Drove the engineers nutty trying to figure it out. It turned out that it was the crankshaft ringing. The harmonic balancer absorbs the reversals and stops the ringing. Just a smooth eccentric orbit. Intake is on the top right.
Compression is across the top.
Spark takes place at left center followed by the power stroke across the bottom and the exhaust goes out the far right just below the intake. Also, since the lobe on the eccentric shaft has such a minor throw, the forces of the rotor are not massively leveraged like the piston is at the end of a long throw on a crank. A nice little side benefit of all this is that the rotary is a very smooth and vibration free engine. The Mazda Gran Prix team uses rotaries. They only rebuild their engine once a season, not after every race like the V8 teams.