Is an electric fan worth doing?

[ellner357]

So I have a long standing debate with my best friend. I though removing a manual fan would technically free up a little hp (no not a lot and not anything you can feel) now he think that's not the case based on the fan being hit and potentially propelled by highway speed wind. Now I am pretty damn sure he's wrong.

On a 3rd Gen 4Runner. Are any of you guys running electric fans? Is it worth it? What fan are you running? Pics if you wanna get fancy lol.

 

[Rudy97]

I'd check what LC Engineering has to say on the matter. I know they sell electric fan kits for 4Runners and Tacos.

I know a few people are running electric fans and the only real common downsides are A) reliability and B) possibility of shattering the fan if entering deep water.

 

[fish0281]

I'm not even sure what fan you're talking about, but if you're talking about the cooling fan in the engine bay, then manual. Any time you convert energy from one form to another, there are inherent losses (usually to heat). So if you convert the engine's rotational energy into electricity to power a fan motor, then that'd be less efficient than driving a fan directly from the engine...

 

[ellner357]

I'm not even sure what fan you're talking about, but if you're talking about the cooling fan in the engine bay, then manual. Any time you convert energy from one form to another, there are inherent losses (usually to heat). So if you convert the engine's rotational energy into electricity to power a fan motor, then that'd be less efficient than driving a fan directly from the engine...

I am thinking of the cooling fan. Though I've never heard that theory in regards to this application. Not being an engineer Or really that sharp lol I can't honestly argue more then is it really less efficient because it's drawing on an existing system where the alternator is already producing and feeding the system?

 

[98OzarksRunner]

So I have a long standing debate with my best friend. I though removing a manual fan would technically free up a little hp (no not a lot and not anything you can feel) now he think that's not the case based on the fan being hit and potentially propelled by highway speed wind. Now I am pretty damn sure he's wrong.

On a 3rd Gen 4Runner. Are any of you guys running electric fans? Is it worth it? What fan are you running? Pics if you wanna get fancy lol.

The only reason to run an electic fan on a vehicle like this is cooling efficiency as low speeds (as in off-roading). The factory fan seems to do quite well, as mine has never gone over 200 deg even on the hottest days on the slowest-moving trails. So, I don't think an electric fan is needed on a 3rd gen, unless you are doing something really strange. If I saw that it was even remotely needed on mine, I'd have one right away.

As far as efficiency, if the factory fan were not clutched, then an electric fan that ran only when needed (at idle, stoplights, off-roading) might gain some efficiency overall, but only because a non-clutched fan would be taking engine power at highway speeds. But since the 3rd gen fan is clutched it isn't taking much, if any, power at highway speeds. And the power it takes to run most electric fans is more than it takes to run the clutched factory fan (a Lincoln MkVIII or Taurus fan takes 30-40 amps to run on high speed).

As for the wind turning it, two things come to mind. First, the fan itself won't add much wind resistance since the A/C condensor and radiator probably provide far more wind resistance than the fan blades will. Second, aside from being clutched (which lets it essentially turn free at highway speeds unless it's overheating), the wind will turn the fan (if at all) in the same direction as the engine rotation, thus ADDING eek a TINY amount of energy back into the system (kind of like regenerative braking on hybrids, but on a microscopic scale). In short, I think the only reason to put an electric fan in a 3rd gen is if you had serious overheating issues on the trail, and if you do you probably have something else wrong.

 

[ellner357]

The only reason to run an electic fan on a vehicle like this is cooling efficiency as low speeds (as in off-roading). The factory fan seems to do quite well, as mine has never gone over 200 deg even on the hottest days on the slowest-moving trails. So, I don't think an electric fan is needed on a 3rd gen, unless you are doing something really strange. If I saw that it was even remotely needed on mine, I'd have one right away.

As far as efficiency, if the factory fan were not clutched, then an electric fan that ran only when needed (at idle, stoplights, off-roading) might gain some efficiency overall, but only because a non-clutched fan would be taking engine power at highway speeds. But since the 3rd gen fan is clutched it isn't taking much, if any, power at highway speeds. And the power it takes to run most electric fans is more than it takes to run the clutched factory fan (a Lincoln MkVIII or Taurus fan takes 30-40 amps to run on high speed).

