E-Fan for 5 years -- Observations
08-12-2014, 04:16 AM
#1
E-Fan for 5 years -- Observations
About 5 years ago I decided to give the Mercury Villager e-fan modification a try. This weekend I removed it and went back to the mechanical fan.
The Villager fan is 2-speed and I wired it up such that the low-speed fan was on thermostatic control (reading near inlet side of radiator, set to 210F) and the high-speed fan was on a manual switch. The fan was installed with full shroud coverage over the new CSF radiator. I sealed it pretty well so the fan would have good suction over the fins.
After running this way for a few months, I added an aftermarket . It reads off the outlet of the thermostat. This gauge allowed me to understand precisely what temps the engine was experiencing.
In sub-70F weather, the low-speed fan worked fine. Engine temps hovered around 200 toodling around town, and were 205-210 on the highway. On hotter days, the engine would run 210-220 on the highway with the low-speed fan running constantly.
... Then I got my A/C fixed. Running the A/C creates a greater heat load and floods the radiator with hotter air. In the Atlanta summer I saw engine temps hit 230 with the AC on. Turning on the high-speed fan helped, but running hard uphill with the AC on I could easily outdo the high-speed fan and would have to slow down to keep from overheating.
This weekend, while on a trip 50+ miles from home, the fan quit.
I limped it home, and focused on reinstalling the mechanical fan, figuring I could diagnose the electric issue later.
Get this -- running fast on the highway, uphill, in 90F weather, with the A/C on, the engine runs MUCH cooler... no higher than 205-210! These are the same conditions that the high-speed e-fan could not handle.
Key learnings:
- Take accurate measurements of what you are trying to control (engine temp) before over-engineering a way to control it.
- A properly-functioning mechanical fan appears to have greater cooling power than even a heavy electrical fan like the villager fan.
- E-fans can quit on you at random. So just hope it doesn't on a hot day when you've got the wife and baby in the truck!
The Villager fan is 2-speed and I wired it up such that the low-speed fan was on thermostatic control (reading near inlet side of radiator, set to 210F) and the high-speed fan was on a manual switch. The fan was installed with full shroud coverage over the new CSF radiator. I sealed it pretty well so the fan would have good suction over the fins.
After running this way for a few months, I added an aftermarket . It reads off the outlet of the thermostat. This gauge allowed me to understand precisely what temps the engine was experiencing.
In sub-70F weather, the low-speed fan worked fine. Engine temps hovered around 200 toodling around town, and were 205-210 on the highway. On hotter days, the engine would run 210-220 on the highway with the low-speed fan running constantly.
... Then I got my A/C fixed. Running the A/C creates a greater heat load and floods the radiator with hotter air. In the Atlanta summer I saw engine temps hit 230 with the AC on. Turning on the high-speed fan helped, but running hard uphill with the AC on I could easily outdo the high-speed fan and would have to slow down to keep from overheating.
This weekend, while on a trip 50+ miles from home, the fan quit.
I limped it home, and focused on reinstalling the mechanical fan, figuring I could diagnose the electric issue later.
Get this -- running fast on the highway, uphill, in 90F weather, with the A/C on, the engine runs MUCH cooler... no higher than 205-210! These are the same conditions that the high-speed e-fan could not handle.
Key learnings:
- Take accurate measurements of what you are trying to control (engine temp) before over-engineering a way to control it.
- A properly-functioning mechanical fan appears to have greater cooling power than even a heavy electrical fan like the villager fan.
- E-fans can quit on you at random. So just hope it doesn't on a hot day when you've got the wife and baby in the truck!
08-12-2014, 06:36 AM
#2
Thanks for this experience, it's interesting.
I read about this mod throughout the forums and didn't think it was necessary. The mechanical fan works very well, it may rob a little bit more power from the engine at full engagement, but it's worth the cooling power.
I read about this mod throughout the forums and didn't think it was necessary. The mechanical fan works very well, it may rob a little bit more power from the engine at full engagement, but it's worth the cooling power.
