Based on exact size and dimensions of the previous remix, I added Added some more details and modifications to the rotor housing, rotor, and e-shaft(crank).

Housing: added an external casing based on 13B-REW block from 93-02 RX-7. Extended the spark plug holes from the origintal size so it reaches the outer edge of the outer housing. Exhaust holes on the side have different outer and inner ports.

Rotor: added round recess balls near the corners on top and bottom surface. Bulged out the outer arches to more accurately resemblance of the engine rotors while retaining the exact corner apex size and shape of the original model.

E-Shaft: extended the hex section to stack more layers of rotor housings and eccentric wheels. 13B shaft for 2 rotors, and 20B shaft for 3 rotors.

Housing Rod: Print 2x to stabilize the housings when stacked together. 13B for 2 rotors and 20B for 3 rotors.

the e-shaft(crank) and eccentric wheels are based on the latest remix by Aggressive. http://www.thingiverse.com/thing:129807

EDIT: Shortened the finger loop connector of the e-shaft(crank) so this model can still be spun while sitting on the table.

The Eccentric wheel has been re-created with the same dimensions as the previous re-mix to look more like the 13B engine with 3 circular holes. (had to alter the scale of these 3 holes from the real engine reference for stronger structural support)