There are some very
thick books about oil and water cooling systems.
There are some engineers who spend whole
lifetimes on this. I am not one of those. But I
have learned quite a bit, mostly the hard way.
So here is some of
that. No flowing system likes sharp corners.
Air, water or oil. Do not use drilled 90s for
fittings. Use sweep 90s and 45s. When building
coolers you find that the chilled media tends to
cling to the tube, causing a loss of efficiency
because the hotter media is then being insulated
from the tube walls.
So, manufactures
tend to use fewer flat tubes (less money) and
add cheap fixes to get back up to minimum
performance. Violent tribulation is required to
keep mixing the cooled media with the hottest
media. So you see a collection of odd things in
the tubes. Mazda uses a Twistoflex watch band
lookalike. Others a cross hatch pattern in the
tube walls. Fluidine is the class of the field
with their inside out radiator design.
Every system has one
sweet spot for every flow rate, every
temperature, every pressure, every media. You
can track that sweet spot with a thousand
sensors and a lap top. And cooler designers do
just that. Everything affects everything.
Rotaries run best
(Best power) when the oil is below 160 degrees.
(Daryl Drummond) . High rotor face temps
tend to expand the
fuel air mixture entering the chamber quickly,
killing off more of the incoming flow. Bad at
low RPM. Less bad at high RPM. We raced at
Grattan Michigan with the temps at 30 degrees.
Water thermostat in place and 2/3 of the
radiator taped off. All of the oil radiator
taped off. Ran the race with water temps at 120
degrees and oil temps at 150. The thermostat had
a 1/8 hole in the edge to let air bubbles
through. This is not to suggest that 1/8 inch
hose is adequate for cold climates.
In olden times when
we still used the stock pump we opened the
lateral gallery plug and took the oil out of the
block right there. Going back into the block at
the stock rear Banjo fitting. And the lateral
gallery in the front iron to the front main
bearing. Later with the massive external pump we
still fed that front bearing with its own
supply. We did not plug the dowels that connect
those two location.
Mistral found the
oil pickup tube and bug screen to be a problem.
The anti vortex disk diameter is stupid small.
And so then is the
bug screen. I removed the bug screen and added a
big flat disc to the end of the tube.
I built up the back
side with braze and ground the sharp edge down
to look like a trumpet bell. The bug screen
would filter out a mouse but not small enough to
stop the grit that will kill the pump or
bearings. I never missed it. Mistral cast up a
new pick up tube but without the bug screen.
they used a baffle plate between between the
pan and engine. It had large areas of screen to
perform the bug screen job.
The object of higher
oil pressure is move oil out of the wedge more
quickly so as not to damage the very soft
bearing material.
Low oil pressure at
idle is usually not a problem. No bearing stress
at all. 5 or 6 pounds is fine. Minimum loaded
pressure not below 60 PSI while looking for
nearest to see where you 80 PSI pressure went.
If you or some
engine builder took out the springs and balls
from the crank then low idle pressure cannot be
corrected. Used only for constant high RPM in
racing. You can put them back in at over haul in
about 15 years. Keep in mind that this advice is
free. And, worth every penny.
Lynn E. Hanover