patsmx5

iTrader: (16)

Well here's a little info for you guys. I don't have a means to measure CFM, so some of this is subjective. But maybe this will help somebody with their fan choice down the road.

I just bought these Ebay 12" Slim fans: 2 x Universal Slim 12" Pull Push Radiator Engine Bay Cooling Fan Mounting Black | eBay

They are rated at 12V, 80W, 1730 CFM, straight blade. I have a pair of them.

I used a battery charger to keep keep the voltage at 14.5V during testing.

I tested one of them:

in free air
sitting flat on an a/c condenser
and then 3/4" away from the surface of an a/c condenser with the fan sealed to the condenser.

These fans, in free air, are not very impressive. They might move 1,000-1,200 CFM. No way in the world they move 1700 cfm.

With them sitting flush on the a/c condenser only, yeah.... maybe 1/3 the airflow. The only part of the fan moving much air is around the edge of the fan, towards the middle it's doing almost nothing.

With them 3/4" away from the surface, about 1/2 the airflow, maybe a bit more. Big improvement vs having it rest against the heat exchanger.

If drug a piece of paper around the backside in different spots, during the test, and it's about what you'd expect. With the fan flush on the condenser, it pulls more pressure, but only in the "ring" of the fan blades, none on the edges or the center of the fan.

With the fan 3/4" off the radiator, it's much more even. I think 3/4" is probably the minimum for a shroud to be effective, 1" is probably better still but I think the minimum should be 3/4".

Interestingly, the fans pulled 0.7 Amps more when sitting flush on the condenser vs 3/4" off the condenser (7.5A vs 6.8A). In free air they are 6.7A.

The ac condenser is 3/4" thick at the core.

For reference, I have a pair of spal extreme performance 12" fans on my radiator, and subjectively, they move 4x the airflow when bolted to my radiator vs these ebay fans, at the same voltage. Spals pull 30-32A each though, these ebay fans only pull about 6.8A each. And the radiator is thicker, and has a higher fin density, so therefore more resistance to airflow vs an a/c condenser. The SPAL fans really are good fans.

Based on what I'm seeing, it looks like Amps and Airflow are pretty linearly related when comparing fan CFM when bolted to a heat exchanger. And it looks like the ebay fans I bought are pretty weak. My guess is I'll probably end up swapping these ebay fans for something better down the road, but for now I have them and am going to give them a shot.

Also it appears that if you're gonna mount a fan without a shroud, if you could still mount it 3/4"-1" off the radiator, and seal it only where it would normally contact the radiator, this would improve fan performance without the air flow penalty at speed that you get from a conventional fan shroud.

deezums

iTrader: (3)

A radiator shroud with lightly weighted flaps that blow open at speed yet fall closed for "vacuum" at idle would likely be ideal, but I doubt even that is necessary.






Cooking pans make excellent 3/4-1" offset shrouds too, slice and splice the things to fit.




I haven't got to the real hot weather yet, but I don't seem to have heat control problems at idle or low speed conditions. I'm using the factory smaller condenser fan only, and it's not shrouded or sealed against my radiator much at all.

I've been considering using a cooking tin and cheap ebay fans in the slim space I've got between the swaybar. I imagine two in tandem ought to be fairly close to the stock condenser fan, would you agree?

Thanks for the post!

patsmx5

iTrader: (16)

I can't recommend these ebay fans I'm using for a radiator, they are a lot worse than the stock fans. I doubt they would pull 1/2 the air the stock fans will. Stock fans are pretty decent and they have a built in shroud which is nice.

I'm doing a rear-mount a/c condenser and for this, I need a very thin fan for packaging. If I had the space, I'd probably run a pair of stock fans given how cheap they are and how well they work. For this they just would not fit though.

patsmx5

iTrader: (16)

Quick update on the fans....

So I decided to cut some of the webbing out of the fans to see if it would help improve airflow. It did, so I ended up cutting all of it out. This surprisingly makes a BIG difference! I'd say at minimum, the fans are moving 25% more air. It's a pretty good difference, certainly significant. I just used a sharp knife, it's plastic so they cut easy, takes about 6-8 minutes to do one fan being careful. I didn't test the current, but I'll do that tomorrow to see if it changed from cutting the fans.

Also worth noting the way the fans are now supported is how my SPAL extreme performance fans are made.

If you run slim fans and they are marginal, this could make a difference! More cooling is always better.





Rear mount a/c condenser pics will be in my build thread.

Braineack

iTrader: (62)

like 10 years ago we all decided the stock fans were better--you are continuously posting stuff we did a long time ago. Sucks you had to miss out on learning trying to **** Rick over with Homemadeturbo.com and making him regret his 5 figure purchase of the site.

patsmx5

iTrader: (16)

I don't just assume that whatever this forum believes to be true is 100% correct 100% of the time. I test things and see for myself.

And sometimes I post what I've learned. Why would you have anything negative to say about that? This is a miata forum and a lot of people here want to build a better miata.

I could give 2 craps about politics, Rick, his finances, HMT, you, or what anyone on this forum or that forum thinks about my post. I'm here to talk miatas and learn, making them faster and more reliable.

