Single fan to dual fan help

Jammer75

Jammer75

Well-known member
Joined
May 5, 2021
Messages
439
Reaction score
377
Car (Subaru ej20 7-8 lbs) built originally in 2008 with single fan(built into wing about 30°-40° angle(intercooler in front of fan)). When it kicks on it draws a good amount of hot air through it. Radiator has been checked and cleaned. Out front restrictor installed. Temps below 60° car runs 210° (fan kicks on at 180°), 80° Car runs 210° Will see 220° occasionally but usually giving it a rest on the throttle at that point. Temps over 85° car will run 210° if kept in the right speed of airflow, around 3 gear 1/3 throttle, otherwise temps more consistently in the 230°+ range and can slow down and cruise and it comes back down to 210°  . Everyone says go to dual fan and I think that would help as I want something that can dune hard for a while. I think I’ll need to cut open my radiator housing a little to accept a dual fan as well to optimize the air it can pull through it. 
 

Question can I just wire the dual fan in to the same plug that was for the single fan? As far as I can tell, not sure which order, it runs to the computer, a relay and probably through one of the fuses on the fuse block.
 

thanks for any input.  

 
Last edited by a moderator:
Pics of your set up would help.  

You should add a second relay, and associated wiring. for the other fan.  Use the same trigger for the second fan as the first.

edit... You probably could just upgrade the fan you have to one that has a higher CFM rating.

 
Last edited by a moderator:
It’ll take a while before pics. But i found a dual fan (24.6amp draw/2600 cfm) being sold with a single 30 amp relay. So I’m assuming if it’s that configuration it should work fine or is there another reason 2 relay should be ran with 2 fans? 

with that being said, if I assume I already have a 30amp relay and 30 amp fuse connected I should be go to go…?

im new to relays but it looks like 1 wire to fuse to 12v source, 1 to key/ignition, 1 to fan, 1 to trigger..?

looks like my current single fan is 35 amp with a cfm of 962. I look into a higher cfm single fan and see what I can find..
 

39613239-5C9C-4326-88E5-9ECDB6580551.jpeg

B98C84A3-8D12-48BB-9BFA-CB797C2006EF.jpeg

65925901-697B-4DBB-A168-EEA434F3A436.jpeg

 
One relay per fan is ideal.  The redundancy will save you in the event of a relay failure.  Both fans on one relay will work, but if it fails you're f*cked.  Whereas if you had each fan on a dedicated relay ( and separately fused), if there was a failure you could still drive back to camp.

The fan you currently have is terribly under sized. Spal has WAY better fans that should bolt right in.  The fan you have pulls max of 8 amps. https://www.spalautomotive.it/axial-fans/va13-ap9_c-35a/32489

Model #va01-ap90_ll-66a/31249 here (search SCU 30103203 around $200) for example, moves double the air, and is still a 12" fan.  This is a 40 amp fan!  Your radiator has a lot of real-estate that would allow you to add more fan.  A good 12", and maybe another 10".  Different shroud obviously..

Wouldn't hurt for the opening in the face of your wing to match the size of the radiator instead of the smaller intercooler..

 
Last edited by a moderator:
the twin fan and relays is a great start.  if that still doesnt work then relocating the intercooler perhaps right over the engine would be next step  that intercooler in that location is not your friend as far as getting good natural air flow across the radiator

 
I like both ideas. I think the final solution is a dual fan/relay setup. But with my time constraints i think I’ll try a fan with more than double the cfm and see what happens and then if needed open up the shroud opening. If still not we’re I want to be I’ll go to a dual. With the dual room for fitment would be the issue. 
 

 
Kraut_n_Rice said:
One relay per fan is ideal.  The redundancy will save you in the event of a relay failure.  Both fans on one relay will work, but if it fails you're f*cked.  Whereas if you had each fan on a dedicated relay ( and separately fused), if there was a failure you could still drive back to camp.

The fan you currently have is terribly under sized. Spal has WAY better fans that should bolt right in.  The fan you have pulls max of 8 amps. https://www.spalautomotive.it/axial-fans/va13-ap9_c-35a/32489

Model #va01-ap90_ll-66a/31249 here (search SCU 30103203 around $200) for example, moves double the air, and is still a 12" fan.  This is a 40 amp fan!  Your radiator has a lot of real-estate that would allow you to add more fan.  A good 12", and maybe another 10".  Different shroud obviously..

Wouldn't hurt for the opening in the face of your wing to match the size of the radiator instead of the smaller intercooler..
Click to expand...
Where did you find that 40amp rating for above fan?

I’m seeing something like this that only has a 22amp draw…?

https://www.summitracing.com/parts/der-16214

 
I was having the same issues with the engine getting hot when the outside temps reached around 80 degrees. I have a 2.5 Subaru, and the radiator and inter cooler are one piece placed right behind the seats and shielded by the side panels and a panel above it where they get pretty much no natural airflow. I had a single 16” fan and at its worst I’d see temps nearing 230. I ditched the single fan and put in two 12” spal fans (I think part number 30102029) and a small 5.2” fan, each with their own relays and fuses.  In may when the temps in Glamis were around 100 I never saw the water temp get over 190 even when duning hard. Basically don't have to think about the water temp anymore. I also cut back on the amount of antifreeze I’m using and add the water wetter coolant additive as well. 

8B933928-7BAD-455D-AAEF-3E35B84CEA61.jpeg

 
Jammer75 said:
Where did you find that 40amp rating for above fan?

