All,
What is everyone using for
oil in their 13Bs? It
appears that the shop manual specifies 10W30 or 5W30 (for
cold weather). Are
people flying regular motor oil or are you all flying
aviation oil (aeroshell, or
equivalent)?
Gordon C.
Alling, Jr., PE
President
acumen Engineering/Analysis,
Inc.
540-786-2200
www.acumen-ea.com
I still know all of that
stuff, I just cannot remember it.
The Mazda and many other
engines use a closed loop cooling system when cold.
Where coolant is free to
move through only the engine block during warm up. This
keeps hot spots from forming and keeps the block from
growing too big on the hot (exhaust) side. It also gets
the engine warm quickly so the total HC is low enough to
sell the cars in the Peoples Republic of California.
In a conventional
system, most thermostats have a little bubble valve and
that allows some coolant (and bubbles) to move out of
the engine and pull some coolant in from the radiator.
This makes the warm up last longer than is good
practice. In the Mazda version the thermostat from the
Rube Goldberg shops has a conventional looking top to
block coolant from leaving to the radiator, and a plug
valve that is open when cold to divert coolant around
only inside the block. When the coolant warms the top
opens and the plug valve closes off the bypass port in
the pump body forcing coolant out the norice to the
radiator.
You can modify the pump
casting by tapping the internal (plug valve hole) for a
pipe plug. Then use a conventional American thermostat.
I use a 160 degree
thermostat with three 1/8" holes drilled around the
perimeter. In the event that the thermostat should fail,
just reducing power allows the three holes to pass
enough coolant to save the engine. On very cold days,
the thermostat never opens and the engine cools only
through the 3 holes and runs about 150 degrees. For
those days we taped off much of the radiator. We have a
big radiator.
The rotary has dozens of
nooks and crannies in which it hides air bubbles to use
to stop the water pump with an air lock when you need it
the most. It can run for weeks with the bubbles in place
and when you rev it up for say a race start, or a take
off, zoom there go the bubbles swept along to the
suction side of the pump, followed by no more pumping
and then no more engine. All of this is the same as any
engine, however the rotary has the water pump mounted
very high on the block where the bubbles can have the
maximum effect on producing cavitation.
All of the air must be
removed from the system. Mazda did all of the
engineering for that in the RX2-3 and 4. The make up
tank on the fire wall (plastic crap that no American
relief cap fits very well) has the pressure cap on it.
The cap on the radiator is just a lid to seal the
radiator and has no pressure relief function. Bubbles
popping to the top of the radiator are forced up the
hose to the pressure bottle, then pop to the surface
inside the bottle. With any pressure reduction inside
the block, resulting in only pure coolant returning to
the block. The pressure bottle need only be filled to
2/3 capacity allowing a compressible air volume on top
of the coolant. After 3 heat cycles you will need to top
off the bottle as the coolant will be in the block and
the recovered air will be in the bottle. Works great.
Works every time. Designed by Mazda. Works on Mazda,
Cosworth, Chevy and even Ford racing engines and
airplanes.
This was no genius move by
Mazda. This is just an Accumulator.
These are used in all kinds
of liquid systems to provide bubble removal and as a
back up supply of that liquid. And to maintain a
specific pressure. As in 3000 pound flight control
hydraulic systems in airplanes.
The make up tank or bottle
need only have a filler neck that will fit an American
style relief cap. (Stant lever cap 17 to 22 pounds)
Consult you radiator manufacturer for maximum pressure.
Taller and thinner is better. Hose to the radiator top
out the lowest point in the bottle. Cap accessible so
you can top off the coolant. The actual location of the
make up bottle is not at all important. It need not be
the highest item in the coolant system. The hose needs
to be about 1/8" in ID however.
In the racer the Mazda make
up bottle from an RX-2 sits on the passenger floor, and
works just fine since 1980. I put that or similar in
every race car I ever built. Never a cooling problem.
If you use a thermostat,
keep in mind that they seldom fail in the open position.
They fail by the bellows cracking and loosing the
alcohol in the bellows (or whatever they use now) and
the damn thing snaps shut. They do not die slowly in
order to give you a warning.
Many racers use
restrictions in the water outlet to limit flow rate to
the radiator. This is so the restrictor is the main
restriction to flow and not the radiator. You do not
want any cavitation occurring inside the radiator.
Notice that the bottom radiator outlet and hose is much
larger than the top (high pressure) hose. Notice also
that the bottom hose has an internal support spring
installed to prevent collapse. Deduce then that it is
possible to collapse the bottom hose via a dynamic
pressure difference between the water pump outlet and
the water pump inlet even though the pressure cap is in
place an fully functional.
They (radiators) die
quickly. If you run the rotary up to 8,000 rpm while
listening to the bottom radiator hose through a
stethoscope,
you will probably install a
restrictor after changing you Depends.
Notice that some aircraft
installations run fine with 1" ID radiator hose to and
from the radiator. That is a lot of restriction. And
still it works.
All of my coolant must pass
through a 5/8" sharp edged 1/8" thick restrictor. And
still it works.
For low RPM installations
such as airplanes, a restrictor is probably of no value.
I have been searching the
archives but to scant successes regarding thermostats
use or lack of use for cooling.
I have been having issue with cooling lately. I use to
be able to idle on the ramp for over an hour in the
middle of a Houston summer with adequate cooling.
However, lately temps are rising faster and higher.
Yesterday, while troubleshooting this issue I noted
that after about a ten minute taxi that the mounting
location of my coolant temp probes was reading about
220 degrees measured with a handheld thermo gage,
close to what was being indicated on the panel
However, the top of the radiator was cool to the
touch. The handheld thermo gage read 45 degrees. Ok.
Seems to be a flow/thermostat/pump issue. I will be
Looking into this ASAP.
This got me to think about thermostat usage. I have
one. I know some do not use them.
It is my understanding that if you remove the
thermostat you have to close some passage off. What
passage is this and why does this need to be done.
Also, what is the accepted method.
While researching I also saw discussion on restrictive
plates. While I am not considering a restrictive
plate, the thread discussed drilling holes in the
thermostat itself. Lynn mentioned do it caught my
interest.
It seems this is something I use to know but now
forget where I saw it. I just finished reviewing my
partial scan of Tracy's conversion manual to no avail
and my archive search is giving me hundreds of
returns.
Thanks,
Chris