Electric fans question/s

[Denee007]

Good morning!
I read somewhere, or maybe I dreamed it, but does an electric fan, such as mine, act as an air dam? Let's say I'm going 60mph, and the electric fan is running, does this keep air from free flowing through the radiator? Seems like the electric fan would be running all the time. Or does the electric fan draw more air than it would ever need even while cruising at freeway speeds? On another note~ I'm amazed of the heat under the hood after driving around a bit~ I could cook a turkey under my hood!
dne'

old picture from my archives:

[Indian113]

I have electric fans on both of my trucks, at 60 they don't seem t be running and my motor runs at the correct temp. My fans are set to come on at different temps as one is a carb motor and I like to run 195 with it, I can get by with a higher temp on my Ls motor in my S10. If your concerned about your fans running hook up a led light in the circuit to come on when the fan is on. Your set up looks good with the shroud and should allow the air to flow adequate for your motor and radiator.

[mknittle]

I would think no more than a stock fan with a shroud. That is if the fans are equal size. I should say equal air flow.
That sounds like something a racer would say given that "every little bit counts" in racing. Books and the internet are full of stuff that only applies to racing

[OrrieG]

When I was in the field we would toss our C ration tins on the exhaust manifolds and take a run down the road to heat them up when we did not have the time or resources to boil water or build a fire. It took a real scientist to make pork, chicken, beef and other mystery meats all taste the same...

As far as air flow the radiator fins will only allow so much air to pass thru, once the limit is reached the rest is pushed around the radiator. My guess is that limit will be reached before the fan blades and housing is a factor. Actually the fan should be free spinning from the air movement, not staying static when the truck is moving, like a pin-wheel.

[lazypineapple]

i dont think the electric fan do much in the way of cooling over 40mph.
if your temp switch is a 195 switch then if the engine is at 195 or better it will trigger the fan ON. moving or not.
i have that same fan/shroud on my 52 w/350sbc with a 195 switch and it runs all the time
my engine in this texas heat is running 205 @ 70mph .
and i dont like that, because when i get caught up in traffic or stop for a train i saw 230
on a 105 day last week.
that Low Profile fan only pulls 1300 cfm.
im upgrading to a 2800 cfm fan, i just got it today so we will see if that helps.
i must make a new shroud and find an inch more of clearence between radiator and pullys,

air follows the path of least resistance,
i had a big gap at the top of the core support and radiator where i was loosing alot of air, that wasn't being forced thru the radiator,
i made a plate to cover it and went for a drive , 105 day 70mph my temp was a steady 196.
but it didnot help the temp when i stopped for the dang train,
so thats why im going to try a bigger better fan.

look at the area in front of your radiator , you want all the air you can to be forced thru the radiator,
then stopped thats when the fans come into play,

from what i read on radiators you look for a 10 degree from top hose to bottom hose
use a infra red heat gun to ck

[Denee007]

Gee, one more "tool" i've been wanting to buy~ an infra read heat gun! Funny, I couldn't find the cfm for my electric fan, but it's about the only one I could find to fit my application. I suppose with a little more hunting, I could. But I really haven't given my system a chance yet. IT held steady the other day, but I'd sure like to know what the temp is under my hood on a blaring sunny day!eek! But it is a machine which develops a great deal of heat, so, I just need to quit thinking about it and enjoy it

[lazypineapple]

This the part number off the back of my fan
Va18-ap10/c-41a
I've seen is stated from 1280 cfm to 1300 cfm
Mine is identical to your photo. Even the shroud.
I got mine from Brothers.
When I shot the temp gun at the air coming out of the radiator air
It said 205 at
The intake where the sensor was was 200
Gauge was reading 208
All at idle
outside temp was 100
It never has
Boiled over.
I'm running 50/50 anti freeze
And and 18 pound cap
A low 90 degree day make all the difference
On a 110 degree day I think I'll drive my Honda :-0
Posted via Mobile Device

[Denee007]

Goodness~ Well, I'm with you! sometimes~ just take the modern vehicle! Give the old Gal a rest for day!

Originally Posted by lazypineapple

This the part number off the back of my fan
Va18-ap10/c-41a
I've seen is stated from 1280 cfm to 1300 cfm
Mine is identical to your photo. Even the shroud.
I got mine from Brothers.
When I shot the temp gun at the air coming out of the radiator air
It said 205 at
The intake where the sensor was was 200
Gauge was reading 208
All at idle
outside temp was 100
It never has
Boiled over.
I'm running 50/50 anti freeze
And and 18 pound cap
A low 90 degree day make all the difference
On a 110 degree day I think I'll drive my Honda :-0
Posted via Mobile Device

[1project2many]

In answer to the question, yes. If the cooling fan is running while you're driving it can actually impede airflow. OEM applications with a computer generally monitor vehicle speed and disengage the fan above a certain mph. The fan then able to freewheel at a speed that matches the airflow through the radiator.

