Thermofan over Viscous?

[Keithy P38]

Good Morning guys and gals,

Before anyone suggests the search function – I’ve already had a look. I’ve done this test purely out of curiosity. I had the BF/FG Falcon thermofan at home doing nothing, and my cooling system (which had no issues and is unmodified) is in perfect working order. I have the same BF/FG thermofan on my 5 litre VS III Commodore Ute and it works the charm. I’m simply chasing opinions and thoughts from you. The fan is a 16” shrouded fan with curved blades. It operates at 1400rpm in low speed and 2800rpm in high speed. It draws about 18 amps in high speed (and much more on startup). I don’t know how much air it flows, but I have read somewhere that it’s around 2300cfm, I’m unsure what kind of flow the standard P38 Viscous Fan offers (but I would assume it to be much more being a 17” fan operated off the engine).

So what I’ve done is install a thermofan controller and temp gauge to the cooling system on my P38 Range Rover. I have established that the temp reading for the controller reads 7 degrees lower than actual engine temps. It’s simple, but complex – I can override the fan, either switching it off altogether or running manually at high speed if not using the temp controller to automatically control the fan speed. This is done with relay trickery, which I’ll show in detail once I’ve finished gathering the necessary photos and videos to back it up. The thermofan controller is designed to operate in a 7 degree band, so for example if I set the temp to 90deg for the fan to switch to high speed, the fan will drop back to low speed at 83deg. The thermofan (once installed) runs continuously at low speed when the controller is set to auto. This aids low-demand cooling, maintains airflow through the engine bay, and also reduces the initial current draw from the fan when starting or kicking into high speed, but can also be switched off manually – quite clever really. For an average joe, I’m impressed with how much I’ve been able to optimize this setup and how neat the install is. One switch controls the lot, with multiple relays covering the loads.

Establishing the baselines is very important, so here’s the vehicle info. The P38 is the last of the last, using the high compression 4.6 V8. It’s far from standard – 33” tyres, 2” lift, and at “everyday weight” it tips the scales at 2.7t with all the other junk that lives in the drawers and what not every day. It also has LPG, which for the purpose of testing, I did not use. I didn’t exactly offer this thermofan an easy introduction to rover life! The fuel consumption data is also very impressive, but I’m not here to discuss that today.

Before doing this series of tests, I cleaned the radiator and removed all debris from in front of the other radiators (condenser, trans cooler, oil cooler, power steering cooler, etc), had the radiator checked over professionally and reinstalled it, and I have a small set of Narva spotlights on the bulbar that may or may not be worth mentioning. I purposely did this testing at the height of the North Queensland summer, so the ambient temps were around 35 – 37deg, and humidity was through the roof. For the purpose of gathering temp data, I drove the car like Peter Brock setting a lap record at Bathurst aiming to get things as hot as I possibly could – I wanted to torture test the thing. I ran the air conditioning as cold as I could and had the electrical system working hard too. With this in mind, I grabbed bucket loads of temp data with the Viscous Fan still attached before putting the thermofan in so that I had data to compare to once the thermofan was installed. Once installed, I had the thermofan controller set to run the fan at high speed once the engine temperature reached 98deg. While noting the vehicle weight of 2.7t and the extremely hot ambient temps, etc., these are my findings:

Viscous Fan attached



Urban Driving – Engine temp sits between 88 – 98deg, varying based on road speed.
Idling – Engine temp continues to rise up to a highest of 110deg.
Highway Driving – Engine temp sits steady at about 92deg, dropping to 82deg on a downhill, zero-throttle condition.
Mountain Climb 1 – “Everyday weight”, 40km/h and very steep bitumen road. Engine temp rises to a maximum of 102deg while driven with much spirit.
Mountain Climb 2 – “Everyday weight plus 1.7t trailer”, 40km/h and very steep bitumen road. Engine temp rises to a maximum of 104deg while driven with much spirit.


BF/FG Thermofan attached



Urban Driving – Engine temp sits between 91 – 98deg, the thermofan bounces between low and high speed as necessary, without drama.
Idling – Engine temp is stable at 93deg with the fan in low speed being sufficient to cool the engine.
Highway Driving – Engine temp rises slowly with the fan in low speed, drops slowly with the fan in high speed, sitting between 91 – 98deg.
Hill Climb 1 – “Everyday weight”, 40km/h and very steep bitumen road. Engine temp continued to rise to 110deg after a few km while driven with much spirit. Pulled over and allowed to cool to 91deg before proceeding again and pulling over again as necessary to cool the engine.
Hill Climb 2 – “Everyday weight plus 1.7t trailer”, 40km/h and very steep bitumen road. Engine temp very quickly rose to 110deg while driven gently. Pulled over and allowed to cool to 91deg before proceeding again and pulling over again as necessary to cool the engine.


From the above data, it’s easy to surmise that the thermofan is not capable of cooling the engine when under extreme load, where the Viscous Fan was ‘adequate’ in all but idling conditions.

What I’m wondering (and this is where you guys really get to shine) is if I’ve overlooked something that might allow the thermofan option to offer the solution to all conditions. Do you think I could do something (such as include the two air conditioning thermofans into the “high speed” mix) to improve cooling under big demand situations? Do you think that I’ve set it up wrong (perhaps I have the kick-in temperature too high)? Do you think there’s a better thermofan that will do the job? Does the water flow at higher revs effect cooling ability (maybe I could do the hill climb in a taller gear and allow the coolant more time to get the chills)? Give me your thoughts!

I’m determined that there is something I can do to improve cooling at high-demand, without having to go to the bank or modify the cooling system to find it. The aim of this project was to keep the already-fine cooling system standard and achieve the results. I know that I can tow all day with the thermofan in, with the only limitation being low speed/high demand situations. I don’t plan to put a larger radiator in – this defeats the purpose of the test, I’ll put the Viscous Fan back in before I think of modifying other things. The fuel consumption benefits (especially when 4wding and around town) make this very viable, however, it was not the sole reason for the test.

I’d imagine if the P38 was completely standard and weighed its standard weight of 2,250kg, I probably wouldn’t have as much of an issue under load, if at all (and the around-town fuel consumption would be better than the highway consumption).

Cheers
Keithy

[AK83]

I would have thought that by 110°C, the ac condenser fans would have well and truly kicked in automatically, no matter if the ac is used or not.
I think they auto kick in once coolant temps hit the low 100's, so I don't think the AC fans question you raised will be of any benefit.

Also on the topic of fuel consumption:
Many many moons ago I converted my 79 RRC to twin 10 or 11"(can't remember exactly) thermos. I just go sick of replacing the useless viscous every 6 months or so.
Came as a kit(Davies Craig) and a variable controller. I set it up the way I thought best, never had any cooling issues, much of the RRC life spent in Lake Eyre country sandy conditions, in close to 40°C temps.
Never over heated(that I knew of).
But fuel consumption saving alone made it worth the effort. On a regular trip easily 0.5 - 1klm /lt saving, that gave close to 50-100km additional range on the highway.
Around town I don't recall it being so dramatic tho.

[sierrafery]

Hi, i've been in your shoes myself few years ago [bigsmile1]... tried with 3 kind of different electric fans on my D2 td5 including a Kenlowe which is sold in UK as perfect replacement for the viscous(this was the worst of all), a 250W 18" chinese fan and a big russian 400W fan which was the best but still not up to the job on long climbs ... none of them was able to keep the ECT below 105 at 30*C ambient temp so went back to the viscous one. I know that the Td5 is not the best to compare with your 4.6 V8 but the gist is that it seems that single electric fans can't deliver enough CFM(at least 4000) to emulate a viscous fan what ever you do. What i know is that a friend of mine had a good result with a double electric fan on his D2 4.0 V8 something like this Camaro1967-68-69Twin Shrouded Thermo Fan cooling fan Include Thermostat Switch70 | eBay (https://www.ebay.com/itm/Camaro1967-68-69Twin-Shrouded-Thermo-Fan-cooling-fan-Include-Thermostat-Switch70/122017385881) (maybe a bit stronger motors cos his draws 25A not 15), he was inspired by this tutorial: Land Rover Discovery VSC Electric Fan - Album on Imgur (https://imgur.com/a/j3YJ9) (might be a 4.6 V8 as well the guy being from USA)

[PhilipA]

It was posted somewhere long long a go in a faraway galaxy, that the VC took 11BHP to run when fully engaged.

My calculations then were that it was the equivalent of 200amps or 2400Watts.

Someone may correct me as it was along time ago.

So you can see that 18 amps doesn't go very far even if the two fans are more efficient..
Regards PhilipA

[sierrafery]

When it comes to any fan IMO the CFM is important not the drain of the motor cos the efficiency can be different from one to another depending on rpm and blades shape or number, the factory fitted VDO electric fan is 250W and i doubt that it delivers more than 2000 CFM

[PhilipA]

I think you have miscalculated by a factor of 10.

You cannot serously think that the fan draws 200 amps at 12 volts.
More like 20 max and usually about 12 .
Regards PhilipA

[sierrafery]

I think you have miscalculated by a factor of 10.