As for the wind turning it, two things come to mind. First, the fan itself won't add much wind resistance since the A/C condensor and radiator probably provide far more wind resistance than the fan blades will. Second, aside from being clutched (which lets it essentially turn free at highway speeds unless it's overheating), the wind will turn the fan (if at all) in the same direction as the engine rotation, thus ADDING eek a TINY amount of energy back into the system (kind of like regenerative braking on hybrids, but on a microscopic scale). In short, I think the only reason to put an electric fan in a 3rd gen is if you had serious overheating issues on the trail, and if you do you probably have something else wrong.

Well I have no issue with overheating and if i did I'd be wondering why as opposed to changing the fan out. I guess I was just working off an uninformed older school of though.

 

[fish0281]

I am thinking of the cooling fan. Though I've never heard that theory in regards to this application. Not being an engineer Or really that sharp lol I can't honestly argue more then is it really less efficient because it's drawing on an existing system where the alternator is already producing and feeding the system?

There will always be energy lost through conversion. It's the same reason your engine creates X amount of power at the crank, but only X-Y power at the wheels. I don't know the number off hand, but even the best systems only convert rotational energy to electricity at like 90% efficiency (on a small scale). So, to put it simply, there's fewer steps in the direct drive fan and thus, less energy lost:

Engine spinning --> Belt --> alternator spinning --> electricity --> fan motor spinning
vs
Engine spinning --> Belt --> Fan spinning


As above said though, an electric could have an advantage if the fan were not clutched... Sorry, I'll stop blabbering on; this sort of stuff is what I went to grad school for though, so I'm sort of into it. :bounce:

 

[ellner357]

There will always be energy lost through conversion. It's the same reason your engine creates X amount of power at the crank, but only X-Y power at the wheels. I don't know the number off hand, but even the best systems only convert rotational energy to electricity at like 90% efficiency (on a small scale). So, to put it simply, there's fewer steps in the direct drive fan and thus, less energy lost:

Engine spinning --> Belt --> alternator spinning --> electricity --> fan motor spinning
vs
Engine spinning --> Belt --> Fan spinning


As above said though, an electric could have an advantage if the fan were not clutched... Sorry, I'll stop blabbering on; this sort of stuff is what I went to grad school for though, so I'm sort of into it. :bounce:

Haha I wouldn't have asked if I didn't want to know. Thanks!

 

[RobD]

Here's what I can tell you about electric fans.

I had a 1991 4Runner, into which I swapped a 3.4 from a 1997 Tacoma.

Drove it like that for several month. Everything was fine and dandy, but I decided to go with an electric fan. Don't ask me the reasoning now. I probably had grandiose ideas of putting a switch on it for water crossings.

Swapped in an electric fan with a Flex a Lite controller. Immediately noticed at least a 5% bump in fuel economy. I went from 400 kms (249 miles for you Americans) per tank of fuel to over 425.

Not much? Nah, but I'll take it. I now own a 1999 Limited and I'll do the same fan conversion, but I'll change to a more sophisticated controller that will bump the fan on when the A/C kicks in, but I'll also be able to kill if I do any water crossings.

 

[ellner357]

Here's what I can tell you about electric fans.

I had a 1991 4Runner, into which I swapped a 3.4 from a 1997 Tacoma.

Drove it like that for several month. Everything was fine and dandy, but I decided to go with an electric fan. Don't ask me the reasoning now. I probably had grandiose ideas of putting a switch on it for water crossings.

Swapped in an electric fan with a Flex a Lite controller. Immediately noticed at least a 5% bump in fuel economy. I went from 400 kms (249 miles for you Americans) per tank of fuel to over 425.

Not much? Nah, but I'll take it. I now own a 1999 Limited and I'll do the same fan conversion, but I'll change to a more sophisticated controller that will bump the fan on when the A/C kicks in, but I'll also be able to kill if I do any water crossings.

Hmmm well 25k a tank adds up really fast. I was getting 400 but now I'm suffering with these 33's when it comes to mpg. Worth it but if I can toss a fan in and still save It's worth thinking about. What fan did you use? What are you thinking you'll use as a controller? Not sure I'm going to do it yet but I'm still on the fence.

 

[twitchee2]

Been there done, that. went back to stock, not worth it. Way more headache then its worth. No noticeable power increases, no noticeable mpg gains. My electric fan caused me to over heat twice because of wiring issues.

