I remember the last time this was discussed (it rates right up there with
rivets) it basically came down to what came first the smoke or the fire.
That said I would think:
1. As long as there are no gaps (air) in the system the absorsion of heat -
from the engine - would remain relatively constant regardless of how fast
the coolant moved (up to the coolants point of boil).There likely was a
minimum flow rate created by the engineers, but I would assume most pumps
meet or exceed that for a given RPM. The engine was designed (for good or
bad) to transfer heat to the coolant based on the engine and coolant
properties in the initial design. You can pull all the heat you want to out
of the engine, but if the radiator can't dissipate it............ . I would
add that this statement assumes a constant and correct returning
temperature!
2. The greater issue seems to be not how the coolant absorbs heat from the
engine (at least after reaching operating temperature) as that is a design
given, but how efficently the radiator disipates that heat. Hence, there
does exist the potential for a high volume waterpump to move the coolant too
fast through - the radiator - and return it to the engine with more heat
then if it was moving slower. Assuming the flow rate is equal to or greater
than the designed minimum flow rate through the engine it is not critical if
it moves faster through the engine, but through the dissipating radiator it
is. I say this because previously we had the arguments that the longer the
coolant stayed in the radiator the longer it was heating in the block.
Since the block/head coolant capability is a design issue we have little or
no control over we need to accept it for whatever it is (right or wrong) or
assume the engineers got it correct.
3. It could be that the designed flow rate of the engine coolant was set low
by the engineers and a high volume pump does in fact help with cooling.
However, if this is the case it would also seem to indicate that the ability
of the stock radiator to dissipate heat has a greater potential (than
perceived). If that was not the case then the ability of the radiator to
dissipate heat would have "maxxed out" and a higher volume pump would show
no change, or as stated in #2 make the car run even hotter because the
coolant didn't spend enough time in the radiator to properly dissipate heat.
In the end I could conclude that:
A. If the coolant is above the minimum flow rate at a given RPM moving it
faster - through the engine - would have no or a minimal effect on cooling
(again assuming a constant and correct returning temperature).
B. If the flow rate is too high and - the radiator - can't dissipate the
heat quickly enough the car could potentially run hotter.
C. Given that the block/heads and coolant properties are pretty much a given
the only possibilities remaining are to increase airflow through the
radiator (which in itself likely has a limit) or to increase the ability of
the radiator to dissipate heat (likely by increasing it's volume).
D. I have left the door open to the fact that a flow increase does in fact
increase cooling ability, but that would indicate a designed flow rate that
was set on the low side and the stock radiator having greater capabilities
to dissipate heat than perceived.
All this assumes there are no secondary issues such as a clogged system,
loose belt, leaks, extreme outdoor temperatures, hard driving, collapsing
hoses, loose or corroded impellers, etc. which has been rightly stated -
"should be checked first." Additionally, issues such as recalculated
radiator air and the like need to be considered. This list and the many
Tiger sites offer a plethora of information in this area.
Tom Witt
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