Cooling fan upgrade comparison: Explorer 11-blade fan and HD clutch versus SPAL 19" 850-watt electric brushless fan

NashvilleTJ said:
Would you get cooler A/C temps if the fan was at max during operation?
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Yes, but there are diminishing returns. That said I do ramp up the fan to max to help cool off the cabin faster on startup.

Effectively, you are supercooling the condensate, meaning that once it passes through the orifice tube, less of it boils immediately and it can absorb more heat in the evaporator. Not really a substitute for increased compressor displacement/RPM, but it does help. It will also help reduce hitting the high pressure limiter in very hot conditions, allowing the compressor to run longer.

Cooler AC was the reason I tried the Explorer fan in the first place. That fan has a negative impact on fuel economy versus stock, but it will definitely allow for colder air. (The SPAL fan does that on demand and seems to save fuel versus cost more.)
 
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Rickyd said:
@freedom_in_4low ?
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Yes, at low vehicle speeds until speed takes over.

It will also be cooler air coming off the condenser and hitting the radiator (because the heat is absorbed by a larger mass of air, so less temperature rise), so the cooling system gets double benefit of both more air, and cooler air.

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The mechanism is that the condenser doesn't have to be quite as far above ambient to reject the heat, so Pcond in the diagram above ends up lower, which moves point 3/3' farther left as it rides down the saturation curve (black), and point 4/4' farther left as a result. Having point 4 to the left means there's more liquid to evaporate, which means more refrigerating capacity.

Shrinking the difference between Pcond and Pevap also reduces the work required from the compressor, which means the engine isn't having to use as much power, and therefore as much heat, to run the AC. This part of it will be tiny, possibly not measurable, but it's there.
 
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Well,

The A/C performance data are in!
In short, higher fan speeds do noticeably and measurably drop the cooled air.

I set up the following test:

Idling in neutral, I varied the fan speed by using a resistor to mimic the lowest fan speed, a pair of resistors to get a sort of "medium" fan speed, and the override switch for maximum speed. All three measurements were taken at an idle RPM of 688. (Note that my idle with AC is tuned lower than most; most TJs idle at 720 RPM with the AC on.) For the "medium" and "high" fan speeds, I also took measurements at 1,400 and 2,000 RPM to simulate driving scenarios. Since a low fan speed would probably be irrelevant at driving speeds, I ignored the low speed. (Also omitted to save my compressor clutch...)

1st, the conditions:
Ambient temperature: 86.0 degrees, relatively high humidity (dew point about 70 deg.)

2nd, the control test:
Duct outlet temperature, A/C off: 97.1 degrees

3rd, the data:

TestLowest SpeedMedium SpeedHighest Speed
Base fan noise frequency:156 Hz339 Hz522 Hz
Estimated fan RPM:850 RPM1,850 RPM2,850 RPM
Power consumption:31 watts236 watts841 watts
Amperage (14.40V)2.1 amps16.4 amps58.4 amps
A/C outlet temperature, idle (688 RPM)61.8 degrees57.7 degrees55.2 degrees
A/C outlet temperature, run (1,400 RPM)Not tested54.5 degrees50.9 degrees
A/C outlet temperature, run (2,000 RPM)Not tested52.1 degrees50.5 degrees
Fake ECT sensor (test resistor) ohms820 ohms451 ohmsN/A
Voltage across fake ECT sensor1.374 voltsNot testedN/A

Notes:
  • High humidity as well as a high starting outlet temperature skew the readings a bit to the hot side. However, the relative values show a consistent trend.
  • I didn't intend to hit the "Medium Speed" RPM exactly between the min/max speed, just got lucky. Note RPM is estimated by taking the loudest frequency tone value in Hertz, and dividing by 11 (the number of fan blades) and multiplying by 60 seconds per minute.
So yes, it turns out higher fan speeds will in fact make things noticeably cooler.
 
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Nice write up! I like electric fans for most driving situations, so I may follow your recipe. My complaint about electric fans in the past has been the binary nature. The variable speed control would be nice!

Factory fan control goes off engine outlet temp, and that makes sense to me. I had a 99 XJ 4.0 and the factory electric fan came on around 220, so I'd start with stetting the fan to come on then, and full speed at 230-240.

Running A/C would turn the fan on, too.

I measured a small mpg improvement removing the mechanical fan. The jeep felt a little quicker, too. I really don't like listening to the mechanical fan in the tj, so that'd be my main motivation for going electric.
 
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NashvilleTJ said:
Great write-up, Steel. Thanks for taking the time. I run a 500 watt 16” SPAL brushless fan in front of the Hemi, and it’s a beast. But an 850 watt 18”? Beast +.

My limitation is the space between the Hemi water pump pulley and the radiator. The SPAL I run is the most powerful fan I could find narrow enough to fit - something like 3 or 3.5 inches.

Do you happen to know how deep the 850 is?
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What fan is that? Any overheating or is it enough?
 
I found that on my stroker, the spal electric wasn’t cutting it with the AC on in high summer temperatures. YMMV, going back to mechanical.
 
srimes said:
What fan is that? Any overheating or is it enough?
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I run the Spal 500W Brushless, and it works very well. It's set up to run variable speed. Out in Moab a few weeks ago, I was running the A/C all day, non-stop, with temps in the high 90's. No issues - and that's with a tranny cooler and a hydro cooler sitting in front of the condenser. Oh yeah, and in front of a 392 Hemi which makes a crazy amount of heat.

