Electric vs. belt driven cooling fan

[Gregte]

Originally Posted by ebacherville

...when id shut the car off in a slight wind blowing and the car faced into the wind it would stay running as the fan was being spun by the slight wind and powering the ignition cloil..

This is very interesting!

In fact, since I can barely, or not even, hear my new electric fan, I wired a small light bulb across its power terminals and mounted the light bulb on my dash so I could monitor when the fan is running and thus be able to adjust its thermostat for best efficiency. Well, having done this, the first thing I noted is that the fan spins with the incoming air from vehicle motion, enough so that it lights the bulb, however dimly.

Actually, I am thinking that it is not desirable to have the fan spin when not being powered because that is putting undue wear on its bearings and brushes. I could configure a relay to put a dead short across the fan's power terminals when it is not being powered. This would greatly reduce its ability to freely spin, thus saving bearing/brushes wear.

[Gregte]

Originally Posted by dremd

I have no #'s for my supra fan swap (mechanical - electric- mechanical) but i don't think that the fuel differance was much.

Thanks for the honest opinion. Most of what I have read from guys who have put on e fans has said "it gained me 3-5 mpg!" or similar unlikely sounding numbers.

My guess was that the fuel savings would be minor. That is why I decided to try to actually measure what the old belt driven clutch fan was actually using after getting the good suggestion/technic from ttoyoda. There is no accurate way for me to measure the before and after FE gain with a mod like this unless the gain is very large or unless you want to do an extensive A B A type of test. Again, my only need to know the FE gain is for pride/ego, since I had already spent the money. Thanks again.

[ttoyoda]

Again, my only need to know the FE gain is for pride/ego, since I had already spent the money.

I would call it science. You are now smarter, you have done a test, taken data, and when you hear someone spout off with inaccurate info, you will be able to correct them. I'm smarter too, I had to think about how to do the calculation, so thanks.

I had originally concluded that it would take 3.6 years of fuel savings to pay for my electric fan. Your insight reduces this to 1.8 years. And this is all at $4 gas. If gas doubles in the meantime (hey, it might) my mod becomes even more worth the doing. In all honesty, I think with me it is more a matter of foolish pride than of the actual fuel savings although saving money, no matter how little, is always good.

I feel that 1.8 years is a pretty good payback time. I do home energy mods that have much longer payback.

[brucepick]

Originally Posted by Gregte

...Assuming that the fan requires 0.19 HP to cruise down the highway at 55 (no tach so I don't know if that's 2500 RPM but seems it must be close) and assuming that it takes perhaps 10 HP to cruise 55 (just a WAG) and also assuming 34 MPG at this speed (quite easily achievable) I wonder if this means that the fan would cost about 2 percent of my fuel to turn it since 0.19 HP is about 2% of 10 HP....

I like this calc. Seems reasonable to me.
And we have to recognize - car makers and modders alike have spent more time and money on other 'FE' mods that yield less improvement.

I too put an e-fan in my car in summer '05. I also put in a light (green LED) to let me know when it's running. Fan is too quiet to hear under nearly all conditions.

I drive more miles. Currently about 14K /year (car pooling saves miles!) but since '01 it's averaged about 40K /year. So my payback was shorter.

A non-turbo Volvo 240 is shall we say, not over powered, at 115 hp and 3050 lb. So I'm glad to have taken that load off the engine and also get some FE benefit. OK, you can't have the FE and power benefits both at the same time - but I get either at any given time, controlled by my right foot.

[ajax_6531]

Some older vehicles don't have a clutch on a belt driven fan. They would have better efficiency with the electric fan because the mechanical fan was always under load.

[bennelson]

I replaced my belt driven fan in my '95 Chevy S10 4-cylinder with an electric fan from my Geo Metro.

Fan works fine, but like you said, it seems like a fan is never needed anyways. I think a big part of this is that the truck has the same size radiator whether you have the 4 or 6 cylinder.

I have ofter heard that radiators are designed for heat of the bigger engine size when it is towing.

If that's true, than a little S10/Sonoma should never need a radiator fan at all, other than maybe stuck in traffic on a hot day, with your engine idling.

What did you use as a switch to operate your fan turning on and off? Mine has been rigged up to run manually. If you have a specific thermal switch, could you please list the model number or where you got it from?

Thanks,

-Ben

[getnpsi]

bennelson I'm with you here. I put an e-fan on my b2300 mazda (ford ranger) and the fan never turned on except when i turned on the a/c or was sitting in traffic a long long time, also when playing in the dirt. Back then I did it for performance, not economy. As long as a vehicle is traveling at least 20mph, the airflow is enough to cool the radiator.

some ecus do have a fan control pin, even if the vehicle has a belt fan.
I used a performance 5.0 mustang fan i had left over when i sold it. It had a thermoswitch, an additional a/c turn on relay AND a manual override.

You can swipe the switches out of cars that came with e-fans from the junkyard.

[max_frontal_area]

Originally Posted by Gregte

able to adjust its thermostat for best efficiency

how do you do that please? does it have a reostat?

also i need to get an electric fan for my rig. which vehicles use large high CFM
fans that i could pull from the JY??

[jtgh]

there are 4 choices . all have pros and cons.

the electric need not run much , in fact only at stop lights .signs.

but the clutch fan is disengages. and uses virtually no power. Slips.

a directly bolted fan will indeed suck tons of power an fuel from any motor.
1950s all over again.?

then there is a flex fan that uses almost no energy and costs little. (tops)

the electric fan needs an inline radiator hose coupling with ECT to work reliably. (the ones that clamp to the hose are no good)
i tried others and all fail.

i installed my first in 1970 so , it's not new . (OTC kit)


the electric fan efficiency is low and so is the alternator, they compound
to huge heat losses total.

direct drive is the bench mark for 1:1 efficiency, IF ever there was.
same blades (like a submarine screw)
same playing field.

YMMV, heheeheheh

ps:
it does take load of pump bearings.
it is quieter then when clutch is hot and fully engaged.
and if clutch fan seizes, then this is a go.
I do like the beautiful simplicity of a flex fan.

[tjts1]

You are confusing viscous clutch with an electric or mechanical on/off fan. 2 totally different technologies. A viscous clutch fan uses some power even when it is 'disengaged'. But it's never really free of friction especially above idle.