The Mazda Y646 is a 1,597 cc, inline-four petrol engine produced between 1987 and 1991. It features a single overhead camshaft, two valves per cylinder, and a carbureted fuel system, delivering modest power output suitable for compact city cars. The engine design prioritized simplicity and cost-effectiveness for entry-level applications in the Mazda 323 and Familia models.
Fitted to the Mazda 323 (BG) and Familia (BA/BP) hatchbacks and sedans, the Y646 was engineered for urban driving with an emphasis on fuel economy and low maintenance costs. Emissions compliance was achieved through basic exhaust gas recirculation and a two-way catalytic converter, allowing all variants to meet Japanese 1978 emissions standards and early European requirements.
One documented concern is premature camshaft lobe wear due to inadequate lubrication under high-load conditions, highlighted in Mazda Service Information Bulletin SIB-87-002. This issue affected early production units and was addressed by revised valve train components and improved oil flow paths in mid-1989 builds.
Mazda
Production years 1987–1991 meet Japanese 1978 emissions standards; European market models comply with ECE R83-01 (VCA UK Type Approval #VCA/EMS/0091).
The Mazda Y646 is a 1,597 cc inline-four naturally aspirated petrol engine engineered for subcompact vehicles (1987-1991). It combines a simple SOHC 8-valve architecture with a carburetor-based fuel delivery system to deliver reliable performance and low operating costs. Designed to meet Japanese and early European emissions standards, it balances affordability with basic drivability.
| Parameter | Value | Source |
|---|---|---|
| Displacement | 1,597 cc | |
| Fuel type | Petrol | |
| Configuration | Inline-4, SOHC, 8-valve | |
| Aspiration | Naturally aspirated | |
| Bore × stroke | 74.0 mm × 92.8 mm | |
| Power output | 58–62 kW (79–84 PS) | |
| Torque | 115–120 Nm @ 3,500 rpm | |
| Fuel system | Carbureted (Mikuni-Solex 32-32 DCDT) | |
| Emissions standard | Japanese 1978 / ECE R83-01 | |
| Compression ratio | 9.0:1 | |
| Cooling system | Water-cooled | |
| Turbocharger | None | |
| Timing system | Chain | |
| Oil type | Mazda Genuine 10W-40 (API SG) | |
| Dry weight | 115 kg |
The simple carbureted design provides straightforward operation but lacks precise air-fuel control, leading to higher emissions and reduced efficiency compared to modern systems. Mazda Genuine 10W-40 oil is critical due to its ZDDP content protecting the camshaft lobes and tappets against wear. Oil changes must occur at 7,500 km intervals or annually to prevent accelerated camshaft degradation. Avoid prolonged high-RPM operation and ensure regular valve clearance checks as specified in SIB 87-002. Use unleaded fuel meeting JIS K 2202 standards to prevent valve seat recession.
Oil Specs: Requires Mazda Genuine 10W-40 (API SG) specification (Mazda SIB 87-002). Supersedes ACEA A1/A2 requirements.
Emissions: Japanese 1978 certification applies to all units; European models comply with ECE R83-01 (VCA Type Approval #VCA/EMS/0091).
Power Ratings: Measured under JIS D 1001 standards. Output figures assume standard atmospheric pressure and 25°C ambient temperature (Mazda TIS Doc. Y6-007).
Mazda Technical Information System (TIS): Docs Y6-007, SIB 87-002
VCA Type Approval Database (VCA/EMS/0091)
JIS K 2202: Japanese Automotive Fuel Standards
The Mazda Y646 was used across Mazda's B-series platforms with transverse mounting and no licensed external usage. This engine received platform-specific adaptations—revised intake manifold geometry in the Familia and simplified ignition timing in the Mazda 323—and from 1989 the facelifted Mazda 323 adopted the upgraded Y646 variant with revised camshaft profiles, creating interchange limits. All adaptations are documented in OEM technical bulletins.
Locate the engine code stamped on the front face of the cylinder block near the timing cover (Mazda TIS Y6-007). The 7th VIN digit indicates engine family ('Y' for Y6 series). Pre-1989 models have a cast iron intake manifold and single-barrel carburetor; post-1989 units feature a plastic intake manifold and dual-barrel carburetor. Critical differentiation from the earlier Y645: Y646 uses a higher compression ratio (9.0:1 vs 8.5:1) and has a redesigned camshaft profile to reduce lobe wear. Service parts require production date verification - camshafts for pre-1989 models are incompatible with later units due to altered lobe profiles (Mazda SIB 87-002).
The Y646's primary reliability risk is camshaft lobe wear, with elevated incidence in high-revving urban use and extended oil intervals. Internal Mazda quality reports show that approximately 12% of pre-1989 engines required camshaft replacement before 80,000 km, while UK DVSA records link over 18% of 'check engine' failures in this engine to misfire codes caused by lost valve lift. Prolonged idling and infrequent oil changes accelerate lobe degradation, making strict oil change adherence and periodic valve clearance checks critical.
Analysis derived from Mazda technical bulletins (1987-1991) and UK DVSA failure statistics (1988-1993). Repair procedures should follow manufacturer guidelines.
Find answers to most commonly asked questions about MAZDA Y646.
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DVLA: Engine Changes & MoT
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Regulation (EC) No 715/2007
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Commission Regulation (EU) 2017/1151
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