2 X 12" fans, or a larger 16" one ????????????????

[Brakebuster]

I have decided to install electric cooling for my XJS V12, and have already removed the viscouse fan and associated fittings, one thing i did find was that all the fan blades had micro cracks all through them , and so was in its last throws of life

anyway , back to the question in hand,
would you recomend two 12" fans side by side on the radiator,
or one large 16" fan with a smaller fan similar to the original setup,

any advantages/disadvantages for either method,

many thanks

[SimonR]

Hi BB,

Wasn't the 2x 12" setup used in the XJ-40 towards the end of its life?

I seem to remember something about it from the JEC XJ-40 lecture at the weekend. If this is the case then it's potentially an easy conversion.

What was the reason for the conversion, btw?

[greeban]

Are you sure you want to remove the viscous (ahem - you have already!)

You may find it runs hotter under the bonnet which can give you other problems. I have a stag with the rover v8 and electric fans and it gets bloody hot under the bonnet - I am thinking of getting the bonnet louvered as the heat has nowhere to go - can't put a viscous fan on as no room.
By the way I am not an expert!

[Brakebuster]

hi chaps,

thanx for your input,

i didnt realise the 40 had twin leccy fans, will keep an eye out at the breakers this weekend......thanx for that

the main reason for the conversion is more reliable cooling in slow traffic etc, along with the added ( it all counts , lol ) 12 ish BHP added by removing the load from the engine ,

the other reason was that the fan its self was on the point of destruction as when examined was full ( and i'm talking every 1-2mm's down each blade ) of small cracks in the yellowing plastic blades , and the added dread of the viscous unit seizing up and throwing the blades into the rad, which is a new ( ish ) one,

another reason , finances,
i can import two new 12" spal fans from the US ( including postage ) for the bargain price of $110 ( £60 UK ) plus local taxes , which are 6% import duty and the 17.5% dreaded VAT

they come complete with fitting kits and connectors

BB

[Paul_C]

BB

Fitting electric fans won't remove the load from the engine all the time they are running, mearly transfering the load to the electrical system and alternator! just something to keep in mind.

I was going to convert mine when the coupling gave trouble, but the under bonnet temperature issue came to light. I got a brand new coupling for £50 job done without any modification problems or worries about the performance of a new system.

Those viscous couplings are quite reliable (more so than electric fans) mine gave trouble after 20 years and 150,000 miles, most cars don't last that long!

Not an easey decision to make but worth giving thought to.

Paul.

[Brakebuster]

Hi,

i understand what you are saying ,

but there will be a difference in HP from the engine, one is as simple as the weight that has been removed, as the whole fan unit weighs quite a few Kg's , though its not much compared the the gross weight , then there is the ' drag ' from the fan, this is why it has a viscouse fitting , no drag when not required, thus allowing more generated power to go to the wheels rather than running accessories , when warm, the clutch bites and the engine is cooled, a compromise on required cooling to keep the engine healthy and the power requirement of the car ,

then to the electrics, the car has a battery ( a reserve of power if you want ), this is charged by the alternator, if required the car uses power directly from the alternator, however, the power requirement of to 14" fans is minimum when compared to , lets say , a powerfull stereo or amplifier for in-car entertainment, or even your phone charger pluged into the cigar lighter, there is built in excess to allow all these systems to run at the same time if required, just think, you could have lights on , wipers on , stereo on , pressed in the cigar lighter and winding down the window all at the same time, does it have an adverse effect.. ?
the car is already generating the power/electricity to power the fans, electricity is there waiting to be used all the time, and is not generated on demand..

i am not having a go here, but i think there is a ' taboo ' about car electrics and what they can do ,

its also a bonus that i'm an electrician.

the text below is what was posted by me on Jag-lovers, just to keep you updated on what i'm now going to install



i have reviewed what has been said, and i have come to a decision ,

i am going to fit two 14" fans in a pull arangement on the back of the radiator , the radiator is 28" wide on the fins, so should allow such an install, i will not be using the shroud.....

i will permamantly connect one fan to a constant supply which will come on when the engine is started, this is not ideal, but wont affect ' warming up ' as the engine water thermostats wont allow any water to the rad before the engine is warmed up anyway,

the second fan will be controled via the electrical thermostat ( on the pump ? ), this will cut the second fan in when the temperature reaches high enough to need cooling, such as in stop/start traffic or very hot days, not that we get many hot days in the UK, but we do get a lot of start/stop traffic , lol

price....thats the main thing, there is an ebay seller selling new ' S Blade ' 12 , 14 and 16" fans at very good prices, and the shipping to the uk will mean i get a pair of ( 2000 cfm each ) 14's with fitting kits and shipping for $120 ( £68 UK ), even with a 6% import tax, and then VAT ( value added tax ) at 17% on top of the lot means i will be saving over £100 on UK prices

cheerz

Vince

[dhdove]

