Using PCM to control aftermarket electric radiator fan?

Steel City 06

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So on my long list of tangents, one of the more random things I considered was an electric radiator fan. The advantage of an electric radiator fan isn't necessarily that it is more efficient by itself or that it cools better (in many cases it is actually less efficient or is less powerful for cooling), but that it can be controlled by a computer than can more restrictively select when it is needed.

Most TJs are equipped with a stock belt-driven clutch fan. The fan always spins at low (~20%) of the engine speed when disengaged. When the clutch senses a predetermined air temperature of radiator exhaust, the clutch engages, and the fan begins to spin closer to the speed of the water pump pulley (~80%). This system works well almost all the time; however there is only one input that affects the engagement of the fan, and that is the temperature of the air flowing out of the radiator.

An electric fan is typically controlled by the computer, meaning it can have a wide range of inputs and logic trees, ranging from coolant temperatures, A/C demands, air temperatures, road speeds, and numerous other values. With careful selection of the inputs and logic trees, modest improvements in fuel economy and range can be found. In addition, the fan can also be selectively engaged in scenarios where it may be desirable, such as during high A/C demands at low road speeds.

The 2.4L TJ was equipped with a 2-speed electric fan; the 4.0L got the stock mechanical fan. On the 4.0L Rubicon models, the relay slots otherwise used for the 2.4L electric fan were instead used to drive the locker pumps.

Electric fan conversions are not well-received on this forum for several good reasons.
  1. The kits don't really provide any significant benefit in power, cooling, or fuel economy. Since they are controlled by a single (sometimes two) inputs, they don't have much better control systems than a mechanical clutch fan.
  2. The most commonly used aftermarket kits use cheap parts that don't provide the rated figures, and often don't last very long.
Regarding reason #2, I believe the issue is that TJ owners are buying the cheap but well-advertised bolt-in kits. These primarily include the Flex-A-Lite kit and the Derale kit. The Mishimoto kit might also be on this list; however I haven't found many reviews of it.

Novak offers a shroud/fan kit (FX3300-T) that uses a SPAL fan. SPAL Automotive builds a lot of OEM fans, and sells to the aftermarket on the side. Their fans are known for being OEM-quality and actually produce their rated numbers. Most of their fans are rated not only in open air, but also have performance curves published that show how they perform at increasing pressure drop across the radiator. Most aftermarket fans are rated only in free air, and often have very poor performance given any restriction, hence one of the issues. The SPAL fans are also sealed like OEM, and tend to have fewer service issues.

Regarding reason #1, I'm pretty confident the reason we don't see performance or fuel economy from most electric fan kits is because they are controlled much like a clutch-driven fan, and have only one or two inputs. As such, they are generally set up to turn on very often to be more conservative and avoid risk of overheating. In addition, they cannot be instructed to turn on due to other inputs (e.g., A/C load), so they really don't see the advertised fuel economy and power benefits typically seen in OEM builds.

You could spend major $$$ building a control system for an electric fan that would take into account all of those factors. Ultimately, you may even spend more than the cost of the fuel saved. With enough temperature sensors, maybe an arduino, a PWM controller, and a few other items, you could build a near-flawless control system to maximize engine cooling and A/C performance while simultaneously maximizing fuel economy.


But what if that control system already existed?
Does it???

According to the FSM, all TJs have pinouts on the PCM for a low speed fan module and a high speed fan control.
1626139548151.png


But my PCM is for a 4.0! Surely it doesn't have any programming for an electric fan.
Let's just check the software on VCM Editor...
1626139723402.png

Wait a second...
It does exist!


So looking at the options, you can select between a one-speed, two-speed, and three-speed relay fan, a two-speed PWM fan, a PWM for BLDC motor fans, and a continuously variable PWM fan. And of course you can turn it on and off.

However, changing the fan types does not change the control options in front of us. So we are stuck with the above control logic. But there is quite a lot we can play with here!

1st, we can select up to three independent fan speeds. However, given that we only know two of the pinouts for the relay controlled fan logic, I'm not sure it's going to be feasible to find that 3rd speed.

