Yikes--there are guys out there with the patience to read my rants!! (I can
imagine Dahlgren out there saying "Yup; but only some of them")
Here's some more thoughts on engine cooling
1.. A few points on centrifugal pumps (engine water pumps) - double the
speed, flow doubles but the pressure at any given flow goes up 4 times and the
power required goes up 8 times. The actual flow rate through the cooling
system will be something less than double and the output pressure of the pump
will be somewhere between 2 and 4 times.
2.. Cavitation usually isn't any issue in automotive water pumps. You can't
get cavitation without water filling the pump impeller. Argue with me on this
and you may get a return dissertation on NPSH and cavitation suppression in
centrifugal pumps.
3.. If you really screwed up you might be able to make the pump lose it's
"prime" and become air or vapor locked. This doesn't happen in our street
vehicles because we mount the water pump well below the radiator full level,
we use large, short noncollapsable hoses (got a story on that one), we run
pressure caps so air can't leak into the coolant and we keep our radiators
flowing freely. Sometimes we get into trouble on race cars by missing one or
two points. I suppose if you made a long run of small diameter suction pipe
from a tank vented to atmosphere you might get a significant pressure loss.
If the pressure at the pump suction drops much more than a few inches Hg below
atmosphere actual cavitation can begin to reduce the pump's flow rate.
Further increase in pump speed may cause an actual "nosing over" of flow rate.
I don't think this is what happens with Ford flatheads; but I have no real
data to support this position. I think the flathead case is simply one of
asking the radiator to handle more heat flow than it can and still keep
coolant temperature below the boiling point.
4.. Ceramics in engines--interesting subject.......I recall a recent news
story about ceramic knife blades. Before I retired I worked for a while with
a ceramics engineer with carbide cam follower development for GM on his
resume. Aluminum nitride has been used for tank armor; and has thermal
conductivity better than cast iron.
Next-Running too cool.....Ed Weldon
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