Figured since I have tried both with success, I would post a brief overview and review/comparison of these cooling fan options for anyone looking for something bigger than stock.
Option 1: Explorer 11-blade fan and HD Clutch
This option consists of swapping the stock mechanical fan and clutch with one out of a Ford Explorer. Like the OEM fan, it simply spins onto the water pump, and the clutch acts just like an OEM clutch, though it is more sensitive. For this you only need two parts:
To install, simply remove the OEM fan and clutch, and install the new fan and clutch. Note that the Motorcraft fan will NOT bolt onto a TJ fan clutch, as the bolt pattern is different. However, the water pump stud thread is the same, hence why you can swap the fan clutches.
Generally, no modifications are needed on the fan shroud. If you have a body lift, check for clearance. The fan is the same diameter as the OEM fan (and I think a bit lower profile) so if your OEM fan works, the Explorer fan will probably work as well. Since the Explorer fan is plastic, it's actually easier to remove and re-install since it is a bit flexible. I've found I can fish the fan and clutch assembly out from between the fan shroud and engine without removing anything else.
Option 2: 19" SPAL OEM Brushless fan, rated at 850 watts / 4,000 CFM (~3,000 CFM installed)
This option involves taking the OEM cooling fan out of a late model Chevrolet Camaro (~2018-ish) and installing it in the OEM fan shroud in place of the stock clutch fan and wiring up a control system to run it. For this you will need a number of parts:
My thoughts:
Option 1: Explorer 11-blade fan and HD Clutch
This option consists of swapping the stock mechanical fan and clutch with one out of a Ford Explorer. Like the OEM fan, it simply spins onto the water pump, and the clutch acts just like an OEM clutch, though it is more sensitive. For this you only need two parts:
- HD Fan Clutch: I used Hayden 2794; any "heavy duty" clutch from a 2001 Ford Explorer will do.
- 11-blade fan assembly: I used the Motorcraft part, but there are aftermarket options that are pretty good as well, such as this Dorman part.
To install, simply remove the OEM fan and clutch, and install the new fan and clutch. Note that the Motorcraft fan will NOT bolt onto a TJ fan clutch, as the bolt pattern is different. However, the water pump stud thread is the same, hence why you can swap the fan clutches.
Generally, no modifications are needed on the fan shroud. If you have a body lift, check for clearance. The fan is the same diameter as the OEM fan (and I think a bit lower profile) so if your OEM fan works, the Explorer fan will probably work as well. Since the Explorer fan is plastic, it's actually easier to remove and re-install since it is a bit flexible. I've found I can fish the fan and clutch assembly out from between the fan shroud and engine without removing anything else.
Option 2: 19" SPAL OEM Brushless fan, rated at 850 watts / 4,000 CFM (~3,000 CFM installed)
This option involves taking the OEM cooling fan out of a late model Chevrolet Camaro (~2018-ish) and installing it in the OEM fan shroud in place of the stock clutch fan and wiring up a control system to run it. For this you will need a number of parts:
- GM Genuine 158927 Cooling Fan, from a 6.2L V8 Supercharged 2016-2020 Camaro. (Note: Don't get the newer part number 85516898 from the 2021+ Camaro - it is exactly the same but has a different control system I could not figure out.) This fan is brushless and has an integral controller. It simply wires to the battery (with an 80 amp fuse and 8ga wire), and will operate at whatever speed a controller tells it at, anywhere from ~5% to 100%.
- Lingenfelter VSFM-002 PWM Fan Controller. This is one of the only fan controllers outside of a ECM that can operate an OEM SPAL fan to its full capabilities. Basically, you wire it to a coolant temperature sensor, set min/max temperatures, and it sends a PWM signal to the fan telling it to run at a particular speed between roughly 5-100%. Unlike a thermostat, this controller is continuously variable and will tell the SPAL fan to run at exactly the speed commanded based on the temperature value between the min and max temperature you set. At the max temperature, the fan runs at 100%. At the min temperature, the fan runs at 5%. If you are 1/3rd the way to the max temperature for the min, it will run the fan at 33%.
- GM 213-928 Temperature sensor and PT1798 Pigtail. This temperature sensor will drive the PWM fan controller. It might be possible to run the fan on the ECT sensor already installed; however, for maximum efficiency it is much better to install a separate sensor on the radiator coolant outlet, since it will measure the efficiency of the radiator at any given time.
- Coolant hose adapter for temperature sensors - Must be 1.5" barb and have a 3/8" NPT fitting for the GM temperature sensor.
- Remove your OEM fan and clutch. Remove the shroud as well and retain for the next step.
- Cut the GM OEM shroud down to the diameter of the TJ OEM shroud, and secure the fan shroud inside the TJ's shroud. The GM fan supports should be about flush with the OEM TJ shroud. Be VERY careful not to nick the fan. Any interference or imbalance will cause major issues. I chose to unbolt the fan and pull it out of the GM shroud while I cut just to be safe. Note if you do this, the three bolts holding the fan into the shroud can fall back inside the fan hat and are VERY hard to re-insert.
- Install the modified fan/shroud assembly back in. Verify clearance to the water pump stud.
- Install the coolant temperature sensor and adapter into the radiator outlet hose. Note you specifically want the radiator outlet, aka the lower hose. The reason for this is that you want the sensor to measure when more airflow is needed for cooling, and not simply measure the amount of heat being rejected. When you're driving at freeway speeds, you're already putting 8,000 or more CFM through the radiator, so there is no point in burning gas to spin a fan that can only push 4,000 CFM.