2nd, we can control when the fan enters those three speeds (plus turning off) based on:
  1. Coolant temperature
  2. Road speed
  3. A/C system pressure
  4. Transmission temperature
If this is possible to use, this could make controlling an electronic fan a whole lot more interesting. You could set it up to maximize A/C cooling, maximize transmission cooling, and/or even fine tune it to a specific coolant temperature range. And best of all, you only have the fan come on when you need it, and only a the speed you need. So you could do all of the above while simultaneously improving the overall efficiency of the system.


My best guess on how to make this work would be to add two pin receivers to the OEM PCM wiring harness (the slots for the 4.0 are empty, but the pins are there on the PCM). The high speed wire (Pin 6) goes to a large relay that turns the fan on, and the low speed wire (Pin 4) goes to a large relay with some sort of speed reducer, maybe a large resistor. Perhaps one of the unlabeled pins is for the 3rd fan speed.


So has anyone ever tried something like this? Thoughts?
 
I'm of the opinion that it's kind of silly to pour this much effort into a non existent issue, but to each their own.

I am, however, curious. You say the pins are present in the PCM. I wonder if the voltage is also present. For instance, if you were to somehow make contact with those two pins while the Jeep was warming up, and watch what temps the PCM throws voltage to each pin. I'd be worried that the computers vary by VIN or something and even though pins are there, they're just dead.
 
I'm of the opinion that it's kind of silly to pour this much effort into a non existent issue, but to each their own.

I am, however, curious. You say the pins are present in the PCM. I wonder if the voltage is also present. For instance, if you were to somehow make contact with those two pins while the Jeep was warming up, and watch what temps the PCM throws voltage to each pin. I'd be worried that the computers vary by VIN or something and even though pins are there, they're just dead.
I think you would have to enable the fan control by flashing the PCM first. By default it is disabled in the PCM software. That said, I'm not sure if it would throw any codes to enable it and have it do nothing, so that could be worth trying.
 
I don't know about the NGC controllers, but the JTECs I have taken apart seem to have many different hardware configurations. There may be no circuitry behind the pins.
It's also worth mentioning the amperage draw when considering electric fans. Some OE fans have 50 plus amp motors. I had a Taurus fan on a car once that had a 75 amp circuit breaker inline. Needless to say my stock alternator that was designed for use with a mechanical fan was not up to the task. It died a horrible death several times.
 
I had FRP Ryan about this but kinda forgot about it. I'd love that have this as an optional instead of (or as a backup to?) my aftermarket fan controller. Good on have you for looking in to it. Jerry's comment was as predictable as it was unhelpful. Ignore that stuff. Jezza makes a good point about the circuitry not being there to support it though. Best thing might be to enable it in the software, wire it up, and see what happens with a test light.
 
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It is indeed possible the programming exists but the hardware doesn't. That's something I'd have to test before trying to set something up.

Another similar example that reminds me of is the PCM alternator charge voltage control. It's set up to adjust based on the output of the battery temperature sensor. But if there is no sensor, it defaults to the worst case scenario and charves at like 13.5 volts, which is a fast way to kill an otherwise good battery, especially an AGM. Fortunately I was able to adjust it to 14.37 volts with very little issue just by altering the slope of the PCM charging voltage via HPTuners.
 
You have me interested. I'm definitely following to see where this goes.

I have done a very similar swap in my 2003 Silverado which appears to work the same way. GM didn't swap to electric fans until 2005, but the high and low speed control pins were present in my 2003's ECU - they just had to be turned on via tuning. I bought an aftermarket harness with relays that pinned into my factory ECU plug for the fan controls.
 
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So in speaking with a representative at SPAL fans and some additional research, I've learned some very good technical information.

Both their brushed and brushless fans are not designed to be speed controlled by reducing the voltage. Reducing the voltage to the fan will result in a shorter fan life. (In addition, you still lose a good amount of power through the resistor.)

Both fans can be speed controlled via Pulse Width Modulation (PWM). However, the process to reduce speed to each of these types is very different.