This setup draws about 42 amps. But - I'm always looking for projects on this thing, so maybe sometime in the future.... :unsure:
 
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I have to say that after years of reading not to use anything besides the mechanical fan (I understand that was true then and now technological advances have changed things) I am pretty close to pulling the trigger on this brushless thing.
 
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While there is likely a degree of truth to that opinion, it's not the unquestioned fact some people around here liked to sing from the rooftops.
 
NashvilleTJ said:
I run the Spal 500W Brushless, and it works very well. It's set up to run variable speed. Out in Moab a few weeks ago, I was running the A/C all day, non-stop, with temps in the high 90's. No issues - and that's with a tranny cooler and a hydro cooler sitting in front of the condenser. Oh yeah, and in front of a 392 Hemi which makes a crazy amount of heat.

This setup draws about 42 amps. But - I'm always looking for projects on this thing, so maybe sometime in the future.... :unsure:
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It'll be interesting to see how the 300W SPAL does compared to the 500W. Hopefully we'll get to see here in just a short while. I'm running a 180* thermostat too. So other than CID we're pretty close to the same. Mine is a Wizard Cooling radiator too but I don't know if that matters.
 
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Wildman said:
It'll be interesting to see how the 300W SPAL does compared to the 500W. Hopefully we'll get to see here in just a short while. I'm running a 180* thermostat too. So other than CID we're pretty close to the same. Mine is a Wizard Cooling radiator too but I don't know if that matters.
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How long have you had that Wizard cooling rad. on your jeep ? Many have a strong opinion against aluminum rads...but if i go through one more radiator i may just try an aluminum one and maybe Anneal it at the welds since many seem to crack from there, Specifically at the end tanks where the core meets the tank ! Not sure yet since this is pure speculation on seeing if the annealing would help.....
Edit- It seems that company makes a decent fan&shroud kit after looking at it for like 20 seconds 😆
https://wizardcooling.com/i-3050488...bl.html#!year=2005||make=JEEP||model=WRANGLER
 
D's Jeep Wrld said:
How long have you had that Wizard cooling rad. on your jeep ? Many have a strong opinion against aluminum rads...but if i go through one more radiator i may just try an aluminum one and maybe Anneal it at the welds since many seem to crack from there, Specifically at the end tanks where the core meets the tank ! Not sure yet since this is pure speculation on seeing if the annealing would help.....
Edit- It seems that company makes a decent fan&shroud kit after looking at it for like 20 seconds 😆
https://wizardcooling.com/i-30504881-1987-2006-jeep-wrangler-yjtj-brushless-fan-shroud-1010-008bl.html#!year=2005||make=JEEP||model=WRANGLER
Click to expand...

Not long enough yet to offer any opinion as to how it holds up. Hopefully once I get this Hemi running I'll get some tail time and can see how it does.
 
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D's Jeep Wrld said:
How long have you had that Wizard cooling rad. on your jeep ? Many have a strong opinion against aluminum rads...but if i go through one more radiator i may just try an aluminum one and maybe Anneal it at the welds since many seem to crack from there, Specifically at the end tanks where the core meets the tank ! Not sure yet since this is pure speculation on seeing if the annealing would help.....
Edit- It seems that company makes a decent fan&shroud kit after looking at it for like 20 seconds 😆
https://wizardcooling.com/i-30504881-1987-2006-jeep-wrangler-yjtj-brushless-fan-shroud-1010-008bl.html#!year=2005||make=JEEP||model=WRANGLER
Click to expand...

The epoxy doesn’t like heat and most aluminum have the tanks epoxied
 
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So I decided to look up the 300W and 500W fans data to see how they might compare to the 835W fan in performance. (Also, I corrected the exact model of fan in the PDF attachment to the original post.)

Performance data here:
https://www.spalautomotive.com/documents/20182/94723/brushless_catalogue.pdf/

Here is an analytical breakdown:
Given that I am seeing about 58.4 amps running amperage at max RPM (14.25V at the connector), I am likely getting around 2,850 CFM actual through the radiator at full power with a static pressure drop of about 210 Pa. This totals about 325 air watts per the chart.

Adjusting the static pressure drop for the 74% area ratio of the 16" to the 18" fan and the change in air FPM, the 16" fan should get around 1,770 CFM at around 150 Pa. Using the fan affinity laws, assuming the 300W and 500W models are similar designs, the 300W model should get around 1,500 CFM at around 105 Pa.

So that means the bigger fan is getting almost double the airflow of the 300W fan, and about an extra 60% airflow on top of the 500W fan. Also, taking into account the increase in radiator area cooled, and the increase in cooling capacity ends up being quite significant.

If you account for the steady-state heat rejection of the air conditioner, then it becomes even more significant for engine cooling. Let's assume the air conditioner rejects 36,000 BTU/h on high on a very hot day. At a maximum ITD of 50 degrees for all coolers combined, this leaves you with 45,000 BTU/h rejection capacity remaining on the 300W fan. But with the 850 watt fan, you have 118,000 BTU/h of rejection capacity left for the radiator. So even though your airflow didn't quite double, your engine can reject more than 3x as much heat.

118,000 BTU/h is equivalent to about 46 horsepower hours per hour, or simply 46 horsepower. Using the old rule of thumb that heat rejected is about equal to power produced, this means you could burn fuel as fast as you would on the freeway, while parked with the AC on, and still not run out of cooling capacity.
 
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I guess I know what fan I'll be upgrading to if needed.

For the price I should just have one on hand.
 
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