Did some browsing (trying to convince myself) & thought I share something…

The 12A series motor was in production for about 15 years, from 1970 through 1985.  During 1974 the 12A became one of the first engines outside the US or Europe to compete and finish in the famous 24 hours of Le Mans The 12A is considered a “bored-out” version of the previous 10A engine.  Although the diameter of the rotors stayed the same, the depth was increased by 10mm (0.4 in) to 70 mm (2.8 in).  Each rotor housing had a displacement of 573 cc, combined the engine had a total of 1146 cc.

During the production of the 12A engine they started using a new method of hardening the rotor housings.  In 1974 the Sheet-metal Insert Process (SIP) would use a sheet of steel similar to a piston engine’s cylinder liner with a chrome plated surface.  They also changed the side housing coating which eliminated the problematic sprayed metal that was used previously.

With the use of the new “REST” process, they were able to create a significantly strong housing.  This would make it possible to start using conventional cast iron instead of the old carbon seals.  The earlier 12A motors featured a thermal reactor, which were similar to the 0866 10A.  Some used an exhaust port insert which reduced exhaust noise.

The fastest 12A motor produced was the turbocharged and fuel injected model.  This was used in the Japan-spec Mazda Luce, Cosmo and the RX-7. Luce, RX-7, and the Cosmo.  This engine showcased a “semi-direct injection” into both rotors at once, this technique turned out to be more successful than it appeared.  They added a passive knock sensor to eliminate engine detonation, and some later models included a specially designed “impact turbo,” which was tweaked to give the rotary engine a unique exhaust sound.  This motor produced 165 hp (123 kW) at 6000 RPM and 186 Nm (137 ft/lbf) at 4000 RPM.

Source: Wesley Mahler, [http://www.rotaryengineillustrated.com/list-of-past-present-engines/12a.html], “The 12A Series: Rotary Engine History”, 28 Dec 2009.