Author Topic: improving thermo fan  (Read 25340 times)

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colcol

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Re: improving thermo fan
« Reply #30 on: October 25, 2013, 06:48:45 PM »
Correct Duk, i run my 33 with the most water i can to prevent overheating and with the least amount of rust inhibutor to prevent rust, always a finely balanced ratio, the thinner the coolant, the better the heat transfer will be.
Some coolants are approved for motorsport, due to they dry up quick when spilt, from my memory, Nulon green coolant is ok for racing, the red Nulon as used in 147's and 156's isn't.
The more crap you have under your bonnet the worse the airflow will be through the radaitor, as the hot air has nowhere to exit, when you take some of the plastic engine covers off the modern cars, they cool better, Colin.
1974 VW Passat [ist car] 1984 Alfa 33TI [daily driver] 2002 Alfa 156 JTS [daily driver]

jazig.k

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Re: improving thermo fan
« Reply #31 on: October 27, 2013, 10:37:51 AM »
Just to clear up the 2.5Lt 3Lt thing, the 3Lt radiator is thicker than the 2.5Lt by about 10mm.

Alfamania

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Re: improving thermo fan
« Reply #32 on: October 28, 2013, 10:56:50 AM »
Just bought a 16 inch Spal High Performance fan , will let you know how it is when fitted  :)
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colcol

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Re: improving thermo fan
« Reply #33 on: October 28, 2013, 08:23:03 PM »
I purchased a SPAL 6 inch thermo fan for the 33, very good little jigger, but not a cheapy, no quality parts are.....and the best thing is that it is ITALIAN!, which suprised me as i thought they were Chinese.
It was the smallest fan that i could fit in, and it moved a good volume of air, Colin.
1974 VW Passat [ist car] 1984 Alfa 33TI [daily driver] 2002 Alfa 156 JTS [daily driver]

Neil Choi

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Re: improving thermo fan
« Reply #34 on: October 28, 2013, 09:10:31 PM »
May I ask whether these super duper 16 inch Spal High Performance fans are light or not, ie lighter than the standard Alfetta fan for example.

cheers
neil

ALF750

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Re: improving thermo fan
« Reply #35 on: February 16, 2014, 09:27:02 AM »
As hinted at earlier in the postings, try running a direct power wire via a relay to the fan (as often done for the headlights).   I think standard the fan power runs through the thermofan switch in the radiator, which deteriorates with age, lowering voltage to the fan.   Activate the relay with the standard thermofan switch, but bypass all the old wiring for fan power.  Cheap option!

Alfamania

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Re: improving thermo fan
« Reply #36 on: February 19, 2014, 03:44:29 PM »
the 16 inch spal fan is lighter and slimmer than the original v6 75 fan. I still havent fitted it because I've been lazy to make brackets for it. Does anyone know a place i can buy flat steel brackets so I can make them to fit? Cheers
Alfa GT 3.2
Maserati Gransport
Alfa 75 V6 3.0
BMW 318i e36
Saab 9000cs
Mazda Rx7 13B Extend port -Turbo
Ford XE ESP 5.8
Mazda RX-4 Coupe 13B Extend Port

colcol

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Re: improving thermo fan
« Reply #37 on: February 19, 2014, 09:15:28 PM »
Yes, go to a steel supply outlet, and get some 3 mm thick - 10 - 12 - 15 mm wide, or however they come, not too thick as you want to be able to bend them in a vice, attach the brackets to the radiator support.
Don't use the ones that go thru the radiator with fibre washers, as the vibration can ruin the radiator.
The ITALIAN Spal is a nice piece of work, unlike some of the cheaper fans i have seen, Colin.
1974 VW Passat [ist car] 1984 Alfa 33TI [daily driver] 2002 Alfa 156 JTS [daily driver]

bteoh

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Re: improving thermo fan
« Reply #38 on: February 19, 2014, 10:30:03 PM »
You can get Spal fan brackets - check out eBay no. 151130505291
Might give you a more professional finish?

Alfamania

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Re: improving thermo fan
« Reply #39 on: May 09, 2014, 07:50:54 AM »
Ive just noticed something interesting.....i was having a look at a 164 engine bay and looks like the radiator is the same but the hose end connectors are opposite orientated to the 75, fair enough. The 164 has a fan with a steel shroud that covers the radiator two thirds. I can also see that the thermo fan is smaller than my 75 one. can I ask if anyone has tried a 164 fan and the shroud in their 3.0 75? only reason i say is that I sourced one recently as a spare?
Alfa GT 3.2
Maserati Gransport
Alfa 75 V6 3.0
BMW 318i e36
Saab 9000cs
Mazda Rx7 13B Extend port -Turbo
Ford XE ESP 5.8
Mazda RX-4 Coupe 13B Extend Port

MD

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Re: improving thermo fan
« Reply #40 on: February 21, 2018, 06:58:24 PM »
The problem with the frequent thermofan operation on the 75 and the 90 is not due to:-

Insufficient fan capacity
Insufficient coolant volume
Inadequate coolant circulation
Incorrect thermostat operation
Blockages in the radiator or hoses
Faulty kick in temp of thermoswitch
Coolant flow throughout the engine galleries.

