the same work cooling, it must necessarily get the energy from the engine - via the electrical system. There's no free lunch here - energy drawn on the electrical system to perform the work of cooling necessarily translates into load on the engine, via the alternator. In fact, given that an e-fan is converting the mechanical energy of the engine to electrical energy (whereas the stock fan uses the mechanical energy directly), then converting it back into mechanical energy (rotating fan drawing air), it will necessarily be the case that the e-fan will take more engine energy to do the same job, due to the inevitable energy losses that happen when converting from one form of energy to another. The alternator's resistance most emphatically does not remain the same with the load of an e-fan, it goes up, a lot.

The problem of an e-fan using engine energy less efficiently than the stock, working clutch fan is compounded by the fact when cooling needs are high - eg, idling in traffic - , the alternator on these cars barely keeps up with demand just to run the engine electrical system, lights, and so on. Ever noticed how just hitting the brakes when idling hot causes the revs to sag, then return to a slightly higher point? That's because just the load of the brake lights on the alternator slows the engine significantly - proof that load on the alternator makes the engine work harder. The surge that follows the sag is an idle compensator, just like for the A/C, that Mazda designed in, recognizing that at electrical loads at idle tax the alternator/charging system. An e-fan is going to tax the charging system further precisely when it is least able to compensate - low engine/vehicle speeds.

The alternator is not a free energy device. If you draw more current from it, then the shaft becomes harder to spin, and the engine must work harder to spin it.

The alternator only supplies the amount of current that the car is drawing...That is, a 70A alternator does not always "push" 70A out into the electrical system. If the electrical draw from the car is only 50A, then only 50A will be produced from the alternator.

This is why cars with flakey (or missing) BAC valves have idle dropping issues under heavy electrical load. Switching in a high current item like the headlights, defroster grid or e-fan causes the idle to fall as the load on the engine increases.

Harder to a certain point, right?

If i was to follow your theory, a stock FC with a 90amp sound system, e fan, AC & headlights on; will barely move...


I am not going to lie, since i don't know if thats true or not; however I know that has RPM increases, so do the alternators amp output.

Yes, as load to the engine increases.

The relationship between how hard it is to turn the shaft vs. how much current is drawn from the alternator is basically linear. The shaft becomes harder to turn as you draw more current, up to the maximum current the alternator can produce. If you had a weak source of mechanical power (small engine, human) then you could draw enough power to drag the shaft down to the point where it could not be turned...Actually 90A at 12V is only 1080 watts, or about 1.3 HP. Most humans could provide this much energy for at least a few minutes...

I'm not sure what this means...Also it's not a theory, but elecromechanical fact. :)

Yes, because more mechanical energy is being input into the alternator.

THANK YOU!

So in conclusion an e-fan amp draw is next to nothing or in the decimal range. If 90amps is equivalent to 1.3hp; then 45amp is equivalent to 0.75hp.

So in reality an efan might cost you what, 0.35hp? A couple of things come to mind, can't think of a single person that can notice the difference between 0.35hp. The second thing that comes to mind is, the loss of HP on an efan setup cancels out with the extra weight that the eshaft is carrying with the stock fan setup, and\or any drag that it might cause on the engine.

Yeah but if the stock fan absorbs 18hp (exageration) and the electric one which in reality draws ~15A running, then you would be gaining a decent amount. But what someone needs to do is head over to a dyno and make 3 runs, get an average, remove the stock clutch fan and make 3 more runs and take that average and that might give a good indication of how much energy it takes to drive the clutch fan, than inverse the drivetrain loss to get RWHP... anyone wanna take a guess?

Damnit i never thought of it like that!! Thats pretty cool.

would it be worth it to take out my a/c pump during the summer is it worth the power or not?

if it works keep it,if not have a shop remove it that can do it right...the A.C weigh's a ton.

is it worth taking out my A/C pump for more power or would i just rost in my car?
Thanks

thanks for the info

I wouldn't take it out if it works. It's not enough to give you enough HP, if it's just sitting there....that's like taking out the carpet in your hatch and expecting a 10 hp gain :p

Basically, yes. But neither does the mechanical fan. That's sort of the point I try to make in the writeup. If the mechanical fan really did draw several HP, several HP worth of electrical power must be drawn from the alternator to do the same physical work (ignoring differences in fan blade efficiency based on different designs). So in truth neither one really takes that much power...

The clutch fan freewheels when it's not needed, so there is no serious drag on the e-shaft.

rx7racerca knows whats up

I am against the e-fan draw HP mentality; and what I am trying to prove is that it doesn't draw any power (well maybe 0.25hp). Notice that I am not claiming that the efan gives more HP; just that itd not how some want to put it...


