Electric fan size choice

[yellomalibu]

I would love to add a shroud but it would hit the front of the A-arms, Anyways the 2 12s almost over cooled so a 16 will work fine Im sure, Now other cars, yes a shroud is a must especially how easy they will fit like a nova or Camaro ETC.

I'll take "over cooling" any day of the week. A thermostat will prevent it from actually over cooling. I get nervous when the temperature creeps up - which takes away from the pleasure of driving whatever it is that I'm driving.

Also, a few degrees cooler can determine whether a car vapor locks or not. I didn't like being put on the side of the road in my Chevelle that hot summer day on my way to the track...

A stock mounted fan and shroud are what I will eventually go back to in my Chevelle. In my personal experience, that has worked the best for keeping temps low. Not best for bracket racing, but best for cooling.

I'm not saying that electric fans can't or won't work sufficiently. Clearly, they can. I just didn't mount mine properly, apparently.

[anotheridiot]

I'll take "over cooling" any day of the week. A thermostat will prevent it from actually over cooling. I get nervous when the temperature creeps up - which takes away from the pleasure of driving whatever it is that I'm driving.

Also, a few degrees cooler can determine whether a car vapor locks or not. I didn't like being put on the side of the road in my Chevelle that hot summer day on my way to the track...

A stock mounted fan and shroud are what I will eventually go back to in my Chevelle. In my personal experience, that has worked the best for keeping temps low. Not best for bracket racing, but best for cooling.

I'm not saying that electric fans can't or won't work sufficiently. Clearly, they can. I just didn't mount mine properly, apparently.

Pretty much what I am thinking. Just mount the shroud you have with the pulley fan, but mount your electric fan on that shroud if you have room. You get the draw from all corners of the radiator that way.

[yellomalibu]

See, I mounted my fans directly to the radiator, like pictured above - and it doesn't cool well.

I never thought about doing 'geek's smoke bomb test, but I'm sure some of the hot air is getting recirculated - certainly not all of it.

First I have to find a fan shroud that fits right... the "correct" ones they sell at NPD stop short of the tank on one side, leaving exposed, un-shrouded radiator - which doesn't make sense to me. Why wouldn't they shroud the entire core? This is why I haven't bought one yet.

The plastic flex-a-lite mechanically mounted flex fans have worked extremely well for me and other cars I've been associated with, when used with a factory shroud. On my car, without a thermostat, the temps didn't get over 160 in the summer, and were as much as 20 degrees lower than 160 while cruising. That's what I call "over cooling". Throw a thermostat in there and never worry about over heating.

[milner351]

Are these the "plastic flex - a - lite" fans you speak of? I just heard from a guy at work here yesterday that these worked great in his sbc luv and s10 trucks

http://www.summitracing.com/parts/SUM-G4947/

[anotheridiot]

Its not that you are recirculating heat, there is a 12 or 16" area of the radiator that is getting cooled, then the cooled water just circulates back to the tank on the other side and is mixed with water that just passed thru without a fan effecting it. Thats what the shrouds do, it draws air thru the entire rectangle of the radiator. So there might be some water cooled in the cycle, but that is just getting mixed back with the hot stuff.

[anotheridiot]

those flex fans, they made those out of aluminum too, tend to flatten out at higher rpm's to draw more air, but higher rpm's is when you are forcing more air thru the radiator anyway isnt it? maybe I just hated my aluminum one since I sliced two fingers open on it when tightening my alternator lol.

seems to go the route of using a stock fan from an airconditioned car so the clutch allows the fan to turn a few revolutions after you shut off your car.

[TC]

Are these the "plastic flex - a - lite" fans you speak of? I just heard from a guy at work here yesterday that these worked great in his sbc luv and s10 trucks

http://www.summitracing.com/parts/SUM-G4947/

Ya flex fans are great, well until a blade snaps off and goes through your hood...... This actually happened to a friend of mine....

[dieselgeek]

Its not that you are recirculating heat, there is a 12 or 16" area of the radiator that is getting cooled, then the cooled water just circulates back to the tank on the other side and is mixed with water that just passed thru without a fan effecting it. Thats what the shrouds do, it draws air thru the entire rectangle of the radiator. So there might be some water cooled in the cycle, but that is just getting mixed back with the hot stuff.

Do the smokebomb test. That combo is without a doubt recirculating heat, or more appropriately, only creating a Donut shaped area on the radiator that uses the same air over and over. He'd be better off to put a flat cover over the uncovered parts of the radiator (this is what some shrouds are) so that he's not using 100% of the same air over and over again.

[TC]

Its not that you are recirculating heat, there is a 12 or 16" area of the radiator that is getting cooled, then the cooled water just circulates back to the tank on the other side and is mixed with water that just passed thru without a fan effecting it. Thats what the shrouds do, it draws air thru the entire rectangle of the radiator. So there might be some water cooled in the cycle, but that is just getting mixed back with the hot stuff.

Also even if air was being pulled back through the radiator as a certain member describes, wouldn't it just mix with the cooler air being pulled through the radiator by the fan??.... Also I doubt that any of the air that would be recirculated as stated would be hotter than the coolant in the radiator, so in effect, it would still cool the radiator......

[dieselgeek]

TC, all it takes is a basic understanding of air pressure to see what's wrong in that pic. That, or doing the smoke bomb test.

Air naturally flows from high pressure to low, and it takes the shortest path possible. Turn on that fan, you have a high pressure area in the rear, and a low pressure immediately in front of the radiator. The high pressure air in the rear immediately goes straight to the low pressure area in the front, and without a shroud that means the air that just came out of the fan is going to go straight back to the front of the fan, and back through it again.

