What's next??

[Paul Blore]

We were at cross-purposes. You originally said that you were going to shroud the radiator, so I presumed that you meant shrouding around the edges of the rad' to prevent air going around the edges and over the top. What you're referring to here is shrouding the fan.

My single fan isn't shrouded and it manages to keep the temperature under control even under extreme conditions (except for when I lose all of the water in the rad' )

Paul

[Roger King]

My understanding of it is, that if the fan is fitted to a shroud, and it's away from the surface of the radiator, and not directly mounted to the radiator, the fan will then pull air from the whole surface of the rad. I did this to my Camaro and it made a huge difference

Nige

Correct. You need to involve the entire surface of the rad if possible.
I have a Becool US setup on the Mustang, very similar to this:

http://becool.com/product-search/produc ... -400-75007

You will see that there are soft flaps which deflect to allow airflow on the move, but if stationary the fans suck these shut and pull air through the entire radiator.
A very scientific study was done a while back using a Sunbeam Tiger. This is most interesting, and highly relevant to us as to all intents and purposes the 260 is the same engine as we have.
The study demonstrates the primary importance of venting hot air from under the bonnet. This would have been why Cobras grew side vents early in their life, but it's still a big issue. A set of NACA ducts set into the bonnet surface would be very effective indeed, but not very period-correct!
The other really interesting point is that all electric fans were found to work significantly better when spaced 1" back from the radiator. Turbulence from the core, maybe??
Also of interest is the fact that all the high-volume and high-flow water pumps were found to be less effective at idle, which is when the cooling system is working hardest. I found this to be the case with my Cobra - I have now fitted a stock water pump and idle temperature has reduced significantly. This is probably due to cavitation of the coolant, made worse by the higher viscosity of Evans. The aftermarket high-flow pumps have a very large number of vanes which are very close together - the stock pump has around 8-10 which are well-spaced and can clearly shift a higher amount of fluid per vane with less likelihood of cavitation.

http://teae.org/cooling-the-sunbeam-tig ... huck-king/

Roger

[peterc]

Phil,
Your idea of adding a shroud an inch away from the rad is in effect a very short section of ducting but this will reduce the effectiveness of the rad at higher speeds. The air will need to go through a far more tortuous route to get through when driving at normal speeds. Personally I think we all need the max amount of radiator core available exposed to the air flow through the grill.

It is important to remember that Rogers Mustang system has flaps to allow the remainder of the rads surface area to be used when the fan is not working.
Personally I would consider twin 10" fans in lieu of the 16" purely on the basis that they will cool a bigger area rather than any form of restriction of the radiator surface.

I am certainly interested that the Tiger report suggested that mounting fans 1" away from the rad was better. I can only assume that it allows the fan to cool a bigger area than its own diameter as per Nige's comment.
I have mounted my fans 3-4 mm away and even have a foam gasket in the belief that I needed to contain the airflow that fan was producing.

[Roger King]

On re-reading the Tiger experiments, they only used a 'pusher' electric auxiliary fan as there is no space behind the rad in a Tiger. I don't know if this would give the same figures for the 1" gap for a 'puller' - I tend to think not, but then again I'm as surprised as they were that the 1" gap made such a big difference.
I'm also surprised at the big change between a 4-blade and mult-bladed fans. I currently have a mult-bladed fan which as far as I can tell gives about 9-10°C temperature drop across the rad from full hot (measured with a Fluke 62 Max +, emissivity taken as 95% for matt-black painted aluminium).
If I can find a 15" diameter casing 4- or 5-blade puller I might see if it makes any difference.

[Phil Riley]

Thanks, Peter. It will be interesting to see what happens, as mine currently runs quite cold when on the move, but not so cold that I need to replace with a higher temp thermostat.

[peterc]

Hi Phil.
I must admit that since blocking off the gap above the rad by adding a deflector between the nose and the rad core thus forcing more air through it the temp does drop a surprising amount when just cruising - sometimes below 80C. It's when one is more enthusiastic that the temp is up at 90C.
As already advised in another posting, I have a manual override and turn the first fan on at 90C when expecting to be sitting in traffic which normally keeps things under control. Nice to know that when I forget to switch on and the temp gets to 100C the fans do cut in at their respective settings. Standard Hawk's recommendation is a Ford Fiesta rad stat with twin temperature settings.
Peter C

[Roger King]

Be aware that running an engine too cool does at least as much damage as too hot. For a Ford engine, the design temp is around 90°C. Running for prolonged periods at, say, 70°C will produce rapid wear. As ever I don't know about Rovers.

[agnoraan]

Phil,
Your idea of adding a shroud an inch away from the rad is in effect a very short section of ducting but this will reduce the effectiveness of the rad at higher speeds. The air will need to go through a far more tortuous route to get through when driving at normal speeds. Personally I think we all need the max amount of radiator core available exposed to the air flow through the grill..

Hi Peter, many race cars have the internal area behind the grille opening panelled in aluminium and all of the holes in the radiator support panels blanked off so that the airflow can only go through the radiator, causing a "ram air" effect. This is probably why Cobras are panelled out like that, the only way that the air can travel is through the radiator
Nige

[clive]

At Silverstone this year, Tony Mountain introduced me to his better half as "The only man whose car he had been in that had three gauges reading 120." Water temp, oil temp and speed!

[agnoraan]

He'll run out of fuel before the next lap
Nige