If anyone needs more info let me know and ill explain more.

 

[Stick Figure]

Had my electric set up for a LONG time now, 100% trouble free. I never did any scientific test to see about MPG gain, but not needing to buy a new idler bracket from Toyota to retain the stock fan was a good enough reason for me to make the switch on its own.

If you want to see more about it check the first couple of pages of my build thread in my sig.

 

[ellner357]

Been there done, that. went back to stock, not worth it. Way more headache then its worth. No noticeable power increases, no noticeable mpg gains. My electric fan caused me to over heat twice because of wiring issues.

If anyone needs more info let me know and ill explain more.

I wouldn't mind knowing more. I am weighing the pros and cons.

 

[RobD]

Hmmm well 25k a tank adds up really fast. I was getting 400 but now I'm suffering with these 33's when it comes to mpg. Worth it but if I can toss a fan in and still save It's worth thinking about. What fan did you use? What are you thinking you'll use as a controller? Not sure I'm going to do it yet but I'm still on the fence.

And that's being conservative. I would say 25-35 extra kms per tank, sometimes a bit more. I did a pretty consistent mix of city and highway.

My brother works at Lordco in Kelowna and the fan was a knock-off Flex a Lite, not sure what size, but I'd guess a 14" or 16" and the cheapo Flex a Lite controller: Flex-a-lite 31147 Flex-a-lite Adjustable Temp Control Switch

 

[revenantdead]

There will always be energy lost through conversion. It's the same reason your engine creates X amount of power at the crank, but only X-Y power at the wheels. I don't know the number off hand, but even the best systems only convert rotational energy to electricity at like 90% efficiency (on a small scale). So, to put it simply, there's fewer steps in the direct drive fan and thus, less energy lost:

Engine spinning --> Belt --> alternator spinning --> electricity --> fan motor spinning
vs
Engine spinning --> Belt --> Fan spinning


As above said though, an electric could have an advantage if the fan were not clutched... Sorry, I'll stop blabbering on; this sort of stuff is what I went to grad school for though, so I'm sort of into it. :bounce:

with respect, this is backwards. this is exactly why you see many "hot rods" and muscle cars with an electric fan and electric water pump conversions. freeing up the what the crankshaft has to turn via the belts frees up those last little bits of horsepower in the engine. an alternator only provides so much resistance. a 300 amp alternator will spin with the same resistance as a 70 amp. the only difference is the higher output amp has been wired differently to do so. that same 300 amp alternator powers the electric fan instead of the the belt.

 

[02_SE_Runner]

On our 65 Mustang we run an electric fan to free up SOME hp, not a lot though. It sure does help, and nothing wrong with doing it. Our only belt drag we have now is from the ALT, and Water Pump. That's it.

 

[fish0281]

with respect, this is backwards. this is exactly why you see many "hot rods" and muscle cars with an electric fan and electric water pump conversions. freeing up the what the crankshaft has to turn via the belts frees up those last little bits of horsepower in the engine. an alternator only provides so much resistance. a 300 amp alternator will spin with the same resistance as a 70 amp. the only difference is the higher output amp has been wired differently to do so. that same 300 amp alternator powers the electric fan instead of the the belt.

I guess I'm speaking from an overall efficiency perspective - but if you're looking to deliver the *most power to the wheels, then I can see where that could make sense. At the end of the day, they're all parasitic losses and it just depends on what is the cheapest (energy wise) and most effective way to implement towards the end goal.

 

[tee-bone]

with respect, this is backwards. this is exactly why you see many "hot rods" and muscle cars with an electric fan and electric water pump conversions. freeing up the what the crankshaft has to turn via the belts frees up those last little bits of horsepower in the engine. an alternator only provides so much resistance. a 300 amp alternator will spin with the same resistance as a 70 amp. the only difference is the higher output amp has been wired differently to do so. that same 300 amp alternator powers the electric fan instead of the the belt.

Also with respect; although a 300 amp alternator may spin at the same resistance as a 70 amp alternator, that would only be so if they were producing approximately the same power at the time. As soon as the 300 amp alternator is producing more power, it takes more power from the engine to produce it; there is no free lunch when it comes to power production.

