Not convinced on fan

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Bobsticle

Bobsticle

De Villes Advocaat
Posts
27,632
Location
Manchester
I have had the standard fan off the series over winter to save on fuel, over cooling, power etc. Not that I am convinced that made any difference, but........................

Instead of putting it back on this afternoon I have fitted a very cheap electric fan of tinterweb.
I fitted it on the outside blowing through the rad but at 14 inches it seems a little small.

Any road up, fired it up and waited till it was up around 65 degrees on the top hose and flicked the fan on.

It stayed at 65.

Dropped a bit when I flicked the heater on and went back to 65 when switched off.

Not sure if its doin owt. Test drive in the morning.
 
If you put an electric fan on ideally have it after the radiator as it will have less of a windmilling effect when it's not switched on
 
Its a contentious subject but the old heavy steel windmills bolted to your water pump take a bit of shifting and as most series diesels need every HP they can muster it makes sense to ditch it and go electric.
At 80watt I should think any advantage of this is lost in the extra effort to turn the alternator but the other advantage is more control of the engine temp. They run cold most of the time and then overheat under load so with a decent thermostatic switch it could be possible to even things out a bit and get a little more out of the motor.
 
Last edited:
Grem said:
If you put an electric fan on ideally have it after the radiator as it will have less of a windmilling effect when it's not switched on
Click to expand...
I thought long and hard about this for no other reason than I didnt want to see the thing spinning away behind the grill. Then I thought I cant see that from the drivers seat so sod em.
I wanted to fit it in the cowl but it just isnt big enough and wouldnt pull anything through the rad coz of all the gaps. I did read however that they are most efficient pushing rather than sucking so that made my mind up in the end. I cant see any other disadvantages in it blowing in the wind.
 
When it's on the front of the radiator, not turned on and tour driving along, it is just slowing down and disturbing the air, therefore not cooilng the radiator quite as well, meaning it has to come on more often. Most electric fans especially cheap ones are really not designed to run for long periods, especially not continuous which may be necessary if ever towing or similar. So the aim is to make everything as good as is reasonably possible to make life easy for the electric fan
 
I did this on my series 2 109 with a 2.25 diesel lump and made zero difference. In Britain fans really aren't needed. I've got a Tdi in my 109 now with no fan and the temperature stays fine on hot days when towing 2 tonnes up a 13% gradient in first gear engine working hard. The 200tdi defender is the same and when someone at work overloaded the trailer I was towing it was moving 3.5- 4 tonnes up the same hill in low range 2nd gear with no fan and no problems.

The myth about electric fans giving more power is just that, a myth.
The load on the alternator to power the electric fan makes turning the alternator harder which makes the engine have to work harder. It makes sense to have one for piece of mind but depends on how you use the vehicle I guess.
 
Ive bought a cheap electric fan for my lightweight which has a tdi ,i hope it wont need it but it will be nice to have just incase and i couldnt put the viscous on as there wasnt room

I cant decide which side of the rad to put it ,if behind it would need to be mounted on the intercooler and if in front it will keep some air from getting to the rad and will get wet when it rains

Does it make any difference
 
You need to check the water temperature in the bottom hose not the top as that water is coming out from engine to be cooled.
 
If the rad is in good condition , most of the year, and depending on what you are doing , you dont need a fan at all.
Once you are traveling at speed :) the fan isnt really doing anything as the airflow is forcing the air thru rad .
If its hot and you are say climbing a hill slowly towing then thats when the fan is needed, the idea of the viscous fan is to freewheel until needed , so no drag on engine . So if you go to leccy fan then it needs to be big(powerful) one as when its needed its going to move a lot of air . Years ago i had 2.25 diesel 109 which i built using all the tropical; spec accessories , including oil cooler, and 13 blade tropical fan (needed twin fan belts to drive it) once climbing thru the Alps towing a broken down VW camper van , i watched the temp guage actually going down as I was flat in 2nd up hill the airflow caused overcooling ! .
 
The only time my mine gets hot is when in traffic. I also once overheated it whilst tinkering on the drive. hopefully it will be enough. I always have the option of popping the windmill back on.
 
I have considered fitting one of the white plastic fans as used on the 2.5NA engine (if it will fit). It looks to be lighter and more aerodynamically shaped.

From photos it looks like it would fit the series engine.
 
No problems so far with the £14 one I fitted during the recent warm weather and at that price I won't mind bunging the odd new one on if and when required.
 
Bobsticle said:
Its a contentious subject but the old heavy steel windmills bolted to your water pump take a bit of shifting and as most series diesels need every HP they can muster it makes sense to ditch it and go electric.
At 80watt I should think any advantage of this is lost in the extra effort to turn the alternator but the other advantage is more control of the engine temp. They run cold most of the time and then overheat under load so with a decent thermostatic switch it could be possible to even things out a bit and get a little more out of the motor.
Click to expand...
But the alternator is not a belt device as far as the output is concerned.... i.e a Serpentine belt spins a magnet in a coil and produces current. There is no extra effort to turn this coil, any power you don't use is simply lost into the batteries/electrical system. The efficiency of the alternator and power of the engine are the only factors on the input side.
 
ER1C said:
But the alternator is not a belt device as far as the output is concerned.... i.e a Serpentine belt spins a magnet in a coil and produces current. There is no extra effort to turn this coil, any power you don't use is simply lost into the batteries/electrical system. The efficiency of the alternator and power of the engine are the only factors on the input side.
Click to expand...
Using the out for nowt physics is there no more force required to take more out?
 
Bobsticle said:
Using the out for nowt physics is there no more force required to take more out?
Click to expand...
Not as far as I am aware, I suggested this on this forum some time ago and some argued, some agreed, There is no contact with the magnet and the wire so why would there be more force needed ? Think of it as generating 100w and that's it.... Its a bit like its raining, catch it in a bucket (its more efficient) don't catch it in a bucket (its wasted)
 
2 things....
1 you always check water temp coming out of the engine as that is where it is hottest, otherwise you are measuring cooling system efficiency.
2 the advantage of a lecky fan, is that it only uses power when it is on, ie rarely, unlike an engine mounted fan which uses power all the time.
 
Daft question.
Is it hottest at the top hose or the bottom one.
I presumed the top one and put my temp sensors in this.
 
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