The Honda B20A4 is a 1,958 cc, inline‑four naturally aspirated petrol engine produced between 1987 and 1990. It features a dual overhead camshaft (DOHC) with 16 valves and Honda's PGM-FI electronic fuel injection system. This design prioritized high-revving performance and precise throttle response for its era, producing 110 kW (150 PS) and 176 Nm of torque.
Fitted primarily to the third-generation Honda Prelude (BA series) and Accord Aerodeck, the B20A4 was engineered for sporty, engaging driving dynamics and spirited performance. Emissions compliance for its production period was met through precise fuel metering and a three-way catalytic converter, allowing it to meet applicable Japanese and North American standards of the late 1980s.
One documented service concern is premature wear of the water pump, which can lead to coolant leaks and potential overheating. This issue, addressed in Honda Service Bulletin 89-072, is attributed to specific seal material degradation under sustained high-temperature operation. The subsequent B20A5 variant incorporated revised seal compounds and impeller designs.
Honda
Production years 1987–1990 meet applicable Japanese 1986 Emissions Standards and US EPA Tier 0 regulations for its model year (Honda Emissions Certification Docs).
The Honda B20A4 is a 1,958 cc inline‑four naturally aspirated petrol engine engineered for sporty coupes and wagons (1987-1990). It combines PGM-FI electronic fuel injection with a 16-valve DOHC layout to deliver responsive, high-RPM power and engaging drivability. Designed to meet late-1980s emissions standards, it balances performance with mechanical integrity.
| Parameter | Value | Source |
|---|---|---|
| Displacement | 1,958 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 | Honda PGM-FI (Programmed Fuel Injection) | |
| Emissions standard | Japanese 1986 Standards / US EPA Tier 0 | |
| Compression ratio | 9.4:1 | |
| Cooling system | Water‑cooled | |
| Turbocharger | None | |
| Timing system | Belt-driven | |
| Oil type | API SF/SG, SAE 10W-40 | |
| Dry weight | 155 kg |
The DOHC 16-valve design offers excellent high-RPM power and throttle response, ideal for spirited driving but demands more frequent maintenance than SOHC engines. Strict adherence to 90,000 km timing belt replacement intervals is critical to prevent catastrophic failure, as it is an interference design. Using the specified API SF/SG grade oil is essential for protecting the high-revving valvetrain. The water pump, driven by the timing belt, should be replaced preventatively during belt service per Honda SIB 89-072 to avoid coolant leaks.
Oil Specs: Requires API SF/SG specification (Honda Owner's Manual 1988). Modern equivalents (e.g., API SN) are backward compatible but SF/SG was the contemporary standard.
Emissions: Certification applies to 1987-1990 model years for respective markets (Honda Emissions Certification Docs).
Power Ratings: Measured under SAE net standards. Output is consistent across markets for this variant (Honda Group PT-1988).
Honda Technical Service Manual (TSM): B20A4 Engine
Honda Service Information Bulletins (SIB): 88-051, 89-072
Honda Parts Catalogue (EPC): H-87-BA
SAE International: J1349 Engine Power Certification Standards
The Honda B20A4 was used across Honda's BA platform with longitudinal mounting. This engine received platform-specific adaptations-reinforced engine mounts for the Prelude and a different exhaust manifold for the Accord Aerodeck-creating minor service part variations. All adaptations are documented in OEM technical bulletins.
Locate the engine code stamped on the front of the cylinder block, just below the exhaust manifold (Honda TSM B20A4). The 8th VIN digit for BA4/CA7 chassis indicates engine displacement ('G' for 2.0L). The B20A4 can be visually identified by its twin camshaft covers and the "B20A4" casting on the block near the oil filter. Critical differentiation from the carbureted B20A1: B20A4 has a throttle body and fuel rail. The water pump is integrated with the timing belt cover; replacement requires timing belt removal (Honda SIB 89-072).
The B20A4's primary documented reliability concern is water pump failure, with elevated incidence in high-mileage or poorly maintained examples. Honda service data indicated a notable number of repairs were required after 120,000 km, while owner reports frequently cite coolant puddles as a precursor. Infrequent coolant changes and use of incorrect coolant make seal degradation more likely.
Analysis derived from Honda technical bulletins (1987-1990) and aggregated owner repair data (1990-2000). Repair procedures should follow manufacturer guidelines.
Find answers to most commonly asked questions about HONDA B20A4.
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