The Honda C30A4 is a 2,977 cc, naturally aspirated V6 petrol engine produced between 1990 and 1998. It features a dual overhead camshaft (DOHC) with 24 valves and Honda's VTEC (Variable Valve Timing and Lift Electronic Control) system. This design prioritized a broad, flat torque curve and high-RPM power, producing 177 kW (240 PS) and 285 Nm of torque.
Fitted exclusively to the first-generation Honda NSX (NA1 chassis), the C30A4 was engineered for exotic supercar performance with an emphasis on throttle response, revving freely to its 8,000 rpm redline. Emissions compliance for its production period was achieved through precise fuel metering and a high-efficiency catalytic converter, meeting the applicable standards for Japanese, North American, and European markets at the time.
One documented service concern is premature wear of the VTEC oil pressure switch, which can cause the VTEC system to engage erratically or not at all. This issue, addressed in Honda Service Bulletin 94-082, is often linked to age-related failure of the switch's internal diaphragm. Honda later revised the switch design for improved longevity.
Production years 1990–1998 meet the emissions standards applicable to their respective markets (e.g., US EPA Tier 0/1, Japanese 1988 regulations, EU Directive 91/441/EEC).
The Honda C30A4 is a 2,977 cc V6 naturally aspirated petrol engine engineered for the NSX supercar (1990-1998). It combines DOHC 24-valve architecture with VTEC to deliver a seamless transition from low-end torque to high-RPM power. Designed to meet the emissions standards of its era, it balances exotic performance with Honda's hallmark reliability.
| Parameter | Value | Source |
|---|---|---|
| Displacement | 2,977 cc | |
| Fuel type | Petrol | |
| Configuration | V6, DOHC, 24‑valve | |
| Aspiration | Naturally Aspirated | |
| Bore × stroke | 90.0 mm × 78.0 mm | |
| Power output | 177 kW (240 PS) @ 7,100 rpm | |
| Torque | 285 Nm @ 5,400 rpm | |
| Fuel system | Honda PGM-FI (Programmed Fuel Injection) | |
| Emissions standard | US EPA Tier 0/1, Japanese 1988, EU 91/441/EEC | |
| Compression ratio | 10.2:1 | |
| Cooling system | Water‑cooled | |
| Turbocharger | None | |
| Timing system | Belt-driven | |
| Oil type | SAE 5W-30 (API SH or equivalent) | |
| Dry weight | Not Available |
The VTEC system provides a thrilling surge of power above 5,800 rpm but requires strict adherence to the 90,000 km timing belt replacement interval to prevent catastrophic engine failure. Using the specified SAE 5W-30 oil ensures optimal lubrication for the high-revving valvetrain. The VTEC oil pressure switch is susceptible to age-related failure; vehicles exhibiting erratic VTEC engagement should have it inspected per Honda SIB 94-082. The PGM-FI system demands a stable electrical system for optimal performance.
Oil Specs: Requires SAE 5W-30 meeting API SH specification (Honda Owner's Manual). Modern equivalents like API SN are acceptable.
Emissions: Certification applies to 1990-1998 models for their respective markets (US EPA, Japanese MoT, EU).
Power Ratings: Measured under SAE net standards. Output is consistent across all markets for this engine code.
Honda Service Manual: C30A4 Engine (Pub. No. 91000-SK3-003)
Honda Owner's Manual: 1991 NSX
Honda Service Information Bulletin: 94-082
US Environmental Protection Agency (EPA) Certification Database
The Honda C30A4 was used exclusively in Honda's NA1 platform with mid-engine, longitudinal mounting. This engine received minor revisions for the 1994 model year (C30A5), primarily involving the VTEC oil pressure switch and minor ECU updates, creating interchange limits for certain components. All adaptations are documented in OEM technical bulletins.
Locate the engine code stamped on the front of the engine block, near the crankshaft pulley (Honda Service Manual). Visually, it can be identified by its distinctive V6 configuration, dual camshaft covers on each bank, and the prominent VTEC solenoid on the intake manifold. Critical differentiation from the C30A5: The C30A4 uses an earlier design VTEC oil pressure switch. While the engines are largely interchangeable, the switch and associated wiring harness may differ.
The C30A4's primary reliability risk is VTEC oil pressure switch failure, with elevated incidence in high-mileage vehicles. Honda SIB 94-082 documents this issue, while owner reports frequently cite it as a source of drivability complaints. Adherence to the critical 90,000 km timing belt interval is paramount for engine survival.
Analysis derived from Honda technical bulletins (1990-1998) and aggregated owner repair data (1995-2023). Repair procedures should follow manufacturer guidelines.
Find answers to most commonly asked questions about HONDA C30A4.
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