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FFCobra Craftsman
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2,315 Posts
Discussion Starter · #1 ·
I have the new FFR electric fan (1810CFM, Maradyne) and a big whopping thick (3" w/dual visteon cores) aluminum race rad. I will be installing a "block off" plate between the top of the rad and the body so that all air entering the nose is forced through the rad.

The question is -- do I really need to build or buy a rad fan shroud? I heard it argued that at speed, the fan shroud will actually limit airflow through the rad which does kind of make sense.

If a shroud is needed, any guidelines to follow in terms of depth, etc to maximize performance ?

-SB
 

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Senior Member
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5,559 Posts
I would try it like it is and wait to see how it maintains temp. In my case I used a Mustang shroud which actually has a much larger diameter opening than the electric fan. I needed to make a sheetmetal ring to cover the extra 2" gap around the fan to get it to keep my temps in a suitable range on hot days - but I just have the single core Mustang radiator, not a race one so you may have better luck. Either way, it is easily accessible from under the car, even after it's finished if you need/want to add a shroud later...

Brian
 

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section 8
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5,136 Posts
They fan will probably be needed at idle mostly and any help you give it will be good. other than that try it
 

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Premium Member
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That's actuallly a two part question.

1. A shroud will definatly increase efficiency. It ensures that air is pulled through the entire radiator, not just directly underneath the fan. Without it, it's like having a 40%'ish smaller radiator in traffic.

2. Do you need the additional efficiency? In your case, probably not. A 306 doesn't generate that much heat. And in Ontario that probably isn't going to be a big deal.
 

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FFCobra Craftsman
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2,315 Posts
Discussion Starter · #7 ·
Personally, I prefer the look of a fan w/shroud assembly as opposed to just mounting the fan on the back of hte rad.

My biggest concern is that the shroud/fan assembly will reduce rad effectiveness at speed, by impeeding airflow through it.

Can anyone comment on this?

-SB
 

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Premium Member
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5,210 Posts
I ran 5 years in Phoenix, AZ without a shroud. Never had a problem.

Mike
 

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Senior Charter Member
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Steve and Mike. What kind of motor do you have?
 

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FFCobra Fanatic
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1,608 Posts
I'm running a 427w with the FFR radiator and a shroud. Runs nice and cool even on the track. With a 195 deg thermostat the temp stays between 195 and 210, right where it should be. The only time the fan comes on is in street traffic.
 

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FFCobra Craftsman
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24,700 Posts
I don't think there is much question that the fan and shroud could reduce flow at some higher speed.No question either that at lower speeds the shroud definately improves the fan performance.The question is what is that crossover speed where the obstruction starts to come into affect.My guess is that it's at a speed we don't see much on the street.For street I'd use fan and shroud.For race only maybe just a fan.Good luck
 

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Senior Member
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I don't think the shroud actually impedes flow at all. It just funnels all of the air flow into the fan so it can do it's job more efficiently. Like just about everything else in nature, air will follow the path of least resistance, so if you don't have a shroud, most of the air will go around the fan instead of through it. At high speed this can be an advantage, but with normal street use, it would definitely be more inefficient, because the fan wouldn't be able to create the vacuum to pull the air through. I found at least on my car it made a huge difference with a standard radiator and supplied fan. With that heavy radiator you have it may not run super hot, but you won't be getting the efficiency benefit that you paid for with that nice radiator. If you look on the Summit site, they have a really nice fabricated aluminum shroud that could be polished, and is pretty inexpensive (I think around $50, or so). That is what I'm going with for my next radiator, mainly because it looks way better than the plastic one, but it is also cut to the correct size opening for the fan, so no extra work is needed like I had to do to the stock one.

Brian
 
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