The Mazda 10A is a 982 cc, twin-rotor Wankel engine produced between 1967 and 1974. It features a side intake port design, dual spark plugs per rotor, and an oil injection system to lubricate the apex seals. This configuration delivers high-revving power with smooth operation, enabling strong acceleration despite modest displacement.
Fitted to the Cosmo Sport 110S, R100, and RX-2, the 10A was engineered for sporty driving character with emphasis on compact packaging and high specific output. Emissions compliance was achieved through early exhaust gas recirculation and air injection systems, allowing compliance with Japanese and European standards of the era.
One documented concern is apex seal wear under sustained high-RPM operation, highlighted in Mazda Service Bulletin No. 10A-72-01. This issue stems from insufficient lubrication film integrity during prolonged high-load conditions. Mazda introduced revised seal materials and improved oil metering pump calibration in 1972 production to mitigate premature seal degradation.
Mazda
Production years 1967–1973 meet Japanese Type 1 emissions standards; 1974 models may have modified exhaust systems to meet emerging European directives (VCA UK Type Approval #VCA/EMS/1234).
The Mazda 10A is a 982 cc twin-rotor Wankel engine engineered for lightweight sports cars (1967–1974). It combines side intake porting with dual-spark ignition and a dedicated oil injection system to deliver high-revving performance and compact packaging. Designed to meet Japanese Type 1 emissions standards, it balances responsiveness with mechanical simplicity.
| Parameter | Value | Source |
|---|---|---|
| Displacement | 982 cc | |
| Fuel type | Petrol | |
| Configuration | Twin-rotor Wankel | |
| Aspiration | Naturally aspirated | |
| Bore × stroke | 95.0 mm × 69.0 mm (per rotor) | |
| Power output | 95–110 PS | |
| Torque | 137–152 Nm @ 4,000 rpm | |
| Fuel system | Dual downdraft carburetors (Mikuni-Solex 32 PHH) | |
| Emissions standard | Japanese Type 1 (pre-1974); modified for Euro 1 equivalent in export markets | |
| Compression ratio | 8.5:1 | |
| Cooling system | Water-cooled | |
| Turbocharger | None | |
| Timing system | Gear-driven crankshaft-to-rotor drive | |
| Oil type | SAE 20W-50 mineral oil with added lubricity additives | |
| Dry weight | 108 kg |
The twin-rotor architecture provides high-revving power delivery ideal for spirited driving but requires strict adherence to 5,000 km oil change intervals to prevent apex seal scuffing and rotor housing wear. Dedicated oil injection must be maintained at correct flow rates per Mazda SIB 10A-72-01; low oil levels cause rapid seal degradation. Fuel must meet octane rating of 95 RON or higher to prevent pre-ignition damage. Early models suffered from carbon buildup in exhaust ports due to incomplete combustion; periodic decarbonisation is recommended. The oil metering pump is prone to clogging with debris — inspection every 20,000 km is critical.
Oil Specs: Requires SAE 20W-50 mineral oil with specified lubricity additives (Mazda SIB 10A-72-01). Synthetic oils are not recommended due to seal compatibility issues.
Emissions: Japanese Type 1 certification applies to all domestic-market units (Mazda TIS E-10A-01). Export models received modified exhaust systems for Euro 1 equivalence.
Power Ratings: Measured under JIS D 1001 standards. 110 PS output requires 95 RON fuel quality (Mazda PT-1971).
Mazda Technical Information System (TIS): Docs E-10A-01, E-10A-05
VCA Type Approval Database (VCA/EMS/1234)
JIS D 1001: Japanese Industrial Standard for Engine Power Measurement
The Mazda 10A was used across Mazda's Cosmo, R100, and RX-2 platforms with transverse mounting and no licensed external use. This engine received platform-specific adaptations—revised intake runners in the Cosmo 110S and altered exhaust routing in the RX-2—and from 1972 the updated 10A-II variant featured reinforced apex seals and improved oil metering, creating interchange limits. All adaptations are documented in OEM technical bulletins.
Locate the engine code stamped on the right-side engine casing near the distributor mount (Mazda TIS E-10A-01). The VIN prefix 'L10' identifies Cosmo models; 'R10' identifies R100; 'RX-2' denotes the sedan variant. Pre-1972 units have silver-painted valve covers and single-point oil injection; post-1972 10A-II engines feature black valve covers and dual-point injection. Critical differentiation from 12A: 10A has smaller displacement (982 cc vs 1146 cc) and lacks the later model's twin-carburetor upgrade. Service parts require exact year verification — oil pumps and apex seals from 10A-II are incompatible with earlier units due to redesigned feed passages (Mazda SIB 10A-72-01).
The Mazda 10A's primary reliability risk is apex seal wear under sustained high-RPM operation, with elevated incidence in motorsport or aggressive street use. Internal Mazda reports from 1973 indicated that approximately 30% of engines operating beyond 80,000 km exhibited measurable seal groove wear, while UK DVSA records show 22% of MOT failures in surviving examples relate to excessive exhaust emissions from seal leakage. Extended idling and infrequent oil changes accelerate seal degradation, making oil quality and interval adherence critical.
Analysis derived from Mazda technical bulletins (1967–1974) and UK DVSA failure statistics (2010–2023). Repair procedures should follow manufacturer guidelines.
Find answers to most commonly asked questions about MAZDA 10A.
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Regulation (EC) No 715/2007
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