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Electric Cooling Fan CFM Rating Tests - DirtBound Offroad

WebDog

NAXJA Forum User
Location
Center City, MN
Here at DirtBound Offroad we wanted to start putting real numbers behind our products, so to start we ordered a Mannix DCFM 8906 air flow meter. After some trail and error we figured the best way to test the fans, after mounting a fan to a box of 11" x 12" we found the free air value of 0.916. The free air value is needed for the tester to find the CFM.

To get a more accurate result we took 12 measurement points and took the average, min and max CFM. The first test was done with a 10A car battery charger as the power source for the test fan, during this test we measured a voltage of 10.70V.

Please keep this in mind when reading the results, as a Jeep running will be closer to 13.8- 14.4V giving more fan output.

We plan to do a second part using power off of a running Jeep. Stay tuned for other tests on our fans, we plan to do a torture test to see what it actually takes to kill one of our fans. This will include up to two weeks of water spraying into the running fan, sucking up sand and maybe even a submersion test.
The data:

Measure Point / CFM
  1. 1032
  2. 1254
  3. 1321
  4. 1391
  5. 1386
  6. 1179
  7. 1125
  8. 1142
  9. 1207
  10. 1140
  11. 1297
  12. 1247
Average CFM: 1225.75

Min CFM: 1032

Max CFM: 1391

Test Voltage: 10.70V


DSC_0007-293x300.jpg
 
good for you for doing some testing. That voltage is very low and will make a big difference. Try a fully charged battery plus the charger and you'll be closer to regular operating voltage.
 
Thanks for the follow-up from the other thread.

A couple questions for you:

1) What fan is that you are testing? It is not a stock XJ fan and it does not look like one from your three fan set-up.

2) Can you test one of your fans from the three fan set-up? Then we can multiply by 3 to get a good number.

3) Can you test a stock XJ fan for comparison?

John
 
It would be interesting to see the CFM of free air vs mounted to a radiator. Also the CFM of the stock clutch fan and stock electric fan would be great too.

I do plan to test it in place later today. I go the tester yesterday afternoon and was itching to get some numbers.

Thanks for the follow-up from the other thread.

A couple questions for you:

1) What fan is that you are testing? It is not a stock XJ fan and it does not look like one from your three fan set-up.
This is one fan from a kit, it has black duct tape holding it to the box.

2) Can you test one of your fans from the three fan set-up? Then we can multiply by 3 to get a good number.
So far at 10.70V (very low) you are looking at 3,675.75 CFM for the kit.

3) Can you test a stock XJ fan for comparison?
I am going to be testing a stock mechanical fan and electric fan from a 93 HO engine. I also have a 99 available for testing so I will also compare the early electric stock fans with the newer s blade design.

John
 
Old lady surprised me with your electric fan setup earlier this week. Very nice setup, CLEAN, with everything labeled and neatly ran. I may be hitting you guys up for a tranny cooler as well. Will I need any other hoses or fittings with the one listed on your site?
 
Old lady surprised me with your electric fan setup earlier this week. Very nice setup, CLEAN, with everything labeled and neatly ran. I may be hitting you guys up for a tranny cooler as well. Will I need any other hoses or fittings with the one listed on your site?

It should come with everything you need.
 
Thanks for the reply. If the 3 fans are close to the cfm of 2 stock fans I will buy yours. I like the slim design (I have a 5.3L and space is tight) and the fact yours covers more radiator than 2 stock fans do.

thats why i got it, it covers more area than my duel stock 97+ fans did. plus the stock ones don't seem to like yo run constant if needed(at least mine didn't)
the motors would get hot and shut down after about 4hrs straight of running them.
 
I wanted to show how I am measuring the fans, the fan has 12 ribs so that gives 12 reproducible locations to test from.

To calculate the Free Area I used the following calucations:

Square:
Length X Width ÷ 144 = free area

Round:
Radius² x 3.1415 ÷ 144 = free area

I am filling out the below sheet for each test and will make them available online to view also.

More tests later today, but I gotta go build Garret a bumper for his Vanagon!

5520146057_4995bd03b0_b.jpg
 
Interesting. I'm going to be following this.

What amperage was the fan pulling?
 
I do thank dirtbound for giving us some (((REAL WOULD))) numbers and details on how they got them. MUCH better then most of the supplier that IMO use a Cristal ball or to get there numbers
 
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