The brushed fans have no internal speed control. As a result, PWM must be applied to the supply wire at the rated amperage of the fan. So in the case of a PCM-supplied PWM signal, this must be run through a solid state relay of sufficient amperage (the 2003 WJ 4.0 uses one; Dorman 902-310 is one example) to effectively reduce the current running through the fan and modulate its speed without burning up the motor. The PWM frequency must be at least 7kHz.

However, the brushless fans are very different. They have all of their own control electronics. In fact, you do not even need a normal relay to turn the fan on and off. Simply hook up the positive and ground wires straight to the battery. There are two control wires. One of them is labeled A for Analog, and the other E for Electronic. And there are actually quite a few different ways to drive these fans.
  1. Simply hook up a giant relay to the ground wire. Connect the positive wire to the battery. Connect A to positive and E to ground. This is on/off only; there is no speed control.
  2. Simply hook up a giant relay to the positive wire. Ground the ground wire. Connect A to positive and E to ground. This is on/off only; there is no speed control.
  3. Hook positive and ground to the battery. Connect A to positive, and E to any switched source to ground. PCM circuits often ground the pin for the fans, so this would simply turn the circuit on and off. No relay required.
  4. Hook up a giant relay to the positive wire. Ground the ground wire. Connect E to ground. A is now an analog drive circuit that can be varied anywhere from 2-10V to continuously adjust the speed of the fan. Unlimited fan speed options. Above 10V the fan is on high; below 1.5 V it is not spinning, but the controller is still active. A requires 1.8 mA of current max.
  5. Hook up a giant relay to the ground wire. Connect the positive wire to the battery. Connect E to ground. A is now an analog drive circuit that can be varied anywhere from 2-10V to continuously adjust the speed of the fan. Unlimited fan speed options. Above 10V the fan is on high; below 1.5 V it is not spinning, but the controller is still active. A requires 1.8 mA of current max.
  6. Hook positive and ground to the battery. Connect E to a low active enable, such as a switch or PCM terminal. Activate the ground to turn it on. A is now an analog drive circuit that can be varied anywhere from 2-10V to continuously adjust the speed of the fan. Unlimited fan speed options. Above 10V the fan is on high; below 2 V it is not spinning, but the controller is still active. A requires 1.8 mA of current max. No relay required.
  7. Hook positive and ground to the battery. Cap off wire A. Hook up E to the PWM signal. The PWM should be between 50-500Hz, and only needs to supply a tiny amount of current (4.8 mA). As the PWM voltage is modulated between low and high, the fan adjusts its speed accordingly. Unlimited fan speed options. No relay required.
  8. Hook positive and ground to the battery. Hook up E to the PWM signal. The PWM should be between 50-500Hz, and only needs to supply a tiny amount of current (4.8 mA). As the PWM voltage is modulated between low and high, the fan adjusts its speed accordingly. Unlimited fan speed options. A is now an analog drive circuit that can be varied anywhere from 2-10V to continuously adjust the speed of the fan. Unlimited fan speed options. Above 10V the fan is on high; below 1.5 V it is not spinning, but the controller is still active. A requires 1.8 mA of current max. No relay required. PWM always takes priority over analog.
So in summary, if the PCM or any controller has a way to either provide a PWM signal or some sort of modulated voltage, the fan can be adjusted to any desired speed between 25-100%. And no relay or controller is required, unlike all of the other aftermarket fan options. Even if the PCM just has an on-off signal, it can easily be used to switch the fan with no relay or any other form of control required.

The SPAL brushless fan 30107101 also happens to be their highest performing fan, rated at over 2400 CFM installed. Some of the cheaper brands do advertise CFM ratings near this number, but those values are taken in free air, and the actual installed values are far lower. In addition, the SPAL brushless fans are rated to between 10,000-40,000 hours of operation depending upon use. So even in the worst case scenario you would have to put like 500,000+ miles on your jeep before you kill the fan. The brushed fans are rated from 5,000-10,000 hours of operation, which is still a 250,000-500,000 mile lifetime. The brushless fans are also very efficient, and the 30107101 only takes about 30-32 amps at full power. The best performing brushed fan takes closer to 36 amps at full power, at around 2100 CFM.


As for the jeep PCM, I am still trying to figure out what it is capable of. At some point I am going to load a few different tunes and see if I can pick out some relay grounds or PWM signals. Based on what I've seen online, it is very common for PCMs to have the hardware and software to run fans, but just have it be disabled by the stock tune.
 
