Electric fan or mechanical? Facts here!

[Davo]

18 hours ago, Snagger said:

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.

However like you, I live in a ridiculously hot climate, but I've found the viscous fan just didn't do the job after a long highway run, or at idle. This is on a carburetted engine, not injected, so I keep it pretty cool in comparison. 

Usually I've found in these discussions people tend to get confused and think the debate is between the original viscous fan and a single electric fan with no shroud. Of course the viscous is better than one of those. It's the fully-shrouded dual fans which move so much air when you need it. 

[FridgeFreezer]

19 hours ago, Snagger said:

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.

Ah, found what I was looking for...

[Bowie69]

Electric fans can move as much air, just need to spec it right.

[Troll Hunter]

Hi,

As I've said in an earlier thread on this topic I've tried both.  My vehicle was originally fitted with a 3.5 V8 in ME spec with a viscous fan and had A/C.  Relatively hard use in Kuwait, both at high speed on the highways and off road in desert sand following pipelines for hours at a time never gave any indication of overheating.  The A/C condenser had its own electric cooling fans (2) mounted in front of the radiator and worked well.  LR engineers got it right for that environment.  

After I had a 300 Tdi dropped in I re-fitted those two small fans, with one ducted - home made - to push air through the intercooler, and the other to push air through the radiator with the standard rad shroud fitted.  I removed the viscous fan and fitted an electric fan, same diameter, resurrected from a local scrappie, but I can't remember details of the donor vehicle.  I wired the small fan for the intercooler to be always on with the ignition, that way ensuring an air flow even when stationary.  The other two fans were wired through an X-Eng dual thermostatic switch, the smaller one coming on at 82 degC and the larger one coming on, I think, at 88 degC.  Yes, I did suffer overheating on rare occasions but only when going up some of the really long and steep passes we have here.  I traced the deficiency to the cabling I had installed supplying the fans.  I noticed that at night if the main fan switched on my spotlights dimmed - powered through the same sub-panel.  I had under sized the cabling, and rather than get into a biggish re-wiring project I removed the larger electric fan and refitted my viscous fan.  I disconnected the small fan for the radiator but still have the small fan dedicated to the intercooler running at all times..

I am in the process of a complete tear down and rebuild of my Landy and I will be re-installing the three electric fans but with adequate sized cables.

Mike

[Bowie69]

So in other words, in the UK electric will be fine....

And also said above, properly engineered electric will be fine in the desert!

[Troll Hunter]

Sorry if I was misunderstood.  My electric installations were only in UK and then in Canada, not in Kuwait.  It was the steering defect evident in UK, turning left at every filling station, that prompted retro-fitting the 300Tdi, and subsequent electrification.

Mike

[muddy]

Red90 that is not a defender 200tdi fan cowl that's a disco 200 or defender 300.

 

just for the threads sake I have a viscous fan cos it works so I left it alone.

[Snagger]

Davo, yes, I am referring to the single electric fan replacements because that is what the vast majority of those who remove the viscous units use.  Multiple electric fans will work far better, possibly incorporating the intercooler too, and, set up right, should have plenty of capacity for northern Europe, but a single electric fan just doesn't have the muscle in the desert or tropics.  Sorry you disagree, Fridge.  Maybe you should be Land Rover's chief engineer, since you can save them so much money?  Or maybe you could try substantiating your position rather than just saying "no"?

[FridgeFreezer]

Snagger, I've not said anything about costs, I've nothing much against engine driven fans (they're just not my preference, and don't work for my applications), but since this thread is supposed to be factual I had to call bullsh*t on your absolute statements that electric fans cannot possibly work, that JLR don't fit them, etc. etc..

A correctly specced electric fan will work as well as a correctly specced mechanical fan. That's it. Easy as that. It doesn't matter if it's one fan or two, cowling or no, if the setup is done properly it will work properly.

So how about putting your willy away?

[Snagger]

Fair enough.  A well researched and specced electric unit will work.  What aggravates me is the cheap, off the shelf "one size fits all" kits sold in so many publications that are typically installed by folk thinking they're getting real benefits that don't exist.  I have a Tdi with its viscous fan in my RR and a Tdi with an electric fan in the 109 because an engine driven fan won't fit without an unreasonable amount of other alteration.  It has given problems, not least initially because it was labelled a puller, with all the associated documents and fitting guide, when it was in fact a pusher, but even after rectifying that, it doesn't have anywhere near the capacity of the viscous unit and the engine takes much longer to warm up than the RR's.  It doesn't come often in the UK, but was very busy in the Alps and I don't really trust it.  I may eventually fit the spare RR aircon twin fans as a back up.  My experience of both types on similar engines gives me a different opinion from yours.

[Bowie69]

But why do you think the electric-fanned engine take longer to warm up?

I would expect the opposite to be true, I assume thermostat etc is the same and known good?

[Soren Frimodt]

TBH I think that no matter how much anybody would want to argue, the question about reliability is quite simple.

