if your familiar with piston engines, porting a rotary is just like installing a bigger cam. the rotary doesnt have to deal with valves, only port timing. that is the amount of time that a port is open to ingest or expell air. when you enlarge the ports, you're making the port open earlier and close later. when you advance the opening of the intake port and delay the closing of the exhaust port enough,you have overlap.
overlap is the amount of time that the exhaust port and the intake port are open at the same time. on a stock ported rotary, overlap is non-existant. that is the hummmmm. on a large street port, half -bridge, bridge-port, monster-port, j-port, and peri-port, the port-overlap steadily increases with each style of port. exhaust gasses are allowed into the intake charge contaminating it and causes a slight to moderate "stumble" or "brap-brap". the more overlap, the higher the idle rpm, the more brap.
one of the drawbacks of overlap is less low end torque and less streetability. the benefit is increased upper rpm range and higher horsepower. hope this helps.
Gotta wonder what that beast of an engine would bring to the table if someone turbocharged it...