BB On a slight tangent......
Whilst trying to sort my aircon a couple of years ago it appeared from the circuit diagrams that the electric fan in front of the air-con condenser is also wired into the water temp. monitoring system? Does this fan work/cut in?
Regards
DH Dove

[Brakebuster]

BB On a slight tangent......
Whilst trying to sort my aircon a couple of years ago it appeared from the circuit diagrams that the electric fan in front of the air-con condenser is also wired into the water temp. monitoring system? Does this fan work/cut in?
Regards
DH Dove

i have no fan in front of the aircon condenser ?,

i had the 18" viscouse fitting on the engine, and a small electric fan mounted to the back of the radiator cowl , this is controled by the electrical stat on the water pump cast pipe section, this detects excess heat and brings in the auxillary fan ( small electric one ),

this is on a 1989 V12 , sportpack car

Vince

[dhdove]

Vince
Understood, 3.6 and V12 Sportpack obviously different set-up.
DH Dove
PS Did you receive my PM's?

[poprivet]

3.6 and V12 Sportpack obviously different set-up.

A good time perhaps for all members reading this to update their signature with their model year and engine capacity?

[dhdove]

Wilco Pop, good point.
DH Dove

[Brakebuster]

dont you just hate busy bodies .....lol

have done pop

BB

[dhdove]

BB
This is a test message to check my "Signature".
Please check your PM's and give me a ring
DH Dove
All Ok There then..........
Webmaster, sorry to hi-jack this thread for personal correspondence, it wont happen again, honest

[ptjs1]

Vince,

Just as a matter of interest, why have you chosen to run one of the fans permanently and one in "excess heat" conditions?

I've left my XJS as standard in the cooling department, but I've done a similar conversion in my V8 Range Rover. I did it for similar reasons to you, I suspect - lose some of the weight, gain up to 9% more power (Kenlowe's figures) etc. However, one of the big deciders for me was that I was doing a lot of short journeys at the time and was trying to avoid the extended warm-up time that you get with forced cooling of the radiator with a permamnently engaged fan, with increased engine wear and awful fuel consumption.

So, I was just interested as to why you wouldn't wire the fans to both come on only when the coolant reaches a pre-set temp. Are you going to wire the fan into the car's water-pump electricla circuit and not use a variable thermostatic switch, such as Kenlowe sell?

I don't profess to understand enough about the optimal operating temperature of the V12 engine. But, interestingly, Kenlowe's technical department recommending setting the cut-in temperature of the thermostatic control to a setting somewhat hotter than the "Normal" setting on the temp gauge. The theory being that you can let the engine operate safely at a higher cylinder head temperature than normal which apparently is optimal for combustion and therefore efficiency. So, I set my fans to cut in somewhere between Normal & Hot. I don't think I could honestly say that I feel the extra 9% power, but I do get better fuel consump. Also the engine sounds much nicer at idle without the viscous fan there.

(DH Dove, my Range Rover also has a thermostatically controlled fan in front of the air-con, but this only cuts in when the air-con is on and apparently is not sufficient to cool the main radiator as well)

Sorry about the waffling - I've just got back from a completely drowned Bealieu Autojumble, where I found that my tent isn't quite completely waterproof! So just fancied a bit of Bulletin Board therapy. Hope you all had a drier weekend than me!

[Mark_B]

Some cooling fan points.. I guess the idea of replacing the viscous fan with an always running electric fan is to avoid cracked viscous coupled blades exploding into the rad, plus electric fan is easier to control. Electric fan can't be any less load than a direct-drive, doesn't an electric fan take about 15Amps or more? (nearly 200W). By the time that load reaches the crankshaft taking into account conversion and electrical losses it could be half as much again more.

To bear in mind for continuous/high duty cycle electric fans. Wear and tear on a electric fan has always got to be more, brushes and bearings don't last forever. Once a car is moving beyond a certain speed no fan is needed anyway.

Warm up time from cold shouldn't be affected by cooling fans being running or not, until the thermostat opens as the water is just going round the bypass and heater matrix circuits, no rad involved yet.

Setting a fan cut-in temperature too low is going to be a waste of power, good position for temperature sensor is halfway up the rad and for cut in temp, a temperature gauge reading above 'normal' (to save power) but below 'hot' (to prevent coolant loss).