Monitoring Radiators development since 1960.

I have been monitoring radiators and their development since the late 1960’s because they were and still can be a problem when tuning cars.
I have seen, tried and tested everything made available or offered to Mini Spares including all the cheap imports such as alloy radiators of which many
are ill fitting or have oversize header tanks. Most customers now want originality
rather than pretty looks unless weight or optimum cooling is more important.


The coolant system transfers heat to the radiator “vertical” tubes which in turn transfer heat to the gills (fins) and the air moving though the gills dissipate the heat.
Wider and taller is better than thicker but in the confines of the mini the core can only be 11”square maximum to fit, unlike a front mounted radiator as fitted
to the MPI which has more efficient “horizontal” tubes which is very efficient
for its size and capacity. It is the evolution of tube sizes, their configuration and gill shape that contribute to the best cooling available for the mini. Our famous
2 core (actually 2 tubes) ended up in China by somebody to copy and has ended up everywhere in many designs as an alloy radiator usually with off the shelf
22x2mm alloy tubes, which are very efficient.

Therefore I will start with our 2 tube aluminum rad C-ARA5000 which the so called technical radiator specialists equivalent of C-ARA4444 which is made
in copper and brass, known as the 4 core as it has 4 rows of tubes, which I introduced in 1978 . The bare cores both cool about the same on test beds
but when fitted with the mounting brackets and in a mini engine bay differ slightly, but the aluminum C-ARA5000 is about 40% lighter.

C-ARA5000

Total tube capacity of the 4 core is 118.84mm as opposed to 88mm on the 2 core but the wider aluminum tubes provide greater surface contact with the fins
and conduct heat more efficiently than the brass tubes and copper fins which have less contact owing to the spaces between 4 tubes, Copper fins and brass tubes
conduct heat much better than aluminum but the solder used in its construction reduce its ability to conduct heat and make it heavier. The 4 tube core is only 5mm
thicker than the alloy 2 core with similar fin count per inch but the aluminum core has V section fins which are best for cooling but worst for collecting and holding sludge,
when used in mucky, oily or dirty environments such as autocross/grass events. The 4 core flat fin design is best for hot, dirty use as stated above but all fins
should be carefully cleaned and jet sprayed regularly, by garden hose.

Fin wise the copper type conductivity is close to 70% higher than the aluminum fin. The 4 core as its known with extra tubes holds nearly 25% more water but as air passes
each row of tubes it will pick up heat on its way. With fin, tube size and core design the core thickness must be taken into account as too thick a core can impede airflow
at low speed or tick over. Usually a bigger core cools better and this all seems about optimum on our mini sized radiator. This makes the 4 core more ideal in larger or unrestricted
engine bays such as Mini Clubman where originality looks are required. If you want lighter and brighter—pick aluminum.

General consensus of opinion by experts and case studies home and abroad seem to conclude the radiators are fairly equal in cooling. On the track at speed the alloy will be
better by about 10%or more.

For commercial vehicles In the USA and some European countries they have now found a way to delete the solder/flux using a non toxic, low temperature brazing alloy based
on the CuNiSnP system which allows the use of common vacuum and controlled atmosphere brazing furnaces (known as Cuprobraze).

Importantly, this method of production can be achieved by existing manufacturers with brazing equipment used for aluminum radiators (laser welding). Using thinner material
and electrophoretic coating also strengthens and adds longevity to the rad further by providing corrosion protection in every nook and cranny with no additional weight.
There should not be any great extra cost if you already have the latest technology and facilities to modify but it might not be viable on mini radiators
owing to the mounting brackets fitted either side which are not best for heat conductivity or air flow, but I have been investigating a single 32mm tube type or 2x18mm tubes.
This method is especially viable for large truck use and looks like replacing some aluminum radiators owing to its longevity.

Cuprobraze radiators are also more efficient at shedding heat, which in theory should alloy engineers to lower cooling module costs and weight. It also means less parasitic
engine losses and better fuel economy for lorries with the ability to give the Cuprobraze radiator a small frontal area but the same air-side pressure drop as a comparable aluminum model.
Brazed copper-brass joints are stronger than soldered metal and do not suffer from galvanic corrosion. Solder to copper brass creates more galvanic corrosion reducing radiator life.

