My cooling project

PeterZRH

Well-Known Member
#1
Hi, this topic has been covered a few times but I hope what I write here might be of use to some mainly as I've tried to refine and optimize my solution to make it more acceptable for everyday use rather than as a backup. I include product numbers and costs if you'd like to try.

Firstly, many have fitted an electric fan but have needed to modify the metalwork for it to fit or fitted a small one as an auxiliary. I had a Chinese cheap model and it lasted less than 2 years previously and generally it was crude but worked but it made the kind of racket that made people look and not in an admiring way.

Well perhaps I've found the very biggest that will fit without surgery: a Spal 16 incher. It's a beast and boy is it tight. You have about 1cm of up-down wiggle room and it won't fit as pictured because the "lugs" in the centre motor hub stick out! Turn it 45 degrees so they clear the narrowing valance and you have literally 1-2mm to spare!!! You'll notice I did make a mount using M6 threaded rod and some metal "L" brackets used in construction. Cost under a fiver and I'm happier with this than using the pull ties through the matrix. As the standard Spal mounts are too big to clear the edge of the rad, they are connected to the fan with a "noodle" and and M6 bolt with plently of loctite and spring washers. If I was thinking at the time, I could have folded the bracket 90 degrees over the back of the rad and bolted it to the two captive bolts and not drilled the top of the rad itself (oh well...) I'll paint these black eventually so its less obvious. It is front mounted which actually isn't the optimal position. However I'm very happy with the extra spanner room engine side, especially as I didn't refit the now pointless shroud.



The model is a Spal VA18-AP51-C41S for reference. It wasn't that easy to get actually and twice I was supplied incorrectly with the half as powerful VA18-AP10-C41S http://www.spalautomotive.com/eng/produ ... AP51_C-41S You really want the 51 and not the 10. One guy on Amazon successfully cools his 289 Mustang with it so it should be enough.

Most fans which shift anything like enough air are absurdly loud and to the most part unnecessarily powerful in normal, general use but you do really need that overhead in reserve. To this end I firstly focus on efficiency rather than outright power and cover as much of the matrix as possible, although the fan is around 150W. From my experiments the P6 rad is pretty effective, indeed as long as you keep moving a I proved a fan is unnecessary even in 34 degree heat. It seems to have specific problems with the tight packaging of the engine bay and the total lack of airflow when parked or in traffic. My solution is that often used in the 1980s and 1990s; use a two range thermoswitch. This feeds through a resistor to lower the power of the fan in general use and still has emergency "hurricane" mode to protect the engine in extreme conditions. It's also far more elegant and/or less leak prone than hacking hoses or sticking things through radiators. This is a standard M22 x 1.5 threaded item and there are HUNDREDS to choose from. Plymouth radiators did an excellent job for £20 (as they did 25 years previously to repair an earlier P6), so doing the job properly is cheaper and gives you more choice than the various kits you can buy.



Now the next issues I had were the themoswitch itself and the resistor value to control the fan. Reading up about resistor packs on various cars, it seems values vary between 1 ohm down to 0.33 ohms. Now the values I saw are all standard values in electronics which leads me to believe this isn't super matched to the application merely a balance of what is enough to cool the engine with the minimum of noise. From the figures the fan draws about 12A @ 13V, so about 1.08 ohms of nominal resistance and 150wattish output. So I bought a couple of 100W 0.47ohm resistors as a pair meaning I can get 0.235 ohm or 0.94ohms in parallel/series as well. Adding the single resistor makes the series resistance about 1.5ohms and drops the power to 112W - however the relationship between power and airflow and indeed the mechanical properties of the fan isn't linear so its more of a drop than you might imagine. It is MUCH quieter and cools well enough and I might try some other values out.

There is of course another advantage of this. The startup currents are very high, this drops the load from 12A down to 8.34A and it's much less of a strain on the thermoswitch relay. Even when it changes up to high speed as there is already back EMF the transient draw which can be over 25A is much reduced.

As for the thermoswitch itself I got this wrong to start with. I had a VW one with the ranges 102C - 91C and 95C - 84C. These are switch on and switch off points respectively. For the lower range 95 degree cut in is fine, but 84 degrees is too cool for an 82 degree thermostat as it's barely open. What tends to happen is the fan switches in and then hardly ever switches off. In the end I swapped this for a Volvo one (reference: Intermotor 50174) with the ranges 100C-95 and 95C-90C allowing 8 degrees over the opening point of the thermostat; 95 degrees pretty much being the "fully open" point of the stat. The car sits quite happily just over the 85 degree mark all day. If I park up in the sun I can't get the upper speed to kick in even in 35 degree heat after 30mins - good enough for me and it doesn't wake the neighbours. If you wanted it to run a couple degrees cooler then a Peugeot/Citreon one might be better as 97C-92C and 93C-88C ranges still allowing 6 degrees over the thermostat opening. However the P6 with a high pressure system can relatively happily work well over 100 degrees. Indeed later engines perhaps ill-advisedly work as normal at 110 degrees. I reckon 90-95 is fairly optimal.

