Thread: Electric Fan Application?
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06-08-2004 08:09 AM #16
Re: pusher fan bad?
Originally posted by jaymaechtlen
Maybe dumb question, but:
What's wrong with a pusher fan?
True, most factory setups are pullers, but that's not a complete answer...
regards
Jay
Some additional thoughts on shrouds. Years ago GM cars had shrouds that were pretty much just a cylinder of metal about an inch larger than the fan (or vice versa depending on your perspective). They made the flow caused by the fan effective only within that circle, and the rest of the core was exposed. Good idea for the ram air flow, but, depending on the cooling demand, could be marginal for low speed. With the advent of A/C becoming nearly standard equipment, that type of system wouldn't work anymore. That's why a "proper" shroud is now considered to be one that covers the entire core surface, and the largest possible fan (s) used to draw the most air through. Of course cfm is important too as not all 16" (for example) fans are equal. There are other factors too, not just core size, # rows of tubes, core material. There's also how well the engine compartment vents (all that rammed or pulled air needs to get out), and how the engine is set up (bare headers/coated headers, rich or lean, iron/aluminum heads, etc. etc. etc.)Your Uncle Bob, Senior Geezer Curmudgeon
It's much easier to promise someone a "free" ride on the wagon than to urge them to pull it.
Luck occurs when preparation and opportunity converge.
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06-08-2004 11:38 PM #17
ok-
Now:
all the air that enters the core must also exit it.
Why would it make any difference whether the fan is obstructing the front or the back of the radiator core?
It will still cover the same surface area, right?
OR: does the condition of the air coming off the fan blades make a difference? When in front, the air will no longer be travelling straight into the core, but at some kind of angle coming off of the blades.
When in the back of a radiator core, the fan gets straight-flowing air, and nothing behind it cares WHICH way the air is flowing coming out of the fan?
However, the above explanation/hypothesis only matters when the fan is running, not when it is of and the system is working on ram air.
???
regards
Jay
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06-09-2004 08:06 AM #18
With an object in front of the radiator the air will "pile up", thus reducing flow. The air being fluid will seek the path of least resistance. This leads to another "theory" in cooling system design. If you look at a factory system there will be some method/effort made to seal around the core support so that all air will be induced to flow through the core, rather than seek another path. Often when folks modify a car they don't take this into consideration and remove "things" (seals, baffles, whatever) giving the air a chance to go over, under, or around the radiator.
A secondary adantage of the shroud on the back is that it creates a venturi effect (admittedly minor) that accelerates the flow of the air away from the core.Your Uncle Bob, Senior Geezer Curmudgeon
It's much easier to promise someone a "free" ride on the wagon than to urge them to pull it.
Luck occurs when preparation and opportunity converge.
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06-09-2004 08:15 AM #19
I have used both types (push and pull) and the pull works so much better. As a matter of fact, I tested the two simply by putting my hand in front or behind the radiator and the pulling action of the puller fan created a very noticable draft as opposed to the push. It just works that much better.
Don't question it any longer and get the puller type and you'll be happy.
The car I have now was set up with a push type and I'm definitely yanking that and installing a puller."Now bring me those cheese sandwich appetizers you talked me out of."
And a Happy Birthday Wish for Mr. Spears. Hope you can have a great one. :)
A little bird