Galvanic corrosion can occur with any electrical faults such as your choke cable becoming your earth wire owing to bad battery connection or early positive earth cars causing
any engine or coolant metals to react. Modern cars are designed for aluminum parts, reducing the risk of galvanic corrosion so when fitting aluminum radiators or other parts to classic
minis cast iron block always check electrics, flush and change antifreeze regularly as instructed with up to a 50/50 mix which helps break down contaminates with its chemical
additives using distilled water only.
The classic mini radiator is 11” wide with most cores at least 10.5” square using fan blades 10.25”(26.1cm) wide with tubes running vertically except the MPI front mounted radiator
which has horizontal tubes which are superior in cooling and electric fan assisted only.
Copper core manufacturers looked at smaller and thinner tubes to break down the coolant into smaller amounts which improved cooling but should be flushed every recommended
interval of anti freeze change as they are more suspect to clog up. Our standard radiator ARP2000 has 3 offset tubes as always used on the mini but only has 9 flat fins(gills)
whereas the Cooper S ended up with 16 flat fins(gills) per inch. The design change with 3 smaller offset tubes an alternative equivalent makes this an easy to produce
well priced standard 3 core radiator which is perfectly adequate for al standard 850/998/1275 engines.

ARP2000

The next 3 tube radiator is the new 2014 super rad ARP1106 which has the V shape fins with larger more oval shaped bores placed inline with nearly a 12% larger water capacity
than the C-ARA4442 which has a 2 bore inline core with 20 fins per inch hence its name since 1982.They are fairly equal except ARP1106 has no drain hole or fan switch
capability but on some race engines it appears to have a better heat dispensation when the engine is turned off, by not boiling over or loosing water and holding pressure
when used with 15lb rad cap. The gills allow more air through them when stationary but the 2 core version is still favoured by most, probably because of many years of proven
success on road and track. Wider size bores are generally better with more surface contact to the fins improving cooling and the 2 core using soft brass tubes is as big as you can go,
to handle the increased pressure as it heats up, raising the boiling point of the coolant allowing it to absorb additional heat from the engine. Brass bore sizes any larger would require
such thick walls to retain its strength it would result in becoming more than double the weight without much increase in cooling under present manufacturing procedures,
(Bring on CUPROBRAZE) whereas aluminum is stronger and can be made much bigger such as the giant single bore C-ARA4441 which has a 42mm x3mm tube and the core is fully
vacuum brazed for durability, made in UK by Radtech with 24 rows of 8mm v section louvered fins which is close to 18-20 fins per inch. These are expensive and the ultimate
radiator except maybe on 1460cc power units like my Cooper S MK3 sprint where I required a special 68mm thick core from Radtech but I still use an expansion tank (overflow tank).
The use of an overflow tank usually solves the problem on any road engine and a plastic version overflow tank was fitted by the factory on mainstream Coopers in 1991
but is now obsolete but they seem to run okay without one.

All mini radiators have tubes spaced (10mm) 3/8” or ½” (12-13mm) and all the V shape fins are the closer tube type 10mm type which is the best cooling type of fins, apart from
the possibility of clogging up as previously stated.

To summarize, there is a lot of criteria to take into account as to which is the best or worse radiator as the mini has seen so many changes in thermostats, 74c known for summer use, 82c for
winter,or all A plus engines and then 88 degrees centigrade from 1990 on to make the engine thermally efficient. Radiator cap
spring lengths and pressures of 7lb to 15lb have been used, hose sizes, efficiency of water pump and any galvanic corrosion in block, cylinder head or radiator, different engine
oils and of course-states of tune, compression ratios.
Engine coolant temperatures are controlled by thermostats which have been increased to 88 degrees since 1990 on-Higher the pressure cap poundage, the hotter the coolant
has to get to boil, 200 degrees Fahrenheit for 15lb cap is sufficient, as fitted minis from 1990. Engines normally work best and thermally efficient at 180-210 F now,
owing to pollution laws, oil and petrol now available.
So lets make life easy—for originality, Copper fins on brass tubes painted black to stop corrosion. If you have an original embossed Coventry radiator or MK1 with the top hose
outlet at the end of radiator-try getting it re-cored. For the MK2 they moved the top hose outlet in about 1.5” to help reinforce it from breakage/cracking through vibration and especially
via the old hoses where they became rigid.

