I would
lean more towards the pulsation set up by the positive displacement pump. I don’t know what the frequency of the
pressure waves would be, but it could be calculated. These pressure waves would transmit to all surfaces of the
oil system. The vibration would
cause stress fatigue on the evaporator core even though it was insulated from
the other engine components. I have
witnessed metal fatigue in the discharge piping of a positive displacement
vacuum pump used in an industrial setting; the remedy was to replace the piping
with heavier gauge material. The stock
Mazda oil cooler appears to be made of significantly thicker material.
Bob Perkinson
Hendersonville,
TN.
RV9A
If Nothing
Changes
Nothing
Changes!
-----Original
Message-----
Rusty,
glad to hear you have reconsidered, especially given the amount of effort and
how close (I think) to working out all the bugs.
Having
experienced several similar heart thumping, cushion gripping
events myself, I understand what you are going though. After all we are
putting ourselves at some degree of risk. However, I personally consider
the most dangerous part of each flight the 10 mile drive to the airpatch on a
narrow two lane road with everything from very senior citizens to huge dump
trucks passing me at a closure rate of 90 mph two feet or so away. Think
about it!
Regarding
the core. I think there are some significant difference between the
pressures and impulses encounter in the coolant system and the oil
system. For one the oil pump is a positive displacement pump meaning that
it is going to put out 156 psi (dropping to 80 psi by oil controller activates)
in rapid pulsation - regardless of what resistance it
encounters. The coolant pump on the other hand is a
centrifugal type pump, it does not have the high peak pulsation of the lobed
oil pump (smoother flow), plus if it encounters flow resistance, it simply
slows down the flow (head pressure increases) or it causes the pump to
cavitate. Also we have a difference in stress between a 80-100 psi
pulsating operating pressure and a 5-15 psi operating pressure in the cores. I
suspect the difference in viscosity is also a factor as the cross channels are
something on the order of 1/8-3/16 sq inches each. I would imagine that cold
40-50 weigh oil encounters considerable resistance to flow in these
channels. Got to cause more stress on the cores than water at
least on startup before the oil has warmed up..
Now
I am not a pump expert (nor any other kind - even on TV) but I believe there
are these significant differences between the stresses encounter in
the two different core applications. Besides, the core has been
used by numerous folks for coolant without problems and if mounted correctly
and with consideration of stresses on fittings I believe you will do just fine
in that application.
However,
if your confidence about using cores is somewhat understandably shakened, then
by all means have custom radiators built - worth it for you peace of mind and
still a small cost compared to your total investment in the project.
Whatever
you do don't sell it, but if you do sell it - don't sell it to Ken Powers, he
has more than enough unfinished projects {:>)
Ed
Anderson