You cannot serously think that the fan draws 200 amps at 12 volts.
More like 20 max and usually about 12 .
Regards PhilipA
You are right, typo error, one zero more, i corrected them

[discorevy]

delete

[Keithy P38]

Thanks for the comments lads!

I had a look at those flex-a-lite fans on old mates disco (thanks for posting that up sierrafery), they look very sufficient :-). The only reason I don’t see them fitting the bill for the P38 is their sheer size. They measure in just over 700mm horizontally, and in a P38 there’s only 620mm from memory to play with between the chassis rails. I may have to have a good look at them and see if the shroud can be tweaked if I were to fit them (still not out of the question). Other option for twins would be to stagger-fit a pair of 14” fans, but they may not match the airflow of the BF/FG Falcon fan.

You raise a good point AK83, I ‘thought’ that I heard the A/C fans running when the temp got right up there, but couldn’t confirm it. It’s easy enough to go for another hill climb to get the temp up, I’ll double check that they came on. Funny enough, the temp gauge even at 110deg didn’t move from half way. Your point on fuel consumption is very valid - significantly better with the thermofan on. The highway consumption in my case was not massively better with the thermofan, but the urban consumption was massively better.

I will keep looking and digging!

Cheers
Keithy

[PhilipA]

Just talking about fan draw on the engine, when you are driving at say 80 kms the wind through the grill is driving the fans and the viscous fan.
This came to me when I was driving in Saudi and there was this squeak that was driving me mad which turned out to be one of the aircon fans turning in the wind.

Jaguars have a system of flaps in the shroud which lets high pressure air out when travelling at speed.
regards PhilipA

[sierrafery]

Funny enough, the temp gauge even at 110deg didn’t move from half way It's not funny it's LR's sh*t engineering as the gauge to stay at the middle between 70 -119*C so it goes up to red zone starting from 120*C... the electric fan kicks in at 110*C to help cooling on D2s, might not be the same for P38 too

[DiscoClax]

On D1 V8s the A/C fans kick in around 104 deg. And the factory temp “gauge” might as well be an idiot light. Stupid thing.

[AK83]

On D1 V8s the A/C fans kick in around 104 deg. And the factory temp “gauge” might as well be an idiot light. Stupid thing.

Yeah, I think on my tdi D1, I notice they come on at 103 on my aftermarket temp gauge.

I thought that as revs rise, the VC hub begins to decouple the fan so to not allow the fan blades to spin too fast too.

[Hoges]

It was posted somewhere long long a go in a faraway galaxy, that the VC took 11BHP to run when fully engaged.

My calculations then were that it was the equivalent of 200amps or 2400Watts.

Someone may correct me as it was along time ago.

So you can see that 18 amps doesn't go very far even if the two fans are more efficient..
Regards PhilipA

As gentle a correction as I can!! [bighmmm][thumbsupbig] ...11BHP is equivalent to 8.25Kw, which at 12V would require 688 Amps...
So it's no surprise that the thermo fan, by itself, is inadequate for the task...

[AK83]

I'd argue that the 11hp figure quoted by Philip will be variable depending on the fan itself.
Judging by sound alone, 11hp probably sounds about right on a V8 landrover!

Does the P38 use the same fan as the D2 v8?

I'm fairly confident that a fan for a tdi .. much much smaller and almost inaudible(ie. much less air movement), probably won't draw that much power itself.
Damn I think 300 tdi only has 11hp in totality! ... damn feels like it sometimes.

[sierrafery]

IMO when it comes to a fan what ever type it is the CFM is relevant and that's based on it's constructional efficiency, other values can be considered just for very rough comparisons

[PhilipA]

I'm fairly confident that a fan for a tdi .. much much smaller and almost inaudible(ie. much less air movement), probably won't draw that much power itself.
Damn I think 300 tdi only has 11hp in totality! ... damn feels like it sometimes.

I can tell you that a tdi fan moves more air than a 3.9RRC one. And a good VC certainly moves tonnes of air and is noisy.

Graeme Cooper gave me one once for my 91 , saying it wouldn't cool a Tdi but was fine on a V8.

I fitted it and it was great and I eventually replaced the VC, except I broke a blade off on the OTT. The Tdi ones are fibre filled so you dont lose blades like a white plastic one. They have to be trimmed about 5MmM to fit a v8 shroud. So the blade stayed in place and just grazed the radiator.
Regards PhilipA

[AK83]

....

Graeme Cooper gave me one once for my 91 , saying it wouldn't cool a Tdi but was fine on a V8.

....

Interesting to know.
Tdi fan has something like 11 blades .. maybe this is why .. no experience with 3.9 RRCs.

I did find an article done for the SAE, where the study found that on a 180hp commercial vehicle the average power draw was between 7-9%
Didn't say what vehicle/motor, and it was dated 2019. It was only the summary, and not the full article.
So your comment about 11hp sounds about right.

Dad used to have a '73 Cadillac. Had a enormous radiator, etc. The fan wasn't viscous coupled tho just hard bolted, but the fan blades themselves were flexible, so as revs rose the fan went from a fan to a less aggressive fan pitch and finally to a basically flat surface.
So CFM would have got lower as revs rose, as the pitch of the fan blades decreased. You could easily feel it with bonnet open, that it sucked tons of air, but then slowly less as revs rose.
Interesting idea.

[slug_burner]

I would have thought that by 110°C, the ac condenser fans would have well and truly kicked in automatically, no matter if the ac is used or not.
I think they auto kick in once coolant temps hit the low 100's, so I don't think the AC fans question you raised will be of any benefit.

Also on the topic of fuel consumption:
Many many moons ago I converted my 79 RRC to twin 10 or 11"(can't remember exactly) thermos. I just go sick of replacing the useless viscous every 6 months or so.
Came as a kit(Davies Craig) and a variable controller. I set it up the way I thought best, never had any cooling issues, much of the RRC life spent in Lake Eyre country sandy conditions, in close to 40°C temps.
Never over heated(that I knew of).
But fuel consumption saving alone made it worth the effort. On a regular trip easily 0.5 - 1klm /lt saving, that gave close to 50-100km additional range on the highway.
Around town I don't recall it being so dramatic tho.

I can’t see how a viscous fan fitted vehicle would consume more fuel on a trip. If that trip had any part at highway speeds the viscous would not be coupled to the engine therefore not consuming additional fuel. The airflow through the radiator at highway speeds is more than enough to cool the engine. Viscous fan only couples when it has air that is hot enough, when cooler than the trigger temperature the air is not hot enough to couple the fan via silicone oil.

If there was a lot of slow speed driving where the natural airflow through the radiator was too slow to provide sufficient cooling then perhaps you would get a fuel saving with electric fans.

The energy consumed by an electric fan does not come for free, the alternator will be pulling power out of the engine.

It might be that electric fan blade are so much more efficient that you do get a saving but I doubt it. Electric fans are quieter because they move less air. The sound levels are one reason they are used on modern cars. You don’t get anything for nothing when it come to power and the conversion of energy.

[sierrafery]

I can’t see how a viscous fan fitted vehicle would consume more fuel on a trip. If that trip had any part at highway speeds the viscous would not be coupled to the engine therefore not consuming additional fuel. The airflow through the radiator at highway speeds is more than enough to cool the engine. Viscous fan only couples when it has air that is hot enough, when cooler than the trigger temperature the air is not hot enough to couple the fan via silicone oil.I tend to disagree. As long as the engine is up to running temp let's say 90*C this temperature will not drop below 80 on motorway cos even if the air flow is higher so is the fuelling. The viscous coupling is managed by the bi-metalic coil on it's front which is close to the radiator and it's triggered by the radiant heat and above 80*C the fan is fully locked which is normal cos the air pushed by it toward the engine has cooling effect too . It's simple to test if you think that the viscous fan is freewheeling at motorway speed: remove it, start from cold and see what happens after 20km on motorway when it's 30*C outside just dont rely on the dash gauge cos when it goes to red might be too late.


.....At low radiator temperatures, the fan operation is not required and the bi-metallic coil keeps the valve closed, separating the silicone fluid from the drive plate. This allows the fan to 'freewheel' reducing the load on the engine, improving fuel consumption and reducing noise generated by the rotation of the fan.

When the radiator temperature increases, the bi-metallic coil reacts and moves the valve, allowing silicone fluid to flow into the fluid chamber. The resistance to shear of the silicone fluid creates drag on the drive plate and provides drive to the body and the fan blades.....

[AK83]

I can’t see how a viscous fan fitted vehicle would consume more fuel on a trip. If that trip had any part at highway speeds the viscous would not be coupled to the engine therefore not consuming additional fuel.....

I don't think that's how VC fans actually work. From my experience they can partially lockup as well as fully lockup.
Trucks seem to do this more nowadays.

But with my old RRC, most of my really long trips into central aus were in fairly high ambients.
The old LT95 transmission produced a very loud noise not far from your left ear, but the VC fan could be heard over even that whine.

