The 2002 Series

Mazda Four Rotor Engines

The engine produced near 180hp @ 6000 rpm, and the engine’s displacement was 491 cc per rotor, with a total of 1964 cc. The 10A was producing around 100 horse power, and they intended to use the 2002 motor for a flagship sedan.

Although almost all of the engine parts could have been produced inexpensively, because they were the same as the two rotors, the 4 rotor eccentric shaft was really what made it not a feasible production engine. It is a very expensive part, hard to manufacture, not strong at the time, and the engine was highly unstable. They made the eccentric shaft from modified stock 10A parts, and the centre housing in the middle of the engine was wider to accommodate the coupling components of the eccentric shaft.

Eccentric Shaft Problems

The challenge was that the early eccentric shaft coupling was not rigid enough to handle the operation of the rotary engine. It was basically two eccentric shafts with a spline that transmitted the power, and a bolt through the center to hold the pieces together.

Look at how unstable, how unsecure the middle piece is.
Connecting two eccentric shafts did not work out to well.

The Solution - Fixed on later models

Engineers would later solve the challenge by developing a single rigid eccentric shaft for the whole engine, with additional slide on lobes. The 20B 3-Rotor shaft has a similiar setup, except for only one side. Look at this picture of the 20B eccentric shaft and you’ll see what I mean.

The eccentric shaft was basically a single piece, two rotor eccentric shaft, and on each side there was a long slide where you’d slide on another piece with a lobe. The lobe being the place another rotor could sit on it. They would use a key to hold the single piece eccentric shaft and the slide on lobes together. The lobes were also called an “auxiliary shaft,” again, that slips over the top and bottom of the shaft. (show eccentric shaft picture)

This image taken from Craig's Rotary Page clearly shows what is described.