These numbers for the Mazda P-port are bogus.
    As Paul has  pointed out, there is an overlap of intake timing
between
    adjacent rotor faces.

    When the apex seal is in the center  of the port, two chambers are
 open
    to the intake. From this  position, after 360 degrees of shaft
 rotation
    the rotor face  which was just beginning intake before the rotation
    would
    still be half open to intake after the rotation. The intake  period
    exceeds 360 degrees of eshaft rotation.
    Reference these numbers to after TDC and it becomes apparent they
    cannot
    be true.

    The intake opening at 86  BTDC is 274 degrees of e-shaft rotation
    After  TDC.
    The intake close of 75 ABDC is 255 degrees After  TDC.
    This gives us 19 degrees of shaft rotation where neither  is open.
    For the exhaust, opening at 73 BBDC is 107 After TDC,  and closing
   at 65
    after TDC - 42 degrees of shaft rotation  when no exhaust occurs.

    It appears to me that the interior  circumference of the rotor
housing
    is about 27 inches; so 360  degrees of shaft rotation is 9 inches. A
    two-inch port opening  then requires 80 degrees of shaft rotation to
    transit, so the  trailing port opening occurs 80 degrees ahead of the
    leading  port closing. The intake period including overlap is about
 440
    degrees of shaft rotation.
    The exhaust port appears to be half  the size of the intake, so 400
    degrees of shaft rotation from  opening to closing.

    Tell me where I am  wrong.

    Victor Roberts

    Are you referring to these numbers as being bogus?

    Mazda Factory Peripheral Port
    IO 86° BTDC
    IC 75° ABDC
    EO 73° BBDC
    EC 65° ATDC


    These are typical representations of timing numbers used  in
rotaries.
    Notice the similarity to numbers for a "J" bridge  port.

    Racing Beat "J-Bridge Port"
    IO 115° BTDC
    IC 72°  ABDC
    EO 88° BBDC
    EC 57° ATDC


    The numbers used are  started at the nearest of four locations.
    A TDC or a BDC.  This to keep numbers small and understandable.
 This is
    adequate to lay out  markings to port an exhaust or intake or lay out
    your

    Pport boring location. And  recover overlap degrees,
    All of these numbers can  be resolved while looking at one rotor
face.
    The two TDCs are minimum  volume right or left side and two BDCs
   maximum
    volume
    top (Intake) and bottom (exhaust).

    While it seems backwards, the Pport engines are more  tractable than
   the
    bridge ported side port engines. Although both have very  little
    torque right
    off idle we could drive the Pport to and from the false  grid with no
    problem where the "J" bridge ported were towed with a small  tractor.
    This to save
    the clutch. A Tilton of course.

    The Madeville modified factory Pport housings had  enormous
 rectangular
    intake ports and are also quite tractible at low RPM.



http://alex62.typepad.com/imsablog/2006/02/mazda_rx7_winni.html_






http://alex62.typepad.com/imsablog/2006/02/mazda_rx7_winni.html



   )
    They ran unmuffled at most locations and even with no back pressure
    idled
    smoothly.

    The idea that much if any fuel will be lost to the exhaust system
 at or
    near  cruise RPM is not founded. It is my opinion that when muffled
    and at low
    RPM  exhaust pollution of the intake charge actually helps smooth out
    the
    idle in the  Pported engine.
    Lynn E. Hanover


    I understand the BDC and TDC references. I converted them to a common
    ATDC in order to make the relationships easier to calculate.
 Because of
    the 3:1 e-shaft to rotor gearing, each face of the rotor requires 360
    degrees of e-shaft rotation to pass over any given point on the
 housing
    circumference.

    I guess there is a question of what "port open" and "port closed"
   means.
    In my experience with piston engines, "open" means when the valve
 comes
    off the seat, and "closed" means when the valve returns to the seat.
    "Overlap" defines the period when neither valve was seated. For
   2-stroke
    engines, "open" and "closed" refer the transition from closed to
    partially open and open to completely closed, respectively.

