George,

Your comment about change in water flow     charteristics when  P-ports are
inserted in a large water  passage  is  a  pertient observation. I
calculated that hole  area is over  4.5 cm2.  Water  flow in the coolant
system  would have to reduce  and/or the  system back  pressure  increase to
maintain stock  water flow when  blocked.   In  affect it is like shutting
a
downstream  valve.  I  would think we want  higher than  stock flow through
the   block as we are working the engine at   higher power  densities.
Anyone
with access to the Mazda Racing   housings  could confirm the  size of the
holes in the water   passages to see if there  is a  difference between them
and  stock  housings.


Doug in   Japan


With the  sealing  block system water can still flow around  the  SS  p-port
tube.  You don't have to pot the area with epoxy if you   are  concerned
with
the
water flow in that area. If you do pot  it  you may  be  able to drill
a 1/2 inch dia. or larger  water passage.   Another possibility  is a small
external  return line from the  rear  rotor housing back to the  input to
the
rad.
This is  common  practice on Chev V8 racing   engines.

I agree that  robust water  flow is a good  thing.

The  blockage is not that  bad. You have to   figure the percentage of the
total  area  blocked and if you look  not  at the rotor housing but at  the
center  housing you  will find the  center housing side ports  block a lot
of  the  return water  flow.

The bottom line is  the metal  temperature adjacent to  both  the wear
surface
and the   spark plugs explained in my book How to Cool   Your   Wankel.

Mark Steitle installed thermal couples in that    location  and found
the temperatures a couple of hundred F below   the  metal  temperatures
in a Continental  liquid  cooled  aircraft  piston engine. I  have tons of
data on  this  subject.

IMHO what  is far more important  is apex  seal  temperature which is
affected
by  rotor cooling and apex  seal   oil supply. Hot apex seals wear faster
and
the apex  seal slot itself  wears  faster. In fact the early RX8  with  what
turned out to be  inadequate oil  supply to cool the  apex  seals resulted
in less  than 100,000 mile life.  Mazda  addressed the  problem by  adding
additional oil injectors about  2007.  I still add a  1/4  ounce of 2 cycle
oil to each  gallon of gas in my 2004 RX8  along   with the  regular
metering pump.


Paul  Lamar

I   just  checked some factory race Periphery Port housings. At the top   of
the
port cavity is a 25/64" [.39"] hole for coolant flow.  Just   one.

Lynn E. Hanover


Lynn

Very good.  Thanks.   I  asked because my O-ringed insert PP  tube
effectively blocks the  water  passageway.  There is  however enough room
near the outer  top of the  passageway to  remove some metal and allow
water to flow  through.  I  take  it the other cavities holes on the
return side  are about the same  as  stock?

Doug in Japan


I will  check on that in  the AM and get back to you.
Lynn E.  Hanover

The stock 12-A  rotor housings are wide open through the area that would
become the intake  runner.

The center iron is blank between the two case bolt holes so no  water would
pass through no matter what the rotor housing look like. The  front and rear
irons have a passage below the case bolt hole  that would be unused, so a
hole  above the runner would  work.

The Pport housing has three interesting features that are not on  the  stock
rotor housing.

The area where the runner is formed  has a reduced thickness next to the
runner, and is rounded at the top to  match the contour of the top of the
runner.  This would connect the  front and rear irons flow wise through the
.039"
hole.

If the unused  case bolt hole and land is completely removed during assembly
and a path is left open above the runner, it would function as a  stock
piece. If  the bolt hole land is left behind, the land could be  notched
between
the inner  wall and the land to provide flow. Or the  land area could be
shortened on each  end.


There is a 1/8"  notch in the case bolt lands above the runner, so some
flow would  occur
and, or, would let air bubbles escape to the top of the  housing.

Along the hot side the case bolt lands are severed from the  inner housing
wall. Only the land area for the spark plugs connect the  outer from the
inner  walls. The stock housing has all of the land  areas connected to both
inside and  out side walls.

If you  expose a bolt hole to coolant you must plug the unused case bolt
hole at  least in the rear iron.

This is 12-A data and may not be  helpful.

Lynn E. Hanover


I think that is .39" Lynn and not  .039" :)


Paul Lamar


Lynn,

Thanks.  That was  helpful. Good point about breaching the unused bolt
land.  I have  heard coolant leaks have occurred that way.

Doug in  Japan


The water pours out about as fast as you can pour it in. I did it once on a
home made P port engine, and again when building a modern engine for a
RX-2,  replacing the 84 rear iron with a [1970's] RX-2 iron so as to use the early
(smaller) bell housing. Just a pipe plug in the rear iron unused case bolt holes
works fine.

Lynn E. Hanover