Yet another "My XJ Runs HOT" Post

[Redemptioner]

Originally Posted by BillabongXJ

Wow running a fan like that is more or less a waste of time with that massive pressure drop on one side and massive increase almost opposite it (not to mention it will significantly shorten the life of the fan). You would be far better off running a much smaller fan (like the one next to it) as it will last longer and pull twice as much air through the radiator or run dual smaller ones and give yourself some redundancy (from memory 2x 10" fans fit perfectly or 3x 7" fans if you want a bit more air flow), I bet it makes an "awesome" sound when running like that .


Not having a go at you man, kudos for having a go but that is some seriously agricultural sh$t

[oldon]

Originally Posted by rainman

Are you using a high flow pump as well?

Not yet mate, have one here but too lazy to fit it. I have the radiator out & haven't found any trace of the restrictor yet. End tank seal is leaking, might pull the tank off for a sticky inside.

[junglejuice]

Originally Posted by Redemptioner

Wow running a fan like that is more or less a waste of time with that massive pressure drop on one side and massive increase almost opposite it (not to mention it will significantly shorten the life of the fan). You would be far better off running a much smaller fan (like the one next to it) as it will last longer and pull twice as much air through the radiator or run dual smaller ones and give yourself some redundancy (from memory 2x 10" fans fit perfectly or 3x 7" fans if you want a bit more air flow), I bet it makes an "awesome" sound when running like that .


Not having a go at you man, kudos for having a go but that is some seriously agricultural sh$t

As this is the same sized fan as the factory one I fail to see your point, it's a common and very effective mod (to use a 16" electric fan in place of the clutch fan), 2 10" fans is nowhere near enough, the factory aux fan is a 12" unit, the only issue is the open lower portion of the shroud, normally this is left intact.....

[Redemptioner]

Originally Posted by junglejuice

As this is the same sized fan as the factory one I fail to see your point, it's a common and very effective mod (to use a 16" electric fan in place of the clutch fan), 2 10" fans is nowhere near enough, the factory aux fan is a 12" unit, the only issue is the open lower portion of the shroud, normally this is left intact.....

lol, if only you knew the maths behind the performance drop you would understand that the 2x 10 inch fans far exceeds that setup, on the OEM setup they make sure that both sides of the fan that extends out past the radiator is even top and bottom and blocked from free air to help ensure the low pressure area is only created through the radiator fins and not out one side (as well as to try and reduce how quickly the fan fails). You will also note that the over diameter fan/shroud is only done to the clutch fan, it is still a very poor way of doing it and I would imagine the only reason jeep did it was because the smallest available clutch fans they had were that size at the time and hence why the extra auxiliary fan is there to back it up because it is such an inefficient way of doing it.....

The 12" Aux fan will be capable of doing far more cooling than either the clutch fan or that 16" electric fan "hack" would ever hope to do (assuming the 12" fan is semi-decent and flows a reasonable CFM for it's size), there is a reason aftermarket kits don't look like that . Grab yourself a cheap pedestal fan and cover up the top quarter of it on the back side (the side the air is being sucked in from) and you will feel just with your hand the performance drop off is much more than a quarter of the flow. If the fan was setup to push air through the radiator with the large gap to one side (and blocked on the other) then there would be far less of an impact on the air flow compared to it being on the suction side but setup the way it is you are realistically wasting your time and money. Most of the "suction" is being created in the last 1/4-1/3 of the blade (the part furthest from the centre), disrupting this means very poor performance for the entire fans rotation and not just the bit that is blocked by the shroud or open to free air. A half decent 10" 12V electric fan should be able to do around 1500cfm in pull format, times that by 3 fans and you have easily over 3500cfm even when pressed hard up against the radiator fins without a gap or shroud (which by the way also reduces performance), I would doubt that 16" fan is even capable of that air flow in free air let alone setup the way it is in the picture, my guess is it would not be getting even close to 1000cfm.