What I will say is this is a huge load on the electrical system, you really feel the fan "rev up" with the engine as the alternator powers up. I have no idea how the guy with the 240W Kenlowe doesn't just melt his electrics and I'm not convinced that despite this power 13" will cool as well as this 16" given this covers more than 1 and half times the matrix area. You really absolutely NEED a 25amp separate fuse. I put mine on the always powered circuit as I'm happy to let the fan "run on" when stopped. Hopefully as well as avoiding localized boiling it might had I not solved this problem with an electric pump prevent vapour lock.

As a bonus, the engine is so much quieter without that mechanical lump spinning around. A large part of what I assumed was top end/tappet noise is actually a function of the engine fan spinning around. Perhaps it'll save the water pump bearings too. If you have a manual car consider it a cut-price flywheel lightening. It certainly seems a bit more "revvy".

Overall I'm not convinced of any economy or warm-up claims but what is nice is driving the car in summer, even in the heaviest traffic with both eyes on the road and not one on the temperature gauge. What might be a benefit come winter time is a bit more output from the heater but we'll see about that.

As I said this is a cooling project and not just a fan fitment and I also fitted the MGB expansion tank. Nice to know that top 2" of the rad is being used. I ditched the front number plate plinth as the Swiss plate is much smaller than the UK one it is modeled on. More airflow for free.

Overall the fan was expensive as you really need decent sealed bearings and Spal are about the best in the business. £120ish, the thermoswitch was a tenner off ebay, the resistors were £4 for two and the work on the rad £20. So allowing for cable, crimps, fuses and various nuts, bolts and brackets call it £155. What I would do differently is find an expansion tank with a coolant level warning and wire an indicator on the dash (maybe make it light up the choke warning so it looks original - I can even just use the "Otter" switch wiring) for extra peace of mind.
 

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PeterZRH

Well-Known Member
#4
So you've gone engine side and avoided the waterpump with twin fans. Whats the noise level like? On full mine is really antisocial.

I've been playing about with this for 2 years now. I really don't think a single speed solution works very well; too noisy or too little cooling.

I'd really recommend the M22 x 1.5 solution.
 
#5
hi just a quick question maybe I am completely missing something here I think u said u opted for a dual thermo switch that switched on at 100 and off at 95 and then the second half switched on at 95 and off at 90. if I am understanding this right the fan switches on at 100 or 95 degrees but wont switch off till 90 degrees. so effectively the fan will always be running above 90 (once a switch on temp has been reached) I appreciate this is to facilitate two speeds. but surly until the engine reaches at least 95 the fan wont operate.

if the engine is safe to run at 95 why cool it below that? if it needs to be at 90 why switch on at 95 either way at 25 amps even with the uprated alternator that is half the current available. for what will ultimately be the majority of the journeys.
please don't think this is criticism im just trying to understand the benefits
coop
 

PeterZRH

Well-Known Member
#6
No the fan isn't always running above 90, it's always running at one speed or other over 95. It'll only run DOWN to 90, not between 90 and 95 going up.

The reason is you are dealing with on/off switches. There is a built in hysteresis to avoid it switching on and off constantly. Basically it uses the temperature range and thermal mass of the water to keep the system stable rather than have it oscillate.

Remember the stat opens at 82, mostly it will find an equilibrium BELOW the switching point whereby the stat valve is partially open and the resulting flow matches the engine's cooling need.

Above that the fan will drag the temperature down and switch off until it heats up again.

95 is perfectly fine, in fact it's technically more thermally efficient. In practice it's below 90 because the rad does the cooling when the car is moving, what you are doing is controlling the overheat in traffic. Remember Rover specify an 88 degree stat which wont fully open until 98 degrees but most people stick to the 82 degree summer stat.
 

Demetris

Well-Known Member
#7
It looks good and effective.
I also think that a great big fan running at two speeds is the way to go.
The cooling demands vary greatly, and while 95% of the time the low speed will suffice, there are those cases where you are going up a steep hill, it's above 35 degrees, you are trapped behind that slow moving lorry / bus, and due to the narrow road and the oncoming traffic you simply cannot overtake. In this case if you have opted for something cheap and cheerful that was perfectly adequate until then, you will fry your engine. Engine rebuilds are expensive, fans less so.
 