Issue I had with the twin fans I fitted was that the alternator couldn't keep up when at night I'd run the two spotties. You used to be able to easily buy 135w halogens back in the day, so on a balmy night with spotties trying hard to spot cows! [biggrin] .. if fans came on you'd see the spotties dim a little, and the reading on the ammeter would go into the negative.
The fan kit I got came with it's temp controller, just had rotating thermostat switch thingie with a hard wired probe.
I tested it to find the 85°C ish degree point, found a suitable plastic knob thing to place onto the thermostat and then found the approximate 90 and 80 degree points I'd need to dial it too to get the fans to operate at those speeds.
Always set them before a trip, and used the 80 point if I knew I'd have to traverse soft sand .. I wanted fans on earlier than later.

I never really towed tho. All trips were solo. Any towing was just get this thing here, or there or whatever.

[peter51]

HI kiethyP38
I also have a P38 - standard form and I measure the temperature at the back of the manifold and at the radiator outlet.
Your data is very interesting - the data with the electric setup doesnt make sense because I helped a friend fit late model commodore fans to a RRC classic with a cracked block. They kept it cool under all driving conditions with that affliction until he changed engines. The coolant hoses were rock hard most of the time and he drove it like that for quite a while. His fan power feed was via the original condenser fan wiring which powered both fans on together. What I did notice was that he was not getting max speed out of the fans due to the undersize wiring of the original loom. These fans pulled something like 50 amps on start and about 35 amps at max speed when tested straight to a battery. On my RRC I wired them differently using 60amp maxifuses and much thicker and shorter wiring direct to the battery via a dual 60 amp relay - they ran a lot faster than his - so check your wiring first.
How is the thermo switch plumbed into the system - did you do a pressure check to make sure the system was holding pressure after that modification because you may be losing some system pressure which would affect the pressure at the pump inlet at higher RPM?? PM me if you want some more info on that because system total pressure must be correct to ensure correct pressure exists at the pump inlet to avoid any cavitation as RPM increase. Pump inlet diameter, system pressure, flow rate, and pump design are all closely interrelated as you know.
I can also state with confidence that your data with the viscous fan is completely accurate as I have an accurate temperature sensor mounted at the manifold where the coolant rises adjacent to number 8, and a sensor on the radiator outlet to see how much the radiator drops the coolant temp at various scenarios.
I just recently towed a boat to Cairns Aug/Sept and the coolant in and out differentials are largest in cruise and least at idle with a standard viscous fan.
To investigate the idle case some more, I installed a manual switch to turn on both condenser thermofans without the AC on - it only moved the temperature differential between in and out by 2 degrees( in both AC on and AC off cases)

[PhilipA]

The whole principle of a VC is that the fan can have a higher /pitch than a fixed fan as they are usually programmed to reach about AFAIR 3000 RPM before they start to slip (when locked).

This is why when people lock up the VC by putting a screw in it they tend to blow blades off.

The VC only locks( albeit partially) at about 94 C so below that it is somewhat freewheeling, based on the temperature airflow through the radiator affecting the spring on the front which expands to close a relief hole .

In RRCs 3.9 the condenser fans come on at 102-104C. based on the switch on the thermostat.

The advantage is that the higher pitched fan delivers more air at low revs, but not obviously as much as an electric fan setup at idle.

You only would see the difference between a VC and electric fans at hot high load conditions such as a 34C-40C driving on dry sand .Under normal conditions the temperature drop across the radiator will be sufficient with either VC or electric fans.
I sometimes think that often people have an old car with say 200KK on it and find the car will not stay cool, and blame the VC , when it can be a combination of old worn VC and partially blocked radiator.

My RRC 3.9 NEVER went above about 98C even climbing long grades towing a trailer. One time only on a 35+ day climbing Mt Pinnibar in low range did it reach 102 when the radiator fans cut in, and it cooled to under 100C.
A clean radiator and a operational VC are all that is needed.

Regards PhilipA

[sierrafery]

The VC only locks( albeit partially) at about 94 C so below that it is somewhat freewheeling, based on the temperature airflow through the radiator affecting the spring on the front which expands to close a relief hole . When the engine is hot the fan is never freewheeling, at lower temps it's turning with lower rpm(down to 40%) than the engine but with power and at high temps with at least 85% or the engine rpm, i measured the temperature on the bimetalic coil with laser thermometer imediately after i stopped the engine and it was 85*C while the ECT was 92*C and it locks at above 74... here's a detailed description of how it should work https://www.fanclutch.com/PicsDocs/BorgWarner_Viscous_Fan_Drive_Test_Procedure_(Bi-Metal_Drives_Only).pdf

[PhilipA]

When the engine is hot the fan is never freewheeling,

Maybe I should have elaborated and said that under lockup temperature the air forced through the radiator will partially drive the fan so that the parasitic drag on the engine is not much.

Regards PhilipA

[Keithy P38]

HI kiethyP38
I also have a P38 - standard form and I measure the temperature at the back of the manifold and at the radiator outlet.
Your data is very interesting - the data with the electric setup doesnt make sense because I helped a friend fit late model commodore fans to a RRC classic with a cracked block. They kept it cool under all driving conditions with that affliction until he changed engines. The coolant hoses were rock hard most of the time and he drove it like that for quite a while. His fan power feed was via the original condenser fan wiring which powered both fans on together. What I did notice was that he was not getting max speed out of the fans due to the undersize wiring of the original loom. These fans pulled something like 50 amps on start and about 35 amps at max speed when tested straight to a battery. On my RRC I wired them differently using 60amp maxifuses and much thicker and shorter wiring direct to the battery via a dual 60 amp relay - they ran a lot faster than his - so check your wiring first.
How is the thermo switch plumbed into the system - did you do a pressure check to make sure the system was holding pressure after that modification because you may be losing some system pressure which would affect the pressure at the pump inlet at higher RPM?? PM me if you want some more info on that because system total pressure must be correct to ensure correct pressure exists at the pump inlet to avoid any cavitation as RPM increase. Pump inlet diameter, system pressure, flow rate, and pump design are all closely interrelated as you know.
I can also state with confidence that your data with the viscous fan is completely accurate as I have an accurate temperature sensor mounted at the manifold where the coolant rises adjacent to number 8, and a sensor on the radiator outlet to see how much the radiator drops the coolant temp at various scenarios.
I just recently towed a boat to Cairns Aug/Sept and the coolant in and out differentials are largest in cruise and least at idle with a standard viscous fan.
To investigate the idle case some more, I installed a manual switch to turn on both condenser thermofans without the AC on - it only moved the temperature differential between in and out by 2 degrees( in both AC on and AC off cases)

Thanks for your reply Peter. I appreciate the comments regarding wiring being a potential factor. It’s definitely something to consider and something that I could try in an effort to give more boot to the fan. I have the exact same fan on my Ute (which is a 5.0 VS III Commodore) and it’s measuring about 35 amps on start, settling to about 18amps at full speed. On the setup in the Range Rover I’ve used thicker wiring and a much neater relay setup, with the power wiring to the fan very short and matching the fan controller and fan itself for size. I don’t recall the exact wire size off the top of my head, but I’m open to re-wiring with something bigger, which I will try.

The temp switch is fed into the top hose via that bypass t-piece just before the radiator. I can’t really see it as being either a restriction or altering system pressure in any way. I fitted the switch up before putting the thermo fan in (drove around for a few weeks like this before fitting the thermo). That’s how I established the 7 degree difference between head and top hose temps. The system was bled properly in all instances and is running the usual 50/50 coolant mix.

It’s very interesting to hear the current draw from the commodore fans on the RRC you mention. Do you recall what model commodore those fans were off?

Ill have a look at the wiring and up the size and fuse/relay combo from 40 amp to 60 amp and see what difference it makes.

Cheers
Keithy

[Eevo]

some food for thought,

most cars coming out now says have a thermofan.
why did the engineers from different companies all go in this direction?

[rick130]

some food for thought,

most cars coming out now says have a thermofan.
why did the engineers from different companies all go in this direction?In an east/west engine layout (front wheel drive) with a rad at the front you have (need) a thermofan.
The majority of cars on the road are front wheel drive. (Only Subaru and some Audi's are north/south layout)

Of the RWD platforms, it could be cost, noise efficiency, packaging or a combination?
You can mount the rad/condenser closer to the engine with a thermofan and have the fan mounted ahead as a forced draft fan?
One less pulley/belt to package? etc.

[peter51]

I think the fans were VE V8 fans. I need to access my old posts from about 4 years ago to confirm but I cannot access them. I have sent a post to the moderator.
I would say that they need to be in dual configuration for the P38 - single for you will not do it unless you go to an X5 type.
I have an article from autospeed(now a broken link) that details how he tried all sorts of single fans to control overheating in a Cobra replica - he had outstanding results with a fan from a 1999 BMW X5 - PM me if you want a pdf copy emailed to you.
I use a dual sensor engine guard https://engineguard.com.au/ to monitor radiator inlet/outlet temp - temps entering the radiator are are 95 in cruise and 98 to 100 idling with AC on hot humid - exit from the radiator is 75 degrees at cruise(78 in traffic - more when downwind). The sensor is jammed between the shroud and the alloy housing - so accurate enough.
Since you have already done all the fabricating work I think it would be better to change the thermosat setup like they do in the US on the V8 Discos - this will achieve the results you want with the current thermo fan in place I believe. The threads on this conversion are easily found.
Fitting another thermofan is more cost and more work. The problem with the X5 fan is that you would need to carry a spare in the bush I believe - same with the commodore option however new ones are easily purchased online if your original seized somewhere up track.
Before you do that I would remove one of the condenser thermo fans and retest - in my opinion all they do is block airflow. Check if they are induced into high rotational speed by your new thermofan at idle - if so this may cause flow/heat exchange issues through the radiator at idle - my opinion only - however as I said if you use a manual switch to turn on both condenser fans on the P38 when idling on a hot humid day it only reduces the engine temp(measured by OBD) by 2 degrees - if that.