Solid fan driven by the belt at all times is, obviously the most reliable (least prone to stop cooling)

Viscous fan, second most reliable in the way that it might in some cases break free in the viscous and not spin, even earlier than some electric fans will stop working but it is much easier to do a roadside repair with a piece of string/shoelace/wire/ziptie etc.

Electric fan least reliable, seeing as there is many more parts that can go wrong, several connections, wires, relay, thermoswitch, the blower motor itself. many of these things can be fixed in the side of the road as well, but would require more tools, parts and time. And if the motor itself stops working there is nothing to do whatsoever.

Am I missing something?

[Snagger]

19 minutes ago, Bowie69 said:

But why do you think the electric-fanned engine take longer to warm up?

I would expect the opposite to be true, I assume thermostat etc is the same and known good?

I would expect so too, and this is one of the marketing claims by several manufacturers.  I'm not talking about a small difference, either - the 109's engine takes roughly double the time/distance to reach normal temperature than the RR.  The thermostat has been replaced three times with new genuine items to no effect, so I put it down to the layout of the engine bay and free flow of ram air.  It's also only the 109 engine that has ever run close to the red zone, the RR never getting above half way up the normal scale.  This is why I think faster warm up times are another unreliable claim from salesmen, and getting back to the video at the beginning of the thread and your comment that the engine bay has a lot of effect, it seems good evidence to your comment and against the validity of their tests for any useful data.

[mad_pete]

I suspect all the extra fuel the engine is chewing through to turn the mech fan helps warm things up nicely. ;-)

[Snagger]

22 minutes ago, mad_pete said:

I suspect all the extra fuel the engine is chewing through to turn the mech fan helps warm things up nicely. ;-)

I doubt that any extra effort on the fan comes close to the extra effort required for a 109's aerodynamics, especially with a Brownchurch rack, lights and plenty of other external additions compared to the smoother lines and smaller profile of an RRC. 

[Bowie69]

57 minutes ago, Snagger said:

I would expect so too, and this is one of the marketing claims by several manufacturers.  I'm not talking about a small difference, either - the 109's engine takes roughly double the time/distance to reach normal temperature than the RR.  The thermostat has been replaced three times with new genuine items to no effect, so I put it down to the layout of the engine bay and free flow of ram air.  It's also only the 109 engine that has ever run close to the red zone, the RR never getting above half way up the normal scale.  This is why I think faster warm up times are another unreliable claim from salesmen, and getting back to the video at the beginning of the thread and your comment that the engine bay has a lot of effect, it seems good evidence to your comment and against the validity of their tests for any useful data.

Perhaps we could surmise that the 109 engine bay is better at allowing air cooling of the engine than the RRC then? And perhaps the removal of the mechanical fan cowling (I assume you have!) has allowed more air directly through the radiator into the engine bay?

Also, maybe the fact the RRC has an air dam effectively screening the bottom of the engine bay from the headwind? Whereas the 109 is just a steel bumper and there's your engine

Perhaps the bonnet gaps also have something to do with it? 

I would love to know all the ins and outs of aerodynamics, but you only have to look at an F1 wing to realise they are extremely complex things to do well or understand properly!

[Snagger]

11 hours ago, Bowie69 said:

Perhaps we could surmise that the 109 engine bay is better at allowing air cooling of the engine than the RRC then? And perhaps the removal of the mechanical fan cowling (I assume you have!) has allowed more air directly through the radiator into the engine bay?

Also, maybe the fact the RRC has an air dam effectively screening the bottom of the engine bay from the headwind? Whereas the 109 is just a steel bumper and there's your engine

Perhaps the bonnet gaps also have something to do with it? 

I would love to know all the ins and outs of aerodynamics, but you only have to look at an F1 wing to realise they are extremely complex things to do well or understand properly!

I have a winch mounted above the bumper, and that has a solenoid bridge.  I also have lights on the bull bar and a steering guard.  So between them and the bikini mount, the airflow into the grille is much more restricted than on the RR.  I also installed seals along the bonnet edge.  This implies the difference is due to the space behind the rad and possibly compounded, as you suggested, by the omission of the shroud; with the rad in the standard Defender position but the engine in the standard 109 position, there is a large void behind the rad.  But despite that advantage, I have seen the 14" electric fan struggle in warm weather in the mountains - it would benefit from a secondary booster fan.  That said, I can't remember the fan activating in normal UK conditions.  

[FridgeFreezer]

14 hours ago, Soren Frimodt said:

Am I missing something?

Fan failures I've seen happen:

- Viscous / water pump bearing failing, fan pulled itself through the rad and ruined it beyond repair

- Viscous failing to lock up, so no cooling

- Viscous knocking blades off when off-road / wading as you can't switch them off

- Viscous permanently locked

- Electric (aftermarket / badly mounted) grabbing a twig & sticking a blade into the rad. Blew the fuse on impact so did repairable damage to rad & fan survived.

- Electric (Kenlowe) thermostat failure (they're utter rubbish)

 

TBH I don't really see any major reliability issues around any type of fan, other than carp aftermarket gear, but that's a different question.

