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Written by Wesley Mahler   


The 10A series was the first Mazda's production Wankel which appeared in 1965. The 10A is a typically two rotor design that a a displacement of 491 cc for a sum of 982 cc in the entire engine. These were the begining of the mainstream rotor dimensions with a 60 mm (2.4 in) depth.

10A Rotary Engine

The rotor housing were crated with sand-cast aluminum plateds with chrome, and the aluminum sides were coated with molten carbon steel which strengthed the housing. Then cast iron was used for the rotors, and the eccentric shafts were a chrome-molydenum steel that was very expensive. Adding the alumnium/carbon apexals address the problem with chatter marks.


10A 0810
Production: 1965 - 1968
Rotors: 2x49 cc
Power: 110 hp (82 kW) (gross)
Torque: 96 ft.lbf (130 Nm) (gross)
Applications: 1965-1967 Cosmo proto
1967-1968 Cosmo L10A
10A 0813
Production: 1968 - 1973
Rotors: 2x491 cc
Power: 128 hp (95 kW) (gross)
Torque: 103 ft.lbf (140 Nm) (gross)
Applications: 1968-1972 Cosmo L10B
10A 0820
Production: 1968 - 1973
Rotors: 2x491 cc
Power: 100 hp (75 kW) (gross)
Torque: 98 ft.lbf (133 Nm) (gross)
Applications: 1968-1973 R100
10A 0866
Production: 1972 - 1974
Rotors: 2x491 cc
Power: 105 hp (78 kW) (gross)
Torque: 99.5 ft.lbf (135 Nm) (gross)
Applications: 1968-1973 R100 (Japan)
The first 10A motor that was created is the 0810, it was used in the Series I Cosmo from May, 1965 to July, 1968. The cosmo and the revolutionary engine at the time were called L10A models. Their gross output was 110hp (82 kW) at 7000 RPM and 130 Nm (96 ft/lbf) at 3500 rpm. Although both of theses numbers were most likely optimistic figures.

Mazda Cosmo SportInside the 10A there are twin side intake ports per rotor, each fed by a one of four carburetor barrels. Only one port per rotor were used under low loads for better fuel economy. For exhaust there was a single peripheral exhaust port that routed the hot gas through the coolest part of the rotor housing, and engine coolant flowed axillay instead than the racidal flow that was used by NSU. Surprisngly a bit of oil was mixed in with the intake charge to help lubricate the motor.

The 0810 was modified for racing Cosmos at the famous Nurburgring. These motors had both side and peripheral intake ports that were switched with a butterfly valve for low- and high-RPM usage.


  • 1965-1968 Mazda Cosmo Series I/L10A


The improved 0813 motor was featured in July, 1968 in the Series II/L10B Cosmo. The consutrction was similiar to the original 0810 but the ports and cabureation were changed to output 128 hp (96 kW) at 7000 RPM and 140 Nm (103 ft.lbf) at 5000 RPM. Please note that these were Japense net output estimates.


  • 1968-1972 Mazda Cosmo Series II/L10B


The 10A was greatly revised for the wide scale production of the R100/Familia Rotary. A lot the changes were made to help reduce the production cost of the motor. Some of theses modifications were the use of cast iron in the side housings, aka the plates, less-expensive molded alminum for the housings (instead of sand-cast), and finally the a new chrome-steel for the eccentric shaft. The port congfiguration reamined the same, although the exhaust was no longer routed around the rotor housing.

The Japanese-spec gross output was 100 hp (75 kW) at 7000 RPM and 98 ft/lbf (133 Nm) at 3500 RPM. With the use of less-expensive material, it did raise the weight of the engine from 224 lb (102 kg) to 268 lb (122 kg).


  • 1968-1973 Mazda R100/Familia Rotary

Mazda RX-30866

The last engine from the 10A family was the 0866 created in 1971. This motor featured a cast-iron thermal reactor which reduced exhaust emissions and re-tuned exhaust ports. The die-cast housing were then coated with a complete new process: TCP or the new Transplant Coating Process that featured spray on steel which is then was coated with chrome. The gross output was now 105 hp (78 kW) at 7000 RPM and 135 Nm (99.5 ft.lbf) at 3500 RPM.


  • 1972-1974 Mazda RX-3 (Japan-spec)

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Last Updated ( 29.10.2006 )
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