08-12-2014, 06:56 AM
#3
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Never did understand the whole E-fan fad from years back. Adding extra electrical systems is counter intuitive to Toyota's reliability.
Good to see some actual facts attached to both the E-fan vs the mechanical.
Good to see some actual facts attached to both the E-fan vs the mechanical.
08-12-2014, 06:57 AM
#4
Driving around I feel very little difference in power. My butt-dyno hasn't been sent out for calibration in a while, FWIW.
My current fan clutch is a Autozone Torqflo, dirty, with unknown miles or history. It came with my truck when I bought it so it's at least 10 years old. But it appears to function OK. I'm replacing it with a fresh Aisin one because it feels like the right thing to do
will be interesting to see if it makes any difference.
My current fan clutch is a Autozone Torqflo, dirty, with unknown miles or history. It came with my truck when I bought it so it's at least 10 years old. But it appears to function OK. I'm replacing it with a fresh Aisin one because it feels like the right thing to do
will be interesting to see if it makes any difference.
08-12-2014, 07:00 AM
#5
Thanks snobdds. Agreed, and furthermore the fan really stressed the electrical system. Running the high-speed fan at idle would cause the headlights to dim significantly.
One e-fan mod that seems worthwhile is to add a small pusher fan to the condenser to help with A/C performance at low vehicle speeds. I may look into this sometime. There are some writeups around where folks have done this.
One e-fan mod that seems worthwhile is to add a small pusher fan to the condenser to help with A/C performance at low vehicle speeds. I may look into this sometime. There are some writeups around where folks have done this.
08-12-2014, 07:31 AM
#6
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One thing to note, and that you've experienced, is that the 12V electrical system is far, far less capable of supplying mechanical power than the engine is directly. To deliver one horsepower, which is trivial for the engine, requires about 60 amps from the alternator for the same equivalent power. Continuously supplying more than a couple of horsepower with a 12V system simply isn't feasible. I expect that your electric fan just didn't have enough power to move the required amount of air, a job which the belt driven fan could handle easily. My guess is that engines designed for electric fans have bigger radiator areas to compensate for the reduced air flow.
Also note that you don't really save any energy by going electric assuming constant operation. The engine either supplys mechanical energy to the fan directly via the belt, or supplies the same energy (actually slightly more, due to conversion inefficiencies) to the alternator to generate the electricity to turn the electric fan.
The biggest advantage to an electric fan is that it can be turned off when not required. That does save some energy during conditions of low engine heat load. The viscous clutch on the mechanical fan is a method of doing the same thing.
Also note that you don't really save any energy by going electric assuming constant operation. The engine either supplys mechanical energy to the fan directly via the belt, or supplies the same energy (actually slightly more, due to conversion inefficiencies) to the alternator to generate the electricity to turn the electric fan.
The biggest advantage to an electric fan is that it can be turned off when not required. That does save some energy during conditions of low engine heat load. The viscous clutch on the mechanical fan is a method of doing the same thing.
08-12-2014, 07:39 AM
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thinking of using to cool engine after parking
Hi
thinking ofusing an ekectric fsn to cool engine after switching off as temperture rockets. sure it would be better to control excessive heat as high heat is libal to damage head gasket etc etc. fan would not have to huge.
thinking ofusing an ekectric fsn to cool engine after switching off as temperture rockets. sure it would be better to control excessive heat as high heat is libal to damage head gasket etc etc. fan would not have to huge.
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08-12-2014, 07:52 AM
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Unless you can also run the water pump I doubt it would help much. The heat is all buried in the engine block and blowing air over it won't improve the cooling much.
Keep in mind that, once you shut off the engine, the heat source is gone (no more fuel being burned). So, temperatures don't go up once the engine stops. Sometimes water boils in the block after the water pump stops, but that's because local hot spots in the engine are above boiling temperature and are able to heat the stagnant water to boiling. That does not, however, mean that the engine has gotten hotter after you shut it off.