 

I think whatever Snagger's got must be faulty because TDi's will run happily for 95% of the time with no fan at all, as several members on here claim to be doing all year round.

[honitonhobbit]

Nick, I was under the opinion that your 109 had a 200tdi in it and your RRC, a 300Tdi. If I'm right, then there is your answer. The 200 has a much larger water jacket and it almost too efficient at cooling (if in good condition)

[task]

I had a Kenlowe on the CSK, 4.6 with long headers, hardly ever came on when actually moving in the UK even when towing and I didn't have any issues cooling when doing a fair whack for hours on end in the south of Romania in 30ish degrees. The CSK had to large spotlights blocking the airflow.

Disco 1 V8 had a mechanical, failed 3 times, stuck on in -7 which made for a chilly holiday!

Currently both the P38 and the RRC have mechanical fans, I've had the mechanical fan kick in once or twice in the classic when pulling up a long hill with a big weight on but it's also cooling the auto box so that might account for the added heat. I haven't really used the P38 much so can't comment. The MGB GT V8 fans only come on when stationary or crawling in traffic.

[Chicken Drumstick]

On 03/05/2017 at 11:17 AM, Bowie69 said:

I think this is the crux of it, I dislike wasting anything, especially power, and as above, even the viscous unit when unlocked WILL use power, the electric none.

Crawling at 5mph with electric fans going all the time is likely to use more power, I would say.... just due to the losses involved in converting mechanical to electrical energy and back again (alternators are only around 50% efficient at best).

That said, an engine driven fan will be designed to run the engine in 50C external temperatures, in our climate in the UK we don't really need that sort of headroom, hence electrical fans do make a lot of sense.

So... if engine driven fans consume more power for every day use, then surely there's additional fuel consumption? Let the fight begin

The other thought is, while crawling around at 5mph might result in electric fans being on and using power, it's not as if you are needing the extra power at that speed, so it matters not that they are using some.

[Snagger]

2 hours ago, honitonhobbit said:

Nick, I was under the opinion that your 109 had a 200tdi in it and your RRC, a 300Tdi. If I'm right, then there is your answer. The 200 has a much larger water jacket and it almost too efficient at cooling (if in good condition)

That is correct.  I had no idea the water jacket was different as the blocks look so similar and the engine capacity, power and fuel consumption are the same.  The 109 also has a 300 rad, so that is another variable that can be ruled out.  But, if the water jacket really does have that much extra capacity, then it makes a good explanation for the slower warm up.

As for anything being broken, no.  The fan is controlled by the X-Fan setup, with a manual back up.  Like I said, it has hardly ever come on in the UK, but lugging around a full load in the mountain tracks in the summer had it kicking in and out (fine on the motorway).  The RR's viscous fan is still in perfect working order after 220,000 miles, and I have only heard of a few people ever having problems with them.  I carry a large cable tie to lock the fan to the hub just in case, which is about as simple a road side fix as you can get, but so far so good.

Bowie, I agree with everything you said above, but would add that when driving at cruising speeds, the engine rpm is typically around 2000 rather than 6-7000, and there is plenty of ram air through the rad, so while the fan is spinning, it's not suffering significant drag as it's essentially idling in the airflow.  That is why the bench test video is worthless.  Of course, engine driven fans are engine rpm related, so if a stationary engine is idling, the fan will be pulling in a small amount of air, but if the engine is working hard, the fan will correspondingly spin faster, so it essentially gives the air demanded for the situation.  I'm sure it's possible to have multi-speed electric fans, but it'd probably not be cheap to incorporate such a controller.

At the end of the day, manufacturers spend tens of millions on wringing out every 0.1mpg from their vehicles, not just to improve sales but because they are taxed based on the average fuel consumption of the vehicles they produce.  That was the whole reason for making the Evoque.  The fact that they continue to use viscous fans must mean that they don't have a significant fuel or performance penalty in real world conditions, else they'd do the easy thing of fitting electric fans.  Whatever their many reasons for chosing engine driven fans, and despite our common knowledge that their vehicles are far from perfect, I suspect that with so much financial pressure on them, their reasons are well justified and I'll trust them.  I still have not seen a shred of evidence that convinces me that electric are better over all.

[honitonhobbit]

Unreliable viscous couplings are a PITA - had to change mine earlier this year; it wasn't even 24 years old..

[Bowie69]

I'm still curious, snags, about your concern over the electric fan kicking in and out while heavily loaded, in summer, up mountain passes, working hard? Surely that just means it works if it was running all the time I could understand the concern, but perhaps there's more you need to explain as to why you think it a bad thing?

[FridgeFreezer]

Snagger - I don't think anyone's saying mechanical are rubbish or electrics are somehow miles better. Both are fine, both are well proven to work, both suit particular applications.

What I'm struggling with is this holy war against electric - no one is criticising your lifestyle choices here, just suggesting that either answer is fine and that there are pros & cons to both.