[AK83]

some food for thought,

most cars coming out now says have a thermofan.
why did the engineers from different companies all go in this direction?

Cost benefit.
if they're getting more common, then by rights prices should come down.
if prices come down, then it makes it more competitive as an option.
Balance any potential fuel saving due to minimal duty cycle in most northern hemisphere countries ... makes sense to go that way.

Buses that I've seen(not a lot, but enough) .. they use a hydraulic system.
Because the engine is longitudinal mounted, and rear at that, the rad is placed on the side with grille opening. Fan then needs to be side mounted, literally no where near the engine.
Think of it as the reverse of what Rick said about transverse mounted cars.
They obviously figured that electric fans wouldn't do the job, so they use a hydraulic system.
On the same plane as the other accessories is a hydraulic pump that runs a hydraulic motor thing that runs the fan.
It's quite complicated and goofy looking too.

[prelude]

I don't think I have one laying around but I will have a look in the shed but...

The best way to test the capacity needed to equal a viscous setup would be to simply hook the current fan up to an electric motor. I have done it in the past with a different fan hooked up to an old washing machine motor. It could not have been more then a few hundred watts at most but then again the fan was much smaller and most electric motors of the grid run at 3000 rpm max.

Like I said, I will have a look around in the shed what I can find and see if I can replicate the P38 setup somewhat. It should be easy to measure the drawn power and from there we can make SOME conclusions as to how much air is being pushed (pulled actually). As far as I know the amount of power needed to run a fan is more or less linear to the amount of air displaced, all other things being equal. So, with the same fan shape and size 500 watts from an electric motor should be more or less 500 watts form the engine :) And yes, there are more efficient fan blade designs and what not but still, if you push X amount of air with fan A and it will cost you Y, pushing the same X amount of air with fan B should also cost you Y and not Z.

So, keithy, if I can't reproduce it because I do not have the gear mate, I'd recommend you do something like this yourself if at all possible and BE CAREFUL since spinning a fan at such speeds can be lethal so you want that motor to be tied down properly and the fan to be mounted exactly centered. You should then be able to get a rough idea of the amount of air displaced and power needed. Spin one of the thermo's up on a free standing workbench or something as well and compare the power consumption.

Cheers,
-P

[Tins]

In an east/west engine layout (front wheel drive) with a rad at the front you have (need) a thermofan.
The majority of cars on the road are front wheel drive. (Only Subaru and some Audi's are north/south layout)

Of the RWD platforms, it could be cost, noise efficiency, packaging or a combination?
You can mount the rad/condenser closer to the engine with a thermofan and have the fan mounted ahead as a forced draft fan?
One less pulley/belt to package? etc.

Dunno. Eevo has a point. The last truck I drove, a 17 litre V8 Scania 730, which truly DID get loaded up, had thermo fans only, no VC in sight. Possibly Euro 5 needed that, but it worked. Course, the rad was huge, as was the frontal area, but climbing the Warrambungles with 60+ tonne and 40˚C was a test. Truck never got any warmer than it did empty on the flat. Thermo fans seemed to work.

[scarry]

Thermo fans are often used to reduce fuel consumption,and load on the engine,or as Rick said,when a vehicle is fitted with an east/west engine.
The VN/VP commodore with the V6 had a huge electric fan,while the 8 stayed with the VF.

FWIW,the D4 has a VF with electric override,and using the Gap tool the actual speed to the fan can be monitored,and recorded.

Both the Puma and the TD5 ran the same, well sized VF,that worked well,with a well sized cooling system.
The VF on these vehicles can often be heard cycling while driving slowly in hot weather.
The thermo fan on the front of the rad on the TD5 was used for the AC system,or when the engine was overheating.

[sierrafery]

FWIW,the D4 has a VF with electric override,and using the Gap tool the actual speed to the fan can be monitored,and recorded.

They started with the electro-viscous fan from D3 already, here's from

WSM-4479 - Workshop Manual - LR3 (L319) - 2005-2009MY
....................
"For additional airflow through the radiator matrix, particularly when the vehicle is stationary, there is an engine driven electro-viscous fan unit fitted to the rear of the radiator. The fan is used for engine cooling and for Air Conditioning (A/C) system cooling. This unit functions as a normal viscous fan, but with electronic control over the level engagement of the clutch. The Engine Control Module (ECM), which determines the required fan speed, controls the level of clutch engagement. The ECM determines engagement based on the coolant, charge air, ambient and transmission oil temperatures and the A/C pressure. The fan is mounted using a left hand thread.
The viscous fan unit is electronically controlled by the ECM to optimise fan speed for all operating conditions."

[prelude]

Well, buggered if I can find the bloody thing.

So unfortunately I can't do this little experiment since I seem to have misplaced my spare fan blade, or I gave it away but I can't remember. Would still be an interesting experiment though. If anyone does get around to doing this, let me know :)

Cheers,
-P

[prelude]

Here we go then, it's only been a (f-ed up covid) year :)

So I was mucking about and was reminded of this experiment and thought, what the hey... Not going anywhere with all these restrictions and taking the fan out of the P38 is an easy job.
I have done some testing and although it is by far not conclusive, I have enough data (I think) that I can make some fair assumptions or extrapolate.

First; the setup. I took a very old AEG drill which was handed down to me from my dad which has two settings, low and high and it also has variable rpm. Low goes up to 750rpm, high is no longer readable on the label but I reckon it would go up to the 3Krpm-ish. The drill is rated at 900 watts. Being an old drill it does not have that newfangled quick stop crap that would break due to the mass of the fan still spinning (I tried it on my makita wireless and it rattled a LOT in protest). With this drill came a circular saw and a wood turning lathe frame/setup. I used the holder for the wood turning lathe frame to hold the drill firmly on a very sturdy and heave steel base (my hoist to be exact) and took an old water pump and pulled the pump propeller. I stuck the resulting axle stub in my drill bit and fixed the pump housing so it would not spin. Finally I fixed the fan onto the threaded end, just as it sits in the car.

After some low powered test runs and a bit of tweaking I mustered up the confidence to give it full throttle and after a few scary seconds I came to the realization that my drill was not spinning at top speed, by far...
Now, I lack a tachometer so I can't be sure what kind of RPM I was getting on the drill or the fan for that matter but visually it seemed to me there was minimal slip in the VC (none) at this stage. I switched down gears into first on the drill and gave it the boot (the thumb) and without issue the drill started making the oh so familiar whine it makes at top speed.

Having done a few test runs, I reckon the drill topped out at around 1500rpm, maybe 2000 in second gear. If I can find a cheap tachometer I'll give that a go some day. I also placed an ammeter in line with the drill and although I forgot to take a no load reading, we'll just assume it's not a lot.

I registered 1.65A at 230volts on the low setting, spinning at 750RPM. This is close to idle rpm of the engine. If I convert that to watts I end up at 380 watts. That's more than most 12V fans pull btw...
Switching to high gear on the drill and give it all she had (not too long before the drill burns out) and waiting for the inrush current of getting up to speed settled I ended up measuring 6.6A at 230 volts which is 1518 watts. Like I said, judging by the sound the fan blade made and the sound the drill made from my experience it is between 1500 and 2000 rpm.

In short, or the TL;DR

750RPM (idle) takes 380watts from the wall
2000RPM maximum guessed (100kph on the highway or thereabouts) takes 1500+ watts from the wall

Some things to take into consideration:

The drill losses have not been measured but can't be that much.
The losses you get from the bearings and seals in the water pump are added to this measurement
slip of the VC is unknown but probably close to zero at this low rpm
the cowling and radiators and such were not present, these would cause drag and thus higher power requirements


When I think about it I do realize that the fan and cowling on a p38 is not really a high tech design and is not the most efficient you can get. A modern, well designed electric fan runs at much lower speeds and thus can use much smaller tolerances since the blades will not deform as much or at all. By that same token, the cowling can be made to fit a lot tighter around the blades causing less loss and higher efficiency. In any case, this is a reasonably fair measurement of power used by a fan I should think.

Regarding electric fans and their potentially more efficient design, my thinking is this:

Air is pushed by the blades no matter the setup. Pushing this air takes energy. A free standing fan blade (like in my test) will push a lot of air in your direction but it will also loose a lot of air immediately to the side of the blades which gets sucked right back into the blades and the story continues. Air has still been pushed, energy has been expended. A fan that loses a lot less air due to better cowling and tolerances can have the same amount of air pulled through the radiator whilst expanding less energy to do so.