So in speaking with a representative at SPAL fans and some additional research, I've learned some very good technical information.

Both their brushed and brushless fans are not designed to be speed controlled by reducing the voltage. Reducing the voltage to the fan will result in a shorter fan life. (In addition, you still lose a good amount of power through the resistor.)

Both fans can be speed controlled via Pulse Width Modulation (PWM). However, the process to reduce speed to each of these types is very different.

The brushed fans have no internal speed control. As a result, PWM must be applied to the supply wire at the rated amperage of the fan. So in the case of a PCM-supplied PWM signal, this must be run through a solid state relay of sufficient amperage (the 2003 WJ 4.0 uses one; Dorman 902-310 is one example) to effectively reduce the current running through the fan and modulate its speed without burning up the motor. The PWM frequency must be at least 7kHz.

However, the brushless fans are very different. They have all of their own control electronics. In fact, you do not even need a normal relay to turn the fan on and off. Simply hook up the positive and ground wires straight to the battery. There are two control wires. One of them is labeled A for Analog, and the other E for Electronic. And there are actually quite a few different ways to drive these fans.
  1. Simply hook up a giant relay to the ground wire. Connect the positive wire to the battery. Connect A to positive and E to ground. This is on/off only; there is no speed control.
  2. Simply hook up a giant relay to the positive wire. Ground the ground wire. Connect A to positive and E to ground. This is on/off only; there is no speed control.
  3. Hook positive and ground to the battery. Connect A to positive, and E to any switched source to ground. PCM circuits often ground the pin for the fans, so this would simply turn the circuit on and off. No relay required.
  4. Hook up a giant relay to the positive wire. Ground the ground wire. Connect E to ground. A is now an analog drive circuit that can be varied anywhere from 2-10V to continuously adjust the speed of the fan. Unlimited fan speed options. Above 10V the fan is on high; below 1.5 V it is not spinning, but the controller is still active. A requires 1.8 mA of current max.
  5. Hook up a giant relay to the ground wire. Connect the positive wire to the battery. Connect E to ground. A is now an analog drive circuit that can be varied anywhere from 2-10V to continuously adjust the speed of the fan. Unlimited fan speed options. Above 10V the fan is on high; below 1.5 V it is not spinning, but the controller is still active. A requires 1.8 mA of current max.
  6. Hook positive and ground to the battery. Connect E to a low active enable, such as a switch or PCM terminal. Activate the ground to turn it on. A is now an analog drive circuit that can be varied anywhere from 2-10V to continuously adjust the speed of the fan. Unlimited fan speed options. Above 10V the fan is on high; below 2 V it is not spinning, but the controller is still active. A requires 1.8 mA of current max. No relay required.
  7. Hook positive and ground to the battery. Cap off wire A. Hook up E to the PWM signal. The PWM should be between 50-500Hz, and only needs to supply a tiny amount of current (4.8 mA). As the PWM voltage is modulated between low and high, the fan adjusts its speed accordingly. Unlimited fan speed options. No relay required.
  8. Hook positive and ground to the battery. Hook up E to the PWM signal. The PWM should be between 50-500Hz, and only needs to supply a tiny amount of current (4.8 mA). As the PWM voltage is modulated between low and high, the fan adjusts its speed accordingly. Unlimited fan speed options. A is now an analog drive circuit that can be varied anywhere from 2-10V to continuously adjust the speed of the fan. Unlimited fan speed options. Above 10V the fan is on high; below 1.5 V it is not spinning, but the controller is still active. A requires 1.8 mA of current max. No relay required. PWM always takes priority over analog.
So in summary, if the PCM or any controller has a way to either provide a PWM signal or some sort of modulated voltage, the fan can be adjusted to any desired speed between 25-100%. And no relay or controller is required, unlike all of the other aftermarket fan options. Even if the PCM just has an on-off signal, it can easily be used to switch the fan with no relay or any other form of control required.