Keep in mind that, once you shut off the engine, the heat source is gone (no more fuel being burned). So, temperatures don't go up once the engine stops. Sometimes water boils in the block after the water pump stops, but that's because local hot spots in the engine are above boiling temperature and are able to heat the stagnant water to boiling. That does not, however, mean that the engine has gotten hotter after you shut it off.
08-12-2014, 03:50 PM
#10
great long term review. I have been driving toyota trucks since 1986. The mechanical fan has never let me down on any of the trucks.
A bigger alternator (IE- convert to CS130 or something) would help to overcome the high amp draw of an electronic fan.
A bigger alternator (IE- convert to CS130 or something) would help to overcome the high amp draw of an electronic fan.
08-12-2014, 04:05 PM
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sorry to hear that the efan did not work out for you.i have been running a taurus fan for 4 years and will continue to.i have a 22r 87 pickup with 88 v6 radiator and taurus fan,185 thermostat and adjustable switch thru a 40 amp relay using only low speed.if i am moving at all the fan never comes on.i have to sit 5 to 7 minutes for it to come on.i have the thermoswitch set for 195 when it comes on it drops 10 degrees to 185.it never comes on highway.at 70 mph it runs barely opens the thermostat and runs 180.i live on west coaet fla.it gets hot here8 months of year .it is hooked to ac to come on when needed.i have an aftermarket temp guage and it matches my temp gun .
08-12-2014, 04:23 PM
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a properly set up cooling system does not need a fan at highway speeds.mine runs this cool because of the v6 radiator.when i had to buy a radiator i bought the bigger one because for 2 years while towing my boat or tractor it would run 210 or more .the tractor and trailer weigh 1500 lbs . changed the radiator for the big one and it never got to 190.for two years three weekends a month i towed tractor 200 miles round trip never a problem.
08-12-2014, 06:43 PM
#14
Good thought on the bigger radiator. I have the smaller 2-core brass one. Shoulda gotten at least the 3-core one.
I was always bothered that the fan had to run so much on the highway. I'm not sure if the shroud design of the efan is worse than the stock mechanical shroud in terms of airflow through the rad while on the highway. It could be compounded by the fact that I have a large TJM winch bumper.
I noted today that the AC actually worked better at idle than I did with the efan running on low. Not quite as good as the highway -- still interested in a small helper fan.
I was always bothered that the fan had to run so much on the highway. I'm not sure if the shroud design of the efan is worse than the stock mechanical shroud in terms of airflow through the rad while on the highway. It could be compounded by the fact that I have a large TJM winch bumper.
I noted today that the AC actually worked better at idle than I did with the efan running on low. Not quite as good as the highway -- still interested in a small helper fan.
08-13-2014, 06:34 AM
#15
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interesting information, this is why Yotatech has some really great threads, and user stories.
I run an eFan, for about 4 years now, and wouldn't go back to mechanical. I'm in no way saying an eFan is superior or more reliable then the mechanical version. I've actually gone thru 3 fan controllers in 4 years, but the first two may have been installer error(due to Toyota A/C circuit). I did burn one fan up because the fan controller ran constantly for about a year(when the truck was on , of course).
I like the efan for the fact that it is quiet. I am constantly working on my rig, and the whirling of the mech fan makes it difficult to hear noises the 3.slo is making. Yes, adding an eFan is complicating the electrical a bit.
Quotes from OP and a few questions
snip....
(reading near inlet side of radiator, set to 210F)
I tried this location first, but then the radiator isn't cooling the hot coolant and your fan runs almost constantly(I was also using a 190°F switch). In hotter climates maybe this approach is necessary, but in MD, on a mid 80°F's day my fan kicks on and off in 1 minute intervals just idling(no load). My thermostat switch(bi-metal switches from a BMW) are placed about 3/4s of the way down on the radiator on the passenger side. this allows my radiator to do the work it was intended for, before the fan is required.
The fan was installed with full shroud coverage over the new CSF radiator.
How many rows or thick is the CSF, I didn't see a Hilux/4Runner radiator on their site? I am running a 3 row, I can't recall what vehicle it is for, but I can run down the hwy(in mid 80°F without the efan turning on, unless I'm climbing a long hill.
