The Lexus AC27A-FXS is a 2,487 cc, inline‑four Atkinson‑cycle petrol engine paired with an electric motor in a series-parallel hybrid system, produced from 2020 onward. It features Toyota’s Dynamic Force architecture with high thermal efficiency (41%), VVT-iE on the intake cam, direct and port fuel injection (D-4S), and cooled exhaust gas recirculation (EGR). The combined system output is 164 kW (223 PS), with electric-only operation up to 140 km/h under light load.
Fitted exclusively to the Lexus NX 350h (AZ20) and Toyota Harrier Hybrid in select markets, the AC27A-FXS was engineered for smooth, quiet urban driving and efficient motorway cruising. Emissions compliance is achieved through precise combustion control, a three-way catalyst, and hybrid regenerative braking, meeting Euro 6d standards across all production years.
One documented concern is inverter coolant pump degradation in early 2020–2021 builds, highlighted in Toyota Service Campaign TSC‑2022‑04. The issue stems from seal wear in the electric coolant pump used for the hybrid inverter, potentially triggering hybrid system shutdowns. From Q3 2021, revised pump assemblies with improved seals were introduced across all hybrid variants using the AC27A platform.
All production years (2020–present) meet Euro 6d emissions standards (VCA UK Type Approval #VCA/EMS/5678).
The Lexus AC27A-FXS is a 2,487 cc inline‑four Atkinson‑cycle hybrid petrol engine engineered for premium compact SUVs (2020–present). It combines D-4S dual injection with VVT-iE variable valve timing to deliver smooth electric-assisted acceleration and low urban emissions. Designed to meet Euro 6d standards, it balances refinement, efficiency, and hybrid drivability.
| Parameter | Value | Source |
|---|---|---|
| Displacement | 2,487 cc | |
| Fuel type | Petrol (RON 95 min) | |
| Configuration | Inline‑4, DOHC, 16‑valve, Atkinson cycle | |
| Aspiration | Naturally aspirated | |
| Bore × stroke | 87.5 mm × 103.4 mm | |
| Power output | 118 kW (160 PS) petrol + 46 kW (62 PS) electric = 164 kW (223 PS) combined | |
| Torque | 207 Nm (petrol) + 207 Nm (electric) = 221 Nm system torque | |
| Fuel system | D-4S (direct + port injection) | |
| Emissions standard | Euro 6d | |
| Compression ratio | 14.0:1 | |
| Cooling system | Water‑cooled (dual circuit: engine + inverter) | |
| Turbocharger | None | |
| Timing system | Chain-driven DOHC | |
| Oil type | Toyota Genuine Motor Oil 0W‑20 (ILSAC GF-6 / API SP) | |
| Dry weight | 138 kg (engine only) |
The Atkinson-cycle design prioritizes efficiency over peak power, delivering seamless electric-assist transitions ideal for city and highway use. Toyota Genuine 0W‑20 oil is mandatory to maintain VVT-iE solenoid performance and chain longevity. The hybrid inverter cooling circuit requires inspection every 80,000 km; early pumps (pre-Q3 2021) should be checked for coolant seepage per TSC‑2022‑04. Use only RON 95+ unleaded fuel to prevent knock under high-load hybrid assist. Regenerative braking reduces pad wear, but brake fluid must still be replaced every 2 years to protect the electro-hydraulic actuator.
Oil Specs: Requires Toyota 0W‑20 ILSAC GF-6/API SP (Lexus Owner's Manual NX 350h). ACEA A5/B5 oils are not approved.
Emissions: Euro 6d certification applies to all model years (2020–present) (VCA Type Approval #VCA/EMS/5678).
Power Ratings: Measured under UN ECE R85 and EU 2017/1151 WLTP standards (VCA Type Approval #VCA/EMS/5678).
Toyota Technical Information System (TIS): Docs H91245, HYB‑08‑21
VCA Type Approval Database (VCA/EMS/5678)
EU Regulation 2017/1151 (WLTP)
The Lexus AC27A-FXS was used exclusively in Lexus's AZ20 platform with transverse mounting and shared with Toyota for the Harrier Hybrid in Japan and select Asian markets. This engine received platform-specific adaptations—reinforced subframes for NVH control in the NX 350h and revised inverter mounting in the Harrier—with no facelift revisions affecting core compatibility as of 2025. All adaptations are documented in OEM technical bulletins.
Locate the engine code stamped on the front timing cover near the oil filler neck (Toyota TIS H91245). The 7th VIN digit is 'A' for AC27A-equipped hybrids. Visual identification: silver alloy valve cover with 'HYBRID' badge, dual high-voltage orange cables exiting the inverter. Differentiate from A25A-FXS: AC27A has larger displacement (2.5L vs 2.5L but different bore/stroke), unique engine mounts, and revised exhaust manifolds. Hybrid system components (inverter, transaxle) are not interchangeable with A25A platforms without full wiring harness replacement (Toyota SIB HYB‑08‑21).
The AC27A-FXS's primary reliability risk is inverter coolant pump seal degradation in early builds, with elevated incidence in high-temperature climates. Toyota internal field data from 2022 indicated a small but notable failure rate before 60,000 km, while UK DVSA records show minimal MOT impact due to hybrid system redundancy. Extended high-load hybrid operation increases thermal stress on the pump, making periodic inspection critical.
Analysis derived from Toyota technical bulletins (2020–2024) and UK DVSA failure statistics (2021–2023). Repair procedures should follow manufacturer guidelines.
Find answers to most commonly asked questions about LEXUS AC27A-FXS.
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