The SPAL brushless fan 30107101 also happens to be their highest performing fan, rated at over 2400 CFM installed. Some of the cheaper brands do advertise CFM ratings near this number, but those values are taken in free air, and the actual installed values are far lower. In addition, the SPAL brushless fans are rated to between 10,000-40,000 hours of operation depending upon use. So even in the worst case scenario you would have to put like 500,000+ miles on your jeep before you kill the fan. The brushed fans are rated from 5,000-10,000 hours of operation, which is still a 250,000-500,000 mile lifetime. The brushless fans are also very efficient, and the 30107101 only takes about 30-32 amps at full power. The best performing brushed fan takes closer to 36 amps at full power, at around 2100 CFM.


As for the jeep PCM, I am still trying to figure out what it is capable of. At some point I am going to load a few different tunes and see if I can pick out some relay grounds or PWM signals. Based on what I've seen online, it is very common for PCMs to have the hardware and software to run fans, but just have it be disabled by the stock tune.
Awesome info! I look forward to hearing what you find in your experimenting.
 
I had a 99 XJ, which comes with a mechanical and electric fan controlled by the computer. I ditched the mechanical and added a 2nd electric from another XJ. Worked great.

I don't know how different the TJ and XJ ecms are, but it wouldn't surprise me if the TJs had the vestigial capability. Or if you could swap an XJ 'puter into the TJ.
 
I did learn that the WJ 4.0 also had an electric fan. The pre-2003 WJs used PWM fed through a solid-state relay to reduce the fan speeds to any number of predetermined speeds. However, the relay was very prone to failure, so for 2003 and 2004 models it was ditched in favor of the two-relay fan that the 2.4L TJs have.

That's the information that makes me hopeful that the TJ PCM might be PWM-capable.
 
One thing I need to find out is if the 2.4L TJ and/or the 03-04 WJ used two fan speeds or three. I have found no definitive answer on this.

There are in fact only two relays for both, but two relays have a total of four possible combinations, and sometimes that is used to drive three speeds on fans (the 4th being "off").

Some three-wire fans will run at a medium speed if both the high and low speed wires are energized. As to if that is by design I really don't know.
 
So in speaking with a representative at SPAL fans and some additional research, I've learned some very good technical information.

Both their brushed and brushless fans are not designed to be speed controlled by reducing the voltage. Reducing the voltage to the fan will result in a shorter fan life. (In addition, you still lose a good amount of power through the resistor.)

Both fans can be speed controlled via Pulse Width Modulation (PWM). However, the process to reduce speed to each of these types is very different.

The brushed fans have no internal speed control. As a result, PWM must be applied to the supply wire at the rated amperage of the fan. So in the case of a PCM-supplied PWM signal, this must be run through a solid state relay of sufficient amperage (the 2003 WJ 4.0 uses one; Dorman 902-310 is one example) to effectively reduce the current running through the fan and modulate its speed without burning up the motor. The PWM frequency must be at least 7kHz.