It reads off the outlet of the thermostat. This gauge allowed me to understand precisely what temps the engine was experiencing.
what thermostat are you using? IIRC stock operating temps thermostat should be 182°F. With that said, I know my top tank, inlet of the radiator gets up too 210°F, but never goes much past. Maybe my ambient temperature isn't as harsh as yours.
My setup:
3Core thick radiator, 182°F thermostat, Villager/Quest eFan, Volvo 2-Speed fan Controller, BMW dual thermoswitch 190°f/210°f, A/C trigger relay(isolates a/c circuit from eFan), MR2 Turbo alternator(2awg to battery). ALL wiring to fan is 10awg minimum, VIllager/Quest & Volvos were all no larger then 10awg wire.
The MR2 alternator puts out 110amps at idle, so I don't really notice the fan kick on and the Volvo controller ramps up the amp draw to avoid a spike. When my fan is on low speed, and you stand infront of the truck(my bumper sticks out about 8") you can feel the efan pulling air past you very noticeably.
... Then I got my A/C fixed. Running the A/C creates a greater heat load and floods the radiator with hotter air. In the Atlanta summer I saw engine temps hit 230 with the AC on. Turning on the high-speed fan helped, but running hard uphill with the AC on I could easily outdo the high-speed fan and would have to slow down to keep from overheating.
Interesting, during a trip two years ago to the Outer Banks, NC, was during a heat wave. When I left my house at 4:15am it was already over 90°f. The trip takes about 6 hrs door to door. Ran the A/C the entire way. Truck on 33's, loaded with 4 adults, a loaded 65qt cooler, and luggage/beach stuff for a week. The return from OBX to Baltimore took 9.5hrs all in 100°f weather, which should only take 6hrs, this was due to traffic(I was seriously going insane during this long hot trip home). The truck maintained constant temperature as we ran the A/C non-stop, I never shut the truck off until we were home, not even when we stopped for fuel.
This weekend, while on a trip 50+ miles from home, the fan quit.
That really stinks, my eFan never died, but it made some noise. Upon inspection I noticed that it wobbled a bit, so I replaced it.I suspect the wobble was because I removed the heat shield on the motor, it was heating up and compromising the plastic housing, allowing wobble. Not to mention the fan ran constantly due to a faulty eFan controller.
- A properly-functioning mechanical fan appears to have greater cooling power than even a heavy electrical fan like the villager fan.
I am not going to disagree, but I wonder if this is due to the fact that the mech fan is always running. Where as, an eFan will only operate when certain conditions/temperatures are met.
thanks for posting up your observations, its really nice when folks do a follow up on their mods.
I run an eFan, for about 4 years now, and wouldn't go back to mechanical. I'm in no way saying an eFan is superior or more reliable then the mechanical version. I've actually gone thru 3 fan controllers in 4 years, but the first two may have been installer error(due to Toyota A/C circuit). I did burn one fan up because the fan controller ran constantly for about a year(when the truck was on , of course).
I like the efan for the fact that it is quiet. I am constantly working on my rig, and the whirling of the mech fan makes it difficult to hear noises the 3.slo is making. Yes, adding an eFan is complicating the electrical a bit.
Quotes from OP and a few questions
snip....
(reading near inlet side of radiator, set to 210F)
I tried this location first, but then the radiator isn't cooling the hot coolant and your fan runs almost constantly(I was also using a 190°F switch). In hotter climates maybe this approach is necessary, but in MD, on a mid 80°F's day my fan kicks on and off in 1 minute intervals just idling(no load). My thermostat switch(bi-metal switches from a BMW) are placed about 3/4s of the way down on the radiator on the passenger side. this allows my radiator to do the work it was intended for, before the fan is required.
The fan was installed with full shroud coverage over the new CSF radiator.
How many rows or thick is the CSF, I didn't see a Hilux/4Runner radiator on their site? I am running a 3 row, I can't recall what vehicle it is for, but I can run down the hwy(in mid 80°F without the efan turning on, unless I'm climbing a long hill.