My conclusion is; yes electric fans with less wattage can probably do the job but it would have to be one large unit with quite a bit of power. The power used by the VC fan is... a lot :) Electric fans with a more efficient design will still need a lot more power to come close to the same amount of CFM pulled through the radiator.

Hope this helps anyone!

Cheers,
-P

[prelude]

A follow up.

I got myself a tachometer and ran the tests again so I have some more info to share.

First of, I did a test run without the fan attached to the water pump assembly to figure out how much power the drill and pump assembly use. To my surprise a perfectly round 1amp at setting 1 and a whopping 1.6amp at setting two. More than I had anticipated.

Also the dry run has shown the drill to be able to get up to 900RPM on setting 1 and 2900 RPM on setting 2 (as measured on the water pump pulley)

With the fan attached it was a bit harder to get a proper reading (since holding my fingers that close to a fast spinning fan is a bit unnerving...) but it ended up being 900RPM on the pulley and near as makes no difference the same on the fan at setting 1. Setting 2 gave me almost 1700RPM on the pulley and 1500-1600 on the fan. The readings fluctuated a bit around those figures and like I said, keeping my hand that close to the fan did not give me a lot of time to get an accurate steady reading so make that a plus minus 100 RPM variability each way and it COULD be that they are just the same.

In conclusion:


The slip on the VC is minimal at low RPM
the slip on the VC MIGHT be higher at higher RPM but I can not be certain.
the maximum speed I got the fan to spin was nearly 1600 RPM
power usage at that speed was 6.6 - 1.6 Amps (which is a nice round 5 Amps) at 230v makes 1150 Watts
power usage at 900 RPM was 1.65 - 1 Amps = 0.65 Amps at 230v makes 150 Watts


My VC runs fairly lightly (when compared to a new one I have laying around as spare) when I move it by hand but it does seem that the slip is still fairly limited under load. I do not care to exchange the two for testing as I think we got the figure we were looking for, at least for starters. The electric motor in my drill is most likely not linear in power consumption, certainly when we push it over it's boundaries and I am not sure about the linearity of a fan in power consumption? but it looks like the stock fan does indeed do more poorly when idling or there about compared to a thermofan but starts to pick up very soon since it already surpasses most if not all thermofans at roughly 1500RPM and up in terms of power consumed and I am assuming with that air moving capacity.

As a final afterthought (for the day anyway) I am wondering if the fan was ever designed to work at 5Krpm. Sure, it has to be able to handle it since it can not explode whilst doing that but practically no one runs their engine at that kinda revs for any kind of time I should think. In other words, the cooling system, in my opinion, was surely designed to work best at the most common revs and engine load which I should think is pulling a heavy load on a steep incline which in most cases would case the gearbox to shift down anyway, say third gear 3.5Krpm. That has been my experience anyway.

If you are still reading up on this topic Keithy, perhaps you can shed a light on the test you did regarding pulling a load up hill?

In any case, it would seem to me that at say 3000-3500 RPM the power needed to move the VC fan would be around the 3-4KW range which equates to 4-6HP all very roughly. Now, I am not sure the full amount of power is needed at that point since I do not live down under with massive heat and pulling such loads but, what we do know is that at the bottom end RPM range the fan is JUST enough, barely. Perhaps that was it's minimum design spec and the rest is overkill, ie. you could get away with obviously more thermofan power than you currently have since it has proven to be insufficient but certainly not need the full 4KW for instance.

Ah well, interested in what the brain trust has for more insights :)

Cheers!
-P

[PhilipA]

Here is an article on the new Toyota 300 series petrol V6.
Please note the Viscous fan sitting on the front.
It seems Toyota build their engines conservatively .
What the New Land Cruiser's Engine Tells Us About the Next-Gen Toyota Tundra (thedrive.com) (https://www.thedrive.com/news/41073/what-the-new-land-cruisers-engine-tells-us-about-the-next-gen-toyota-tundra)

Regards PhilipA
BTW the Google specific AULRO search engine did not pick up this thread. I wonder why. I found it by chance in technical Chatter when I was going to post a new thread among the half dozen or so existing threads that petered out over time.

[scarry]

And the torque curves for both new engines, compared with the outgoing model.

Gee,we are way off topic now.....[bighmmm][biggrin]


https://www1.picturepush.com/photo/a/16397442/640/16397442.jpg (https://picturepush.com/public/16397442)

[350RRC]

A follow up.

I got myself a tachometer and ran the tests again so I have some more info to share.

First of, I did a test run without the fan attached to the water pump assembly to figure out how much power the drill and pump assembly use. To my surprise a perfectly round 1amp at setting 1 and a whopping 1.6amp at setting two. More than I had anticipated.

Also the dry run has shown the drill to be able to get up to 900RPM on setting 1 and 2900 RPM on setting 2 (as measured on the water pump pulley)

With the fan attached it was a bit harder to get a proper reading (since holding my fingers that close to a fast spinning fan is a bit unnerving...) but it ended up being 900RPM on the pulley and near as makes no difference the same on the fan at setting 1. Setting 2 gave me almost 1700RPM on the pulley and 1500-1600 on the fan. The readings fluctuated a bit around those figures and like I said, keeping my hand that close to the fan did not give me a lot of time to get an accurate steady reading so make that a plus minus 100 RPM variability each way and it COULD be that they are just the same.

In conclusion:


The slip on the VC is minimal at low RPM
the slip on the VC MIGHT be higher at higher RPM but I can not be certain.
the maximum speed I got the fan to spin was nearly 1600 RPM
power usage at that speed was 6.6 - 1.6 Amps (which is a nice round 5 Amps) at 230v makes 1150 Watts
power usage at 900 RPM was 1.65 - 1 Amps = 0.65 Amps at 230v makes 150 Watts


My VC runs fairly lightly (when compared to a new one I have laying around as spare) when I move it by hand but it does seem that the slip is still fairly limited under load. I do not care to exchange the two for testing as I think we got the figure we were looking for, at least for starters. The electric motor in my drill is most likely not linear in power consumption, certainly when we push it over it's boundaries and I am not sure about the linearity of a fan in power consumption? but it looks like the stock fan does indeed do more poorly when idling or there about compared to a thermofan but starts to pick up very soon since it already surpasses most if not all thermofans at roughly 1500RPM and up in terms of power consumed and I am assuming with that air moving capacity.

As a final afterthought (for the day anyway) I am wondering if the fan was ever designed to work at 5Krpm. Sure, it has to be able to handle it since it can not explode whilst doing that but practically no one runs their engine at that kinda revs for any kind of time I should think. In other words, the cooling system, in my opinion, was surely designed to work best at the most common revs and engine load which I should think is pulling a heavy load on a steep incline which in most cases would case the gearbox to shift down anyway, say third gear 3.5Krpm. That has been my experience anyway.

If you are still reading up on this topic Keithy, perhaps you can shed a light on the test you did regarding pulling a load up hill?

In any case, it would seem to me that at say 3000-3500 RPM the power needed to move the VC fan would be around the 3-4KW range which equates to 4-6HP all very roughly. Now, I am not sure the full amount of power is needed at that point since I do not live down under with massive heat and pulling such loads but, what we do know is that at the bottom end RPM range the fan is JUST enough, barely. Perhaps that was it's minimum design spec and the rest is overkill, ie. you could get away with obviously more thermofan power than you currently have since it has proven to be insufficient but certainly not need the full 4KW for instance.

Ah well, interested in what the brain trust has for more insights :)

Cheers!
-P

Hi,

This topic has been so done to death....................

There are cars in Oz that just happen to have twin elec engine cooling thermo fans in a shroud that is a very close fit to the rear of a RRC radiator.

My POS has one of these and has had for a very long time cooling a tired 350 Chev (on LPG) with a stock RRC rad even in stop start traffic in 40 degree heat.

I've had no need to upgrade the massive 55 amp alternator to run this system. I'm even too lazy to refine it further so one fan is still on all the time the ignition is on, the other fan is on a temp switch.

You should import these fans and shrouds. You also gain about 100mm of free space in front of the motor.

DL

[Keithy P38]

G’day folks,

A great read after my last post - I’m upset with myself for not coming back to update it last year! I’ve done up a video series on it, and I’m re-visiting this now as it’s starting to get hot again. Bear with me here, I’ll put heaps of video links to my research to back up the HUGE fuel consumption benefits with the thermofan, as well as its downfalls in extreme driving conditions.

As mentioned originally, the viscous fan is pathetic at idle or low speeds (low range off road for example), but great everywhere else - with the exception of fuel consumption. With the thermofan in and operating, the fuel savings around town were about 7% better than the viscous fan could muster up. But the thermofan sucked (not literally) when the going got tough.

Thermofan Installation Series - YouTube (https://youtube.com/playlist?list=PLjuYKRXivJ98HbfpH9BEy5Fn2bs-GxVcV)

REAL WORLD Fuel Consumption Test Ep4 - Modified Mk 3 | Electric Thermofan | What's your guess? - YouTube (https://youtu.be/EB_6_10Cn58)


I’m re-opening this now (and will update in the next few weeks) to see if a bit of backup via the factory A/C thermofans can help the extreme temp/extreme driving situations to make it a viable long term thing - or at least for the summer months.