When talking about drag, yes you are right; however its weight will always be a burden on the e-shaft.

the reason i opted for the electric fan was the room that it made in the engine bay.

I did my e-fan setup coz all tha mad powah comes fRUM da fanz yo.

I SWEAR I'VE SEEN A THREAD LIKE THIS SOMEHERE BEFORE??? :dunno:

Can also read the thread below in my sig about the E-fan and clutch fan.

Your correct in knowing that the e-fan does not claim as much HP as the clutch. The clutch has a greater chance of claiming more HP then the e-fan but nothing you may be able to feel.

In the e-fan link in my sig, click on the link about the S4 Fan Estimation, that gives you good info about the clutch fan.

To get a closer approximation, you want to do the math using 13v and not 12v. Not a large difference though.

Also, the clutch fan does not take anything over 5hp. It would take less then 2 most of the time but usually in the decimal range.

I thought the E-Fan conversion was to make more room in the engine bay... :confused:

Thats why I would eventually like to do it... :pat:

What are you making room for? Most of the people who say they swapped to e-fan "to make more room" don't actually use any of the space they've freed up.

Your right but its easier to work on the engine without that large shround in the way.

+1

I dont have an overly modded car but like any other 7 it needs to be worked on regularly... Its nice to clear as much crap out of the way as possible... Plus it just looks nicer... :D

Yes. But the same holds true for the stock fan as well. It freewheels when not in use.

Being that the weight is very close to the center of the shaft, and the freewheeling nature of the clutch fan, I don't know if it would make that much difference. Certainly when I installed my e-fan (because my clutch fan died....) I couldn't tell that I had switched (well, save for the fact that my alternator now struggled to keep up).

Are there over drive pulleys one could install?

Actually this is incorrect. Although you may have just worded your phrase wrong compaired to what you actually ment. The amp draw for a fan is most of the time about 10amps, a lot of times near 15+. Im guessing you were talking about the HP consumption of the e-fan due to the amp draw compaired to the clutch fan, in which case, you are correct.

While the fan is running, you would have the extra drag from the alternator. Still would be minimal. While the e-fan is off though, you have lost nothing and have free'd up any little hp that was taken by the previous clutch fan, as well as the current e-fan.

I have never seen any but im sure you could get some made. Doing this though could over spin the alternator or water pump, depending on what you "overdrive". Personally, I would like to overdrive the alternator slightly, havn't done the math to figure out how much I could go but at idle, it seems to spin to slow to charge much.

That's what i'm thinking, however I believe you can swap out the diodes to get a similiar affect, however I think the output would still be rather low at idle.

an Overdrive pulley would be smaller than the shaft pulley(?), but i'd imagine it would only need a few mm to a cm in difference to get the desired affect.

What i'm curious about though is why anyone would want HP at idle? since both the efan and clutch fan usually only spin at low speeds or at idle. There's rumors of better throttle response from an efan and most who have done the conversion agree. Besides that and space it makes no real difference in the amount of usable HP. As for my reasons for conversion the fan and shroud were broken and I'm also planning on doing a N/A->turbo conversion (so with that space I can run intercooler piping).

Right, if you notice the alt pulley is already smaller then the main pully but in some situations doesn't seem small enough. They are that size for a reason though, If you do a lot of high rpm racing around then I would stay away from overdriving the alt even more.

Its not getting HP at idle, its trying to free up and HP through the poewr band that the clutch fan is said to consume. As I state before, its usually in the decimal range but can take as much as 2+ hp.

I can't remember if switching to an e-fan increased my throttle responce or not while the fan was off or on. Its been about 5 years. I can see how it would, but I don't think its anything to jump up and down over either.

yeah, that's what I was thinking--but (correct me if i'm wrong) the stock electrical system already struggles to keep up with demands. As previously stated it's only going to produce the amount of amps that is drawn from it. I think a better way to go might be to replace the diodes in the alt to produce more amps at all rpm range, but that would require finding an upgrade kit and what not. It just seems that some people swap over to an FD alt to fix their power consumption problems, but i'd imagine it all depends on what's consuming your power, I doubt an efan would consume enough by itself to warrent an upgrade, but combine it with an aftermarkte stereo system it might.

I see what you're saying now, but it seems a little asinine to me. But that's just my opinion.
My sentiments exactly.