At least in the test I performed, all the smoke was collected and recirculated through the radiator fan. Taking away the smoke bomb, caused the smoke to STAY in that "donut" shaped loop.

I learned this because whenever I run into a car problem we can't figure out, I always do my best to test what's going on. I had no idea this is how a fan would work without a shroud. From what I can see, the shroud is there NOT to guide airflow through the entire radiator, but to keep the high and low pressure areas in front and behind the fan separated as possible. The smoke bomb test was suggested to me by another car guy in this case and it all made sense.

Thus my stance on what is wrong with that installation above. The air is just recirculating through the radiator and quickly becomes as hot as the radiator, not doing much cooling.

Do the test, see for yourself.

[TC]

Also putting a flat cover over any part of the core is a bad idea since it will prevent air from passing through the radiator core in that area and not allow that area of the radiator to do its job of cooling the coolant.....Your effectively making your radiator smaller by doing that, you'd be better off leaving it open..... Or like I said make a fan shroud that puts the fans an inch off the radiator...... And if space is limited you can go as much as a 1/2 inch off the radiator, but you need at least that much to allow air to pass through the core.....

[dieselgeek]

Also putting a flat cover over any part of the core is a bad idea since it will prevent air from passing through the radiator core in that area and not allow that area of the radiator to do its job of cooling the coolant.....Your effectively making your radiator smaller by doing that, you'd be better off leaving it open..... Or like I said make a fan shroud that puts the fans an inch off the radiator...... And if space is limited you can go as much as a 1/2 inch off the radiator, but you need a at least that much to allow air to pass through the core.....

That's funny because putting a flat piece on all the non-fan-covered areas of our problem car, was how we solved the problem. Our logic was that it's better to block off parts of the radiator then it is to allow hot air to recirculate through it. We called this a "shroud" but in reality all it did was cover the open parts of the radiator.

It worked amazingly well for us too.

Car was a 2001 Mustang GT with a single 76mm turbo, air conditioning still in the car and functional. Real car.

Your mileage may vary!

[TC]

TC, all it takes is a basic understanding of air pressure to see what's wrong in that pic. That, or doing the smoke bomb test.

Air naturally flows from high pressure to low, and it takes the shortest path possible. Turn on that fan, you have a high pressure area in the rear, and a low pressure immediately in front of the radiator. The high pressure air in the rear immediately goes straight to the low pressure area in the front, and without a shroud that means the air that just came out of the fan is going to go straight back to the front of the fan, and back through it again.

At least in the test I performed, all the smoke was collected and recirculated through the radiator fan. Taking away the smoke bomb, caused the smoke to STAY in that "donut" shaped loop.

I learned this because whenever I run into a car problem we can't figure out, I always do my best to test what's going on. I had no idea this is how a fan would work without a shroud. From what I can see, the shroud is there NOT to guide airflow through the entire radiator, but to keep the high and low pressure areas in front and behind the fan separated as possible. The smoke bomb test was suggested to me by another car guy in this case and it all made sense.

Thus my stance on what is wrong with that installation above. The air is just recirculating through the radiator and quickly becomes as hot as the radiator, not doing much cooling.

Do the test, see for yourself.

I call BS, the fan is blowing air at a high rate of speed which means that the smoke should be being blown out from under the car and to the back of the car..... Though I'm not saying that a small percentage of air can't be recirculated like your describing but it's not going to be enough to cause overheating problems, basically the outside air no matter where it comes from won't be hotter than the coolant in the radiator so it will still cool the radiator...... Think about my '99 Camaro and how it picks up the air that cools the radiator form under the car, then think about summer time here and how the asphalt can get as hot as 150+ degrees, but my car runs 190 degrees all day long........ Then there is the fact that none of it matters when your driving down the street where the air becomes pressurized in front of the radiator and is pushed through it, no fan needed...........

[dieselgeek]

I call BS, the fan is blowing air at a high rate of speed which means that the smoke should be being blown out from under the car and to the back of the car..... Though I'm not saying that a small percentage of air can't be recirculated like your describing but it's not going to be enough to cause overheating problems, basically the outside air no matter where it comes from won't be hotter than the coolant in the radiator so it will still cool the radiator...... Think about my '99 Camaro and how it picks up the air that cools the radiator form under the car, then think about summer time here and how the asphalt can get as hot as 150+ degrees, but my car runs 190 degrees all day long........ Then there is the fact that none of it matters when your driving down the street where the air becomes pressurized in front of the radiator and is pushed through it, no fan needed...........

no big deal, my actual testing trumps your theory all day long. Stationary fans don't blow air to the rear of the vehicle, they blow air to the nearest low pressure zone.

A simple smoke bomb test would set you straight, but I am not really concerned with winning any battles with you today. Every single member on this forum knows that one of us works on cars and the other doesn't ;-)

[TC]

That's funny because putting a flat piece on all the non-fan-covered areas of our problem car, was how we solved the problem. Our logic was that it's better to block off parts of the radiator then it is to allow hot air to recirculate through it. We called this a "shroud" but in reality all it did was cover the open parts of the radiator.

It worked amazingly well for us too.

Car was a 2001 Mustang GT with a single 76mm turbo, air conditioning still in the car and functional. Real car.

Your mileage may vary!

So your saying putting a flat piece of metal against the core and not allowing air to pass through it made the radiator cool better??...