What would be best, Triple or twin fan?

guyph_01 · Post by **guyph_01** » Mon Sep 05, 2011 12:54 am

Hi guys.

Ok this is for my ej25 L-seires build. A little bit of history first.
When i had my ej22, both fans were running off the ECU and the car used to overheat as soon as i went off road. Turns out the ECU wasn't supplying enough to power for both fans and they were working at about 35 and 65% of their capacity. So to solve this i only hooked one fan via the ECU and the other was with a switch. This improved greatly the cooling power of the fans and the car would only overheat when i forgot to turn the manual fan on, LOL. Fans used were two ebay 12inch, Placed between the engine and radiator.

For the new build, I went with two 10inch Davis Craig fans as i was placing them in front between the radiator and the front grill and they had to be smaller. From the specs of the 10 inch Davis Craig and the 12inch ebay specs, the 10 inch Davis Craig are said to displace a similar amount of air. I guess this is because they are a better quality brand.

Anyway I was able to squeeze one of the 12 inch ebay fans in between the engine and the radiator opposite to one Davis Craig fan. I thought the more the better but than Dave had a good point.

He pointed out that if the DC fan was pushing more than the ebay one, the ebay would be useless and actually restrict the air flow in a way.

Basically what i wanted to know are your thoughts on this. Is that true or not?

I wanted to add the third fan as the air flow needs to go trough my twin core radiator but also the air-con condenser and though it might help to flow better.

What do you guys think? Should i keep it or remove it?

daza · Post by **daza** » Mon Sep 05, 2011 9:54 am

Yes the third fan can restrict airflow take it out.
The problem you had was a lack of power to the fans, that is what needs fixing, and it's not hard to fix.
You just need to add a relay to switch the fans by the ECU, but power them directly from the battery.
There have been diagrams posted a few times, if unsure ask around.
Daza.

Post by **TOONGA** » Mon Sep 05, 2011 10:09 am

What Dave has said is correct, the way you have the fans set up you are restricting the air flow where the 12 inch ebay fan is sitting.

Having said that the way the Davis Craig fans are set up you will have really cool aircon but less cool air actually reaching the radiator.

I would remove the Davis Craig that is in front of the Ebay fan, leave the bigger Ebay fan in place to pull more air through to the radiator.

in the end it is your call Guy

TOONGA

Post by **Alex** » Mon Sep 05, 2011 10:43 am

with my EJ20G i ran two craig david fans inbetween the rad and motor. This kept it cool. I was running one from the ecu and one from a hard wire switch.

I also had a small 8inch fan hooked up to my WAIC cooler which was on permentantly.

I'd get rid of the ebay fan. They blow very litte air compared to the craig davids.

Also (im sure you have MANY lying around) play with standard liberty fans, i realise they arent as slim as aftermarket fans but they do move ALOT of air.

alex

2coupedup · Post by **2coupedup** » Mon Sep 05, 2011 11:12 am

similar problem when running my EA on the sand for too long... only had this problem with A/C fitted, but was great without A/C... i guess it restricted the airflow too much...

but as said above i would go the DC ones and attatch the ecu fan swith wire to a relay instead of directly to the fans, that way you get full capacity...

shouldnt be an issue with fans infront instead of behind, pretty sure its been done that way many times by others...

if they need to turn on earlier to prevent it getting to hot to start maybe either a 2nd wire to a switch to bypass the ecu and turn them on manually...
or a nice cool thermo switch in the radiator to activate the relay???

just some thoughts...

looks great BTW, cant wait to get stuck into mine...

cheers

guyph_01 · Post by **guyph_01** » Mon Sep 05, 2011 1:04 pm

Ok. Well the DC fans are already hooked up via relays that are activated but the ECU but are getting power straight from the battery.

At the moment even with the ebay fan in but not connected the two DC fans are able to cool the engine (sitting there idling, can't drive yet).

I agree that if say i had a single core radiator that having both the Ebay and DC fans opposite each other would be useless.

But i was wandering if you thought that having the ebay fan on the other side would help suck the air that been restricted by the air-con core and twin core radiator and thus increase air flow. (as there is a huge different feel of air flow when i put my hand in front of the DC fan by itself and then putting my hand behind the path (aircon, twin core rad and fan).

d_generate · Post by **d_generate** » Mon Sep 05, 2011 2:40 pm

If you want to get rid of one of the Davis C fans let me know & I'll probably grab it off you, I want it for under the bonnet scoop, the standard rad fan is about half an inch too thick unfortunately.

2coupedup · Post by **2coupedup** » Mon Sep 05, 2011 4:31 pm

guyph_01 wrote:Ok. Well the DC fans are already hooked up via relays that are activated but the ECU but are getting power straight from the battery.

At the moment even with the ebay fan in but not connected the two DC fans are able to cool the engine (sitting there idling, can't drive yet).

I agree that if say i had a single core radiator that having both the Ebay and DC fans opposite each other would be useless.

But i was wandering if you thought that having the ebay fan on the other side would help suck the air that been restricted by the air-con core and twin core radiator and thus increase air flow. (as there is a huge different feel of air flow when i put my hand in front of the DC fan by itself and then putting my hand behind the path (aircon, twin core rad and fan).

ah yes in this case i would believe the 3rd fan would help because even if the flow rates are different the radiators would stop the majority of the air and the 3rd fan would have enough grunt to atleast keep the air flowing...

keep it...

cheers

guyph_01 · Post by **guyph_01** » Mon Sep 05, 2011 6:29 pm

2coupedup wrote:ah yes in this case i would believe the 3rd fan would help because even if the flow rates are different the radiators would stop the majority of the air and the 3rd fan would have enough grunt to at least keep the air flowing...

keep it...

cheers

What do you others think now? keep it or ditch it? DR Urabus, any thoughts?

steptoe · Post by **steptoe** » Mon Sep 05, 2011 8:17 pm

I'm just trying to picture two of Craig Davids fans stuck under your bonnet sucking air through your radiator Alex!!