That shroud is very close to the radiator. It looks like it might slow airflow at higher speeds. If you have problems you could try a simple cylinder from the fan to the radiator rather than that large shroud. Also, an air dam under the core support can create a low pressure area immediately behind the engine to help draw air down and under the cab. It can make a noticeable difference when moving but unfortunately it won't help you when sitting still. The only answer if you're too hot at idle may be more airflow. And this might be too little, too late but if I were building a system in hot country like Texas I'd probably try and install the a/c condenser down toward the bottom of the radiator. Hot water enters the top of the radiator so I'd try to get the coolest air possible there in order to create the most effective cooling. I'd even consider dual fans mounted vertically or kiddie-corner with a primary fan tied to coolant temp at the top, and the secondary fan tied to a/c pressure or temp near the bottom.

[fabguy]

I think it will impede airflow at higher speeds if it comes on, mainly due to the closeness of the fan to the radiator this is part of why I spaced mine away 1-3/4" clear on the inside. A quick fix (which I still have to do on mine) is to cut 2 ea) 3"round holes in the lower part of the shroud. Then take some 1/16" rubber flat and mount over the holes but only bolt it at the top of the rubber. Reasoning for this is to allow airflow at higher speeds but at the same time the "flap" should seal itself when the electric fan comes on because the fan will pull air and therefore pull the flap tight kind of creating a vacuum (for lack of a better word).

As for being the same effect as a factory fan, I don't feel that is correct because the factory fans usually have about an inch or so if not larger gap from the blade to the shroud which in turn allowed enough air to pass past the fan so to not restrict the airflow across the radiator.

I am by no means an engineer nor an expert on this, although these are just my thoughts and $ .02 As I said I am going to do it to mine, If there is an engineer on here that can correct me or agree with me please chime in.

[solidaxel]

Originally Posted by fabguy

I think it will impede airflow at higher speeds if it comes on, mainly due to the closeness of the fan to the radiator this is part of why I spaced mine away 1-3/4" clear on the inside. A quick fix (which I still have to do on mine) is to cut 2 ea) 3"round holes in the lower part of the shroud. Then take some 1/16" rubber flat and mount over the holes but only bolt it at the top of the rubber. Reasoning for this is to allow airflow at higher speeds but at the same time the "flap" should seal itself when the electric fan comes on because the fan will pull air and therefore pull the flap tight kind of creating a vacuum (for lack of a better word).

I am by no means an engineer nor an expert on this, although these are just my thoughts and $ .02 As I said I am going to do it to mine, If there is an engineer on here that can correct me or agree with me please chime in.

I have the same holes cut into the bottom of my shroud on the 55 GMC. I was told to do that by Madson Rad. or the Fan Man. it seems to work here in the desert with the AC and it has been a bit warm for the last 40 days.

As long as your temp gauge is staying put and not boiling it should be OK.
Try turning the fan off at highway speeds and see if the ram air will cool the engine, or keep it steady temp.

[Denee007]

Do I have enough room for the holes? what size holes and where would I get rubber flaps or maybe, light aluminum plate(seen it at ACE hardware) then make some hinges, then pop rivet? I would like a little light on my dash to let me know when the electric fan is on, maybe Dave can give me an idea of how to accomplish that. I wouldn't put it past myself to go back to a regular fan and shroud!
Further thought, lets say the fan cuts off at highway speeds, then the elec fan freewheels, will enough air cross the radiator, but I guess obviously if the elec fan cuts off, then it is getting adequate air. doah!

[Indian113]

At highway speeds neither of my electric fans run. Even in really hot day's, I've driven in 105 temps and the only time my fans kick on are at speeds lower than 50 mph.

[65Ch3v3LL3]

The flaps will help with high speed cooling but if you aren't having a problem there then I wouldn't worry about it. Many of the OEM fan setups have these flaps to let high pressure air through.

If you are having heating problems at low speeds or idling then you need more airflow. Not sure if you can fit it or not but the Ford Taurus electric fan is a 2 speed fan that flows over 5000 cu ft of air at full speed. You can pick up a new one for around $50 from the parts store. Just make sure you get some big relays to run it. 2 40 amp relays should work.