PeterZRH

Well-Known Member
#8
Hi Demetris, what's it been like in Greece lately? We've had 38 degrees here in Switzerland but frankly driving a non-air conditioned car wasn't my idea of fun.

I did have the engine fan back for a while and I went into the red in traffic at about 35/36 degrees after about 15 minutes that's what prompted me to go electric again. I'm assuming the "red line" equates to 100 degrees so I reckon I was up at about 105ish which makes me uncomfortable.

Now coincidentally, the high pressure system in the V8 is 15psi which is the same as a standard pressure cooker and water boils at 121C. Ultimately as long as the coolant doesn't boil the engine can still run, so technically 115 degrees or so is possible and this is bourne-out by the later Range Rovers which run to 110. However I'm assuming the mineral oils in a P6 thin out and break down unlike more modern synthetics and wear increases dramatically so really not good news if I heat the car up like this on a regular basis.

I'm guessing with the 2000 you have a lot more room around the rad and don't get this so hot.
 

PeterZRH

Well-Known Member
#9
Actually, spot the error, it drops the fan all the way down to 70W or pretty much "half power" (I^2 * R, you can't use V^2/R because it's not 13V across the fan, its 13V across the fan and resistor).
 

1396midget

Well-Known Member
#10
PeterZRH said:
So you've gone engine side and avoided the waterpump with twin fans. Whats the noise level like?
very loud!

kicks out a huge amount of hot air under the front doors - enough to raise the dust on the garage floor...

Some modern things have 2 fans, a slow one and a fast one. Mine are both fast ones... Cools it down well when stopped in hot traffic after motorway blasts... Did have an issue with it running hot at speed but seem to have 'mended' that with the next tank of fuel...
 

Demetris

Well-Known Member
#11
PeterZRH said:
Hi Demetris, what's it been like in Greece lately? We've had 38 degrees here in Switzerland but frankly driving a non-air conditioned car wasn't my idea of fun.
Well, it really depends on humidity. I can stand 40+ with dry weather but even 30+ on a humid day is rather uncomfortable. Regarding cars, a modern without A/C is unbearable, but it depends on a classic. For example i don't mind the open road in the 1100, but the heat soak in the P6 makes it rather uncomfortable in the summer. Hence the retrofit of A/C. It doesn't really freeze you, but it makes it bearable. Last wednesday i had to leave the P6 parked in the sun from early in the morning until 3 pm. When i returned to take it, the interior seemed to have something like 80 degrees, burning steering wheel and all that. It took 20 mins on the road, with the A/C at full blast (= noisy) to start feeling somewhat cool inside. It is an unfair battle with heat soak from the bulkhead and transmission tunnel despite that i have insulated everything as best as i could. It is rather common to arrive at my destination on a hot summer day with the cabin cool from the A/C, park in closed garage, leave the car for 30 minutes, and upon my return find the cabin uncomfortably hot again.

PeterZRH said:
I'm guessing with the 2000 you have a lot more room around the rad and don't get this so hot.
Actually i always had the impression that the engines in my classics were not built to withstand continuous running at temperatures above 90 degrees, so i never allow them to do so. The TC was running steady at 85 degrees no matter what with the upgraded radiator and the big viscous fan. However, after the fitment of the A/C as someone would expect with the extra heat of the condenser dumped into the radiator and engine bay, and the reduced airflow to the radiator from the condenced and fan, i always keep an eye on the temp gauge. With the front number plate removed from the usual place and bolted at a "blanc" space of the front valance, even at speeds around 90 Mph there is no overheat evident. However, stationary at traffic for ages with the A/C on, i can see the gauge going past 90 degrees.
 

ghce

Well-Known Member
#12
Why not use switch mode techniques for the fan speed rather than a resistor, there are many cheap PWM or PPM ( less than US$5.00 ) available ex China or eBay which will readily deal with a 150 plus watt load this give you the advantage, maybe dubious advantage, of continuous speed control.

Graeme
 

PeterZRH

Well-Known Member
#13
Yep, perhaps people here don't appreciate it's worse in LHD cars of course as the exhaust goes under you as the driver. The heater unit controlled with flaps instead of a water valve doesn't help either as the whole unit heats up anyway. Perhaps an isolation valve or bypass for summer might help?

I'm also doing a soundproofing project which as a side-effect will hopefully also reduce heatsoak. I'm using the butyl vibration control pads on the firewall and front floor and a layer of tecsound 50 as a sound/heat barrier.
 