Cheers
Keithy

[350RRC]

G’day folks,

A great read after my last post - I’m upset with myself for not coming back to update it last year! I’ve done up a video series on it, and I’m re-visiting this now as it’s starting to get hot again. Bear with me here, I’ll put heaps of video links to my research to back up the HUGE fuel consumption benefits with the thermofan, as well as its downfalls in extreme driving conditions.

As mentioned originally, the viscous fan is pathetic at idle or low speeds (low range off road for example), but great everywhere else - with the exception of fuel consumption. With the thermofan in and operating, the fuel savings around town were about 7% better than the viscous fan could muster up. But the thermofan sucked (not literally) when the going got tough.

Thermofan Installation Series - YouTube (https://youtube.com/playlist?list=PLjuYKRXivJ98HbfpH9BEy5Fn2bs-GxVcV)

REAL WORLD Fuel Consumption Test Ep4 - Modified Mk 3 | Electric Thermofan | What's your guess? - YouTube (https://youtu.be/EB_6_10Cn58)


I’m re-opening this now (and will update in the next few weeks) to see if a bit of backup via the factory A/C thermofans can help the extreme temp/extreme driving situations to make it a viable long term thing - or at least for the summer months.

Cheers
Keithy

Mate............. you need the shroud to seal all around the core to get a thermo fan set up to work properly in tough conditions.

You want the effort of the fan being used to suck air only through the core, not around the sides.

You want to surround ALL the core, otherwise it will never work as well as the stock system that surrounds all the core in all conditions.

That's the beauty of EL twin fans and shroud on an RRC rad...........like a factory fit, that's why they work so well.

cheers, DL

[Keithy P38]

Mate............. you need the shroud to seal all around the core to get a thermo fan set up to work properly in tough conditions.

You want the effort of the fan being used to suck air only through the core, not around the sides.

You want to surround ALL the core, otherwise it will never work as well as the stock system that surrounds all the core in all conditions.

That's the beauty of EL twin fans and shroud on an RRC rad...........like a factory fit, that's why they work so well.

cheers, DL

Thanks mate, I do agree there is room to be improved upon with the fan setup. Perhaps itÂ’s time I customised the shroud in those areas where thereÂ’s an air gap. IÂ’ll get handy with some sheet metal or thin box section and see if I can improve it, most definitely before giving up on it.

For now, IÂ’ve added additional fan cooling to try and improve upon whatÂ’s there, hereÂ’s the results! The next logical step will be to use your great feedback to give this thing some improvement.

Operation extra-cool with a TWIST - Can I enlist a helper to back up the Range Rover thermofan? - YouTube (https://youtu.be/wWokW6f3bFU)

Cheers
Keithy

[350RRC]

If you'd posted that list of vids on Pirate back in the day using that fan / shroud on that rad they'd have torn you to pieces.

I'd suggest taking them offline till you get an appropriate thing for that rad and do it all again.

I'll post a pic tomorrow of what an EL thermo set up looks like on an RRC rad.

cheers, DL

[350RRC]

Hi,

Hope the pic works.

You can see that the shroud fits over the core very accurately, the bottom of it actually sits in the original mounting brackets.

The only trimming required was a bit on the sides, a bit on top and around the bottom rad hose.

Tin work on top was just to neaten it up. All done about 20 years ago.

You can see how much space is freed up around what was the old fan hub. That was all shroud before.

cheers,DL

174479

[onebob]

Thanks mate, I do agree there is room to be improved upon with the fan setup. Perhaps itÂ’s time I customised the shroud in those areas where thereÂ’s an air gap. IÂ’ll get handy with some sheet metal or thin box section and see if I can improve it, most definitely before giving up on it.

For now, IÂ’ve added additional fan cooling to try and improve upon whatÂ’s there, hereÂ’s the results! The next logical step will be to use your great feedback to give this thing some improvement.

Operation extra-cool with a TWIST - Can I enlist a helper to back up the Range Rover thermofan? - YouTube (https://youtu.be/wWokW6f3bFU)

Cheers
Keithy

Have you considered a FLEXIFAN at the same diameter as the viscous fan so you can use the stock fan shroud. A FLEXIFAN is ‘most’ efficient at low rpm which is what you are chasing ……. whilst engaged in low speed low rpm track work !

[350RRC]

It'd be really interesting to see Keith's fuel figures with the fan and shroud sorted out.

DL

[onebob]

It'd be really interesting to see Keith's fuel figures with the fan and shroud sorted out.

DL

Aye, it would ….

[Keithy P38]

Mate that looks the goods right there! It would be nice to see it in person! Do you happen to have the dimensions of that fan by chance? I do recall looking into it, and width was the reason I didn’t go for it (the BF/FG fan and shroud is narrower so fits easier between the chassis rails).

I bet it cools like a charm!!

I did consider the different flex fan option as well, but wasn’t game to sacrifice the uphill cooling as the factory P38 viscous fan already gets it warm enough on those kinds of drives.

I’ll definitely put up my results with the improved shroud design. I’m working on that solution now 👍

Cheers
Keithy


Hi,

Hope the pic works.

You can see that the shroud fits over the core very accurately, the bottom of it actually sits in the original mounting brackets.

The only trimming required was a bit on the sides, a bit on top and around the bottom rad hose.

Tin work on top was just to neaten it up. All done about 20 years ago.

You can see how much space is freed up around what was the old fan hub. That was all shroud before.

cheers,DL

174479

[350RRC]

The other thing to watch is the weight of the fan /s in a 4wd application.

The shroud on mine sits in the brackets on the bottom of the rad but the weight is carried by aly brackets each side.You can just see the LHS one above the aux battery.

RRC rads are prone to splitting the tank seams if it's not right.The weight of the rad has to be taken by the grommets underneath, even without thermos.

I know p38 rads are different, but it might be helpful to take this into consideration.

cheers, DL

[onebob]

…….
I did consider the different flex fan option as well, but wasn’t game to sacrifice the uphill cooling as the factory P38 viscous fan already gets it warm enough on those kinds of drives……

…. sorry, I could have explained it better and that is according to the manufacturers, a flex fan pulls more air at idle than does a regular fan and that should “improve” uphill cooling.

[prelude]

g'day, let's see if we can drag this old topic kicking and screaming back into the daylight :)


I recently revisited this topic in my head since I was working on the build of my own car and was searching for PWM controllers for fans. That long story I'll keep very short: it's not easy if you want to figure out what the PWM frequency should be to run a DC motor optimally. My homebrew setup with an arduino has a "nice" 500hz tone coming from the coils of the AC fans... Anyway, I digress as usual.


The reason I started thinking about "to viscous or not" had to do with the above experiment. I want/need the A/C fans to be there, no choice really, and I want to use them whilst stationary. In order to get the thing as quiet as possible I wanted the RPM to be variable, hence the PWM since it is more efficient than regulating the voltage through a beefy transistor. Since I need two fans anyway for this purpose and the two already on the car take up about half of the radiator I began my research and thought I'd share my thoughts here.


The last we discussed in detail was the power requirements of the fan. I seem to recall that I did an experiment with a drill and the actual range rover fan. at around 1500RPM it consumed about a kilowatt and if air is linear (which it is not entirely) at around 3000RPM, the speed a hard working engine is usually running, it would consume double that. It was also mentioned that the VC eats around 11hp. I did some searching and found a video of a bloke who had a belt driven fan (not clutch like ours) on a pickup with a tuned V8 to 400HP. He had a flex fan installed, ie one of those models that bend when speeding up which is about the same as our clutch driven fans, they ask less of the engine when the RPM really go up. On a dyno run he lost about 8HP. This translates to 6KW which is A LOT in terms of 12V and I think we concluded quite definitively that we do not need that much power.


I have seen tests of spal vs contour vs some other brands and what stuck out the most is that indeed some fans work better than others but the most important take away, I think, was that the guy could not get all the shrouds to fit as well as they could and thus lost air flow. Another thing that I noticed is that the general consensus is that a push fan is 80% less effective as pull fans.


That last part had me thinking: the way the myriad of radiators is mounted in our P38's make air flow a bit difficult. At the front there is the A/C condensor (and technically 2 fans on the upper part), then there is 2 oil coolers (I have 3 since I run my winch hydraulically so need cooling) and then there is the actual engine coolant radiator. The shroud for the coolant radiator fits snugly but the stuff that comes in front of it has barely any ducting whatsoever, in other words air can slip through between the radiators. It seems the engineers either did not care or did not find it important to do so and I think all this combined explains why the AC fans are not that useful for lowering ECT.


The AC fans push, which is less effective to begin with, through the condensor and do that job fairly well. Behind them sit the oil coolers which will have some benefit of the extra air as well but there is enough space for the air to escape around them and blow out the sides. Whatever air is left pushes through the radiator at the back. Since they were never designed and meant to cool the radiator, they are indeed only a small added bonus. As for the VC fan, it pulls through the radiator with the help of a nicely fitting shroud and thus cools ECT quite well, at least when it is spinning hard enough. Even though it then starts sucking air from wherever it can for the purpose of cooling the engine it does not matter since it is from outside of the engine bay at that point and thus "cool" air. With its copious amounts of over capacity it will do the job of the rest as well, even if it sucks in air from the sides and what not (between the radiator, oil coolers and condensor), whatever is left will be quite enough under most circumstances. The only part that needs the extra cooling is the A/C when driving very slowly, thus the thermo fans.


