Thanks for the feedback Lynn. Unusual to see a "poor port design" actually aid performance.

 

Mike Wills

 

It is not obvious until you start graphing the open and close events, but the side port which uses the side of the rotor as a shutter to open and close the port, offers Mazda great latitude in port timing.  In the periphery ported engine (both ports) it is impossible to arrive at zero overlap, and have an engine that will produce any power at all. The apex seal does not close off either port at all, it just valves gasses in one direction or another.

 

In addition, the overlap of the periphery ported engine is far more effective flow wise than overlap in the side ported engine. One apex seal is above the intake port when the opposing apex seal is below the exhaust port. Flow between the two is unobstructed.

 

So, at low RPM you get fresh mixture leaving through the exhaust port, and combinations of burned and unburned fuel and exhaust gasses flowing partway back into the intake runners.

 

This reduces the low RPM output to the point that the engine seems quit docile, and is easy to drive around in the car, slowly, or possibly taxi in an aircraft.  This would make off idle tuning data useless as there will be fuel burning right on top of the EGT probes, and unburned fuel reaching the F/A sensor. 

 

The engine will act along the lines of a piston engine with a long duration cam. When the engine reaches its happy RPM where all of the mixture is burning inside the engine, it will step up on the "CAM" and you will see what a good idea this was. Use slow throttle inputs until you find the "WOW" RPM, and be ready with all available rudder.

 

When we first ran a factory periphery port engine, we found that there were places on the track that would not allow full throttle. This with 11" wide slicks. Thank Heaven for rev limiters. The driver reported the rear end getting real loose cresting hills and bumps.

 

Why yes it was..........

 

Lynn E. Hanover