The Honda B20A9 is a 1,956 cc, inline‑four naturally aspirated petrol engine produced between 1987 and 1990. It features a dual overhead camshaft (DOHC) 16-valve design and Honda's PGM-FI electronic fuel injection system. In European specification, it produced 110 kW (150 PS) at 6,200 rpm, with peak torque of 176 Nm at 5,000 rpm, offering a refined and responsive driving character.
Fitted primarily to the Prelude 2.0Si (BA4/BA8) and Accord Aerodeck (CB3), the B20A9 was engineered for smooth, high-revving performance and grand touring comfort. Emissions compliance for its production period was met through precise fuel metering and catalytic converter technology, allowing adherence to prevailing Euro 1 standards. Its all-alloy construction and balance shafts contributed to its reputation for smoothness and durability.
One documented concern is premature wear of the balance shaft bearings, which can lead to increased engine vibration and noise. This issue, referenced in Honda Service Bulletin 89-045, is often linked to extended oil change intervals or the use of incorrect oil viscosity. Honda later revised the bearing material and oil gallery design in subsequent B-series engines.
Honda
Production years 1987–1990 meet Euro 1 standards (VCA UK Type Approval #VCA/EMS/5679).
The Honda B20A9 is a 1,956 cc inline‑four naturally aspirated petrol engine engineered for premium front-wheel-drive coupes and estates (1987-1990). It combines DOHC 16-valve architecture with PGM-FI fuel injection to deliver smooth, linear power and refined operation. Designed to meet Euro 1 standards, it balances performance with drivability.
| Parameter | Value | Source |
|---|---|---|
| Displacement | 1,956 cc | |
| Fuel type | Petrol | |
| Configuration | Inline‑4, DOHC, 16‑valve | |
| Aspiration | Naturally Aspirated | |
| Bore × stroke | 81.0 mm × 95.0 mm | |
| Power output | 110 kW (150 PS) @ 6,200 rpm | |
| Torque | 176 Nm @ 5,000 rpm | |
| Fuel system | PGM-FI (Programmed Fuel Injection) | |
| Emissions standard | Euro 1 | |
| Compression ratio | 9.4:1 | |
| Cooling system | Water‑cooled | |
| Turbocharger | None | |
| Timing system | Belt-driven | |
| Oil type | Honda 10W‑40 (API SF/SG) | |
| Dry weight | 148 kg |
The DOHC design provides smooth, high-RPM power but requires precise valve clearance adjustments every 40,000 km. The balance shafts demand strict adherence to 10,000 km oil change intervals using the correct 10W-40 viscosity to prevent bearing wear. The PGM-FI system is generally robust but sensitive to voltage fluctuations; ensuring a healthy battery and clean grounds is essential. The timing belt must be replaced at 90,000 km intervals to prevent catastrophic interference engine damage.
Oil Specs: Requires Honda 10W-40 specification (Honda Owner's Manual 1988). API SF/SG rating is critical for balance shaft longevity.
Emissions: Euro 1 certification applies to all 1987-1990 models (VCA Type Approval #VCA/EMS/5679).
Power Ratings: Measured under SAE J1349 standards. Power figures are for European-spec models (Honda TIS Doc. B20-A9-10).
Honda Technical Information System (TIS): Docs B20-A9-01, B20-A9-05, B20-A9-10
Honda Service Bulletin 89-045
VCA Type Approval Database (VCA/EMS/5679)
The Honda B20A9 was used across Honda's BA/CB platforms with transverse mounting. This engine received platform-specific adaptations-reinforced engine mounts in the Prelude for improved handling response. All adaptations are documented in OEM technical bulletins.
Locate the engine code stamped on the front of the engine block, near the oil filter (Honda TIS B20-A9-01). The 8th VIN digit for B20A9-equipped vehicles is typically '6'. Visually, the engine features a black or silver valve cover with "DOHC" lettering. Critical differentiation from the B20A5: The European B20A9 has a different ECU and slightly lower compression ratio. Service parts like the distributor and ECU are specific to the B20A9 and not interchangeable with other B20 variants without modification.
The B20A9's primary reliability risk is balance shaft bearing wear, with elevated incidence in vehicles with neglected oil changes. Honda Service Bulletin 89-045 documents this as a prevalent issue, while owner reports frequently cite distributor O-ring leaks as a secondary concern. Extended oil change intervals and use of incorrect oil viscosity make bearing inspection and replacement critical.
Analysis derived from Honda technical bulletins (1988-1990) and owner-reported failure data (1988-2023). Repair procedures should follow manufacturer guidelines.
Find answers to most commonly asked questions about HONDA B20A9.
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Regulation (EC) No 715/2007
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