With this in mind and eager to see if I can find a way to get my car "full electric" I started browsing fan solutions. Since Spal is a well known brand and available just about everywhere I started with their product offerings first. It turns out that they make a number of nice 11" fans that are actually quite cheap. With the dimensions of the radiator I could fit 4 11" fans over the entire area. with 1100 CFM a piece they would add up to 4400CFM in total. They use around 10,5A a piece which would add up to 42A in total. At 12v that is 500watts of power. Even with your average alternator being around 40% efficient at most that means you rob the engine of 800 watts of power which equates to just about 1hp.


The figures say that it SHOULD work out and I am tempted to try this. Since I could ditch the two front A/C fans and the VC fan and shroud in terms of weight it should be close to the same. With 4 fans I would have plenty of redundancy to get out of trouble should one fail, I might have to slow down but that's ok and it would suit my stationary silent condensor cooling as well though it might be less efficient. I could however improve the ducting around all the radiators and since the oil coolers are on top, I could switch on the lower 2 fans for A/C duty only and make it more efficient.


The only real downside I can see is that the VC fan is much farther back and combined with the shroud does not really block the radiator in any way, ie. the full surface area of the radiator is cooled since the air can pass freely. When using 4 11" fans the shrouds would block a significant area of the radiator since they are not as deeply mounted, not to mention 4 electric motors that can block the flow. Even so, from the front point of view, ie. the air being pushed into the radiator whilst driving, we actually increase the aperture by 35%. Not sure how much of that is taken up by the fan motors though.


I think that is what has gone "wrong" with Keithy's experiments; the fan probably does not fit well enough, the shroud for so far it has one sits to close to the radiator and blocks it a bit and potentially it is not quite powerful enough to do the job. It would be "cool" (pun intended) if he were still on the case because I am quite curious of it can be done :)


these are the brushed fans I had in mind, I would have to make my own PWM controller for them: Spal va04-ap70/ll-37a | Spal Lufter 12V 280mm | Spal Axial fans (brushed) (https://www.spal-vertrieb.de/en/product/va04-ap70-ll-37a/)
Spal also make a brushless PWM fan, though they are about 3x as expensive and I would need to make a shroud: Spal va99-abl315p/n-101a/sh | Spal Lufter 12V 280mm | Spal Brushless axial fans (https://www.spal-vertrieb.de/en/product/va99-abl315p-n-101a-sh/)


Also, the PWM version has a MUCH higher CFM rating at around 2400 a piece which would add up to 9600CFM in total, if that ain't enough... The current draw at full tilt would also be quite the thing :) 18Amps a piece for a total of 72A. My guess is that would be overkill.


When I read about the disco 2 experiences and the classic rangies with only 2 fans I tend to believe I should be able to make this work, or not?


Cheers,
-P

[350RRC]

g'day, let's see if we can drag this old topic kicking and screaming back into the daylight :)............................

...................When I read about the disco 2 experiences and the classic rangies with only 2 fans I tend to believe I should be able to make this work, or not?


Cheers,
-P

Hi, I wrote a long piece about why you shouldn't try this on a P38 but got timed out.

In short, thermos work well for a RRC coz there's a common Ford set up with the shroud and 2 fans that is almost a perfect fit.

This set up has cooled older Ford 4 and 5 lire engines for decades now.

It works because of the stock tight tolerances. It's way more efficient than a VC fan, so needs way less 'power'.

These things don't come close to fitting a P38 radiator.

There are pics of mine on the previous page. Keith looks like he gave up............... I'm just trying to save you some time consumed, expensive disappointment.

cheers, David L

[prelude]

Yeah, that time out is quite annoying at times [bigsad] What I do these days is select my entire reply, copy it, press submit, log back in, get a blank screen, reload the site, get back to the topic, press reply and paste the entire thing in the text editor and press submit again. Of course things like lists, quote's and links need to be redone but I usually manage within the time limit :)

In any case, thanks for your reply. Indeed I think that you are right that the RRC solution will not work for the P38. That is why I was looking into using 4 fans with shrouds that will cover the entire radiator and be a near perfect fit. You think there are other factors that might not make it work? like airflow through the engine compartment or something?

Cheers,
-P

[incisor]

session cookies are set to 3600 seconds (60 minutes)

if you get logged out prior to that then something is playing with your session cookies

cheers

[prelude]

David, I agree that the RRC setup would not work on a P38 since we do not have similar radiator designs. The P38 has an almost square radiator whereas the RRC and the discovery 1/2 have a more rectangular one at least that I could see. This helps a lot with fitting fans since it is much easier to place two fans next to each other covering nearly all of the core. It also helps with the shroud since you can have a better angle which helps airflow, more on that later.


This weekend I have been going over all the data once again and have also been double checking my numbers and as it turns out, I made a bit of a mistake. The space for the radiator in the P38 is roughly 600mm wide and something like 560mm in height. Whilst four 11" fans would fit that area, there is of course the small matter of the tanks and in/outlets. The dimensions of the core are more like 580mm by 490mm. It would be harder to mount 11" fans this way, although fans by their very nature are circular we could modify the shroud where we would need the space for the in/outlets whilst still presenting a very large surface area to the fan. The biggest downside I reckon would be that you lose a lot or surface area of the fans that simply suck at parts of the radiator where no air can flow anyway, unless one would make a shroud that is fairly deep.


As an alternative I started looking into a setup that would fit the core as perfect as possible, I ended up with four 225mm fans. I also tried fitting the largest fans that would fit diagonally and ended up with two 385mm fans. The largest single unit fan(s) I could find were around 18" whereas the "perfect" size for our radiators would be around the 19" mark. It seems though that 18" fans are already quite rare and may not be readily available. Examples from a BMW X5 or 750 V12 came along and even spal has one, although not on their european site. I could not even find places to buy them other than in south africa and on ebay. 19" find from a reputable brand I have yet to find but then there is the question; would we want a single fan? Let's look at the powered flow numbers first:


4x225mm fans : 743cfm a piece which is 2972cfm for all four.
2x385mm fans: 2016cfm a piece which is 4032cfm for the both
1x465mm fan: 3600cfm


The last unit we should be comparing is the VC fan to begin with of course. Let us ignore the power usage for now, we have gone into that theory a lot in previous posts, and try to figure out it's performance. We know that a good VC bi-metal unit achieves at least 85% of input RPM when hot but it will also start slipping at higher RPM to prevent the blades from flying off. It seems 3000RPM is a much quoted figure for top speed in regards to VC operated units. Makes sense I guess since most of us will not run above 3500RPM for any extended periods of time? In any case we know the diameter of the VC fan to be around 450mm in a shroud that has an opening size of around 500mm. There is quite a bit of tolerance between the both since the engine can move in it's mountings but the radiator and shroud are fixed so we need those tolerances. This no doubt decreases efficiency but I do not know by how much. For now let us assume 3000RPM at max and compare it to the closest contender in our list. It can produce 3600cfm at almost 3000RPM. I am sure the VC can spin a bit faster still but then again the thermofan is of a more efficient blade design so I guess the bottom line is that we can expect around 4000CFM from the VC unit under most conditions, no matter how we load the engine up since RPM = RPM.

I did not take into account pressurized operation at this point (ie. the resistance through all components) but suffice it to say that one would pick the best functioning unit at higher pressures since we already concluded there is a lot of resistance with 3 radiators stacked in a row and considering the original fan, as pointed out above, has it's limits in performance as well. What I mean to say with this line is; not all fans are created equally and looking through the available fans in different size you get different performance specs. Some are more quiet, some push more air. We'll go with more air.


Anyway, let's step back a bit and see what Keithy's problem was in running the thermofan: he could not maintain decent temps with 40km/h at a steep gradient. From the top of my head I would think that engine RPM at that speed to be around 2500? My car is in pieces so I can't confirm at this time :) His conclusion was however that where the VC fan had no problems his thermofan was not up to the task but that is just part of the story as I mentioned to David above; it's just as much a case of fitment and airflow as anything else. Let's take a look at the surface area numbers for air to flow through.


I calculated the effective "open" area assuming a perfectly fitting shroud for all the options and also deducted the surface area of the motor.


4x225mm fans: 398cm2 a piece with a motor that is 98cm2 resulting in 1200cm2
2x385mm fans: 1162cm2 a piece with a motor that is 124cm2 resulting in 2080cm2
1x465mm fan: 1700cm2 with a motor that is 314cm2 resulting in 1386cm2 (this figure is also very close to the VC fan area, it would be slightly larger, say 1500cm2 at most)



Mind you, the total theoretical surface area of the radiator, ignoring grilles, bumpers and what not is 58x49 roughly and that makes for 2842cm2. Looking into Keithy's setup and designs using thermofans in stead of the VC fan in general found all over the net I am beginning to see a pattern: Most thermo solutions use a near square and tight shroud, and with that I mean the angle and distance between the radiator and the back of the shroud, whereas the VC solutions generally do not since the fan is close to the engine and the radiator is reasonably far away facilitating a more sloping design. I have also noticed that in some applications of thermofans the radiator shroud has one way flaps that open up when driving to let air through the shroud but they close when the fan is producing more air flow. This got me thinking: what is the air flow at 40km/h such as Keithy tested?