    On a p-port rotary, does "open" refer to  the time the apex seal:
    A. enters the port ;
    B. clears the port; or
    C. some other time?
    What event defines "closed"?

    For an engine to have a volumetric efficiency of 120%, the intake
must
    have been charged with pressure greater than 120% of ambient at the
   time
    the intake port closed,  or part of the intake air must bypass the
    intake stroke directly into the exhaust. It would appear most likely
    that an elevated intake pressure would both charge the intake above
    ambient, and force air into the exhaust during overlap, a period when
    exhaust back pressure is at it's lowest. Since most of the
 operation is
    at cruise power, it is this condition I am concerned with.

    I ask here because I have attempted to research these questions and
   have
    been unable to find the answers.

    Victor Roberts

    Here are some diagrams that might help.

    Paul Lamar


   Thanks - that helps a lot. I amend my opinion (not that it bears any
   weight ) concerning direct injection at the oil injection hole; it
   appears that as the exhaust port closes, about 40% of the included
   volume of the intake is ahead of the oil injection hole, and the air
   inflow might very well cause the mix to be richer around the leading
   plug.

   I'll shut up about this now.

   Victor Roberts





   Hello Victor,


   I'll give it a try too. We use these numbers:



   Mazda Factory Peripheral Port

   IO 86° BTDC
   IC 75° ABDC
   EO 73° BBDC

   EC 65° ATDC




   To define a bit more the opening and closing events look at it this
 way.
   The leading apex seal opens a port, while the trailing apex seal
 closes a
   port. That applies to both, the inlet and outlet ports.

   Looking at this scenario, from TDC at combustion the [rotary] piston
   travels around
   until the leading apex seal comes to the edge of the outlet port
 when the
   outlet begins to open. Using above numbers this is at 73 deg. BBTC.
 When
   the leading apex seal comes to the other side of the outlet port the
 port
   is fully open.

   The blow down occurs over the next stroke of generally 180 degrees
 minus
   the early opening of the inlet port which happens when the leading
apex
   seal of that same chamber comes to the inlet port at 86 deg. BTDC.
   This is
   73+180-86 = 167 degrees later.


   When the leading apex seal crosses the other side of the inlet port it
   will
   be fully open and both ports, outlet and inlet, are fully open. This
   condition exists until the trailing apex seal has passed over the
 outlet
   port and closed it at 65 deg. ATDC. The beginning of closing is a bit
   earlier.



   The duration of both ports being open is between IO at 86 deg. BTDC
   and EC
   at 65 deg. ATDC or over 151 degrees. On the racing beat J-Port the
   duration
   is IO at 115 BTDC to EC at 57 ATDC = 172 degrees. For overlap only
 these
   two numbers count.



   IC determines the degrees of chamber filling in connection with rpm as
   well
   as IO due to its size needed for breathing.  EO should preferably be
   later
   for more expansion but due to its necessary size it sets the
 position and
   therewith the timing of EC as well.



   Due to these restrictions side ports are being used that however have
   higher flow restrictions.



   I hope that helps.



   Rolf


  You defined opening and closing in the same way I have understood them.
  The apex seal entering the port area is opening of the following
  chamber, and completing transit is closing of the leading chamber.
  Therefore, opening of the following chamber occurs prior to the closing
  of the leading chamber. When the apex seal in in the port, both leading
  and following chambers are open. One shaft revolution later, the
  following chamber is still open as it's trailing apex is now in the
port
  and in the process of closing..
   Port opening occurs before port closing.
  I am easily confused by top and bottom and before and after, so I
  referenced all events to TDC and tried to follow them around beginning
  from the top.  So TDC can be represented by 0 or 360, and BDC is
  represented by 180.
  If we represent all events as ATDC, we get the following:

  EO 73° BBDC  = 107 ATDC  (180-73)
  EC 65° ATDC   = 65  ATDC

  IO 86° BTDC  = 274 ATDC   (360-86)
  IC 75° ABDC = 255 ATDC  (180+75)

  This has the ports closing before opening. Confining our discussion to
  pports, according to our agreed definitions this cannot be true. The
  duration of the intake or exhaust is 360 degrees PLUS the rotation
  required to transit the port.
  I apologize for continuing, I was going to let it drop as Paul's last
  post gave me the info I needed, but unless you can show me an error I
  continue to believe the port timing charts to be wrong.