The conversation is past this, but I'll add these two sentences anyway:

• The clutch fan taps the engine's mechanical power directly, while the electric fan converts to electrical power at the alternator, then back to mechanical power at the fan, and each conversion is less than 100% efficient.
• Reasonable electric fans have an upper-limit of airflow, while the stock fan has a much higher limit.

Those don't tell the whole story, but they're interesting to keep in mind!

I still think this is more in people's heads than anything else, because it makes such a difference visually. There's not that much "on the engine" that's blocked by the shroud. I've worked on pretty much every part of my engine at some time or another, and only needed to remove the shroud once to remove the water pump. I'm doing something in the engine bay often and if it actually got in my way on a regular basis I'd be much more interested in removing it. What regular tasks would actually be made easier?

^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

I guess on the other hand... Since I have removed the stock intake, the shroud does work great as a place to set tools while I work on it...

would you gain any throttle response by getting an e-fan?

the only reason i'd get an e-fan is cause i would like to install a reverse vented hood, which WOULD help reduce engine bay temps.

Listen, I work at Advance Auto and test a lot of alternators. When you put a load on an alternator, it puts an electrical resistance on the shaft, and makes it harder to spin. If this wasn't true - then an alternator would produce max output at idle or at WOT - which is also a known fact that it doesnt.

The alternator does not increase amps based on RPM solely.

Any Mechanic will verify what I have said to be true. I am a mechanic myself. Maybe you should research your stuff before you make ignorant claims...

-Chris

Ohhh lord, a mechanic working at AAP :wallbash:

How about kicking my 90 amp sound sytem at full blast while the car is at idle; will the alt put out its "100" amps?


Yeah, didn't think so :sadwavey: :rlaugh:

So in conclusion, an alt will not put its max amp output at idle, irrelevant of load...

There is something you can do with an EFan that you can't do with a clutch fan. Switch it OFF before a run on the drag strip. That and controlling the exact on and off temps, and having it kick on and run after the car is shut down too cool things off.

But I would gladly go back to the clutch fan any day if I could. On my current setup it would spin backwards.

oh hey look! a battery! it can STORE and RELEASE electrical energy? no shit!

We are not talking about batteries :dunno:

On any case, where is that energy coming from?

And if the demand is MUCH HIGHER than the supply?

The battery is part of the equation if adding electrical draw to the system, be it an e-fan, or high-power stereo system, or auxiliary lighting, cause the load to exceed the alternator's output at idle or low speeds. As has already been noted, the FC charging system struggles to keep up with demand at idle - for example, idling with my headlights on, if I use the power windows, the idle sags, due to the extra load on the alternator, and lights dim. Same if my foot is on the brake, lighting the brake lights.

Under such conditions, where the alternator is not supplying sufficient amps for the electrical draw on the system, the battery "chips in" from it's stored energy. Two problems follow from this - one is, that cannot go on indefinitely, as the battery will eventually run flat and voltage/amps supplied to electrical system will drop below that needed to keep the car running - although in practical terms, that would take a lot of time idling - possibly hours, depending on how much the battery has to "make up". Secondly, if extra load on the electrical system from an e-fan, for example, causes the car to draw on the battery while idling or at low speeds, the alternator will work harder once engine speeds increase to recharge the battery again, meaning it is possible that the extra load of the e-fan effectively remains on the engine, via the alternator and battery, after the fan may no longer be running - effectively, a deferred load.
I just read Mr. Cake's writeup on "the efan myth" - he's pretty much nailed it - and he effectively deals with the reasons you might want to use an efan - its just that hp gain isn't one. You'd almost certainly gain more by switching your tranny and diff lubes to a quality synthetic.

dejavu i swear we comment on this way too much.........

No understanding from you on many subjects eh?

This is the reason why the electric fan is a SIDEWAYS Add-on and not an UPGRADE. I like the looks of a cleaner, less cluttered, engine bay and so do many people. You on the other hand must be an old timer :)

You should go to your local community college and take some automotive classes.

Did I say that an alternator will put out max amps at idle? No.

Let's see what i said:
"The alternator does not increase amps based on RPM solely."

WOW! I said "solely". When I test an alternator while it is on a car, I rev the engine to 2000 rpms so that I can put a full load on it. Then I test it at idle and it puts maybe 50-65% of a load on it - the exact percentage I do not know.

By the way we are talking about batteries. A battery is part of the charging system - it is a capacitor and a power conditioner. If you say that a battery has nothing to do with it, then please please please go take an automotive class and stay away from car forums for 3 months.

Well isn't that something? Once again you should research stuff before you make claims, and please read posts carefully