Radiator Fan Test Data

[Bitsyncmaster]

I'm installing a new EU radiator and thought it's a good time to test the fans. I have the Special T fans from John and my set of OEM fans which I can run on my same test setup for compare numbers.

OEM radiator is 194 oz. EU one is 118 oz.
OEM unit is 1.257" thick. EU one is 1.681"

I think the thicker EU radiator is the reason it's almost the same air flow as the denser fins on the OEM radiator.

[Mark D]

While I don't doubt that you'll be able to compare air flow between the fans using the setup you're showing, there is quite a bit more to how the fan will actually perform related to cooling performance...

Distance of the fan leading edge to the core as well as immersion distance of the fan into the shroud will affect how many BTU's the fan will be able to pull from the radiator in a real world scenario. If the fan mounting distances change between the various aftermarket fan vendors then this will change one or more of these parameters. We routinely do cooling performance tests on our heavy duty trucks where I work, and changing the core separation distance by as little as 1/4" can have a drastic impact on the performance of the overall cooling package. Same is true for fan immersion depth into the shroud.

So for example:
Even if an aftermarket fan "Brand A" can pull X more cubic feet per minute of air through an open tube than Brand B, Brand A's performance at pulling heat from the radiator may actually be less than Brand B's if the arrangement of Brand B's fan/shroud mounting is more optimal than Brand A.

[Bitsyncmaster]

I completely agree this is not a test of cooling capacity. That would be more involved than I want to set up.

The radiator is bolted right to the fan shroud that is used in the car. So your first concern is not a problem.

Anyway here is the OEM fan test data.

[Exolis]

This is Fan-tastic!

Though I am curious as how Cooling performance would actually differ from the two. I would love to borrow a Datalogger from work one weekend and stick some thermocouples around, or just monitor temp sensor voltage, or just ask HVAC department how they test this kinda stuff. However this would also require new fans lol.

[Bitsyncmaster]

I did the no radiator test just to show the difference in current the fan draw.

As far as cooling, maybe the slower velocity has better cooling. I'm not a thermodynamics engineer.

The real test is running the car, knowing what your temp gauge reads and then change the fans or radiator and note if that temp gauge changes.

[Elvis]

Hi Dave,

just want to let you know some theory about fans.

Airflow V is proportional to fan speed.

V2 / V1 = n2 / n1

( V = Airflow, n = speed in rpm)

power consumption is:

P2 / P1 = (V2 / V1) ³ !!!!!

P1 = power at lower airflow (new fan)
P2 = power at higher airflow ( OEM fan)

(1130 / 800)³ = 2.8 !

P2 = 2.8 * P1 !!!!


Open for discussion. ( the formula is science, not invented by me
after some cans of beer)

[Bitsyncmaster]

Here is the same test run with a Toby fan. I must say these fans are really nicely built. These must be a custom made fan just for Toby.

[Bitsyncmaster]

I forgot to post that the OEM fan blade and motor is 47 oz. and Toby's fan blade and motor is 37 oz. I may just for kicks try to fit the fan blade off John's fans to Toby's motor and run the test like that. I'm just curious of the difference the four blade design compares with Toby's high blade count fan.

[Bitsyncmaster]

I've decided to buy an new fan shroud. My old one is undercoated, has a chip in it and I want to keep playing with fan testing. I should have ordered the fans on a new shroud which Toby offers. Anyway, I'm making some modifications to my test setup. Think I will bolt my 4 foot test tunnel to the shroud (it's taped on now). I'm looking to buy a hot wire anemometer to get more consistent air speeds. I want to test if air temp and air density (humid) air makes any differences.

I still have one original OEM fan and motor to keep everything referenced to that standard.

[Bitsyncmaster]

Got my hot wire anemometer. I could not get stable reading via the 4 foot tube. It must make to much turbulence. So I tested at a half inch from the fan blades and that looks more stable. It's actually pretty good over ends and near the hub but best flow at center of blade. Here is my first set of new data. I also measured the fan RPM.

[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.

[Bitsyncmaster]

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

I would be willing to run the same testing I did on the OEM and Toby fans if you would like the data.

Now I know we need to do a cold power test. You would not want that fan problem I have if your AC is cycling the fans.

I've been running the bad fan for about another hour. I will let it run another hour and see if there is any improvement when I test it tomorrow.

[Elvis]

Nice infos Dave.

Are you sure the new fans are still brushed fans ?


comparing your measurements tells me what I always thought.
The new fans are not as strong as the OEM ones !

The difference in airflow is only 15%.
but 1.15³= 1,5 -> to get Tobys fans up to the same airflow they would need
50% more power- instead of 8Amps at 14V they would draw 12Amps.

Compared to 16Amps of OEM - that's what I can believe is the improvement
in the last 30 years.

If I need new fans in the future - I probably would give the new ones a chance.