However, the brushless fans are very different. They have all of their own control electronics. In fact, you do not even need a normal relay to turn the fan on and off. Simply hook up the positive and ground wires straight to the battery. There are two control wires. One of them is labeled A for Analog, and the other E for Electronic. And there are actually quite a few different ways to drive these fans.
  1. Simply hook up a giant relay to the ground wire. Connect the positive wire to the battery. Connect A to positive and E to ground. This is on/off only; there is no speed control.
  2. Simply hook up a giant relay to the positive wire. Ground the ground wire. Connect A to positive and E to ground. This is on/off only; there is no speed control.
  3. Hook positive and ground to the battery. Connect A to positive, and E to any switched source to ground. PCM circuits often ground the pin for the fans, so this would simply turn the circuit on and off. No relay required.
  4. Hook up a giant relay to the positive wire. Ground the ground wire. Connect E to ground. A is now an analog drive circuit that can be varied anywhere from 2-10V to continuously adjust the speed of the fan. Unlimited fan speed options. Above 10V the fan is on high; below 1.5 V it is not spinning, but the controller is still active. A requires 1.8 mA of current max.
  5. Hook up a giant relay to the ground wire. Connect the positive wire to the battery. Connect E to ground. A is now an analog drive circuit that can be varied anywhere from 2-10V to continuously adjust the speed of the fan. Unlimited fan speed options. Above 10V the fan is on high; below 1.5 V it is not spinning, but the controller is still active. A requires 1.8 mA of current max.
  6. Hook positive and ground to the battery. Connect E to a low active enable, such as a switch or PCM terminal. Activate the ground to turn it on. A is now an analog drive circuit that can be varied anywhere from 2-10V to continuously adjust the speed of the fan. Unlimited fan speed options. Above 10V the fan is on high; below 2 V it is not spinning, but the controller is still active. A requires 1.8 mA of current max. No relay required.
  7. Hook positive and ground to the battery. Cap off wire A. Hook up E to the PWM signal. The PWM should be between 50-500Hz, and only needs to supply a tiny amount of current (4.8 mA). As the PWM voltage is modulated between low and high, the fan adjusts its speed accordingly. Unlimited fan speed options. No relay required.
  8. Hook positive and ground to the battery. Hook up E to the PWM signal. The PWM should be between 50-500Hz, and only needs to supply a tiny amount of current (4.8 mA). As the PWM voltage is modulated between low and high, the fan adjusts its speed accordingly. Unlimited fan speed options. A is now an analog drive circuit that can be varied anywhere from 2-10V to continuously adjust the speed of the fan. Unlimited fan speed options. Above 10V the fan is on high; below 1.5 V it is not spinning, but the controller is still active. A requires 1.8 mA of current max. No relay required. PWM always takes priority over analog.
So in summary, if the PCM or any controller has a way to either provide a PWM signal or some sort of modulated voltage, the fan can be adjusted to any desired speed between 25-100%. And no relay or controller is required, unlike all of the other aftermarket fan options. Even if the PCM just has an on-off signal, it can easily be used to switch the fan with no relay or any other form of control required.

The SPAL brushless fan 30107101 also happens to be their highest performing fan, rated at over 2400 CFM installed. Some of the cheaper brands do advertise CFM ratings near this number, but those values are taken in free air, and the actual installed values are far lower. In addition, the SPAL brushless fans are rated to between 10,000-40,000 hours of operation depending upon use. So even in the worst case scenario you would have to put like 500,000+ miles on your jeep before you kill the fan. The brushed fans are rated from 5,000-10,000 hours of operation, which is still a 250,000-500,000 mile lifetime. The brushless fans are also very efficient, and the 30107101 only takes about 30-32 amps at full power. The best performing brushed fan takes closer to 36 amps at full power, at around 2100 CFM.


As for the jeep PCM, I am still trying to figure out what it is capable of. At some point I am going to load a few different tunes and see if I can pick out some relay grounds or PWM signals. Based on what I've seen online, it is very common for PCMs to have the hardware and software to run fans, but just have it be disabled by the stock tune.
Or, run a mechanical thermostat and a viscous clutch and drive on…
 
Or, run a mechanical thermostat and a viscous clutch and drive on…
That is one option.

The primary goal here would be to get the high airflow of the 11-blade Explorer fan and clutch at idle and low speeds without sacrificing engine power and fuel economy at higher engine and higher road speeds.

Thus you can boost the performance of the A/C without it hurting something else.

In addition, this is a mod that would eventually pay for itself. A typical clutch fan uses about 4 hp on average (a lot more when locked and a good amount less when unlocked). So let's do that math:
4 hp = 10,200 btu/h power
Assume 30% thermodynamic engine efficiency
33,920 btu/h gasoline
At 116,090 btu/gallon of gasoline
0.292 gallons per hour
Assume 100,000 miles remaining vehicle life at an average of 50 mph
2,000 hours of operation
584 gallons of gasoline burned for clutch fan
Assume gas is $3.50/gallon
$2,045 in gasoline is required to run the clutch fan.