It reads off the outlet of the thermostat. This gauge allowed me to understand precisely what temps the engine was experiencing.
what thermostat are you using? IIRC stock operating temps thermostat should be 182°F. With that said, I know my top tank, inlet of the radiator gets up too 210°F, but never goes much past. Maybe my ambient temperature isn't as harsh as yours.
My setup:
3Core thick radiator, 182°F thermostat, Villager/Quest eFan, Volvo 2-Speed fan Controller, BMW dual thermoswitch 190°f/210°f, A/C trigger relay(isolates a/c circuit from eFan), MR2 Turbo alternator(2awg to battery). ALL wiring to fan is 10awg minimum, VIllager/Quest & Volvos were all no larger then 10awg wire.
The MR2 alternator puts out 110amps at idle, so I don't really notice the fan kick on and the Volvo controller ramps up the amp draw to avoid a spike. When my fan is on low speed, and you stand infront of the truck(my bumper sticks out about 8") you can feel the efan pulling air past you very noticeably.
... Then I got my A/C fixed. Running the A/C creates a greater heat load and floods the radiator with hotter air. In the Atlanta summer I saw engine temps hit 230 with the AC on. Turning on the high-speed fan helped, but running hard uphill with the AC on I could easily outdo the high-speed fan and would have to slow down to keep from overheating.
Interesting, during a trip two years ago to the Outer Banks, NC, was during a heat wave. When I left my house at 4:15am it was already over 90°f. The trip takes about 6 hrs door to door. Ran the A/C the entire way. Truck on 33's, loaded with 4 adults, a loaded 65qt cooler, and luggage/beach stuff for a week. The return from OBX to Baltimore took 9.5hrs all in 100°f weather, which should only take 6hrs, this was due to traffic(I was seriously going insane during this long hot trip home). The truck maintained constant temperature as we ran the A/C non-stop, I never shut the truck off until we were home, not even when we stopped for fuel.
This weekend, while on a trip 50+ miles from home, the fan quit.
That really stinks, my eFan never died, but it made some noise. Upon inspection I noticed that it wobbled a bit, so I replaced it.I suspect the wobble was because I removed the heat shield on the motor, it was heating up and compromising the plastic housing, allowing wobble. Not to mention the fan ran constantly due to a faulty eFan controller.
- A properly-functioning mechanical fan appears to have greater cooling power than even a heavy electrical fan like the villager fan.
I am not going to disagree, but I wonder if this is due to the fact that the mech fan is always running. Where as, an eFan will only operate when certain conditions/temperatures are met.
thanks for posting up your observations, its really nice when folks do a follow up on their mods.
08-13-2014, 06:47 AM
#16
One comment on RBX's reply.
1. The mechanical fan does not always actively run, therefore it is not always drawing energy or always making noise. It always 'spins', but it's passive unless the heat goes up enough and it locks up and then you hear it properly.
A general comment for those running and E-fan and saying that at highway speeds it has less cooling power. I'm pretty sure that it's NOT supposed to run at hwy speeds (as stated earlier by others), and the fact that it IS running causes more drag on the air trying to go through the fan, which slows down the flow all together. If the fan is left off (like the mechanical fan would be at hwy speeds under normal conditions) it will be in passive mode and spin freely as the air rushes over it (or, as the fan rushes over the air to be most correct ) . Once the electric motor is activated, it doesn't spin freely anymore. So, having your fan on, especially on 'slow' mode, you are doing more bad than good and adding more resistance and so on.
Those are my thoughts.
1. The mechanical fan does not always actively run, therefore it is not always drawing energy or always making noise. It always 'spins', but it's passive unless the heat goes up enough and it locks up and then you hear it properly.
A general comment for those running and E-fan and saying that at highway speeds it has less cooling power. I'm pretty sure that it's NOT supposed to run at hwy speeds (as stated earlier by others), and the fact that it IS running causes more drag on the air trying to go through the fan, which slows down the flow all together. If the fan is left off (like the mechanical fan would be at hwy speeds under normal conditions) it will be in passive mode and spin freely as the air rushes over it (or, as the fan rushes over the air to be most correct ) . Once the electric motor is activated, it doesn't spin freely anymore. So, having your fan on, especially on 'slow' mode, you are doing more bad than good and adding more resistance and so on.
