P38A Viscous fan capacity?

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Datatek said:
The majority of cars these days use electric fans, quicker warm up when cold helps meet emissions regs.
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That's very true!
I was servicing a gaylander this morning and when I set the Aircon to run for the sanitiser to work, all the fans kicked off, sounded like a bloody aeroplane!!
Agree with quicker warm up and some power saved from the engine.
I remember fitting an electric fan on my old series 2a, bigger tyres and getting 18mpg!!
Isnt technology brilliant:D
 
Mark Piercy said:
Well they don't wammers, you know that.. I suppose in comparison to the old fixed blade .. then yes!;)
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The viscous nor the fixed blade makes any difference to warm up or very little. There is no heat in the radiator to cool until the engine warms and the thermostat opens.
 
Mark Piercy said:
Point taken. Why didn't they keep the :)fixed blades then?
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Fixed blades were not as efficient as the viscous fan. They were engaged all the time, viscous is only engaged when air behind rad reaches a certain temp then disengages when temp lowers. That's if it's working properly of course. It is not engaged all the time as some would think. It is only engaged about 5% to 10% of the time. Most of the cooling is done by ram air. So this talk of i removed my viscous fan and gained X amount of BHP is pure fiction i am afraid.
 
wammers said:
The viscous nor the fixed blade makes any difference to warm up or very little. There is no heat in the radiator to cool until the engine warms and the thermostat opens.
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No cold air blowing over the engine from start up aids warm up. The viscous is never fully disengaged, it's more a case of variable speed. Even after the initial blast on start up, it continues to blow cold air over the engine. The speed of warm up in winter is quite marked. Without the viscous in winter, normal temperature is reached after about 3Km, with the viscous it was still not fully up to temperature by the time I stopped at the bakers at 5Km.
No measurable difference in power as you say and no difference in fuel consumption except in short runs in winter.
 
Datatek said:
No cold air blowing over the engine from start up aids warm up. The viscous is never fully disengaged, it's more a case of variable speed. Even after the initial blast on start up, it continues to blow cold air over the engine. The speed of warm up in winter is quite marked. Without the viscous in winter, normal temperature is reached after about 3Km, with the viscous it was still not fully up to temperature by the time I stopped at the bakers at 5Km.
No measurable difference in power as you say and no difference in fuel consumption except in short runs in winter.
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That is because the engine has to warm from a lower temperature and has little to do with the viscous fan. The viscous fan engages and disengages as required. Put some ice in your kettle and see if it takes a little longer to boil than water from the tap.
 
wammers said:
That is because the engine has to warm from a lower temperature and has little to do with the viscous fan. The viscous fan engages and disengages as required. Put some ice in your kettle and see if it takes a little longer to boil than water from the tap.
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The viscous fan never disengages. If it did the blades would stop rotating which they do not. The silicone compound that provides the coupling via the variable vane viscous coupling always has enough drag to drive the fan. Put an anemometer behind it with a cold engine if you don't believe me.
 
Datatek said:
The viscous fan never disengages.
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Yes it does. It will always rotate when the engine is running but that rotation is due to frictional reasons. When the engine is ticking over before reaching temp it can be easily stopped with a bare hand using light finger pressure.
 
wammers said:
Yes it does. It will always rotate when the engine is running but that rotation is due to frictional reasons. When the engine is ticking over before reaching temp it can be easily stopped with a bare hand using light finger pressure.
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Friction from what? Apart from the silicone medium??
 
Datatek said:
The silicone provides the main drive. Regardless, it takes 5 Km to reach full temperature with the viscous and 3Km without it.
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When the engine is cold it should be disengaged. When the engine is at normal running temp it should be disengaged. It should only be engaged when the engine temp exceeds normal. All other cooling whilst in motion is taken care of by ram air.
 
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