- Wire the sensor and fan control wire to the Lingenfelter controller. Follow the instructions for setting the dials and dip switches. I recommend starting the "Min" temperature at about 130F and the "max" at 190F.
- 190F is a good target for the max, because if the thermostat is fully open, at full throttle steady state conditions, you will have 20-25F of temperature rise across the engine, thus you will need 20-25F of temperature drop across the radiator. Assuming the thermostat is fully open at 210F, you you would ideally want a target outlet temperature of no more than 195 degrees on the return. Set this value any lower, and you will simply waste energy overcooling the coolant, and the thermostat will close a bit, so no additional heat will be rejected. So there is no gain whatsoever in setting this below 180F.
- 130F is my recommended target for the min, but you can (and should) play with this. The goal (at least in regards to efficiency) is to set this to the highest temperature you can without resulting in the fan and thermostat cycling as they fight one another. I found at 150F, the fan controller would result in oscillations in the fan speed and coolant temperature at idle, but at 130F, these oscillations were minimal if non-existent. 140F also seems to be a decent balance, and might work well in hotter climates. Note that your coolant temperature at the radiator outlet will naturally be far lower than the engine operating temperature when the thermostat is partially open, especially when you have massive airflow like you would at freeway speeds. So if set correctly, your cooling fan should not turn on above about 40 mph during steady-state conditions.
- I also recommend wiring the controller to two switches. One switch is for your ignition wire that tells the unit to turn on. I put this on a switch with a green LED, and this switch is generally on all the time. Thus, when the ignition is switched on, the fan controller switches on (as long as this switch is on). The fan will not come on until it sees hot coolant flowing through the radiator, so it will not run unless the engine is on and fully warmed up. When you shut the engine off but leave the ignition on, the fan may run for a short period until it cools the radiator long enough to shut down. This switch is optional, but recommended as you can disable the fan entirely.
- The second switch is a "max speed enable" for the fan, that you will normally leave off. If the controller is on (ignition on and other switch on) and you turn on this switch the controller ramps up the fan speed to the max, ignoring the temperature sensor data altogether. This is useful for testing, and for select use cases like wanting maximum A/C at idle or wanting to cool off the engine bay.
My thoughts:
- The SPAL OEM fan moves a LOT more air at max speed than the Explorer fan moves at idle (clutch engaged). However, I would qualitatively guess that the thoroughput is similar at about 1,500 engine RPM. The SPAL fan is rated at around 4,000 CFM with the static pressure of a typical radiator/condenser at full fan speed (2,800 RPM). So at idle, the SPAL fan certainly has more airflow, probably more than is needed. Above about 2,000 RPM, the Explorer fan seems to dominate when engaged, though it is pretty rare the clutch is engaged at 2,000+ engine RPM for more than a few seconds.
- The SPAL fan is certainly way less of a drag on the engine when it is running compared to when the Explorer fan is engaged. When the Explorer fan is engaged, the differences above 3,000 RPM are quite noticeable, and at 5,000 RPM, the difference of engaged vs disengaged is drastic. The drag from the SPAL fan is far less, and generally not noticeable. Given that the SPAL fan consumes about 850 watts at full power, you're looking at about a 2 HP loss through the alternator (assuming ~55% efficiency) when the fan is at full power, which is almost never the case. If we assume that the power draw of the Explorer fan is about 1 horsepower at 1,500 RPM (~750 watts mechanical), using the fan affinity laws, this would mean a loss of 8 HP at 3,000 RPM and 27 HP at 4,500 RPM (extremely rough numbers, but you get the point). However, the fan clutch is normally rarely engaged at normal road speeds for more than a few seconds after starting from a stopped state.
- The Explorer fan always has some power draw when the clutch is not engaged (20% RPM is a good assumption), and most (~80%) of this energy is converted to heat in the fan clutch. When the clutch is engaged (~80% water pump RPM), 80% of the energy goes into moving air, and only 20% is lost as heat. However, in accordance with the fan affinity laws, the fan blades consume 64x the energy since the shaft speed has quadrupled. Thus, the power consumption of the Explorer fan/clutch combination is about 16x the value when engaged vs disengaged.
- The SPAL fan has near-zero power draw when not turned on. Probably on the order of 10 watts is all that is needed to idle the controller and fan electronics. At power off, the current is generally nearly non-existent. As the fan ramps up, the current does not follow a linear curve, but instead a seemingly parabolic curve. So even at low to mid speeds, then fan is only using a small portion of its max wattage. The SPAL fan also has much more efficient blade design, but also moves less air per revolution, and thus has to spin a bit faster than the Explorer fan. However, to move the same amount of air, the overall energy consumption (from a fuel standpoint) is pretty much the same. The big advantage of the SPAL fan is that it only spins when needed, and only as much as needed.
- The Explorer fan is certainly way less complex and cheaper upfront. However, the long-term fuel costs associated with the Explorer fan will more than certainly cause the overall lifetime cost to exceed the SPAL fan lifetime cost.
- Both make a big difference in A/C performance. The SPAL fan is better for this since it can be engaged manually, and moves more airflow at idle.
- Even when not engaged, the Explorer fan/clutch does seem to slow down how quickly the engine can rev up.
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