Cooling Fans

Hi Dave,

I've been looking for replacement of the stationairy fan also and when you're on a budget I can recommend the following:

-first make sure your system is not crudded up, air can escape and it's a good idea to fit a header-tank.
-the stationairy fan I've replaced by a fan from an Citroen BX 1.9 (TGI or TRD, doesn't matter). It needed some work to fit behind the rad on the left lower corner (seen from engine-side).
-I added a (secondhand) slimline 12" pacet fan on the front of the rad in the right upper corner of the rad. Fits in nicely whit only two tyrewraps.
-I didn't do any modifications to the strtucture of the car.
-both fans are temp controlled of course (the electrics are the only thing I bought new).
-when the engine heats up above the setpoint of approx 90 C, both fans start and about 3-5 min later the temp is back to 85 C.

O, after fitting in the eletric fan I didn't notice a lot of improvement on performance nor fuel economy. But the cooling of the engine is definately more in control.

Succes with cooling our V8!

Rene
 
Rene,
thanks for the information :D . I already have an expansion tank from an SD1 fitted to one of the cars and have another sitting in the boot of another (hasn't improved the cooling and is making my boot look untidy :LOL: ) which I will fit shortly. The rads will have to come out regardless so these will get a thorough flush at the same time. I'm hoping they will be pretty good as I flushed 2 before and they get regular coolant changes (the last time I had a generator commissioned the contractor left me with 60 gallons of antifreeze because he didn't want the trouble of carrying it down a 6 story building from the roof :shock: ) Citroen BXs have all but disappeared in Ireland so I wouldn't hold out much hope of finding a fan off one, however, I am now armed with the dimensions of several different fans so I will get the measuring tape out Saturday morning when I get home. My father also found a 12" kenlowe in the workshop that I'd thought disappeared so I might use that on one. I'll keep you posted on the results.
Regards,
Dave
 
I managed to fit two 10" fans across the top of my (3500) rad replacing the (aussie spec) viscous unit and 13 bladed fan. there was no room for a 16" fan as the long thread on the water pump was too much, but did have to cut the tread down a bit and fit a spacer to keep the fan belt pulley in place, to get clearance to fit the 10" fans. Manufacturers usually reccomend to replace the factory fan with the same sized electric fan which is why i tried to see if a 16" fan would fit but i thought that two 10" fans will be the equivelent of a 20" fan so should do the job just as well, as they do. The fans are from my local motor factor and are their own brand (made in china job) which happen to fit neatly side by side between the header tanks on the 3500 P6 rad.

IMG_6657.jpg


I managed to do this without removing the radiator but had to cut the thread with a hacksaw just to get the viscous unit and fan out, It would have been easier to remove the rad but I had to cut back the thread a bit more to get clearance for the new electric fans and then fit a spacer for the pulley. There was enough space between the fins to use the fixing bolts that came with the kit but as they have thread all along their length i wraped insulating tape around the thread in case damage might occur to the fins over time. I wanted fans on the engine side as I want to fit auto trans oil cooler to the front sometime and maybe aircon one day.
 
Hello Scott,

That looks very neat! The beauty of running thermatic fans is the benefit that they provide when caught up in traffic, especially on a warm to hot day. I still have the 13 bladed engine driven fan to cool mine, so I'll be interested to hear how they perform.

Just on a side note, in terms of surface area, the two 10" fans have a combined area 28% less than a single 16" fan, so if they were all of the same design turning at the same rpm, the twin 10" fans would move noticeably less air per unit time. Even so, the distinct advantage that they afford is being able to turn at far more than engine idle speed while in traffic, and this provides the advantage.

Ron.
 
i tried to see if a 16" fan would fit but i thought that two 10" fans will be the equivelent of a 20" fan so should do the job just as well, as they do
Click to expand...

Archimedes; a stand-up comic who 1st cracked the joke about 3.14159 guys going into a restaurant and ordering "Pi", wouldn't agree with you

2x 10" fans will sweep an area of 157.08 sq. ins
16" x 1: 201.06 sq. ins
20" x 1: 314.16 sq. ins, twice the swept area of your 2 x 10" fans

Not knocking your setup, only your maths

GW
 
Surely you can't compare the fans just on diameter ? Doesn't motor wattage etc and overall efficiency come into it ?
 
Yes, you're right Dave

I have a 14" fan which is almost exactly the same area as the two 10" fans, but it doesn't shift as much air by any means.

It does however shift more air than the 12" kenlowe that was originally fitted and keeps the temperature very well controlled, so no problem there.

I suppose that the two 10" fans can be rigged to come on at different temperatures to make them more efficient.

Richard
 
The ammount of displaced air goes up in what looks more like a squared function with increasing diameter when you look at manufacturer specs based on diameter alone.

Graeme
 
I think the best guide to how much air is being shihted is the motor wattge. Graeme is right abour a square function being involved. This is due to the tip velocity of the blades being rather important to the amount of air shifted - and that indeed has a square function in it!

Also, don't forget that volume of air shifted is nopt the only criteria - it has to acieve something on its passage through the radiator. To illustrate this take it to an extreme. Suppose the given volume of air per minute is actually delivered through a point of zero area - thus the velocity of the air willl need to be infinite;y large. The cooling effect is not going to be in proprtion to the volume of air! Thus a very large fan is better than a very small fan for the same delivered air volume.

I think my rule of thumb test is now developing after listening to all the responses. I'd want to get as close as I could to a 250W motor on a 16" fan. And prepared to compromise down on fan diameter to 14" and down on power to around 200W, but not both.

Chris
 
I took the below from the Davies Craig website.

"Is there any advantage to having two slightly smaller fans as opposed to the one larger fan?
One of the very important factors with engine cooling fan/s is the volume of air any specific Thermatic Fan can pull or push through a radiator. In general terms 2 x 14" fans will match the volume flow of 1 x 16” fan but not 2 x 12" fans. There are other factors including core thickness and clearly the thicker the radiator core a more powerful fan is required. Therefore a single 16” fan will out-perform 2 x 12” fans in almost all situations. E.G. If your radiator is 4 core or greater then 2 x 12" fans wouldn't be recommended. Therefore 1 x 16" fan could be sufficient.
Remembering that any Thermatic Fan will cease to be effective once the vehicle speed has reached 50-60 KPH after which the ram air takes over. We also recommend Thermatic fans be fitted to the downstream (engine side) of the radiator"

And here is a link to Mathworks where they give an example on how to improve an engine's cooling fan.

http://www.mathworks.com/products/stati ... fan.html#2

Ron.
 
my apologies to archemedies, for my incorrect inferrance/interpretation of cooling fan dynamics etc, and thanks to all for enlightening us all that it is not just a matter diameter but swept area. As you refer to ron any electric fan set up will be inneffective (electrically will not cut in anyway) once ram air takes over, but as I mentioned for use while idling my set up seems to work ok when it cuts in and out (at the speed the fans run at) without any temp guage worry and is a neat installation albeit having to cut down the thread on the water pump shaft to suit.
 
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