BTW - any infos about original replacement fans ?
My list says it's an VW type: AU-431-959-455B can somebody confirm that ?

[Bitsyncmaster]

Looks like the bad fan is just getting worse with running. Now it starts out jumping between 3 to 5 amps. When it finally settles, it draws 7.1 amps and as it heats up (about 1 hour running) that current is down to 6.1 amps. Note: this is with 12.0 volts at the fan connector.

The other fan looks rock solid. Starts right out a 7.1 amps and still has the same current after running for one hour.

I hope Toby will replace my bad fan if I find I can not fix it myself. I think I can open it up to look at the brushes and commutator. A DC motor has to have brushes unless your driving it with some electronic controller.

I wonder how common these fan motor problems are. I think my fan fail unit will lend more data about failures. A lot of people have to turn off the current compare function to not get a flashing fan fail light. My Hervey's fans never had problems.

[WelmoedJ]

I may have an alike problem, Dave.
I have the new fans from DMCEU.

As I already told you in a private mail, I had to set the comparison check to zero.
Otherwise I would have a flashing fail fail light all the time.
Anyway now with the comparison test I find the FF light flashes that the driver's side fan is not in good shape.
This flashing however fades away the longer I use the fans (with A/C).
Peculiarly enough, if the fans kick in because of high coolant temperature, it almost never happens that the FF light is flashing.

I still have to check with Ed.
That's also because the afore mentioned fan seems to produce a higher pitched sound that the other fan (because it may have a bad bearing?).
Eds fans also have more - curved - blades than those of John H. (if I counted correctly Eds have 10 of them).

This is just to provide additional info, but not relevant to your testing Toby's fans.

[Spittybug]

Looks like the bad fan is just getting worse with running. Now it starts out jumping between 3 to 5 amps. When it finally settles, it draws 7.1 amps and as it heats up (about 1 hour running) that current is down to 6.1 amps. Note: this is with 12.0 volts at the fan connector.

The other fan looks rock solid. Starts right out a 7.1 amps and still has the same current after running for one hour.

I hope Toby will replace my bad fan if I find I can not fix it myself. I think I can open it up to look at the brushes and commutator. A DC motor has to have brushes unless your driving it with some electronic controller.

I wonder how common these fan motor problems are. I think my fan fail unit will lend more data about failures. A lot of people have to turn off the current compare function to not get a flashing fan fail light. My Hervey's fans never had problems.

I have the Toby fans and your module and have experienced the same problem from day 1. I haven't bothered to set your comparison to off and haven't monitored the fan currents. I have physically eyeballed that both fans were working so I never bothered to delve into it any deeper. Good to hear (?) that I'm not alone.

[Elvis]

...

I hope Toby will replace my bad fan if I find I can not fix it myself. I think I can open it up to look at the brushes and commutator. A DC motor has to have brushes unless your driving it with some electronic controller.


simple test - if you swap + and - -> does it spin backwards ? if yes - it's a brushed fan.
in this case you can measure the resistance of the coils.

[Bitsyncmaster]

I did a lot of checking on fan blade design. The pitch is much higher in near the hub than at the edges. That is to provide a consistent air flow over the full length of the blade. I found the Toby fan blade to be very good, center was a little more than at the hub or end of the blades. There are lots of other tricks with fan design. Taper of the blade, sweeping the blades, number of blades even offset blades where some blades are closer to each other than other blades. The OEM fans have offset blades. Hervey's blades have "wiglets" on the front side. I guess that is to make the fan work like a longer blade.

But with my testing so far, not much difference in airflow. Just that more power to the motors will of course increase airflow.

I don't think the OEM fans with twice the power consumption is worth the minor airflow improvement. It made a big difference without the radiator blocking the inlet but that improvement dropped way down with the radiator. Probably would be almost no improvement had I tested with the AC condenser also blocking the inlet.

From the Fan Fail light problems, I have not seen a way to change the software to help. If it were just when the fans start, I would delay the current checking for maybe 5 seconds.

[Bitsyncmaster]

Got the fans removed but it looks like the motor is glued together. I send an email to Toby requesting a replacement so if he needs the old one back I won't open it.

I've got a crack in my new fan shroud. Don't know how that happened since there has not been any engine run (up to temp) or any force used in the installation or removal. Wonder if I tightened the mounting bolts to tight (cracked at the bottom right corner). Also wonder if those mounting bolts should be left not tight so it gives a little clearance for the heating and cooling of the shroud and radiator.

[Bitsyncmaster]

Got the replacment fan motor and ran if for 40 min. to seat the brushes. The test is to watch the current draw when first turned on and then verify the current holds while running for 15 min.

Passenger side starts at about 7.5 amps and within a second or two is holding7.1 to 7.2 amps @ 12 volts.
Drivers side starts at about 7.5 amps and within a second or two is holding 7.0 amps.

So it looks like these fan motors are working very good.

[DeloreanJoshQ]

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

What diameter are those Josh?