Those are my thoughts.
08-13-2014, 07:33 AM
#17
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Gevo^^^
1. The mechanical fan DOES constantly run, the engine temperature controls the full or partial engagement of the clutch. I get what you are saying, but the fan does always spin, and make noise...thats what i was trying to say before.
snip...
"Once the electric motor is activated, it doesn't spin freely anymore. So, having your fan on, especially on 'slow' mode, you are doing more bad than good and adding more resistance and so on."
Air doesn't flow thru the grill and radiator freely, unfortunately whether mechanical or efan. The air does flow thru, but not at the rate of mph to CFM we would hope on the hwy. all the obstructions build up and make our trucks harder to push thru the air at higher speeds, this air while affective, doesn't move thru to the engine bay so freely without the spinning fan 'helping'. The mech fan always spinning, and an elfan will spin freely just like the mech fan on the hwy. Is this helping or hindering? I can't say for sure, but I am guessing it is negligible.
IIRC there was a member that was having major cooling issues after a 3.4 swap, and he used a bunch of sensors under the hood to measure temps, and found that he needed to get more airflow. he removed his grill, replaced with wide mesh, and a cowl to funnel air into the radiator. The radiator itself restricts a ton of air movement.
I had a mech fan go up on me a few years ago on my 92', sitting in traffic during the summer, truck would overheat. turn the a/c on(no efan for the condensor like newer models) truck would overheat as expected. Get on the hwy, no problem with cooling and running A/C. Granted, it was relatively flat where I was driving.
I'm not sure if any fan would have less cooling power on the hwy with the added help from on coming air. The OP experienced some issues, but I can't figure out why. I've run my truck with no fan at all, however, never in traffic, and never in hot conditions.
I will admit to overheating because i forgot i turned off the efan manually.... a downfall to the eFan.
1. The mechanical fan DOES constantly run, the engine temperature controls the full or partial engagement of the clutch. I get what you are saying, but the fan does always spin, and make noise...thats what i was trying to say before.
snip...
"Once the electric motor is activated, it doesn't spin freely anymore. So, having your fan on, especially on 'slow' mode, you are doing more bad than good and adding more resistance and so on."
Air doesn't flow thru the grill and radiator freely, unfortunately whether mechanical or efan. The air does flow thru, but not at the rate of mph to CFM we would hope on the hwy. all the obstructions build up and make our trucks harder to push thru the air at higher speeds, this air while affective, doesn't move thru to the engine bay so freely without the spinning fan 'helping'. The mech fan always spinning, and an elfan will spin freely just like the mech fan on the hwy. Is this helping or hindering? I can't say for sure, but I am guessing it is negligible.
IIRC there was a member that was having major cooling issues after a 3.4 swap, and he used a bunch of sensors under the hood to measure temps, and found that he needed to get more airflow. he removed his grill, replaced with wide mesh, and a cowl to funnel air into the radiator. The radiator itself restricts a ton of air movement.
I had a mech fan go up on me a few years ago on my 92', sitting in traffic during the summer, truck would overheat. turn the a/c on(no efan for the condensor like newer models) truck would overheat as expected. Get on the hwy, no problem with cooling and running A/C. Granted, it was relatively flat where I was driving.
I'm not sure if any fan would have less cooling power on the hwy with the added help from on coming air. The OP experienced some issues, but I can't figure out why. I've run my truck with no fan at all, however, never in traffic, and never in hot conditions.
I will admit to overheating because i forgot i turned off the efan manually.... a downfall to the eFan.
08-13-2014, 07:43 AM
#18
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Good or bad experience, this is a great write up for others to think about if going that route. Always nice to have actual experience and info for things like this.