What is it? It's too many fins per inch of the radiator preventing adequate airflow to extract the heat. From memory there is around 20 FPI.
To fix the problem, leave everything as is and reuse. Install a new radiator core with around 12FPI and your problem will be solved.

I have explained this point before but perhaps the topic wasn't preceded by a search...
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Colin Edwards

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Re: improving thermo fan
« Reply #41 on: February 25, 2018, 09:58:16 PM »
My 75 3.0 struggled to lose heat at anything over 30C.  Using a bit of smouldering cardboard as a smoke source, I was amazed at how little air was drawn through the grille.  Much of the air was drawn from below the bumper and then expected to flow up then turn at a right angle and flow evenly across the full face of the radiator!  At best not much more than 2/3 of the radiator saw any decent airflow. 
I then spent around 6 hours removing much of the honeycomb type plastic latice from the grill, however managing to retain a much more open honeycomb pattern.  I figure I have removed maybe 2/3 of that part of the grill.  The smoking cardboard confirms a more even distribution of air through the radiator.
The next measure was to install a front splitter.  More to reduce lift and drag, the splitter reduced air pressure under the car - much of this just forward of the sump.  The reduced pressure assists removal of hot air from the engine bay without the need for a more effective fan. 
The final measure was to track down the source of a rough idle.  Replacement of EVERY vacuum hose has resulted in a very smooth idle even though the engine is fitted with tuned cams.  The elimination of vacum leaks due to life expired hoses has resolved the lean mixture at idle issue.  Restoring the correct mixture means the engine runs a bit cooler and idles smoother. 
« Last Edit: February 26, 2018, 10:22:24 AM by Colin Edwards »
Present
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2018 Abarth 124 Spider
1987 75 3.0

Past
2015 Giulietta QV
2009 159 3.2 Ti Q4
2012 Giulietta TCT Veloce
2006 147 Ti 2 door Selespeed
1979 Alfasud Ti 1.5

Duk

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Re: improving thermo fan
« Reply #42 on: March 13, 2018, 09:58:52 AM »
My 75 3.0 struggled to lose heat at anything over 30C.  Using a bit of smouldering cardboard as a smoke source, I was amazed at how little air was drawn through the grille.  Much of the air was drawn from below the bumper and then expected to flow up then turn at a right angle and flow evenly across the full face of the radiator!  At best not much more than 2/3 of the radiator saw any decent airflow. 
I then spent around 6 hours removing much of the honeycomb type plastic latice from the grill, however managing to retain a much more open honeycomb pattern.  I figure I have removed maybe 2/3 of that part of the grill.  The smoking cardboard confirms a more even distribution of air through the radiator.
The next measure was to install a front splitter.  More to reduce lift and drag, the splitter reduced air pressure under the car - much of this just forward of the sump.  The reduced pressure assists removal of hot air from the engine bay without the need for a more effective fan. 


Most cars get the majority of their cooling air from the bottom opening. The opening is in a high pressure area when the car is moving. Look at something like an EF/EL Falcon, they basically have no grill at all.

A well designed undertray that goes from the leading, lower edge of the front bumper to just under the cross member that is in front of the engine and extends to the wheel arch liners (if you still have them) should tidy up the airflow under the car a bit and help the air exit the engine bay.
Most people think that the plastic pannelling under the car is for dirt and rock protection.
It aint.
It's to smooth the air flow under the car.
With approximately 1/3 of the air that the car moves out of the way when it's driving down the road going under the car, keeping that air flow a smooth as possible reduces aerodynamic drag and improves cooling system performance.
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Colin Edwards

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Re: improving thermo fan
« Reply #43 on: March 15, 2018, 09:29:42 AM »
Yep.  The underneath of the 75 is pretty rudimentary compared to my 159.  And the underneath of the 159 is prehistoric compared to the new Giulia!
Agree managing the hot air exhausted from the cooling system is critical.  Although at a lower density, the hot air increases in volume by more than 50%.

« Last Edit: March 15, 2018, 11:33:28 AM by Colin Edwards »
Present
2020 Giulietta Veloce
2018 Abarth 124 Spider
1987 75 3.0

Past
2015 Giulietta QV
2009 159 3.2 Ti Q4
2012 Giulietta TCT Veloce
2006 147 Ti 2 door Selespeed
1979 Alfasud Ti 1.5