Is an Electric fan conversion worth it? My testing procedure
 

So I have been thinking about converting to an electric fan to try and save some fuel. The mechanical fan seems to pull a lot of air even when the truck is cold/fan clutch is disengaged. I have never noticed the fan cutting in except for when towing or climbing big hills during the summer, so the electric fan would not have to run very often.

I wanted to test how much drag the mechanical fan actually puts on the engine and was hoping someone could verify that my test makes sense...

I plugged in my code reader which has a live data feature that can display Load %.

With the mechanical fan still in place I drove a loop and recorded the Load % value on a flat stretch of road at 60 km/h to be a 10.5%, and on a long hill at 50km/h the load read 25.0%.

Then I removed the mechanical fan and drove along the same route, and on the same flat section of road the Load was a steady 9.0% and on the same hill as before it was 22.0%.
The temp gage stayed between 80-90 Celsius during both tests.

So thats a 14% reduction in load on the flat, and a 12% reduction on the hill?? It surprises me much load could be from the fan alone. From my test results I think I'm going to go ahead with an e-fan, it seems like I should see some noticeable fuel economy gains, should be close to a 4% increase in mpg if you figure the engine converts 1/3 of the fuel to mechanical energy (as long as my math is correct and 1/3 may be a bit optimistic I'm not sure).

I have heard that if you take the fan off your water pump can wear out quicker as it is used to having the fan pull on the shaft/bearings, I've also heard that it will last longer because you don't have the fan hanging off of it? If anyone has done an e-fan conversion please let me know if you've had or heard of any water pump issues.

To me you should have done another test after putting the fan back on just to make sure that it wasn't something like your fuel being warmer (return line from the engine) or tires being warmed up.
but all in all, your fan is running at crank shaft speed, right? if you put that fan on an electric motor and ran it at the same speed how many watts would it pull?
Our truck at work is used as a truck towing near it's own weight half the time, so from that point of view it's most likely using the cooling of the fan while it's running and converting mechanical energy to electrical and back to mechanical seems like a round about way to get work done, but for your use it seems like it's not needed very much.

I like the idea of putting the fan on an electric motor. Then would you just use P=IV? but how would you know what rpms its turning? and what is the average efficiency of an electric motor? 90%ish?

On a technical note, as Ryland said, an e-fan is "less efficient". However, the key is that it only draws power when it's turned on, which isn't all that much. A mech fan has a parasitic load all the time, which is why an e-fan gives better mpg despite the conversion losses.

Almost all viscous fan -> electro conversions have made some mpg benefits.
I don`t know how much difference it does on a truck with a big engine, but people have been doing it on BMWs and Mercedes. The added benefit is also a faster warm up and, more so on a performance car, the willingness of the engine to rev more freely.

I have been wanting to do this for some time on my truck. The mechanical fan seems to stay engaged quite often, and seems to engage more in the winter than summer, which is odd. There is a noticeable drag on my engine when the fan kicks in. I saw an episode of Trucks! where the host was performing mileage modifications to his truck, and one of the things he did was replace the mech fan with an electric fan. He said he gained a little more than 1 mpg. Not bad.

1mpg on a truck that gets less than 20mpg is a huge gain. I was planning doing the swap also when it is warmer out takes forever for my truck to warm up with that huge grill opening.

if your fan is out of balance it will kill your waterpump bearings it would be nice to drop 10lbs off the waterpump nose.

Switching to an electric fan helps 2 ways. It improves FE, and it frees up power when you want.

My F150 has had no fan at all for about 3 or 4 years now. It rarely is sitting still in city traffic; as long as it's moving it's been fine, even when working hard. But then I haven't worked it real hard on a really hot summer day either.

i did this on my starlet 3 years ago, you will notice straight away an acceleration boost and that it warms up quicker, i suggest a hotter thermaostat while your at it, believe me it makes a difference in warm up times, as for wear on water pump, mines 3 years on and shows no signs of giving up so dont know where you heard that from.

when i did my conversion i gained 1.6kw on the dyno (thats a 3-5% gain for me
believe me it is worth it and it takes a load off the motor bearings as it has less mass to try and spin :)

if you want anymore answers feel free to ask no matter how stupid they sound :)

pounsfos, does your electric fan run continuously or is it connected to a thermostat that kicks it off and on? Did you wire it directly to the battery post or did you tap in to something else? It would be helpful if someone could provide some wiring info.

Thanks!

I am planning to use a thermostat switch to run the fan automatically, I've found some pretty cheap fan controls (jegs and summit racing) that either have a probe that pushes in between the radiator fins or a sensor that threads in. I'm thinking a thread in sensor would be better as its in direct contact with coolant, but I don't know where I would put it... guess I'll have to take a close look for somewhere to thread in the sensor. I've found this kit that seems pretty cheap and comes with 2 14" electric fans and the wiring/temp switch. Not sure about the quality of the kit though, I'm not familiar with the brands. The kit is on amazon.com PROCOMP DUAL 14" INCH ELECTRIC FAN W/ DERALE THERMOSTAT 16739
My radiator core is about 17x28" but I think if I make some sort of shroud the 2 14s could work pretty well.
If anybody has any suggestions as to a better fan set up I'd love to hear them.

I picked up an electric fan out of a ford Taurus/mercury sable from a junk yard for $20. The Off road groups swear by them as being able to move more than enough air that they rarely have to go to high. Then I have a thermostat from summit on order with the fit between the fins format.

The Taurus fan is a 2 speed fan, usually low will get the job done. I am planning on running the thermostat to the low normally with a manual override switch off of the ignition circuit to give me high if I need it through a relay that will bypass the temperature sensor control circuit. The only time I anticipate needing to go to high though is when I have it bogged down and stuck with a heavy load on the engine and no movement.

Hey TheEnemy, would you happen to know the dimensions of the taurus fan shroud??
Thanks

One (from a V6 sable I think) measures 20X17 with a 17" fan, the other two from a Taurus measures 24X16 with a 16" fan.

Some junk yards like a U pull and pay let you go in and you can measure fans and pull whatever you want. One note about the Taurus fans, in high they pull a lot of juice.

Ecotruck assuming that you have a SBC engine twith a stock manifold you should have 2 or 3 places to insert a probe usually on a stock manifold there will be a plug or 2 also on drivers side behind the 3rd sparkplug 1 on the head one on the block there should be a waterjacket plug also check your radiator sometimes 1 if not 2 plugs there if you have a manual then there will definately be 2 plugs auto maybe just 1.

Or just swap out your waterneck. add in a probe from jegs/summit as mentioned befoe easy job to do while your at it you can add that new thermostat.

I had one of my old race cars set with the electric fan on a sensor and also with a bypass switch the sensor was because I forget to turn it on :rolleyes:


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pickup a summit fan or better yet check out Autozone if they have them buy you crazy 40% off sales goinng on now.

Good luck

Hey Bill thanks for the info that should help get me started, my truck has the 4.3l V6 but i guess that is still a sbc, just missing a couple cylinders, not sure if the manifold is similar to the V8 manifold or not. I think I'll check the rad for plugs once I get some free time, now that you mention it I think I remember seeing something like that on the rad tanks.

sorry about the late reply,
my electric fan is connected to a temp reader just by the thermostat so when it reaches approx 98 degrees celcius it turns on until it is at about 88 deg again.

i got mine done professionally, but if you want to D.I.Y then

install a switch in your dash connected to your fan that turns it on and off

my skid weapon car has this done so when im popping tyres i dont have to worry about it over heating!!

its very affective and you have control of when you want it on or off, just dont forget haha