I scaled out this drawing two years ago and I still have the
drawing.
It is not that hard to do if you have a program like Pagemaker
(now
InDesign).  The Leman p port was constantly on my mind as we
designed
our implementation.  Our port is smaller and opens later which
should
help with the overlap.   I expect to have better BSFC than the
Leman
engine at our RPM for this reason.  The main difference between
the
Leman  engine and  stock is the additional spark plug.  .
Jerry

The thrid plug was worth about a 3% increase in torque and a 3%

reduction

in BSFC. Hard to measure. More like 2% in the 4500 to 6000 RPM
range.
SAE paper 920309.

Paul Lamar

Jerry Hey wrote:

Looking through my p port folder, I came across this drawing which
I am
attributing to Rolf, though I can't remember for sure.  This
drawing
uses the intake and exhaust information I derived from scaling the
drawing published by Mazda. It is particularly valuable because it
also
shows exhaust ports timing.   Jerry

You did a good job Jerry. The actual intake port diameter according
to

Doug

is 51 mm.


Paul Lamar

Paul,
For those interested, I just found some old info on the Le man's
port
timing
and factory P-port.

Factory P-port        Le man's
IO 86 BTDC          IO 105 BTDC
IC 75 ABDC          IC   74 ABDC

EO 73 BBDC
EC 65 ATDC

The closing (IC) events are very similar, which leads me to believe
this
about as far as you can go without too much back pressure affecting
the
inlet charge. At 75 ABDC is pretty high up on the housing anyway.

Interestingly the Le man's opening (IO) event is 20 degrees sooner
than the
factory P-port which indicates to me that the exhaust gas
contamination (
overlap) is considered the lesser of the two evils as they would opt
for
more overlap and limit the backpressure.

I don't know the Le mans exhaust timing, they could very well have
made it a
little sooner as well. Anyone got those numbers?

So my conclusion is that a preferred IO is sooner rather than later
and IC
sooner rather than later with distance between the IO and IC being
closer
rather than wider. This approach results in a rectangular type port.

Now having said that I superimposed this type port over a round port
like
Jerry's and found there wasn't a hell of a lot of difference - I
assume
Jerry did the same exercise and found a round hole is so much easier
to cut.
I don't remember but I doubt that Jerry has exceeded the IC 75 ABDC,
so his
position falls within these figures.

For those not interested, excuse my ramblings, but for people like
Richard
Sohn, who I'm sure is interested, this will mean something as I
believe he
has opted for an early timing whereas Jerry has opted for a slightly
later
timing.

George (down under)

Here is Jerry diagram and my diagram derived by scaling the Leman
engine drawing.

What is really confusing about the opening and closing is referencing
the numbers to the e-shaft position. To eliminate confusion it is
best to reference the numbers to the drawing angles as both Jerry and
I have done here.

Remember the intake  port stays open for roughly 360 degrees of
e-shaft
rotation. This is because the rotor is rotating at one third
e-shaft speed.

To show how confusing this can be the flank of the rotor
ahead of the flank doing the intake process  goes through and well
beyond top dead center while the intake flank is opened and
closed. Using old piston engine nomenclature of top
dead center and bottom dead center just confuses the issue.

To further confuse the issue a side port located  at the same drawing
angle as a P-port would open many e-shaft degrees later as the rotor
flank must move away from the rotor housing inner wear surface.
If this were not the case you would lose the corner seals out of
the intake port hole. This is one reason a bridge port shows so much
more power than a simple side port. It opens much earlier.

The bottom line is you can't compare P-port timing with side
port timing in any simple fashion.

Paul Lamar

Jim Mederer ( Racing Beat) sells PP housings that have less overlap
for
turbo applications.

Hans

Paul,  here is another drawing comparing very clearly my p port and the
Leman P port.  Both close at nearly the  same time but the Leman port
opens much earlier.   Once one determines the closing event timing, the
opening event is fixed by the diameter of the opening.  I did not want
an opening larger than our operating range required, thus the bore of
1.5 inches which was determined by Rolf to be adequate up to 8500 rpm.
If one wanted to run the engine at even  higher rpm, the capacity of
the port  would have to be changed . However,  my goal was to have a
safe (easy on seals), efficient p port that would operate up to 7500
rpm. If my engine generates 240 hp I will be thrilled.  But if it only
generates 220 hp,   that will be o.k. too.      Also,  George was
right,  it is much simpler to simply bore a round hole as opposed to
grinding a rectangular opening.  I was relieved when it was determined
the round hole  would be sufficient.   jerry

 
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