HI dave,

Just a data point for you to consider....

I've been working on this Eagle540 V8 powered Lancair IVP for the
last several
years.  When we received the engine we installed it, put coolant
in it (50/50
anti-freeze/water) and started to run it in order to work the
bugs out of the
instrumentation.  During a call to the engineer who designed the
motor he went
apoplectic when he heard that we were running 50/50 coolant/water
in there, as
the engine has a magnesium intake manifold and may well suffer
from corrosion
from the water.  We drained it and replaced it with Evans NPG+.  This was
about a year or so ago.  At that time the folks at Evans also
suggested to Ted
(owner of this Lancair) that since this coolant was so superior and has
hundreds of proponents running it in their race cars and other
vehicles, that
250*F coolant temps are just fine.

Fast forward to now.....

One time during the most recent testing phase, when we were
working our way up
to full power, Ted let the coolant temp (on the hot side, coming
out of the
engine to the thermostat housing and on to the radiator) rise to abou 240
degrees.  I saw a couple puffs of black smoke from one of the
exhausts, Ted
saw a cloud of something fly over the top of the cockpit, and so
shut down.
 We had coolant on the outside of the engine, at the front on the
gearbox,
about 4 feet away from the coolant overflow bottle.  It looked
like we sprung
a leak between the intake manifold and the head on the right side of the
engine.  I pulled the mamifold, found a kinked o-ring, replaced
it, put things
back together and tried again.  More coolant outside... bummer.
Tried dealing
with the manifold once again and during the next test discovered
that the leak
was coming from the right head gasket.  Replaced it and went back to
testing... new leak from the left head gasket, or more likely
just another one
that we didn't see when the right leak happened.  When Ted got it
up to 240 he
managed to blow both head gaskets.  That's not the worst of it...
the internal
metal temps of the engine had to be considerably higher than the
240* we were
seeing on the coolant, as when we pulled the left head we found cylinder
scoring, and perhaps even evidence of a couple broken rings in
there... the
engine is being removed from the aircraft and being sent to the local
pro-stock engine builder for a complete bottom end tear down,
inspection, and
replacement of damaged parts... rebalance, etc, etc......

The moral of the story is that the folks at Evans might know
everything there
is to know about the chemistry of their product but they don't
know everything
about the metallurgy of every engine their product might be used
in.  While I
understand the argument that there's only a relatively small difference
between 200* and 240*, the heat load that the metal parts are
seeing can be
far greater.  Other components may suffer as well.  Before you go
merrily on
your way, convinced that 250* is ok for your rotary you might want to ask
yourself this question:  If that's the case, how come everybody
sets their
redline at 210 or thereabouts?  We already know that water has a higher
specific heat carrying capacity than other checmicals, so why is
it ok to pump
more heat into something that doesn't work as well as water?

Don't get me wrong, you might be perfectly ok setting your
redline with NPG+
at 250.  Then again, you might not, and wind up going down the
same road we
are with this monster V8.  Personally, I'd rather see you make the
water/anti-freeze system work... higher temps could well take certain
components right over the edge, and who needs that aggravation?

  <Marv>