bktaco

anyone have this experience? i installed the fan a couple weeks ago. when it kicks on, it seems to be drawing it's power in a surging rhythm. kind of like cycling surges. hard to describe, but if you've noticed it, you'll know exactly what i'm talking about.

any clues? its a little bothersome. i almost hate to hear the fan come on for that matter, otherwise i imagine that i would be stoked to hear the fan come on.

only other data: i havent completed the wiring yet: the a/c relay isnt hooked, and both power leads are hanging off the battery until i get in there to finish the job all pretty. but i can't see how these would factor...

midiwall

Does it do this with the engine running as well as off? What if the engine is running and up above 2000rpm?

If it only does it with the engine off, then I'd say that your battery is on it's last legs. By it not happening with the engine running, (and/or with the engine at a fast idle) then that's because the alternator is kicking in the extra power required.

4RUNR

Don't you have an A/C unit that does the same thing?

Btw, how would an electric fan be more efficient than a mechanically driven one? Is the stock one overcooling? Mine spins very freely at normal op temperature.

midiwall

The issue is one of the HP it takes to spin an 18 pound object sitting right on the crankshaft that also happens to be dragging it's legs through the air. It's quite measurable, and after moving to an electric you'll find a bit more torque down in the bottom end.

4RUNR

I'm not trying to be an ass here, but there are few things I honestly do not understand:

#1: If anything attached to the crankshaft is already spinning, it does not require any additional power to maintain the same momentum, that is unless there is drag... which leads me to the next observation...

#2: The drag comes from the fan, that's indisputable, but, the fan with a properly working clutch that reached the operating temperature can be effortlessly rotated around a stationary crankshaft with a pinky finger! Which is indicative of the air resistance the crankshaft sees when spinning.

The question is: how can this resistance be noticeable on a 200+ lb/ft engine?

midiwall

You're not being an ass, not at all. Questions and questioning are good things.

You're 100% correct with point #1 - if the fan's already spinning, then no additional HP is required to keep it spinning. But.. When you blip the throttle you're burning HP to increase the speed of the fan to match the engine speed. This is where HP is gained by removing the fan. It may better be said that the HP which used to be wasted in overcoming the mass of the fan can now be transmitted to the rear wheels.


The issue with point 2 is that you're talking about moving the fan slowly through still air. Things change as the speed increases. Think about how "windy" it is in the engine compartment with the engine at 3000rpm. The air flow is of course coming from the fan blades moving the air, and there's (a lot of) drag associated with that.

I'm trying to think of a way to demonstrate this.... I have a vision of creating a large pinwheel (say, 12" in diamter). Note that you can easily turn the pinwheel in your hand.

Now stuff it in a drill chuck. With the the drill trigger full depressed, the pinwheel will spin at a certain RPM. Now remove the pinwheel and pull the trigger again - the drill will spin faster.

Nothing outside of removing the pinwheel has changed - the line voltage to the drill is the same, the motor in the drill is the same. The drill turns faster because there is less drag on the motor.


Does that help or am I confusing the situation more? Hopefully someone else can pop-in and be clearer.

4RUNR

The fan clutch is a fluid coupling type right?

So, effectively when the engine spins the fluid increases its viscosity and can't be compared to the resistance right after the engine is turned off?

MTL_4runner

Now is this sentence were true, that means you could start the truck while holding onto the fan blades and rev it right up to 3000 rpm with no fear at all.....well, let me tell you.....don't do it or you may lose a finger or two. There is alot more resistance there than you think.

Fan Clutch
The fan clutch is a small fluid coupling with a thermostatic device and controls a variable-speed fan. It ensures that the fan will rotate at just the right speed to keep the engine from overheating, and reduces drive to the fan when it is no longer needed. The fan clutch has a fluid coupling partly filled with silicone oil designed for just that purpose. When the temperature of the air passing through the radiator rises, the heat alerts a bimetal coil spring to "uncoil" or expand. When it expands, it allows just a little more oil to enter the fluid coupling, so the fluid coupling starts to rotate the fan. If the air coming through the radiator is cool, the opposite happens; the coil spring contracts, the oil leaves the fluid coupling and the fan slows. Slowing the fan when it is not needed reduces fuel consumption, makes less noise and saves engine power. Sometimes a flat bimetal strip spring is used instead of a coil spring; it bows out and in when the temperature rises and drops, letting oil in and out of the fluid coupling.

I think what Mark is trying to get at is that there is rotating inertia associated with the fan and that the fan does not fully disengage (even at highway speed) although it is minimized. The electric fan is not mechanically tied to the rotating inertia of the engine and thus allows the engine to rev faster (which also makes for a quicker launch).

Darx

I never understood the use of the electric fan but I assumed it was used by offroaders to keep the engine cooled during low speed, basically idling, situations when crawling around all day. Whereas the fan hooked up to the engine would be going slower due to low rpm the electric fan could keep going full blast.

Is this a correct assumption?

bktaco

sorry i've been out for a few days. pls allow me to pull this thread back to point.

the power draw surging occurs at all rpm, lesser with higher rpm. also occurs after engine is off. so i guess this would preclude your battery hypothesis?

and to respond to 4RUNR, the A/C unit did not do the same thing. it put a more consistent power draw on the engine, not a cyclical-type surging.

any other takers? if i cannot figure/fix this, i may be opting for the flex fan instead, and offering the e-fan here. thanks in advance-

midiwall

Hmmm... Have you noticed any other electrical component havign trouble as the fan surges? Like, will your headlights dim in sync with the fan surging? If so, then there's a global electrical issue (like maybe the regulator). If not, then the problem is either in the wiring or the fan controller.

Did you use crimp quick connectors for the fan or did you solder things up? I know I had some trouble with the crimps but havn't had any issues since I soldered everything.

amusement

Time to get some measurements!

You need to measure the voltage of the battery during electric radiator fan operation with engine isn't off but warm

You need to measure the voltage of the battery while the electric radiator fan is operating and the engine is running.

Is there a difference? If so how much?

You need to measure the amperage of the electric radiator fan when it's operating and the engine is off.

You need to measure the amperage of the electric radiator fan whin its operating and the engine is on.

Is there a difference? If so, how much?

Come back to this thread with the details of your research.

Midiwall has done a very good job in describing what benefits electric fans offer and some of the basics of a mechanical / hydropstatic radiator fan clutch.

Electric fan clutches offer advantages over convential fans.

- More low end torque (as Midiwall stated earlier)
- Greater fuel economy
- Great control on cooling

But, there are some down sides to electric radiator fans.
Mostly is the complexity and relying on a sensor, DC motor and eletrical power to both devices. The convential radiator fan is a proven and extemely reliable device.

I would consider getting a eletric radiator fan if;

- did alot of slow high RPM four wheel driving
- was in bumper to bumper traffic for more than 30 minutes a day
- lived in a hot environment that constant "pulling" air would cool engine and A/C radiators.

bktaco

thanks fellas. will measure, interpret and report. maybe this week sometime.

in the meantime, any experience with the flex fan (ie, http://www.lcengineering.com/TacomaR...ex%20Fan%20Kit )?

tanks in advance-