It's as broad as its long. Ignoring turbulence and hot-spots for the time
being, as the flow rate of the coolant increases then as well as not having
so much time in the radiator to give heat up it is not spending as much time
in the engine to pick it up. If the coolant flow is too fast for the heat
produced by the engine the thermostat will never be fully open and you are
wasting engine power in excessive pumping losses. If the coolant flow isn't
enough for the heat produced by the engine then the engine coolant
temperature will be higher than it should be, the thermostat will be
permanently fully open, and the engine will, nominally, be overheating.
Manufacturers choose pump flow rate to suit their application. Unless you
are getting very specialised I wouldn't expect an after-market high-capacity
pump to add anything except cost. With standard installations, and most V6
and V8 conversions, if you are getting overheating problems it is because
there is a correctible defect in the existing installation, not a design
error in the coolant circuit.
However my V8 was getting into the red on the temp gauge in temps of 90F,
although not losing coolant so not strictly overheating. An uprated rad
didn't do as much as I expected. In the end I discovered that the cooling
fans were only getting about 75% of the system voltage for various reasons,
some PO inflicted and some where the original design *wasn't* ideal such as
being powered from the green circuit and long runs of standard gauge ground
wire. I changed this for a direct feed off the alternator and local heavy
gauge grounds, and now the gauge never gets above mid-way between N and the
red even in test conditions of about 105F.
PaulH.
----- Original Message -----
> Actually I can see both sides of the argument. If the water goes through
> the radiator too fast, then hot water comes out the bottom and back into
the
> engine.
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