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Electric fan or mechanical? Facts here!

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22 minutes ago, Bowie69 said:

So basically it comes down to application, and making it specific/suitable to your vehicle and expected use :) 

Hehe just like everything else yes :D But there's no fun in that, we need arguments for this never ending battle :D 

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Is this the 5 minute argument or the full half-hour? :ph34r:

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But I just gave you 5 pounds !

 

i don't quite see why this is made out a battle. I had a viscous fan it was fine, I went to electric which was also fine and for my current engine I went back to viscous. Overall I've settled on simplicity over efficiency but the electric fan was fine and with a nice x eng controller I'm sure would be great.  Both will work but the video was nice indication on how much a mechical fan asks of the engine (albeit at 6,500 rpm).

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4 hours ago, FridgeFreezer said:

Just to throw some variables in: I have smaller twin electrics, set to come on half speed then full speed as temp rises. Pretty much never come on full speed, and draw is less than 20A at half speed.

It's zero when they're off which is most of the time, so less than any mech fan no matter how good.

Entirely true, but a viscous fan will be windmilling at most rpm/road speed combinations too, so will not be using significant engine power.

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7 hours ago, FridgeFreezer said:

Is this the 5 minute argument or the full half-hour? :ph34r:

Depends what your willing to pay? If you subscribe to the full One-Year Unlimited Banter and Bashing deal we will keep going for 12 months..

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Posted (edited)

With the 200TDI, the stock shroud restricts intercooler flow quite a bit.  You can see a significant change when it is removed.  So, at least for that engine, the argument is not valid.  No cars that I know off have fans on the intercoolers.

Edited by Red90

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For a pure off road vehicle, a temperature switch on the intercooler running a small fan could be a good way to overcome this?

Oh, and for charge coolers, fans are often fitted to the radiator.

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14 minutes ago, Red90 said:

With the 200TDI, the stock shroud restricts intercooler flow quite a bit.  You can see a significant change when it is removed.  So, at least for that engine, the argument is not valid.  No cars that I know off have fans on the intercoolers.

I've heard exactly the opposite said as well, so who knows?!  These comments were in reference to the viscous fan pulling more air over the intercooler with the shroud fitted vs with it removed. 

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1 hour ago, Red90 said:

With the 200TDI, the stock shroud restricts intercooler flow quite a bit.  You can see a significant change when it is removed.  So, at least for that engine, the argument is not valid.  No cars that I know off have fans on the intercoolers.

If you remove the shroud, no air gets drawn through the intercooler, as the fan sits behind the radiator. Also, the fan in free air is not as effective as when inside a tunnel.

All the electric fan installations I have seen, did not draw any air through the intercooler.

Taking off the fan immediately saw a 10 degree temperature rise in the intercooler temps at modest speeds, and much more when stationary (almost stuck).

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17 hours ago, Red90 said:

With the 200TDI, the stock shroud restricts intercooler flow quite a bit.  You can see a significant change when it is removed.  So, at least for that engine, the argument is not valid.  No cars that I know off have fans on the intercoolers.

That's the complete inverse of reality - the intercooler needs the shroud even more than the rad, and the fan is very inefficient at cooling the rad too without the shroud.  Manufacturer names don't affect the laws of thermodynamics.

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The shroud on a 200TDI Defender blocks air flow.  It was very poorly designed.  I've done the testing.  IATs and EGTs drop when it is removed.

You (obviously) do not use the mechanical fan with the shorud removed.  That is the whole point of this thread, discussing the switch to an electric fan.

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I saw an electric fan take a bite out of a radiator recently (1st time I've seen it happen), the interesting point was that the bite was relatively small and the fan fuse blew, stopping the fan and preventing further damage. Rad could be patched & fuse replaced.

I've seen radiators chewed beyond repair by mech fans, which of course don't blow a fuse...

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This is the 200TDI Defender shroud.  I marvel of bad engineering.

13468-2.jpg

 

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10 minutes ago, Red90 said:

The shroud on a 200TDI Defender blocks air flow.  It was very poorly designed.  I've done the testing.  IATs and EGTs drop when it is removed.