Braineack

iTrader: (62)

I stuffed an ebay fan into a stock shroud and it seemed to work well. the shrouding is MUCH better than the direct mounts.

Im not surprised by your finding on cutting away all that material behind the fan.

But I'm still in the "use stock fans" camp unless you actually cant fit them.

patsmx5

iTrader: (16)

I read that thread before starting this one. Agreed shrouding is important.

I never found anyone who cut the material off the fan to test that and posted about it. I just looked at it and damn, the plastic blocks probably 20-30% of the area, it's a lot! My SPALs aren't like that so I figured why not and started cutting.

I remember a long time ago Jason posted that a shroud should be 1" away to be effective. My test shows 3/4" is usable if you need the space, but less than 3/4" really hurts performance. My shroud is 1".

EDIT: And yes I agree, use stock fans vs these if at all possible, even as they are now these ebay fans don't move the air a stock fan does. I have another '99 miata to compare to that's stock, and the stock fans on a stock radiator are for sure better.

mcfandango

iTrader: (1)

Your Spal's also probably also have beefier support ribs that what is left after you cutting up the cheap fans. I would be worried about one of those remaining ribs breaking and sending a cheap fan into what is hopefully a decent radiator. Although if you are going cheap on non-Spal ebay fans, I doubt the radiator is anything better than cheap ebay as well.

patsmx5

iTrader: (16)

Yeah the spals are much beefier, but have less total ribs. And they are made from fiberglass too, not plastic.

Still I tried bending the motor on the ebay fan, and the motor does move, but it moves where it's bolted to the plastic hub in the center. If I twisted enough, I think I'd break the 2 tiny plastic spots that hold the motor to the plastic hub int he center. So the ribs should be ok but we'll see.

These fans are going on an a/c condenser located in the rear of the vehicle. And it's a cheap a/c condenser. Only reason I bought them is because I need a thin fan, I was actually hoping to use stock fans but when I measured there was no way... If these don't cut it, I'll buy some SPAL fans down the road. But I actually just tested these fans on my new shroud, and they're..... ok. Not bad once the shroud was finished. For an a/c condenser I think it will be alright, but it will be a bit before I know for sure.

18psi

iTrader: (76)

i did this in 08 fwiw

Eipgam

Here is the custom shroud I had fabricated, that includes SPAL fans (12" 1225 CFM 140 watt - from memory). On the track the temp does not go above 95 deg c when used as a daily drive stop start traffic has very little effect on the temp. Only mod that needs to be done is seal around the radiator so that all the air goes through it and not around.

humming

iTrader: (2)

Here's my set up using Spal 30101504(12", 1097 CFM each):

patsmx5

iTrader: (16)

Here are the SPAL fans on a modified FM shroud I run on my MSM Radiator.






And here's the Ebay fans on my custom shroud

patsmx5

iTrader: (16)

How did it work? How did it compare to stock fan? Looks identical to the fans I bought.

18psi

iTrader: (76)

It was an ebay fan, so it was mediocre. CAr never overheated so there's that, but I wasn't too happy with it. Definitely wasn't an improvement over stock
The only reason I ran it on my 1st setup is cause I was space limited and needed something slightly slimmer than the stocker

GeneSplicer

iTrader: (14)

Alright - so i have to do something here. My NB overheats when i have the ac on - or on track after 3 laps. That's at 92f ambient temps. Last night, after struggling with track temps sat, i installed trackspeeds dual pass radiator i had bought for the track car. It helps some, but not enough.
Objects of airflow resistance - begi #3 ic, factory ac condenser, TSE dual pass, reroute, hood vents, no ducting, running single 12" egay fan.
I was surprised it was overheating cruising on the interstate at 80 when i kicked on the ac - which i ain't about to settle for when it's 95f outside.
Now, i can duct, which i will, but what else - better fan? Run dual 12" fans on a shroud? (You can't fit dual 12" on the tse rad), high flow ac condenser?

patsmx5

iTrader: (16)

Ducting ducting ducting.

If you're overheating at idle, or below ~25mph, you need better fans. Above that, ducting.

BTW ducting is only gonna work so well when there are 3 heat exchangers up front. I recently just pulled the a/c condenser and moved it to the rear as I've struggled for years to get enough air to the radiator with 2 other heat exchangers blocking it.

Leafy

iTrader: (1)

The shrouding on the ebay fans is there to prevent finger removal, not so much strength. My silicone intakes fans have it too, they pull 8 amps when mounted directly to the radiator based on my clamp meter, they're rated for 6 amps. The blades look the same as the Spal fans Epifan has but the housing is different. Interesting that you managed to get that much more flow from cutting them out. I'll have to try it on mine, new ones are cheap enough if I screw them up.

hornetball

iTrader: (4)

I just used Pat's cut away the finger-protectors trick on a condenser fan setup I just built -- although I only cut away half of the structure, not all of it. Jeg's heavy duty slim-fan, which are slightly more expensive than the mid-grade Spals and rated a little higher. Wish me luck, although at the rate I'm going the weather will be cool by the time I'm driving.

https://www.miataturbo.net/build-thr...8/#post1242422