  Victor Roberts


  Hello Robert,

 the answer is that a 4-cycle operations happens over 720 degrees.

 Best is to think of a reciprocating 4-cycle engine. I trust it makes it
 easier to understand.
 Per your distinctions of angles lets say we start out at TDC at firing
 when
 the power stroke begins and call that 0 degrees and count from there
 as you
 did.

 EO 73° BBDC  = 107 ATDC  (180-73)    (*this is correct*)

 EC 65° ATDC   = 65  ATDC (*this is a rotation later*,* should be 425
 deg.*)
 From EO at 73 deg. the piston goes to 180 degrees and then to 360
degrees
 and then travels another 65 degrees until the EC happens. The exhaust
 valve
 is open all that time.
 EC is at (360+65) 425 deg. Valve opening of outlet is over (425-107) 318
 deg.

 IO 86° BTDC  = 274 ATDC   (360-86)  (*this is correct*.)

 IC 75° ABDC = 255 ATDC  (180+75)  (*this is the second rotation,
 should be
 615 deg*.)
 From IO (at 86 BTDC) = 274 deg. the piston goes to TDC then to BDC and
 then
 travels another 75 degrees until it finally closes. The angular
 position is
 (360+180+75) =
 615 degrees. Duration of IO is (615-274) 341 deg.

 The inlet is a bit longer open than the outlet.
 Between outlet open and inlet open we have (274 - 107) = 167 degrees.
 (close to one stroke of 180 degrees, the blow down).
 Overlap when both ports (valves) are open is (IO - EC) (425 - 274) =151
 deg.

 I could provide a relation between port lip location and timing
 values. But
 usually one can't or rather does not change that anyway. It does involve
 some calculation and I rather not go there as it is the realm of engine
 designers. P-Ports cause limitations in port timing.

 Regards
 Rolf




Please put aside the timing chart.
Let us observe a port transition.
Begin with an apex between the spark plugs.
Rotate the eshaft so as to move the observed apex toward the exhaust
port. As we proceed, we reach TDC (0 degrees) and continue rotation
until at some point the apex reaches the exhaust port - we call this EO,
(exhaust open). DO YOU AGREE that EC (exhaust close) has not yet
occurred in this rotation?
As we continue rotating, we pass the center of the port, and the angle
ATDC is increasing. Continuing, we reach the other side of the port, and
we call this EC, exhaust close. Granted that it is a different chamber
that is closing, but this the shaft angle that will close the original
chamber on the next rotation.
If EO occurred at some angle, and EC occurs LATER in the rotation, how
can the angular notation of EC be a number smaller than that of EO (
both expressed as ATDC) ?

As the the suggestion that the duration of either port opening is less
than 360 degrees, consider the following:
An apex is in the middle of a port, so the chamber following the apex is
open to the port. Rotate the shaft one revolution, and the following
apex is in the middle of the port, and the same chamber is, and has been
continuously open to the port. Additional rotation is required to close
the port. Therefore, the duration of the opening is 360 degrees plus the
rotation required for the seal to transit the entire port.

Victor Roberts

Forget all this port timing stuff. It is too confusing and a waste of
psychic energy.
Think of it as a jet engine. Air comes in.... is compressed and explodes
in more or less a continuous process.
Nothing really  opens or closes in the piston engine analogy.

Paul Lamar

I apologize for the noise on port timing. I have discovered that BDC is
not 180 from TDC, ti is  270 degees of shaft rotation (90 degrees of
rotor rotation) from TDC. Changes everything.

Victor Roberts