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Old 06-06-2012, 05:41 PM   #1
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Default radiator shroud needed?

I'm going to be replacing my stock radiator soon since it's getting pretty old (and lookin pretty shitty). Might as well anyway as i am collecting turbo parts here and there. I think i'm gonna go with a cx racing aluminum radiator. Is the shroud really necessary? It's like 150 bucks extra. for my old turbo gsr setup, i used an aluminum half size radiator with a slim fan ziptied to it, and it sufficed. Just wondering what were your guise' thoughts. thanks
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Old 06-06-2012, 05:47 PM   #2
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My street car with an AC will always have a fan shroud, my track car has one fan with no shroud.
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Old 06-06-2012, 05:51 PM   #3
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Shroud can do without for a track car. Ducting (from bumper mouth to rad) is vital.
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Old 06-06-2012, 07:58 PM   #4
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alright thanks, i guess i should get one then... going to be daily driven and probably going to keep PS/AC
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Old 06-23-2012, 06:19 PM   #5
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Quote:
Originally Posted by Spookyfish View Post
Shroud can do without for a track car. Ducting (from bumper mouth to rad) is vital.
I am going to recall this if you want to run the car hard and then pit you need a shroud. I run the TSE monster radiator and a single chinaland fan. My temperatures on track are <194F but when I pit in without a cool down lap (red flag e.d.) and idle too long, temperatures explode.

So either the fan is really crappy, or a shroud is needed.
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Old 06-25-2012, 12:18 PM   #6
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Interesting. I would wager on the fan being crappy and that a high flow Spal would solve the problem. You know the ducting's good, you know the radiator sheds the heat if it sees enough airflow, so you need a better airflow creator.

Edit. I have the opposite problem, my FM shroud is too good, and temps go to about 220 on track. I just finished wiring the parallel fan mod and installed a switch for manual activation. Next track day we'll see how it does with both fans going. I have the big spals FM provides with the stage II airflow kit.
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Old 06-25-2012, 12:23 PM   #7
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how is your shroud too good if you see 220F and need to wire parallel fans?

you shouldnt need a fan at all on track, unless you're red flagged.
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Old 06-25-2012, 12:38 PM   #8
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It blocks too much airflow. I haven't done my ducting around the sides of the ac condenser etc yet, so I lose a lot of air that way because my radiator's got a big wall across the back of it. ECU temp trigger for the second fan isn't until 226 or so, which is too high. First fan by itself can't keep it cool under load.
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Old 06-25-2012, 12:49 PM   #9
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so you shouldn't say it's too good...
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Old 06-25-2012, 01:15 PM   #10
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Yes, I should. Look, a fan shroud's primary function is to *block* airflow. It is there to increase the efficiency of the fans by making sure all the air being pulled by the fans is being pulled through the radiator, and not recirculating in a ring vortex around the edges of the fan.

My radiator doesn't see a lot of passive airflow even at speed. The shroud is completely sealed to the back of the radiator and to the fans. The fans themselves, compared to the OEM fans, allow much less passive airflow through them. They have more blades and obscure more area than the OEM fans, so when they aren't powered on they're a significant obstruction to airflow.
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Old 06-25-2012, 02:32 PM   #11
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A running fan will almost always have a positive effect on airflow/pressure diff compared to a stalled one. I can see how a shroud with stalled fans could be a downside.
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Old 06-25-2012, 04:25 PM   #12
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1. Put 1-way air flaps in shroud



2. Achieve baller status



Or just pick up some aluminum dryer vents at your lowe's racecar improvement warehouse

Attached Thumbnails
radiator shroud needed?-82914.jpg  

Last edited by fooger03; 06-25-2012 at 04:38 PM.
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Old 06-25-2012, 07:32 PM   #13
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Don't use the ebay/FM/whathaveyou shroud. Use stock fans and shrouds. I like them much more due to their tapered design, rather than a flat sheet of aluminum with holes only for the fans. Ebay slim motors and blades can be adapted to fit in the stock shroud/fan plastics.

I also did it cause it cost $30, since I had to buy a 2nd hand A/C fan.
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Old 06-25-2012, 08:39 PM   #14
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There is some merit to what you say. There is no doubt in my mind that my fans move a relative crap-ton of air.

There's nowhere on my shroud to add dynamic vents. Both fans are basically occupying as much real estate as possible. In the middle FM has added a rubber flap of their own to allow some airflow.

If I don't get to it beforehand, one of this winter's projects will be to get the ducting finalized and then to remove the fan shroud and run just the fans. One experiment then would be to run just the bigger spal with the AC on in traffic in heat - if it can pull enough by itself with no shroud, then that's the way I will go. Just enough to survive the worst low-speed situations while maintaining maximum unblocked real estate for at-speed cooling.

Hmm, massage a spal into one of my OEM housings...
Fans used:
VA10-AP70/LL-61A (2460M3/h) tech sheet
VA10-AP50/C-61A (2270M3/h) tech sheet
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Old 06-25-2012, 10:17 PM   #15
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Quote:
Originally Posted by Mobius View Post
If I don't get to it beforehand, one of this winter's projects will be to get the ducting finalized
I found your problem

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Old 06-25-2012, 10:45 PM   #16
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You can't claim to have found something I already said was a problem, fool!
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Old 08-13-2013, 05:14 PM   #17
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Quote:
Originally Posted by curly View Post
Don't use the ebay/FM/whathaveyou shroud. Use stock fans and shrouds. I like them much more due to their tapered design, rather than a flat sheet of aluminum with holes only for the fans. Ebay slim motors and blades can be adapted to fit in the stock shroud/fan plastics.

I also did it cause it cost $30, since I had to buy a 2nd hand A/C fan.
Bump from the grave for a pic request...

Curly, Can you post up a pic or a quick description of how you modified the stock fan shrouds with the ebay slim ones.

Those shitty ziptie things that the ebay one comes with keep breaking and this seems like a good solution for flow and better mounting.
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Old 08-13-2013, 05:19 PM   #18
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https://www.miataturbo.net/build-thr...s-72535/page4/


Not a perfect guide, but you get the idea.
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Old 08-13-2013, 05:47 PM   #19
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Quote:
Originally Posted by dieselmiata View Post
https://www.miataturbo.net/build-thr...s-72535/page4/


Not a perfect guide, but you get the idea.
Thanks for the post! I get the general idea. I wish i didn't give away my oem fans now. fml.
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Old 08-13-2013, 11:01 PM   #20
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I'll throw my updates in.

Currently still running the FM Crossflow radiator, with the single large spal fan, and no shroud. Airflow is about 80% ducted in through the mouth. Airflow goes through intercooler/rotrex cooler/condenser/radiator in that order.

On track temps are much better than last year, rarely goes over 210. I have no temp issues idling in pits or driving in traffic.

Second interesting datapoint is that if I leave the fan on (via my switch) during a track session temps are significantly worse. At speed you want the fan not rotating with the blades stalled. It creates more of an obstruction spinning than not when the car's at speed.
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