Radiator Fan Test Data

[Bitsyncmaster]

I ran a baseline test with my new test setup today. Takes about 3 hours of work so don't expect the same test with Toby's fans until next weekend.

I'm doing all this just because I find it interesting learning this new stuff. So some of you other engineers may find it interesting. I should be able to compute the CFM rating of the OEM fan with this data. If any of you want to do the calculations pleas do. I took three air speed readings. I plan to compute the fan area in three areas each occupying 1/3 of the fan blade length.

The OEM fan motor gets quite hot running 14 volts. I would not expect it would ever get 14 volts with it's high current draw and voltage drops of the car wiring.

[Bitsyncmaster]

Here is the test data with Toby's fans. One thing I noticed is Toby's fan does not degrade as much as the OEM fans when tested with the radiator in front of the fans. Makes me wonder if the AC condenser was also in front if the CFM would be the same as OEM fans. I guess this is due to the 10 blade design and lower RPM.

Like the OEM fan motor, Toby's gets very hot at 14 volts. I'm going to do some temperature measurements (at 12 volts) and see if I can do something to keep the motor cooler. Both motors are sealed units.

[dmc6960]

Just got to say, love the info.

[Bitsyncmaster]

Here is the data of how the fan motor heats. So the hotter they get, the less CFM you get.

TOBY temperature data
This data was taken with one fan mounted on the OEM shroud. The thermo couple was taped to the back of the motor in a glob of heat sink compound. Looks like I need a better mounting of the thermo couple since when I pushed it to contact the motor my temp readings when up.
Current of the motor decreased when hot because the copper wire resistance goes up with increased temp. The temp and current stabilize when the motor surface area can dissipate any additional heat generated by the input power.
Just goes to show how test data can be skewed. Example: One person comparing fan current is so dependent on how long he ran the test and the room ambient temp.
I could see the advantage to mounting the fans on the front side of the AC/Rad unit to keep the fan motors running cooler and give more CFM and longer life.

[Bitsyncmaster]

I pulled the set of fans (John's) off my car and his shroud is only 3/4" shorter than the OEM shroud. So the EU radiator is longer than the OEM unit. But John's shroud has a very sharp slope on the outer edge and the center where the two shrouds are welded together would also block air flow. John's shroud is very thin (a few inches less than OEM). He even had to grind the nut that holds the fan blade onto the motor shaft to clear the radiator. This means his fan blade is very close to the radiator. My guess would be only the area of the fan blades is where you get air flow through the radiator.

Someone would need to do a cooling test "BTU" to really compare effectivity. I must say when running John's fans, my engine temp would only go up when I was in the mountains climbing a long hill.

[Bitsyncmaster]

Got the Toby fans installed. Turn the key on, then the AC on and.....Fan Fail light flashing. Crawled under the car and sure enough one fan was not running. Spun the fan by hand and it started turning but not much power. Pulled the connector off and attached it to my bench supply and it started turning but only 4 to 5 amps. Let it run about 30 seconds and suddenly it kicked up to 8 amps.

Now it started and stops fine with no Fan Fail light. Will have to see if it ever does that problem again. I suspect one of the brushes was not seated on the commutator very well. At least my Fan Fail light will show me if it acts up again.

[Bitsyncmaster]

That fan is still setting my fan fail. It still starts at around 5 amps and takes about 30 seconds before the current jumps up to 7 amps. From there is seems stable. I may have a defective fan motor but will run it for an hour or two just to seat the brushes.

I will test the other fan to see if it has the same problem.

[Bitsyncmaster]

I doesn't look good. I think I have to pull it out which means pulling the shroud out. My thought is there is oil on the commutator since after it warms up for 30 seconds it then works fine.

[Delorean Industries]

I doesn't look good. I think I have to pull it out which means pulling the shroud out. My thought is there is oil on the commutator since after it warms up for 30 seconds it then works fine.

Would you like to test our set up? We have dual 650 cfm fans mounted to a custom tig welded shroud.

[Bitsyncmaster]

Would you like to test our set up? We have dual 650 cfm fans mounted to a custom tig welded shroud.

That looks like a nice setup but I'm already > $500 invested on fans.