Again, I did not take into account all the stuff that is in the way but just calculated the maximum theoretical. with a frontal area of the radiator of about 3 square foot (since all fans have a rating in CFM I calculate it in feet) and an air speed of 2178 feet per minute (or 40kmh) we come to a staggering 6561CFM. I guess there is much in the quote "do not underestimate cooling from driving" that has also been uttered in regard to alternator cooling elsewhere, a subject I am into as well at the moment.


So, finally, for those of you who hung in here and had the patience to read trough my ramblings: I believe the reduced airflow of Keithy's setup to be the biggest problem. Not just the fact that his fan can not do more CFM at full speed but that the entire flow of air through the radiator is severely restricted due to the shroud design.


Perhaps as a final note I should clarify my own desire to have an electrical setup in stead of a VC one. Apart from the fact that I wish to reduce components on the one hand, ie. the push fans for the radiator condensor should I not need them, I also want to make the rest of the cooling system more reliable. Arguably a belt driven system is one of the most reliable to be had however genuine landrover parts are drying up for some vehicles (such as the P38) and in the end a single fan is still but a single fan. If it breaks for any reason, no cooling. Having multiple electric fans would certainly increase redundancy since if one breaks the other(s) will continue to work in most likelyhood. Yes you increase components and possibly complexity but I believe it to be manageable.


At this point I might be trying to do too much at the same time but I have found this thought experiment worth while and I'll ponder on it some more to see what I will do going forward.


Always interested in hearing from you guys!


Cheers,
-P

[prelude]

Hello again folks ;)

I couldn't help myself in trying to pursue the cooling puzzle and since I have been delayed by many reasons I had some time to do some more research and testing on the P38.

After a lot of puzzling, soul searching and discussion with other people (too much to repeat here) I decided to bite the bullet and order the biggest, most powerful (and power hungry) fan currently on the market: the SPAL VA164A-ABL1002HT/R-124A. This absolute beast of a fan can do a LOT of CFM using even more power, see the datasheet here: Axial Fans with Brushless Motor 12V/24V DC - SPAL (https://www.spalautomotive.com/en/brushless-axial-fans?productcode=va164-abl1002ht-r-116a&articleid=96915)

It took me a whopping 750 euro's excluding VAT and 6 weeks of waiting to get one of these in my hands, they seem to be unobtanium for some reason and I was very excited to get it up and running. I already found the documentation I needed for the pin-out and the PWM specs for the fan (100hz, to ground if someone should care). When it arrived I hooked the PWM controller up and all that and... nothing. Back to the drawing board. The unit also has an analogue input, ie. put a variable voltage on that line and it will regulate its RPM as well so that is the next thing I tried. Well, it spun up alright, all the way to the point my 60A power supply said "that's enough".

All in all the conclusion unfortunately is that I got a broken specimen. The slow start function works but none of the external regulation. Still, it was very insightful to do some experiments with the fan since I had it in anyway. After hooking this bad boy up to one of my Lithium batteries I also hooked up the analogue line to 12v and let it spin up to full speed. The fan will actually launch itself like a drone if it is not bolted down! After bolting it down :) I found that at top speed the current draw was in excess of 80 Amps at 13.2 volts (charged lithium battery). My word... That is a whopping 1KW of power. Highest I recorded was 1.2kw of power draw in total.

Personally I think we are getting real close to the performance, if not exceeding, the VC driven fan since the design of the fan blades and all is much more efficient.

So, next thing I tried to determine is the total airflow through the radiator stack. Most if not all fans have a CFM rating but nearly all of them are measured in free air. The SPAL is no different. The only exception I have found is the Delta-Pag product but more on that later. Since most of us do not know what the static pressure of the radiator(s) is I set out to try and determine what mine was using an anemometer. I measured ~13m/s which equates to around 45km/h in free air. The second measurement was just behind the A/C condenser (mind, the fan is a PUSH model so I had it mounted on the front for this test). It topped out at 7,5m/s and the last measurement was taken behind the radiator since there was not enough room to fit the anemometer between the oil cooler(s) and the radiator I skipped that part. It read almost 5m/s.

As we can clearly see the speed reduces quite a bit. Plugging this into Bernoulli's equation we get a static pressure figure of about 100Pa or almost 0.4 inches (10mm) of H2O which seems quite good for such a large stack of radiators/condensers.

Unfortunately since the fuel tank is out I can not do a similar measurement with the viscous fan for comparison, although the static pressure figure will not change, the maximum air displaced could be higher although I am beginning to be a bit doubtful of that since the much bigger tolerances and less efficient blade design already mentioned in the post above.

But (there is always a but isn't there?) here is the kicker: the placement of the fan. I already kinda alluded to it in the post above but I again came to a similar conclusion when I was working towards a solution looking from the A/C condenser side: how much air are you pushing over what area? You see, to summarize part of the post above, the viscous fan sits quite a bit back from the radiator and has proper cowling. This in turn facilitates proper flow of air through ALL of the radiators surface area. Yes, sure, we are diluting the total capacity of the fan over a larger area so the speed at which the air moves decreases but all of the radiator can radiate it's heat to the air and thus cool the engine.

This brought me neatly back to my original requirements for improving the fan setup, to reiterate:


the best possible performance for the condensor fan(s) when parked (engine off)

lowest possible consumption
lowest possible noise


the best possible performance for the radiator when the engine is running

electrical consumption is almost no issue
noise is irrelevant



I have slowly come to the conclusion that these are almost diametrically opposed. To serve the A/C condenser the best way possible you want a pusher fan close to the condenser on the front. This wil blow as much air as possible through it to lower the temperature and keep your A/C happy and running. Even better would be a pusher with sufficient cowling but nobody has that kind of space in the front of their car right? To cool the engine coolant radiator you want a puller fan with cowling to get as much of the surface area of the radiator to do its job. Sound familiar to anyone? ;)

Yup, that is exactly how the P38 range rover is set up. It has two fans up front directly pushing up to the condenser and has a big powerful fan inclosed in a cowling to cool the radiator. Now, normal people who do not go overboard in over designing their rig do not technically need the second part so I will concentrate on that first. What I mean by that is: the only reason the 12V fans exist in the P38 is because the VC fan is not sufficient to cool the condenser and thus run the A/C in stop and go traffic or idling. The fan simply can not turn fast enough even when the clutch is fully engaged so the thermofans were added. The engine also get's scarily hot but the added bonus of a tad bit more airflow from the electric fans helps with that problem too.

In conclusion to the thermofan question then: I believe a thermofan in a P38 is a very doable thing. With the SPAL mentioned above mounted in a proper cowling that snugly fits and with the engine running, assuming you have the amperage available, it would be more than adequate to cool the engine, even on long pulls and keep the A/C happy as well with the added benefit of seriously reducing fuel consumption. SHOULD I not be able to get a rebate on the SPAL I'll bring it with me to oz as a spare and Keithy can play around with it :) I mean it still works as a fan that you switch on and off, just not as a variable speed fan.

For those of you not interested in my particular use case, you can switch off now!

This brings me back to my dilemma. I want the almost impossible, but let's look at the fan I have. The best way to mount it is as a puller behind the radiator stack and let it do it's thing and loose a bit of efficiency in the A/C department which IS an important point for me. In that position the HUGE motor that drives the fan is simply not that much of an issue. And I did mistake the size of that thing I must admit. SPAL has decided to mount the ECM inside the motor compartment and combine that with the massive power that thing uses and also needs to dissipate it has resulted in a unit that is at least 15cm across easily. I reckon it is about as big as the VC on the range rover as it is. Now normally this is not an issue since the VC fan always runs, even if it is a a reduced rate, since air can escape quite easily. Remember my calculations above? 5m/s is a very very lazy RPM for that big boy in our cars so even if you are doing 120kph the ram air through the radiator is easily managed by a lazy spinning VC and thus fan. The other way around however, mounted as a pusher, the fan blocks even more of the condenser and in turn the rest of the radiator stack as the original twin thermofans.

To find a solution to my broken fan and anticipating problems with SPAL (I mean 6 weeks for the first fan, the second will probably not be any faster) I hit the internet again to follow up on a link that I had remembered; the Delta-Pag 18" fan. I first noticed this unit when I was researching the PWM control of the SPAL fan I already had on order so I dismissed it. But...

The Delta fan is of a much thinner design with more optimized and thinner blades that would not hinder the ram-air flow as much. It is also rated at "only" 30 Amps, it does not need as much with the higher efficiency blade. What this also means, together with the fact that the ECM is an externally mounted unit, the motor is much smaller and thus much less obstructions.

So, we'll see what happens with the warranty on the SPAL but if there is any problems there I might go for the Delta 18" unit and use that in place of the dual fans for the condenser only and stick to the VC. Again, not because I do not think the P38 can not be cooled by electric fans but simply because my use case is different.

Cheers!
-P