For standard original cars use ARP2000 and GRD172 which are sufficient and always try to fit an electric fan unless you are keeping car perfectly original as all modern day
cars use them for keeping cars at correct working temperatures. Under most circumstances you should never require an oil cooler, but if you do always fit an oil thermostat to stop it
working until oil reaches correct engine temperature.

If you want pretty, lightweight or for best cooling go for the C-ARA5000 which has a 30% greater cooling area by design and near equivalent to 4 core and 2 core.

Average life span of Copper radiators was 6-10 years and alloy 8-12 but this was based on cars being used every day 12,000 plus miles a year (not very valid now on Minis in the UK?)
If you have a tuned car and sit in traffic jams or only use your car in summer try to fit an electric fan and the 3 inline tube core ARP1106 or 2 in line tube core with a 15lb cap.

C-ARA4442

A 1380cc or high compression engine with either of the previous 2 radiators mentioned may get very hot and an erratic tick over when sitting in heavy traffic on a hot day
but it should not overheat and cools quickly on movement, but fitting an electric fan usually overcomes this problem.

Main difference between ARP1106 and C-ARA4442 is price on how they are manufactured and the lack of sensor/drain hole on the former.

The 4 tube C-ARA4444 is as stated previously, the early design with thicker core, more tubes and larger capacity did cool better but takes up more space and later day radiators
with improved fin to tube area design seem to be favoured by manufacturers and mini owners, especially as the 4 tube core sometimes required slight
modifications to fit early inner wings and radiator shrouds.
Remember anti freeze restricts cooling and the old mini manual says use Ethylene Glycol type but for any the following applies 25% mix is good down
to minus 13 Centigradee before freezing - a 33% mix is good to -19c before freezing and 50% down to -36c but many manufacturers say 50/50 split is good for the chemicals
to keep contaminates away and the system clean, but refer to each individual guideline and use distilled water only. Reducing anti freeze levels in summer to about 25%
will help cooling as anti freeze absorbs heat about half the rate of water. Minis with heater usually hold 6.25 pints (7.5 US pints,3.55 litres)and without heater 5.25 pints
(6.6 US pints,3 litres)all dependent on plumbing of course.

CLICK TO ENLARGE

All radiators cores are approximately 10.5”-11" square and with the side frames added to fit the original radiator surrounds they are all 11” wide. Capacity, is a guide and
comparison test to see how much water each radiator held by blocking of the outlets and filling to the bottom of the radiator neck. Tube size is per tube in mm
and total tubing size is circumference area size per tube.

Total tube size area is the amount of rows per radiator, multiplied the by amount of tube size circumference area, to give a comparison but does not include tube length capacity
Tube lengths are approximately the same, but cannot be measured for true capacity. Frame width is the panels either side of the core with the bolt locating holes for fitting
to the radiator surround.
This chart only shows the core sizes and tube capacities that the water travels, but does not constitute to the best cooling radiator as design designates best efficiency.
Apart from tube size the other main components are the gills (fins). V shape fins cool better than flat semi louvered. Flat semi louvered cool better than flat brazed but the
tube size and spacing play a vital design part also.
V shape are often known as louvered gills (fins) and usually cool best but can be prone to holding debris if used off road (autocross) or in dusty humid climates.
ARP2000 and GRD172 are the standard radiators perfectly adequate for road use.
Never run an engine to cool and fit a thermostatically controlled electric fan to ensure correct running temperature. The same applies for an oil cooler which is rarely
required but if fitted always fit an oil thermostat MOCOT1 to ensure that the engine reaches correct working temperatures before cooling starts.