Charles Wilhite wrote:

1.  Could someone please tell me how attempting to cool an engine that runs
at BSFC of 0.6 instead of 0.45 ......and utilizes a temperature differential
of (200-100) vs. (400-100) can result in less cooling drag?  Surely it takes
so much mass of air heated so many degrees to cool so many BTUâ??s of reject
heat??  Doesnâ??t that lead to more sq. in. of air inlet in the airstream?

How can water do more with less??  More options for the shape of the devices
for
utilizing the ultimate cooling medium: AIR, yes!  More options for placement
of devices, yes!  But.......less lbm. of air???   Obviously, I am missing
something!

I am not an engineer, just an old hot rodder.  But I have a few
observations to share.  I worked on solar collectors way back when, and
we learned that there is almost nothing better for moving heat around
than water. The water carries the heat away from the cylinders much more
efficiently than all those large cooling fins and air.  The water to air
radiator then does a better job of dumping the heat into the air.  The
real advantage though is the packaging.  Look at Charlie Airsman's
article in _Contact!_.  The air needs to go through the radiator in as
straight a line as possible.  A lot of the problem with air cooling is
all the drag from the path the air must take to get to and from the
cooling fins.  A really good plenum system is worth a lot.  On a friends
RV-4 is was worth at least 5kts!  If the air has to travel a torturous
path and then just dump into the cowling there may not be much
advantage.  The plan is to reduce the amount of air used for cooling AND
minimize the drag acting on that air.

3.  With an RPM limit of 7,000-7500 (whatever??), it is difficult to believe
that Mazda would put on a waterpump that cavitates at 6,200 RPM?  Not
likely......!  Stewart Engineering says NEVER underdrive the waterpump.
Their recommendation is 1.0-1.3 C/S RPM for the waterpump.  I can imagine
10,000 RPM will cavitate the waterpumps and underdrive is perhaps the way to
go.  But why does everyone think they need to underdrive the waterpump at
6,200 RPM??  Obviously, I am again missing something.

Water pumps can be underdriven as long as the time at idle is
minimized.  Drag racers get away with it regularly.  At higher engine
speeds the reduced pump rpm is adequate.

For some radical ideas I'm not sure I would be ready to test in the air
check out these pumps.  The Davies Craig unit is especially interesting
as it has a 2 year warranty, and has an optional variable speed
controller that maintains water temp measured in the head (or block in
our case!)

http://www.daviescraig.com.au/

http://www.meziere.com/cgi-bin/web_store.cgi?page=/index2.html&cart_id=9006042_28861

Charles

 
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