Doing the 16" electric fan hack might be a commonly done modification (and I use the term modification lightly) but it certainly does not mean it is a good modification or even come close to being the way you should be doing it if you want to change over to electric only. Don't worry I have heard people going "but the engine stays way cooler when sitting in traffic and cools down quicker when when I stop"..... they never bother to think about the fact that the electric fan is going at full speed vs the clutch fan barely spinning when the engine is at idle (clutch fans are only making decent airflow above 3000rpm), the only reason people seem to think it is effective is because the clutch fan had been failing for a while when they finally notice the increase engine temp and decided to change it out compared to after the electric fan is installed and when the electric fan turns on it is running at full pelt rather than being dependant on engine speed like the clutch fan.

[BillabongXJ]

16" flows as much as 2 10" fans. This chart 1900cfm and 650cfm.

This electric fan modification was done so it can be switched off in water crossings not necessarily to improve the cooling from clutch fan. I use the original setup in one of my XJs and the temp gauge sits lower by about 1/8th on the gauge compared to my twin electric.

Electric fan is used with shroud sealed almost hard against radiator.

Over diameter wont be an issue with air being pulled through the radiator. Gases can travel upto 800km/h. An intact original shroud would help direct the suction to the radiator core.

The half shroud was done by someone for convenience to take it off the vehicle. Im trialing my mark II fan which has a full intact shroud, pics in previous post, and the temp is staying straight up and down.




Sent from my iPhone using Tapatalk

[junglejuice]

Originally Posted by Redemptioner

..... they never bother to think about the fact that the electric fan is going at full speed vs the clutch fan barely spinning when the engine is at idle (clutch fans are only making decent airflow above 3000rpm), the only reason people seem to think it is effective is because the clutch fan had been failing for a while when they finally notice the increase engine temp and decided to change it out compared to after the electric fan is installed and when the electric fan turns on it is running at full pelt rather than being dependant on engine speed like the clutch fan.

My electric fans run in series when on low speed so each fan gets approx 6-7v meaning they run considerably slower then when running on full power, and yet they still cool very well in traffic, hmmm...

Also the bottom of the fan isn't "blocked" it is ducted albeit reasonably sharply....

[Redemptioner]

Originally Posted by BillabongXJ

16" flows as much as 2 10" fans. This chart 1900cfm and 650cfm.

They are terrible fans you are showing there for a start so lets just make that clear, this is particularly so when you have a fan pulling 230W for only 1900cfm in the 16" (should be only be around 80W for that same flow in a decent fan). Like I said a half decent 10" fan is around 1500cfm for about 80W so maybe start with a chart that has a 10" putting out around this then look at what their 16" fan does, so using that chart you found for anything other than saying "they are really crap fans" is a waste of time.

Electric fan is used with shroud sealed almost hard against radiator.

Almost as bad as running the fan overlapping the radiator with one side open to free air...... You need a gap to allow the blades to operate at a higher pressure (move a lot more air while reducing load and wear on motor) and to ensure that the blades don't/can't hit the fins along while ensuring the vibrations don't wear through on the sides where it is touching the radiator (especially on a aluminium radiator).

Over diameter wont be an issue with air being pulled through the radiator. Gases can travel upto 800km/h. An intact original shroud would help direct the suction to the radiator core.

I don't think you understand the blade element theory or aerodynamic principles at play here, suffice to say you are probably losing over 50% of the fans possible capacity setup as per previous image, as a result it will run hotter and draw more load.

The half shroud was done by someone for convenience to take it off the vehicle. Im trialing my mark II fan which has a full intact shroud, pics in previous post, and the temp is staying straight up and down.

I absolutely get that people are doing it because it is easy, that doesn't change the fact that there is a far better way of doing it for around the same money and I would imagine it probably works out being much easier to install as you don't have to make a fan fit an existing shroud.

Originally Posted by junglejuice

My electric fans run in series when on low speed so each fan gets approx 6-7v meaning they run considerably slower then when running on full power, and yet they still cool very well in traffic, hmmm...

Ummm no one is arguing there, probably should read again , what was being stated is the electric fan (or fans in your case) will be running a lot more air through the radiator when engine is at idle then the clutch fan will be even if the electric fans are at half speed.

Also the bottom of the fan isn't "blocked" it is ducted albeit reasonably sharply....

More or less the same as being blocked as the really low pressure zone and parasitic drag will eat any benefit you might gain from having a slightly large opening on the other end of the restriction. You are interrupting the intake side of the fan, even a little bit of restriction has great impacts and here we are talking about 2 massive square restrictions before we even look at modifying the the shroud or ......