PeterZRH

Well-Known Member
#14
ghce said:
Why not use switch mode techniques for the fan speed rather than a resistor, there are many cheap PWM or PPM ( less than US$5.00 ) available ex China or eBay which will readily deal with a 150 plus watt load this give you the advantage, maybe dubious advantage, of continuous speed control.

Graeme
Did think of that but it seems most manufacturers keep it simple with a resistor pack, presumably for long term reliability. PWM for motor control or any inductive load isn't a trivial matter either due to large transient currents during switching.
 
#15
hi, the exhaust thing is a good point, I was under the impression that the exhaust had to exit the car on the offside of the car so it didn't cover pedestrians with exhaust fumes. but thinking about it all English rovers are wrong in that case (I think)

I know the Talbot my father converted into a camper had a different exhaust for right hand and left hand drive versions as the exhaust broke in France and we had a hell of a job getting the right part.

coop
 

Dave3066

Well-Known Member
#16
cooper1203 said:
I was under the impression that the exhaust had to exit the car on the offside of the car so it didn't cover pedestrians with exhaust fumes. but thinking about it all English rovers are wrong in that case (I think)
Scottish, Welsh & Irish Rovers are also wrong then :wink: :D

Dave
 
#17
Dave3066 said:
cooper1203 said:
I was under the impression that the exhaust had to exit the car on the offside of the car so it didn't cover pedestrians with exhaust fumes. but thinking about it all English rovers are wrong in that case (I think)
Scottish, Welsh & Irish Rovers are also wrong then :wink: :D

Dave
um wrong side of the borders too :wink: :D
 

PeterZRH

Well-Known Member
#19
The SPAL fan had to be ordered through a local air-conditioner specialist. They are environmentally sealed for the motor and the blades are balanced.

At full power, you can hear it inside the house with the doors closed. But then I remember my father's Renault 21 being the same. The truth is if you want to cool the car in extreme conditions then there is no avoiding this. I've yet to have this cut in in normal use. If I run it like this by hard-wiring it, then at 36 degrees parked in the sun it'll settle at about 87 degrees, below the off point of the low speed and even the stat not fully open. So this is enough to make me confident of ANY conditions.

At half power you are just about aware of it in the car when parked, on the move not really at all. In fact mostly it doesn't run at all because the 82 degree stat is fully open at 92 ish and it tends to find a balance around 85-90, the fan at both speeds is really protection in traffic.

Cooling is actually counter intuitive. It's normal to panic as the needle heads towards the red. However the cooling becomes more efficient, you might remember the rate of cooling is proportional to the EXCESS temperature.
 

PeterZRH

Well-Known Member
#20
Little update. I swapped in a 93/88-97/92 degree switch (£3 well spent - you see the advantage of having the rad modded to take a standard switch?) which is from a Peugeot 405 diesel I think.

This is rated only 2 degrees cooler on the lower range and 3 degrees on the higher range. Well all I can assume is the Rover gauge is spectacularly non-linear around the center "85 degree" mark because although I'm sure 2 degrees is neither here nor there in practice it looks a lot more comfortable on the gauge it now just passes the "5" at most.

I think the 0.47ohm choice has turned out to be pretty much bang on and the fan is absolutely the right choice for the P6. It might even be possible to go one or two values higher and lower the fan speed further but it's been up to 38 degrees here and I'd like to test it. I don't think it's an issue at this extreme if the higher speed cuts in.

Anyway at an ambient 28 degrees parked, the fan kicks in at low speed for between 50-70 seconds to haul the temperature down the requisite 5 degrees C. It then cuts out for another minute or two before it kicks back in again and repeats the cycle. You can just about hear this sat in the car stationary and not at all when on the move - result. A bit like the heater blower at low speed for comparison. You tend to only really notice it when it spins down.

I could not get the higher speed to kick in at all after 15 minutes, so I disconnected the low speed to test the high speed. The fan could cool from 97-92 degrees in under 20 seconds @ 28 degrees ambient. 97 degrees is fine but not what you'd want to run the car continually at. So as well as being spectacularly effective at cooling, being noisy its also a useful temperature "alarm".

So in conclusion, with care, you barely need 80 watts worth of fan to keep a 3500 cool in nearly all conditions you'd find in the UK, which is somewhat contrary to legend. The rad is really good itself, its just there ain't much air around it. Really, like the manufacturers discovered in the 1980s when this became common, you really do need a two speed solution to be comfortable and quiet in normal use and with the capacity to cope in extremes. Modern systems tend to be linked to engine management and are variable.

I can't help but wonder in other leyland cars, notably the Stag how much better the reputation would have been with the simple decision to use an electric fan. Engine driven fans truly suck in both meanings of the word in modern traffic condition. Mine is now where it belongs; hung up on the garage wall.
 
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