The reason you need the slide throttle near the
rotor housings at part throttle is because as soon as the leading
apex seal passes the lower edge of the p-port
the considerable vacuum and volume in the intake runner
immediately sucks exhaust gas in at just the wrong time. Later,
as the exhaust cycle is more complete, the exhaust pressure is lower,
the intake cycle is further along and at a higher pressure
so it is less of a problem.

When the slide throttle is near the rotor housing one side
is vacuum and the other side is atmospheric pressure so
there is less contaminated exhaust gas making its way
into the intake system. The opening and closing angles
shown in this chart are misleading. There is always
over lap in a p-port engine between intake and exhaust
because of the depression in the rotor face.

If you want to reduce this use a high presser air
curtain seal as shown in the last two 3Ds.

Paul Lamar ...No rotor no motor.

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