P-ports misfire at low RPM because good mixture gets
contaminated by exhaust gases due to the high overlap
between the exhaust and intake ports.

There fore it helps to keep the throttle plates close
to the rotor housing to minimize the volume of
contaminated gases.
--
Paul Lamar ...No rotor no motor.

Does a p-port have to be straight in? What would it do if you came in from

a

higher angle giving more separation from exhaust and a more oblong intake,
thereby basically hopefully giving you more intake without extending
overlap?
jofarr, soddy tn

----------------------------------------------------

Might help. Lots of sizes and a few different angles have been tried.
I can't say if there is an optimum angle.
--
Paul Lamar ...No rotor no motor.

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Having given this plenty of thought and asked many questions of so called
experts, I've come to the conclusion that the early post opening is as Paul
suggested. That is overlap which contaminates the inlet charge. This is only
a problem at idle, as the exhaust evacuation speed ( reaching supersonic
speeds) is more likely to suck inlet charge through the rotor depression and
into the exhaust at higher rpm.

A much later opening subjects the inlet to increasing pressure (start of
compression cycle), which is even more likely to push inlet the fuel air mix
back into the inlet manifold and may well reduce volumetric efficiency.
There is a suggestion that this back pressure can cause the fuel droplets to
drop out of suspension and cause alternating rich, starved running.

The best solution ( at present) is Tracy Crooks method of early air inlet
with a slightly delayed fuel injection.

Future direct injection will eliminate overlap and increase atomization by
reducing fuel droplet sizes, as part of the DI process.
George (down under)

--------------------------------------------------------------------
The port timing has little to do with the overlap. The two ports are ALWAYS
connected together in a P-port engine by the depression in the rotor. In that regard
a P-port rotary engine is somewhat like a gas turbine engine.  The flow of
exhaust and intake gases, one way or the other, depends on the instantaneous
pressure differences in intake and exhaust. Pipe tuning has a large
effect.  Everett Hatch found that 32 inch exhaust pipes worked
the best for 6000 RPM on a dyno. A muffler can greatly change the balance.
A turbo charger will make a huge difference in the balance.
Anybody wishing to really see what is going on needs to instrument
the intake and exhaust port with high speed pressure sensors.
Unless this is done everything else is speculation.
Here are some charts from Mazda that used such instrumentation.

So far DI has been unsuccessful in doing anything but perhaps make the BSFC worse.
Super high pressure DI (20,000 psi and above) has not been tried to my
knowledge.

Placing the injectors way up stream giving the fuel more time to mix
works the best with p-ports. Racing Beat has done extensive dyno testing
with this configuration and confirmed the effect. A turbo p-port in theory
is slightly better in this regard as the air intake temperature is higher
vaporizing the fuel better. NA the intake pipes are very cold at high power.
Almost freezing.

Passing the intake tubes through the oil pan on the Lycoming engines
to warm them aid in fuel vaporization but hurt max HP.

BTW Francois mentioned to me at OSH that injection timing is critical with
his (Mistral) NA intake manifold that shoots directly into the side port.

As far as I know Tracy has done no experiments with p-ports and as far
as Francois is concerned he does not think injector timing is as critical
with p-ports.


Paul Lamar

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