Yet another "My XJ Runs HOT" Post

[BillabongXJ]

Originally Posted by Redemptioner

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.

Earlier you quote 1500 and 3750cfm respectively for 10 and 16" fans. So a little bit of maths thats a 2.5 multiplication, the same as the chart I posted with 650 and 1900cfm fans. That chart is good for something even if the fans are 'terrible'.

Im familiar with what a properly engineered thermo fan set up looks like. Are you taking dimensions into consideration at all here? Jeep didnt leave a lot of room when they jammed a 4.0 i6 in their XJ but us would still like to keep it over the chev v6. Thank you very much! So if you plan on trying your 3000cfm fan in an XJ you might want to take the time to look at the images in my previous posts you will see any larger fan will simply crash into the engine.

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).

This might actually count for something if it was a taxi we're talking about but for a weekend driver, ive got a lot of use out of my $45 fan motor and Ive done a much neater job with my mark II fan. Has the lower portion of the shroud intact and ive milled a notch to let degree from water crossings pass out also my 16" fan doesn't run all the time. So it should last the rest of the life of the car.

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.

that may be true if 50% is missing... and it isnt.

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.

No, you just have to make the shroud from scratch. Much easier! Since your offering, Id really like to hear about your solution that's cheaper, better and easier.

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.

And this is *why* people like electric fans, they can sit in traffic and dont over heat. Cars used to come with manuals telling the owners to put the car in neutral and rev the car in traffic to keep it cold. You would rather go back to the good old days?

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 ......

There is no restriction, the fan is mounted in the shroud. if the fan was mounted flush against the radiator there would be no point for the shroud to be there. The shroud allows enough space for the ambient air to normalise after passing through the radiator matrix. We're not dealing with compression here the fan is just pushing around some ambient pressure air at sub sonic speed. The ducting works fine.

[BillabongXJ]

Originally Posted by Redemptioner

lol, if only you knew the maths behind the performance drop you would understand that the 2x 10 inch fans far exceeds that setup,

I dont think 2 10" fans will pull more air, theres definitely more radiator surface covered by the fan using a 16" fan compared with the 10" fan. The motors are the same size. Also your own admission bigger is better and stuff about tip speed. It all goes to say a 16 inch fan is better when fitted in the factory shroud is the way to go. You haven't backed any of your solutions up all we are getting is a lot of hand wavery about 1500cfm 10" fans. Do they even fit?

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.....

You could say that the 4.0i6 is a hack. It was hot rodded from factory because it was designed for a short V6 and they knew this would compromise some things. One of the things that they ended up with the weird long skinny radiator. They weren't trying to put the 'smallest available clutch fan' in there they put the biggest they could fit, any taller and it would hit the bonnet that's why it was pushed down.

[Redemptioner]

Originally Posted by BillabongXJ

Earlier you quote 1500 and 3750cfm respectively for 10 and 16" fans. So a little bit of maths thats a 2.5 multiplication, the same as the chart I posted with 650 and 1900cfm fans. That chart is good for something even if the fans are 'terrible'.

So we can add bad maths to your terrible chart, 650 with a "2.5 multiplication" does not equal 1900

Im familiar with what a properly engineered thermo fan set up looks like. Are you taking dimensions into consideration at all here? Jeep didnt leave a lot of room when they jammed a 4.0 i6 in their XJ but us would still like to keep it over the chev v6. Thank you very much! So if you plan on trying your 3000cfm fan in an XJ you might want to take the time to look at the images in my previous posts you will see any larger fan will simply crash into the engine.

Ummm I support using 2-3 (dependant on size) smaller electric fans and not trying to jam in a 16" fan in or did you miss that bit.....

No, you just have to make the shroud from scratch. Much easier! Since your offering, Id really like to hear about your solution that's cheaper, better and easier.

If only there was some sort of world wide database you could type a question or string of words into and have it search the database for a list of matches.....

And this is *why* people like electric fans, they can sit in traffic and dont over heat. Cars used to come with manuals telling the owners to put the car in neutral and rev the car in traffic to keep it cold. You would rather go back to the good old days?

What on earth are you talking about man?

There is no restriction, the fan is mounted in the shroud. if the fan was mounted flush against the radiator there would be no point for the shroud to be there. The shroud allows enough space for the ambient air to normalise after passing through the radiator matrix. We're not dealing with compression here the fan is just pushing around some ambient pressure air at sub sonic speed. The ducting works fine.

and that space is where exactly?

[BillabongXJ]

Divisible by 2.5 gives you the same difference.

So where is your cheaper easier and better? You must be a magician, hard to beat a $45 fan...


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[BillabongXJ]

Ummm I support using 2-3 (dependant on size) smaller electric fans and not trying to jam in a 16" fan in or did you miss that bit.....

how is this cheaper than a $45 16" fan. who are your suppliers? and are you friendly with the lazercutters to make the shroud? are you now ok with hanging 3 thermo fans through your radiator matrix with nylon cord? How do you get the rocks out of those? do you have to fit them to the radiator before you put it in? wow where can i buy these? how much!

If only there was some sort of world wide database you could type a question or string of words into and have it search the database for a list of matches.....

What on earth are you talking about man?

Re your unusual concern that half speed electric thermo fans still flow too much air in traffic. That will be the day when an XJ owner complains about their engine being too "cool" lol

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.

[/QUOTE]

There seems to be something not lining up with the bottom radiator lugs.

Wouldnt be an issue for you running tripple fan setup, going by your earlier posts you would argue to throw away a couple of purpose made plastic shrouds and make your own out of a piece of tin and thread it through the radiator core with some nylon cord.

Try this one for space between engine and fan that's with a slim line 6.25cm fan
http://www.ausjeepoffroad.com/forum/...&postcount=123

some other points in favour of the 16" fan

2 screws and a plug and i can remove the 16" fan out. to clean it or for access to do maintenance.

going down the highway the 16" fan would be less restrictive to natural airflow than the 3 smaller fans so the fan will have to come on less often.

[junglejuice]

Originally Posted by Redemptioner

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.

I read it, fact remains that on low speed mine cools effectively in heavy traffic, once moving along at a 40-50kmh I can turn the fans off with no change in operating temp, if I use high speed (selectable manually) it gives me significantly more cooling capacity due to a large increase in airflow.
After all low speed (traffic, offroad crawling etc) is where you NEED effective cooling, once driving the fans do nothing......

[junglejuice]

Originally Posted by Redemptioner

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.


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.


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 ......

I too would love know where these magical (cheap) fans are being sourced from? My 16" fan was from ebay, cost around $50 and fitted pretty well straight up to the stock shroud. mp custo, shrouds required, yet you'd have us believe that a full custom shroud and 2 new fans is "around the same money", I call BS.
Plus I still fail to see why you're advocating ditching the stock 12" fan with full shroud to go back to a 10" fan, makes zero sense to me.....

Also I fail to see how a flat sheet run directly behind the radiator with a hole cut into it can be considered a "good" ducted shroud with large areas effectively blocked off from airflow.....