You (obviously) do not use the mechanical fan with the shorud removed.  That is the whole point of this thread, discussing the switch to an electric fan.

I may have completely the wrong end of the stick here, but are you saying you compared the mechanical fan + shroud to an unshrouded electric fan setup?

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It is the whole topic of this thread.....  Mechanical fan with its shroud versus electric fan with its shroud.....  Normally you would not shroud the intercooler with the electric fan as it will restrict flow at speed unless the fan runs all of the time.

Earlier people were saying that one reason to keep the mechanical fan was that it moves "some" amount of air even when the clutch is not locked up and this provides intercooler air flow during low speed driving.  I do not disagree.  I was trying to point out that in the specific case of the Defender 200TDI, the stock shroud restricts intercooler air flow because of its poor design.  When you remove the shroud, you will see much better intercooler performance.

The reality is there is not much need for intercooler air flow at low speeds.  It is very hard to find a situation where you are running sustained full throttle while driving slow.

 

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I think Red90 is referring to when driving down the road, rather than when almost stationary off road, just in case it wasn't clear :)

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19 minutes ago, Red90 said:

The reality is there is not much need for intercooler air flow at low speeds.  It is very hard to find a situation where you are running sustained full throttle while driving slow.

 

1st and 2nd low are pretty slow with potentially sustained throttle?! Most things you'd do offroading won't be that fast!

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22 minutes ago, Red90 said:

The reality is there is not much need for intercooler air flow at low speeds.  It is very hard to find a situation where you are running sustained full throttle while driving slow.

 

And nor is there much need for 6000rpm at no or low speed, but that is what the test did...

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Burnouts? Come on, can't believe you didn't think of that one ;)

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Posted (edited)
21 hours ago, Red90 said:

 

The reality is there is not much need for intercooler air flow at low speeds.  It is very hard to find a situation where you are running sustained full throttle while driving slow.

 

An odd statement to make when I know you drive rough terrain. An intercooler is working from the moment forced induction takes place - in fact in some cases it works prior. A reduction in input temps by even the tiniest amount equate to additional volume of air. When driving through deep mud, sand, thick gravel, uphill, through deep water and many more situations and intercooler is working to some degree

Edited by honitonhobbit

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To be fair, I've never needed an intercooler at low speeds thefinger.gif

On a technical point, didn't Daan instrument his 200TDi a while back with a collection of thermal sensors and post his results up? Much as I hate to introduce science to a good internet argument :P

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It's such an old argument, but it still boils down to this: if electric fans are so damned good, why have LR, Jaguar, BMW, Roll, Mercedes and such all avoided them?  How many tens of millions of cars have they made with engine driven fans?

Electric fans might be OK for small hatchbacks and town cars which drive in moderate conditions and only need short spells of mild cooling flow while sitting in traffic or at junctions, but think about how they work - they either produce a low to moderate amount of airflow or none at all.  They cut in after the engine is already getting hot and fight the temperature back down.  They can do that on an idling engine, but take the off roader's or towing vehicle's conditions where the engine is now working hard at low speed and that fan is not going to produce enough airflow to do the job.  An electric fan will keep a Land Rover's engine temperature well under control for a drive through town, but mudplugging or roack crawling, even desert driving, and it's not going to be enough.

As for the shroud being bad engineering, it's the best that could be managed in the space available, and while it does block ram flow at high speed, it doesn't cause any impediment at low speed when the fan is pulling air through the rad and intercooler.  Conversely, unless you have twin fans with one covering the intercooler, low speed high boost is going to suffer.  So, that imperfect shroud if far superior engineering to a typical electric fan installation.

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The *only* time my fans come on full speed is doing donuts in low-range for prolonged periods. The rest of the time (including towing at the weight limit, or driving up Trollstigen or Susten_Pass for example) they only ever run briefly on half speed.

My Jaguar has an electric fan, my Freelanders had electric fans.

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55 minutes ago, FridgeFreezer said:

My Jaguar has the engine stuffed in sideways, my Freelanders had the engine stuffed in sideways.

 

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