I have never had trouble getting a rotary to idle at stupid low RPM. Even the factory Pport engines. The problem with doing that is the rotary changes crank shaft speeds during each rotation at low speeds. So, if connected to a transmission or a speed reduction unit it will shake the gears to death. Accelerating and then slowing twice per revolution. The trans mission sounds as though a bag of hammer heads had been dropped into the gears. Has anyone picked up a Mazda flywheel. A bit heavy was it? This is required to reduce this shaking.
The flywheel or fluid damping of the automatic eliminates the problem. When the flywheel is replaced with a button flywheel for use with a 6" disc and a 5 1/5" clutch, then there is very little damping. A propeller on the reduction unit damps very well and moves the problem RPM lower in the rev range. So while the rotary can idle very slowly. It should not be allowed to idle very slowly. If you hear that problem, just raise the idle RPM a bit. So, that is why the racers have high idle RPMs. because of lighted or missing flywheels and lightened rotors.
Easy....Lynn E. Hanover
And another thing.Even without overlap, if the exhaust system retards the removal of most of the exhaust gasses some will be incorporated into the next fuel air charge and reduce oxides of Nitrogen and HP.
It tunes like a dirt bike.
Lynn E. Hanover