08-13-2014, 08:35 AM
#19
Thanks for all the positive comments. Part of my motivation for laying this out is that I was always under the impression that the e-fan mod was superior in every way (except electrical complexity) to the mechanical fan. I want others to have some good real-life info before tackling this mod. Personally, I'm not disappointed that I tried it. Engineers always overthink things and it caused me to learn alot about electrical systems, cooling systems, and it was just fun.
My fan controller had an adjustable setting. I set is such that i came on around 210F with vehicle stopped and about 220F when moving (airflow caused this drift).
My 88 came with a thermostat housing that has no ports in it. I found one from an 87 that has a 12mmx1.5 port for a sensor. That's what I plugged the aftermarket gauge into.
The radiator is a . Looks like it's a 1-5/16", 2-core.
I have the Toyota 2-stage t-stat. Pretty sure it's a 195F. That would make sense since the truck will idle along all day at 190F (tstat just barely opening).
Having the fan run while on the highway can only help increase airflow, there's really no way it could slow it down as long as the fan is creating suction, not pushing. But whether or not it *should* run is a good question.
I did also "upgrade" the alternator to a 94-amp 12si. It helped with headlights dimming, but not at 750rpm idle.
My fan controller had an adjustable setting. I set is such that i came on around 210F with vehicle stopped and about 220F when moving (airflow caused this drift).
My 88 came with a thermostat housing that has no ports in it. I found one from an 87 that has a 12mmx1.5 port for a sensor. That's what I plugged the aftermarket gauge into.
The radiator is a . Looks like it's a 1-5/16", 2-core.
I have the Toyota 2-stage t-stat. Pretty sure it's a 195F. That would make sense since the truck will idle along all day at 190F (tstat just barely opening).
Having the fan run while on the highway can only help increase airflow, there's really no way it could slow it down as long as the fan is creating suction, not pushing. But whether or not it *should* run is a good question.
I did also "upgrade" the alternator to a 94-amp 12si. It helped with headlights dimming, but not at 750rpm idle.
08-13-2014, 09:22 AM
#20
Quick research of some energy usage and airspeed data of these fans yielded the following: A typical radiator/cooling fan (electric of course) at 5000rpm draws about 15 to 20 amps standing free from upstream obstructions. That yields about 15 to 20 m/sec, which translates to a top end of 45mph.
According to fluid dynamics, an obstruction downstream does in fact effect the behavior of the fluid (in this case air) upstream. So, if you are at hwy speeds of 55mph or more, your fan that is pushing air through at 45mph, is restricting the natural flow of the air (when otherwise your fan is free wheeling). Lets approximate that there is a 15% drop in air speed as it travels over the veins of the grille and radiator, that means that just about 55mph, you are even with the airspeed that the electric fan is drawing over the system. This will also be your most efficient usage of the fan since it requires less load to draw the air. Anything above 55mph, you are affecting the aerodynamically efficiency of the airflow, and according to fluid dynamics this in turn disrupts the upstream flow. How far upstream? That requires a white board full of partial differential equations, but I am sure that the radiator falls within that range.
I think you can test this practically with a hair dryer and some setup to mimic the situation.
Keep in mind though, I used an avg of the data I found. And I used the higher end of the fan's speed ability, so the slower you work the fan at hwy speeds, the more it will affect your airflow resulting in less efficient cooling.. etc...
I don't know EXACTLY what the mechanical data is (no quick search results), but i'm fairly confident that it draws in a lot more air due to it generally being larger with bigger blades (understandably it does not spin at 5,000 rpm usually). Also, I am fairly certain it free wheels when not engaged allowing for as minimal of an obstruction as mechanically possible with it still being there.
Note, to have a TRUE comparison of the electric and mechanical fan flows, you would probably need to translate airspeed to volume.. etc.. but I think that will only benefit the case for the mechanical fan (when a fan is needed to be on).
If there is somebody out there that has a properly installed electric fan and a coolant temp gauge, can you test this idea?
unplug you fan, check steady state temp at 65mph. plug fan in and work it at lets say 75% of capacity, and again test steady state temp at 65mph, report your findings