Next, the electric fan:
Upfront costs
Shroud $100
SPAL 30107101: $300
A few random wires: $10

Assume fan is PCM controlled and only engaged when needed by coolant, A/C, or trans temperatures. Assume fan is 2-speed.
Average current draw: 8 amps (32 at max power, 4 amps at half power, 0 amps off). Note that per the fan affinity laws, power increases with the cube of shaft speed. Shaft speed and flow are linearly related. Amperage rated at 13V.
Alternator efficiency: 50% (typically closer to 60%)
Engine HP to run fan:
0.278 HP
= 709 btu/h engine power
= 2,364 btu/h gasoline
= 0.0204 gallons per hour
At 100,000 miles at 50 mph average:
40.7 gallons of gasoline
$142 to run fan
Add in the installation costs, and you're at $552 total to install and run the electric fan.

Even if you assume the clutch fan uses less than a third of what I did you still end up saving money.

But even if you're not concerned about the money, there are several other distinct advantages to the electric fan:
1. Frees up horsepower at higher speeds
2. Engages based on A/C demand
3. Can be easily "tuned" to increase or decrease cooling based on various inputs like road speed, ECT, A/C pressure, transmission temperature
4. Can be manually turned on or off if appropriately wired for user control and for water crossings
5. Slightly increased range
6. Less risk of punching a fan through the radiator in a collision or off-road impact

That said, the MPG gains are going to be small and probably not noticeable on a day to day basis. Assuming a 15 gallon tank fill cycle (19 gallon tank with 4 gallons reserve) and 13 mpg, you would see about a 1 mpg gain (to 14 mpg) and about a 15 mile increase in range.

Note, to calculate the MPG gain you must convert both units to gallons per mile and back. So in this case it is MPG = 1/(1/13 - .290/50).
 
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That is one option.

The primary goal here would be to get the high airflow of the 11-blade Explorer fan and clutch at idle and low speeds without sacrificing engine power and fuel economy at higher engine and higher road speeds.

Thus you can boost the performance of the A/C without it hurting something else.

In addition, this is a mod that would eventually pay for itself. A typical clutch fan uses about 4 hp on average (a lot more when locked and a good amount less when unlocked). So let's do that math:
4 hp = 10,200 btu/h power
Assume 30% thermodynamic engine efficiency
33,920 btu/h gasoline
At 116,090 btu/gallon of gasoline
0.292 gallons per hour
Assume 100,000 miles remaining vehicle life at an average of 50 mph
2,000 hours of operation
584 gallons of gasoline burned for clutch fan
Assume gas is $3.50/gallon
$2,045 in gasoline is required to run the clutch fan.

Next, the electric fan:
Upfront costs
Shroud $100
SPAL 30107101: $300
A few random wires: $10

Assume fan is PCM controlled and only engaged when needed by coolant, A/C, or trans temperatures. Assume fan is 2-speed.
Average current draw: 8 amps (32 at max power, 4 amps at half power, 0 amps off). Note that per the fan affinity laws, power increases with the cube of shaft speed. Shaft speed and flow are linearly related. Amperage rated at 13V.
Alternator efficiency: 50% (typically closer to 60%)
Engine HP to run fan:
0.278 HP
= 709 btu/h engine power
= 2,364 btu/h gasoline
= 0.0204 gallons per hour
At 100,000 miles at 50 mph average:
40.7 gallons of gasoline
$142 to run fan
Add in the installation costs, and you're at $552 total to install and run the electric fan.

Even if you assume the clutch fan uses less than a third of what I did you still end up saving money.

But even if you're not concerned about the money, there are several other distinct advantages to the electric fan:
1. Frees up horsepower at higher speeds
2. Engages based on A/C demand
3. Can be easily "tuned" to increase or decrease cooling based on various inputs like road speed, ECT, A/C pressure, transmission temperature
4. Can be manually turned on or off if appropriately wired for user control and for water crossings
5. Slightly increased range
6. Less risk of punching a fan through the radiator in a collision or off-road impact

That said, the MPG gains are going to be small and probably not noticeable on a day to day basis. Assuming a 15 gallon tank fill cycle (19 gallon tank with 4 gallons reserve) and 13 mpg, you would see about a 1 mpg gain (to 14 mpg) and about a 15 mile increase in range.

Note, to calculate the MPG gain you must convert both units to gallons per mile and back. So in this case it is MPG = 1/(1/13 - .290/50).
I think my brain just sploded…

Great info in this thread, Dude. I always enjoy learning the detail on how things work.