I’m seeing something like this that only has a 22amp draw…?

https://www.summitracing.com/parts/der-16214
Click to expand...
Those screen shots are directly from Spal's website.  I linked them in my earlier post.  Where the fan is at it's least resistance, and highest CFM, it only draws 25 amps.  But, there is going to be some airflow resistance in your (anyone's) setup.  Build the wiring out to handle the max the fan will need.  Skimping on wire size just gets you voltage drop, that just leads to lower performance of the fan.  And, possibly damaging one of the components in your circuit.  One should also take into account the inrush amperage something like a fan will pull.  It takes more power to get it moving than what is calculated at speed.  50% more isn't uncommon.  This will come into play with your fuse/circuit breaker selection.  I typically size my circuit protection double the rated run amperage of a high inrush component like a fan.

The Derale fan is larger, 14" vs 12", and it's blade profile is much less aggressive than the Spal.  Maybe that makes a difference..?..  I'm no PhD in fluid dynamics...

 
Dylanshaffer said:
I was having the same issues with the engine getting hot when the outside temps reached around 80 degrees. I have a 2.5 Subaru, and the radiator and inter cooler are one piece placed right behind the seats and shielded by the side panels and a panel above it where they get pretty much no natural airflow. I had a single 16” fan and at its worst I’d see temps nearing 230. I ditched the single fan and put in two 12” spal fans (I think part number

) and a small 5.2” fan, each with their own relays and fuses.  In may when the temps in Glamis were around 100 I never saw the water temp get over 190 even when duning hard. Basically don't have to think about the water temp anymore. I also cut back on the amount of antifreeze I’m using and add the water wetter coolant additive as well. 

View attachment 11027
Click to expand...
That is a nice setup! I think that’s where I’ll end up. 
 

 
Jammer75 said:
I like both ideas. I think the final solution is a dual fan/relay setup. But with my time constraints i think I’ll try a fan with more than double the cfm and see what happens and then if needed open up the shroud opening. If still not we’re I want to be I’ll go to a dual. With the dual room for fitment would be the issue. 
 
Click to expand...
If you replace the fan, you'll have 2.  Move the existing over to the "cold" side (engine return) and put the big guy on the "hot" side.  Fan placement is just as important as CFM.  The hotter side of the radiator is the more efficient side and where you want more airflow if there's a limitation.  EDIT: just noticed your radiator is top/bottom.  fan placement doesn't really matter as much here, but 5 minutes with a laser thermometer (or a brave hand) can tell you which side is hotter if any.

You can also put weather stripping between the radiator and shroud so the fan doesn't just suck air from around the shroud (easy) rather than through the radiator (harder). 

Either way it goes, I'd use a 2 fan setup: even if they're not used as much, it gives you overhead, and also allows more air to naturally flow through the radiator since the back of it isn't 50% blocked by shroud.

Relay wiring:

61nhrNUV22L._SL1200_.jpg


****************** WARNING *************************

Many ECU fan triggers are GROUND, not positive.  Use a multimeter to confirm what your fan trigger from the ECU is BEFORE wiring or you will run the risk of damaging this circuit.  If it's ground trigger, simply reverse the landing points for 85/86: ECU trigger is ground on 85, 86 goes to switched/fused power.  

For the fans @Kraut_n_Rice spec'd, you will need min 12g, preferably 10g, and ground has to be the same size.  Don't do something stupid like running 2 14g wires, or using the existing ground, or whatever. :biggrin:

 
Last edited by a moderator:
I had a similar issue when I added a windshield.

I replaced my single 1500cfm with a 3000cfm, now I can run in any temp.

 
Rockwood said:
If you replace the fan, you'll have 2.  Move the existing over to the "cold" side (engine return) and put the big guy on the "hot" side.  Fan placement is just as important as CFM.  The hotter side of the radiator is the more efficient side and where you want more airflow if there's a limitation.  EDIT: just noticed your radiator is top/bottom.  fan placement doesn't really matter as much here, but 5 minutes with a laser thermometer (or a brave hand) can tell you which side is hotter if any.

You can also put weather stripping between the radiator and shroud so the fan doesn't just suck air from around the shroud (easy) rather than through the radiator (harder). 

Either way it goes, I'd use a 2 fan setup: even if they're not used as much, it gives you overhead, and also allows more air to naturally flow through the radiator since the back of it isn't 50% blocked by shroud.

Relay wiring:



****************** WARNING *************************

Many ECU fan triggers are GROUND, not positive.  Use a multimeter to confirm what your fan trigger from the ECU is BEFORE wiring or you will run the risk of damaging this circuit.  If it's ground trigger, simply reverse the landing points for 85/86: ECU trigger is ground on 85, 86 goes to switched/fused power.  

For the fans @Kraut_n_Rice spec'd, you will need min 12g, preferably 10g, and ground has to be the same size.  Don't do something stupid like running 2 14g wires, or using the existing ground, or whatever. :biggrin:
Click to expand...
Great information. Thank you!

 
John@Outfront said:
the twin fan and relays is a great start.  if that still doesnt work then relocating the intercooler perhaps right over the engine would be next step  that intercooler in that location is not your friend as far as getting good natural air flow across the radiator
Click to expand...
What is needed to do an over the engine intercooler?

Thanks,

 
You must log in or register to reply here.
Back
Top