I say, wait for the very soon release of engine watchdog unit - the TM4. Gives a digital metal temp readout, adjustable temp alert and the big new feature of TM4 is the ability to set off a relay at any temp you like.

GOD · Post by **GOD** » Mon Sep 05, 2011 9:02 pm

2coupedup wrote:ah yes in this case i would believe the 3rd fan would help because even if the flow rates are different the radiators would stop the majority of the air and the 3rd fan would have enough grunt to atleast keep the air flowing...

keep it...

cheers

No. The air thrown into the radiators by the front fans doesn't stop unless the fan stops. I say ditch the back fan.

Guy, do some measuring:
1. Get an anemometer and check the flow rates with a single Davies Craig (or Craig David if that's what floats your boat) fan and with that same fan in series with the ebay one.
2. Measure temperature drop across the rad with different fan arrangements.
3. Measure current drawn by the DC fan alone, the ebay fan alone, and see how they change when you put the two in series.

Dane.

Battlewagon · Post by **Battlewagon** » Mon Sep 05, 2011 9:53 pm

Coming from a background of speedway racing, I would suggest that you fit both the davies craig units behind the rad.
Fans in front of the rad don't work nearly as well as ones behind, dunno exactly why, but they don't. Perhaps they are designed to pull air, not push it?
Using the ecu signal to switch a relay so that your fans get power direct from the battery may help too.

discopotato03 · Post by **discopotato03** » Tue Sep 06, 2011 2:30 am

When engine cooling and longevity become the No 1 priority you rip the AC gear out .
People generally find that larger diameter fewer elec fans work better but are harder to fit at times .
If my RX ever had them it would have had the largest one that could fit on the front of the rad core and if necessary another the same on the back of it . They would have been on opposite sides (L & R) for obvious reasons .

I've never seen 10" or smaller elec fans work terribly well because they generally can't move enough air .
Most people don't do it for cost reasons but properly set up oil coolers make a big difference . A real BIG difference if you can get reasonable airflow through them .

A .

guyph_01 · Post by **guyph_01** » Tue Sep 06, 2011 2:38 am

discopotato03 wrote:When engine cooling and longevity become the No 1 priority you rip the AC gear out .
People generally find that larger diameter fewer elec fans work better but are harder to fit at times .
If my RX ever had them it would have had the largest one that could fit on the front of the rad core and if necessary another the same on the back of it . They would have been on opposite sides (L & R) for obvious reasons .

I've never seen 10" or smaller elec fans work terribly well because they generally can't move enough air .
Most people don't do it for cost reasons but properly set up oil coolers make a big difference . A real BIG difference if you can get reasonable airflow through them .

A .

Thx for this but it doesn't really help me in my application and don't care!!!!, I WANT to keep my air con and I can ONLY fit 10inch fans on the front. SO again with my question, with what i've got do you think its best to keep the third ebay fan to help pull more air or remove it???... Keeping in mind its got the air-con condenser and a twin core rad to push air through!
Thx

steptoe · Post by **steptoe** » Tue Sep 06, 2011 9:21 am

Think you are gonna be able to tell us when you have worked it all out. If I was you with three , I would try the front fan with manual over ride to see if it is a hindrance or a help by simple switch.

2coupedup · Post by **2coupedup** » Tue Sep 06, 2011 11:25 am

just leave all three...

the 2 DC's may not stop blowing air, but... by the time the air passes through the A/C condensor and dual core radiator as you say will have lost quite a large amount of volocity....so the 12" may help the flor rate...

for example, (experament at work for a cutomer...) a SMALL HIGH Volume exhaust fan (barrel fan) sucking dust from a work area and blowing through ducting to a filter panel was greatly assisted by a secondary LARGE LOW volume fan sucking from the other side of the filter... there was a large improvement on dust collection...

nothing to do with cars but hey...

also in this instance not all of the air blown by the DC fans in forced through the radiators... i would imagine (unlike my example being a sealed tunnel to the filter panel - like a vacuum cleaner) that some of the air would not even reach the radiators let alone make it all the way through the radiators, the air would deflect up, down, left, right and all angles inbetween and escape...

this is why some high performance radiators come with nicely moulded shrouds around the fans to enclose the air path... stops the fans blowing/sucking from the wrong direction... no air wastage...

sometimes i think waaaayyy too much

cheers

2coupedup · Post by **2coupedup** » Tue Sep 06, 2011 11:29 am

also get all the fans going and stand over you engine and if you can feel more air blowing up or around the motor this way than you do with the 2 DC's then it can only help airflow...

guyph_01 · Post by **guyph_01** » Tue Sep 06, 2011 12:09 pm

thx 2coupedup, this is what i was after, Thoughts about my problem and not what most people do and don't do thats not applicable to my problem:)

Any other thoughts?

Post by **TOONGA** » Tue Sep 06, 2011 12:47 pm

try a wind tunnel simulation ahahahahahahaha... I hear you all laughing.

it is as simple as getting a device that emits a thin stream of steady smoke.

like this

Im sure you can find some silicon and some bits and pieces to put something like this together.
just make sure you don't get raided by the police or the will think it is a pipe of some sort

blow smoke through the grille at the front and see which configuration of fans pushes the most smoke out the other side and how quickly

TOONGA

Post by **Alex** » Tue Sep 06, 2011 1:03 pm

im not really a fan of this thread anymore.

dont want to blow too much more wind outta my arse :P