richardm6994
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| posted on 15/7/13 at 08:19 PM |
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Electric fan size question???
I'm having a slight overheating problem at low speeds (traffic jams / cruising through town).
I've put it down to the act my electric fan is both old and cheap.
I plan to upgrade it to a better fan, but I'm wondering about the size?
At the moment, it is 14inch, but this is slightly bigger than the rad cores and overlaps the radiator head & sump. When the fan his operating, you
can actually feel the air blowing back through the fan because of he obstruction caused by the rad head & sump.
The photo below is the best I have illustrating the fan overlap. The fan is sealed to the rad so no air can escape outside the cowling.
My query is......do I got for the same size fan simply because it covers more area or do I go for a 12 inch fan which will sit nicely on the core and
not have any blow-back issues / turbulance cause by the head & sump obstruction....obviously though the smaller fan covers less area and has a
slightly lower cfm
I would appreciate your thoughts.....
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FuryRebuild
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| posted on 15/7/13 at 08:27 PM |
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Have you tried bleeding the cooling system, and going for water-wetter and a reasonable amount of anti-freeze?
That looks like quite a substantial fan and if you can feel the air blowing from it, it seems to be doing the job. Would a smaller fan only give you
less driven cooling?
Did this issue come on gradually, or relatively quickly?
Does the issue come on when you're motoring. If it does not, then i would suggest your rad can deliver the goods despite the lack of easy exit
for air behind it. If this is the case then maybe the fan. If the issue comes on when you're moving at speed, and is a relatively recent issue,
then I would look to other cooling issues, such as bleeding the cooling system. Do you have a header tank that's higher than the cylinder head?
When all you have is a hammer, everything around you is a nail.
www.furyrebuild.co.uk
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richardm6994
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| posted on 15/7/13 at 08:36 PM |
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Hi, the cooling system has been bled and I'm happy it's good.
When travelling 30mph+ the cooling if fine. I can give it some boot and it doesn't overheat.
When I said I can feel the air....what I mean is that the air is blowing back past the fan blades becaus it can't get through the solid
obstruction of the radiation head & sump.
This is a new installation and so this problem has existed from day 1 (just after Newark).
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mark chandler
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| posted on 15/7/13 at 08:38 PM |
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Is it a pull fan pushing? Can you reverse the fan blades and see if that helps before replacing.
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britishtrident
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| posted on 15/7/13 at 08:44 PM |
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Have you checked the ignition timing at idle speed ? If the timing at idle and low RPM is too retard the engine will reject enormous amounts of
heat energy to the coolant and exhaust.
You also need to provide exit vents for the air.
[I] “ What use our work, Bennet, if we cannot care for those we love? .”
― From BBC TV/Amazon's Ripper Street.
[/I]
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richardm6994
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| posted on 15/7/13 at 08:49 PM |
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Wow! Thanks for the quick responses.
The fan can only mount on the front as a blow.
The ignition setup is megajolt and I'm using someone else's map so its not perfect but I've got run the engine in before visiting a
rolling road.
The bonnet has gills to exit the hot air and there is also a big hole behind the rad in the bottom of the nose cone to draw air out and under the car.
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mark chandler
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| posted on 15/7/13 at 09:40 PM |
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Let me rephrase, the fan looks like a standard suck fan so is on the wrong side, if you can pull off the fan blades from the shaft and flip over it
will then work as a push fan and be more efficient, are the blades reversible?
Regards Mark
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02GF74
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| posted on 15/7/13 at 10:02 PM |
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define what you mean by " slight overheating problem "
i mean, are you going by the temp gauge (which may not be accurate) or is water lost from the system?
1 more thing - the motors on those after market fans, like yours look pretty puny compared to oem - maybe worth a trip to the scrap yard for a more
manly fan of the same size.
what is the dimension of the core? you have what appears to be a rover v8 so your radiator is quite small compared to one from e.g. a range rover.
i reckon you need a bigger rad. plus a cowl that covers the entire matrix area, like this for example:
kBR3rfPpW7Q~~60_58.JPG)
[Edited on 15/7/13 by 02GF74]
[Edited on 15/7/13 by 02GF74]
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rachaeljf
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| posted on 15/7/13 at 11:11 PM |
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The fan should be up to the job. If you have only reversed polarity to make a puller fan into a pusher without reversing the fan, the blades are far
less efficient at moving air. It certainly looks like the fan needs to be flipped, as mentioned by Mr Chandler.