This next part is pure theory on my part, so feel free to shoot holes in it. I would wager that electric fans are more efficient because they turn at one of a couple speeds, or within a fairly narrow range. The RPMs on a belt driven fan vary widely, and it is hard to design a fan that is efficient and effective across a wide range of speeds, even with flexible vanes. An electric fan* can be designed to be highly efficient at its low speed; and the vast majority of the time it is on, it will be turning at exactly that low speed.

*the whole assembly, really, including fan, shroud, and electric motor.

 

[fish0281]

You're still spinning the same fan and at the speeds they rotate, the energy requirement really wouldn't vary much. You bring up a good point though, hot rods likely have pretty serious ignition systems and probably have alternators that are capable of creating a lot of juice... so in that particular case, there's likely extra electrical power anyway (at little/no additional loss). Also, if the system has multiple belts and they can ALL be replaced with a single alternator, then you may see an advantage (reduced parasitic losses). Good points you brought up!

Edit: another thought... the alternator's conversion efficiency is related to its power output. So, if it's putting out 100 watts of total energy at 90% efficiency, it has 10 Watts loss. If it puts out 1000 watts at 90% efficiency, then it's losing 100 watts.

 

[98OzarksRunner]

with respect, this is backwards. this is exactly why you see many "hot rods" and muscle cars with an electric fan and electric water pump conversions. freeing up the what the crankshaft has to turn via the belts frees up those last little bits of horsepower in the engine. an alternator only provides so much resistance. a 300 amp alternator will spin with the same resistance as a 70 amp. the only difference is the higher output amp has been wired differently to do so. that same 300 amp alternator powers the electric fan instead of the the belt.

Actually, with respect, there are a couple of things wrong with this. First, a 300 amp alternator and a 70 amp alternator DO require nearly the same amount of power to turn when providing up to 70 amps. The power required to turn an alternator is directly dependent (though not necessarily directly proportional) to the power the alternator is supplying, based on the load. Adding an electric fan that draws 20 amps will require the engine to supply roughly 1 HP to run the fan (roughly since estimates vary based on the efficency of the alternator), regardless of the size of the alternator (70 or 300 amp) - and the alternator is taking that 1 HP from the engine through it's belt. The larger alternator can supply more current, but the amount of power needed to turn the alternator is dependent on the load, not the size of the alternator.

Second, an electric water pump typically does free up a small amount of power but the main reason for using one is that the electric pumps run at the same speed all the time, thus don't cause cavitation and other power-sucking issues at high RPM. It also takes about 1 HP to run one. bangshift tested an electric vs mechanical pump and found there was no difference in power until over 5100 RPM, then the electric pump took less power to run (probably due to cavitation in the mechanical pump). The difference was 7 HP (or a little over 1% gain), and they ran it from a battery. Thus, the mechanical water pump wasn't putting enough load on the engine to even measure until over 5100 RPMs, and the electric pump wasn't taking anything from the engine since there was no alternator. Turning an alternator to power the electric pump probably would have negated any gains and maybe cost more power at lower RPMs. Usually the power gain comes not so much from the pump itself (or the fan) but because the cars that normally use them (looking for every last HP) are drag cars that don't have alterators at all - they power the fan, ignition, and water pump from the battery and make short runs and recharge the battery. On a street car an electric pump is an expensive (start at about $400) thing to brag about but not going to make much difference. But, we are talking about electric fans not pumps.

The main advantage to an electric fan (other than cooling efficiency at low RPMs) is that it only runs when needed (if it is wired correctly). Thus, at highway speeds it's not running and not pulling any current. When compared to older fixed mechanical fans (often found in those muscle cars) that are always turning (and eat power at highway speeds) electric fans do free up some power. When racing (and looking for every last bit of power) the electric fan is off (since we're pushing air through the radiator and don't need a fan) so we don't lose any power to the fan (via the alternator), which results in a little extra power. But compared to a thermostatic clutch fan the overall gains generally aren't much in the 'real world', and they come from running the electric fan only when needed, and due to a slight amount of drag when the clutch fan is disengaged. And it does take more power to generate electricity (turn the alternator) and convert it back to mechanical energy (electric fan) than to directly power the mechanical device (belt-driven fan) but measuring that would be difficult since the fans would have to be identical in size, position, and run at precisely the same speed. The difference wouldn't be much but there will be some (physics 101).