Electric Radiator Fan - to shroud or not to shroud?

[Healey3000]

Hi,

 

I've been going back and forth on this in my mind - shroud or no shroud?

 

Having a shroud ensures that most of the radiator's area is subjected to airflow.  Granted, there is still a bias to the area directly in front of the fan blades but still, you maximize the active area.  On the other hand, not having a shroud probably makes for better cooling at speed, when the fan isn't needed.  Some OEM's seem to use flaps that can be opened or closed to expose the "corners" of the shroud.  The 2002 does not seem to have a cooling problem at speed so it may be fine.  The shroud will come into play at idle.

 

I have a WN high-cooling radiator on the way and am considering one of the Spal 12" fans, probably the 1360 CFM one.  I'd like to mount it by making a bracket/shroud that attaches to the radiator mount.

 

The engineer in me says a shroud is a requirement, as it also reduces blade tip loss and reduces vortex generation that degrades useful flow.  The engineer in me also whispers "might you be overdesigning this?".

 

Thoughts?  Thanks!

 

****************EDIT - I spoke with Spal**********

 

I called the very helpful folks at Spal - why didn't I think to do that earlier??  This is what I learned:

 

• Fans placed in front of the radiator should not use a shroud, but those placed behind the radiator should.  Do seal the fan face against the radiator
• Isolation mounting is not required since these are very low vibration fans
• Fans can be driven using a PWM frequency higher then 7 kHz.  15 kHz is the sweet spot
• Recommended 12" model for tight spaces is the 30102030
• Preferred 12" model if you have the room is the 30102025

Edited June 21, 2018 by Healey3000

[tzei]

I think you've got it. Shrouded puller it is then. I'm happy with Spal fan. Can't comment about sizing as i can't remember what you've as an engine got but i needed to go as big as i could fit with turbo engine.

Edited June 21, 2018 by tzei

[Healey3000]

1 minute ago, tzei said:

I think you've got it. Shrouded puller it is then. I'm happy with Spal fan. Can't comment about sizing as i can't remember what you've as an engine got but i needed to go as big as i could fit with turbo engine.

I don't think there's room to install a puller in our cars; just not enough room between radiator and water pump.

 

I should clarify - what tech support said is that a fan placed in front of the radiator should not use a shroud.  I'll edit my post, above.

[tzei]

14 minutes ago, Healey3000 said:

I don't think there's room to install a puller

Make a carboard mock up with spal dimensions (schematics are on their site somewhere) and try?

[jimk]

1 hour ago, Healey3000 said:

as it also reduces blade tip loss and reduces vortex generation that degrades useful flow.

I think these fans have a ring on the blade assembly? that takes care of this.

Just put it in and run it.  Many are in pusher and no heating issues.  Besides the fan is only needed at speeds less than 40mph and at idle the engine is not putting out that much lost heat.

Mine is cooling a S14 using variable speed from a SSR relay and rarely runs at over 75% of full speed.  It reads the coolant outlet flow from the radiator, begins the ramp table at 158F and would be at full speed at 180F radiator out.

[Healey3000]

Hi Jim,

 

I like the idea of PWM-ing the fan but I don't know if MegaSquirt can handle the high frequency.  Do you know what frequency your ECU runs it at?

 

Thanks.

[Dudeland]

Watch engine masters. They test fans. They noticed that the shroud made a huge difference.

FWIW


Sent from my iPhone using Tapatalk

[jimk]

2 hours ago, Healey3000 said:

Do you know what frequency your ECU runs it at?

Way too low.  I didn't know what to set it at and have been running at a very low 100 Hz.  Info you found is the only frequency I have seen.  So I took a look and the max I can set it to is 12kHz.  So I'll try it there to see if it stops growling the very low duty cycle (or if it runs at all??).

Edited June 22, 2018 by jimk

[Healey3000]

27 minutes ago, jimk said:

Way too low.  I didn't know what to set it at and have been running at a very low 100 Hz.  Info you found is the only frequency I have seen.  So I took a look and the max I can set it to is 12kHz.  So I'll try it there to see if it stops growling the very low duty cycle (or if it runs at all??).

Do you have a Spal fan?  I imagine different brands have different PWM frequency preferences.  Spal tech support did say that a low duty cycle will cause the fan to be noisy, almost like a cordless drill at low speeds.

[xr4tic]

It really depends on the size of the fan vs. the radiator.

 

If the fan is 12" on a 15" wide radiator, a shroud won't do much for you because the fan covers most of the radiator already.

 

Besides, there's not a lot of room for a puller, and a shroud will space it even further away.

 

Also, from personal experience (and talking with other owners), the Spal PWM controller is junk.  You can do a simple 2-speed setup with a dual temp switch and a resistor.

[jrhone]

No room for a puller.  A pusher is fine.  Lee at massive makes a bracket for the Spal fan to mount to the radiator bolts.  Easy peasy.  

 

http://www.massivebrakes.com/accessories.php?p=Spal_12-13_brackets

 

 I’m using the 12” Spal pusher fan. Using an e21 fan switch.  Car never gets hot.  I was in 118 degree Arizona heat and while I was miserable the car ran like a champ and didn’t get hot. Just a tick over half on the temp gauge.  No need for a two speed fan.  No need for a Spal controller that most say is junk. Keep it simple.  My fan pretty much only comes on at idle stopped for long periods of time. Like sitting in a drive through or bumper to bumper traffic.  

[jimk]

13 hours ago, Healey3000 said:

Do you have a Spal fan?  I imagine different brands have different PWM frequency preferences. 

I have a Hayden 3640 installed 2003 (15 years ago).  I ran a test at 12kHz and it runs very quiet where it used to be noisy electrically (5-15% duty).  My table is 3 dimension, radiator out on x-axis, road speed y-axis and % load in the cells.  If I am stopped the fan duty begins at a lower coolant temperature  than when I am moving.  It keeps the fan from running unnecessarily.

Edited June 22, 2018 by jimk

[DaHose]

I am a fan of shroudless pusher fans when possible.  They work awesome, the motor gets exposed to less heat, and more open space behind the radiator helps cooling.

 

Jose

[Healey3000]

13 minutes ago, DaHose said:

I am a fan of ...

 

Jose

Pun intended? :-)

[DaHose]

?

Edited June 22, 2018 by DaHose