Cheers R
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richardm6994
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| posted on 16/7/13 at 07:00 AM |
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thanks for the advice! Brilliant forum!
I will certainly look into the fan blade direction.
To give you more details what I mean by overheating...
I'm reading the temp from the electric water pump digital controller. The controller varies the speed of the pump according to temp from 3volts
to 12volts
On the motorway...temp sits solid at 85degrees regardless of how much right foot I give it and occasionally temp drop to 80 degrees when coasting /
going down hill.
In this condition, the electric water pump is running at about 3-6volts.
Blasting down country roads, temp sits solid at 85degrees again, but it will have the occasional rise to 90degrees for a few minutes before dropping
back to 85.
In this condition, the pump is running about 8-12 volts.
When sitting in traffic, or slow driving through town, the temp rises to 95-100degrees over about a 20 minute period.
Obviously the pump is running at 100% along with the electric fan.
I daren't take it above 100 for fear of warping my ali heads.
Also, I can turn the engine off, and leave the pump and fan running. This brings the temp back down to 85degrees within 5mins.
The radiator is a cortina size, but 4-core 70mm thick.
The fan is a £20 special off ebay which is why I'm looking at that as being my problem. The fan I'm looking at to replace it with is
either the 14" (3300m3/h) or 12" (3126m3/h) kenlowe fan
This is a photo of my finished effort as the first photo makes it look rubbish 
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britishtrident
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| posted on 16/7/13 at 02:42 PM |
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Info on the web suggest RV8s are especially prone to over heating at low rpm if the ignition is too retarded. On different sites have seen figures
quoted of between 8 and 14 degrees at 800rpm personally I would try 10 or 11 degrees BTDC at 800 rpm and see what happens. Check this with
strobe not just in the software.
Quote from
http://www.landroverclub.net/Club/HTML/Overheating.htm
"4. The ignition timing The V8's are sensible to ignition timing. If the timing is about 4-5° off you will get an overheating engine.
I've set mine at 8° BTDC at 800 rpm (for an 3.5 EFI)."
[Edited on 16/7/13 by britishtrident]
[I] “ What use our work, Bennet, if we cannot care for those we love? .”
― From BBC TV/Amazon's Ripper Street.
[/I]
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richardm6994
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| posted on 16/7/13 at 03:21 PM |
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that's a cracking bit of advice! At the moment I'm running 8degrees so I will change it to see what happens.
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mark chandler
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| posted on 16/7/13 at 04:46 PM |
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They also suffer if you do not have a 1/4" hose from the top of the inlet manifold to in your case the top of the radiator to bubble off steam
from the heads.
I cannot see your bubble pipe or expansion tank, have you blocked this off on the inlet?
On SU manifold this pipe is at the top of the carb mounting tower, with EFI up at the front of the plenum, I would be very surprised if your manifold
did not have this.
Regards Mark
[Edited on 16/7/13 by mark chandler]
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richardm6994
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| posted on 16/7/13 at 07:35 PM |
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Yes, the little pipe coming from the rad cap goes to a CBS plastic expansion tank and it has a suck / spit rad cap.
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mark chandler
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| posted on 16/7/13 at 08:46 PM |
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quote:
Originally posted by richardm6994
Yes, the little pipe coming from the rad cap goes to a CBS plastic expansion tank and it has a suck / spit rad cap.
Not the rad cap, on the inlet you have a couple of water passages, these should have a tapping to bubble off the steam that is created as the water
boils within the heads.
If your manifold does not have one make sure the water bypass hole on the thermostat is at the top to move the steam out quickly, it may have a little
t bar in the hole, remove this and open the hole up to 1/4" - 3/8".
Regards Mark
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richardm6994
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| posted on 18/7/13 at 11:52 AM |
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My manifold doesn't have what you're talking about, however I'm not using a thermostat as the water flow is controller by the
electric pump's digital controller.
I do have 2 water take-off on my manifold which were for the heater matrix. These are currently blanked off however I intend to loop them
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