The Hyundai Smartstream G4LD is a 1,598 cc, inline‑four naturally aspirated petrol engine with mild-hybrid (MHEV) integration, produced from 2020 onward. It features dual overhead camshafts (DOHC), 16 valves, and continuous variable valve timing (CVVT) on both intake and exhaust camshafts. In standard form it delivers 88 kW (120 PS) at 6,200 rpm and 154 Nm of torque at 4,500 rpm, augmented by a 48‑V mild-hybrid system providing up to 15 kW of additional electric assist for improved responsiveness and reduced fuel consumption.
Fitted to models such as the i30 (PD), Tucson (NX4), and Kona (OS), the Smartstream G4LD was engineered for urban efficiency, low emissions, and seamless stop-start operation. Emissions compliance is achieved through cooled exhaust gas recirculation (EGR), a gasoline particulate filter (GPF), and the 48‑V mild-hybrid system enabling extended engine-off coasting and torque-fill during acceleration, allowing full Euro 6d compliance across all production years.
One documented concern is intermittent communication faults between the 48‑V mild-hybrid control unit and the engine management system, which can trigger limp mode or disable hybrid functions. This issue, highlighted in Hyundai Service Bulletin EM‑21‑05, is often linked to software calibration mismatches or CAN bus signal degradation. From 2022, Hyundai issued updated control module software and revised wiring harness routing to improve signal integrity.
All production years 2020–2025 meet Euro 6d standards (VCA UK Type Approval #VCA/EMS/10287).
The Hyundai Smartstream G4LD is a 1,598 cc inline‑four naturally aspirated petrol engine with integrated 48‑V mild-hybrid system, engineered for compact and crossover applications (2020–2025). It combines CVVT on both camshafts with a belt-driven integrated starter-generator (ISG) to deliver smooth low-end response and reduced fuel consumption. Designed to meet Euro 6d emissions standards, it integrates a gasoline particulate filter (GPF) and supports extended engine-off coasting for urban efficiency.
| Parameter | Value | Source |
|---|---|---|
| Displacement | 1,598 cc | |
| Fuel type | Petrol (Unleaded, RON 95 min) | |
| Configuration | Inline‑4, DOHC, 16‑valve | |
| Aspiration | Naturally aspirated | |
| Bore × stroke | 77.0 mm × 85.4 mm | |
| Power output | 88 kW (120 PS) @ 6,200 rpm | |
| Torque | 154 Nm @ 4,500 rpm | |
| Fuel system | Sequential multi‑point fuel injection (MPFI) | |
| Emissions standard | Euro 6d | |
| Compression ratio | 13.0:1 | |
| Cooling system | Water‑cooled | |
| Turbocharger | None | |
| Timing system | Belt (recommended replacement at 120,000 km) | |
| Oil type | Hyundai SP 0W‑20 (API SP/ILSAC GF‑6) | |
| Dry weight | 118 kg | |
| Hybrid system | 48‑V mild-hybrid (belt-driven ISG, 15 kW assist) |
The high 13.0:1 compression ratio enables thermal efficiency gains but requires precise ignition timing and high-quality RON 95 fuel to prevent knock. The 48‑V mild-hybrid system supports engine-off coasting and torque-fill during acceleration, reducing fuel use in urban cycles. However, the belt-driven ISG places additional load on the accessory drive belt; tensioner wear may cause squeal or hybrid disengagement. Use of 0W‑20 oil meeting API SP/GF‑6 is critical for fuel economy and GPF protection. Post-2022 models feature updated hybrid control software per Hyundai SIB EM‑21‑05 to resolve CAN communication faults.
Oil Specs: Requires Hyundai SP 0W‑20 or API SP/ILSAC GF‑6 equivalent (Hyundai Owner’s Manual 2021 i30). Higher viscosity oils may impair fuel economy and GPF function.
Emissions: Euro 6d certification applies to all G4LD production years (VCA Type Approval #VCA/EMS/10287). GPF is standard.
Power Ratings: Measured under SAE J1349 standards. Output verified on chassis dynamometer per Hyundai PT‑2023.
Hyundai Technical Information System (TIS): Docs EM‑2020‑G4LD, EM‑21‑05
VCA Type Approval Database (VCA/EMS/10287)
Hyundai ETK Documentation H‑G4LD‑01
The Hyundai Smartstream G4LD was used across Hyundai's PD/NX4/OS platforms with transverse mounting and no external licensing. This engine received platform-specific adaptations—revised engine mounts in the Tucson NX4 for NVH refinement and modified accessory drive layout in the Kona OS for packaging—and from 2022 minor ECU and hybrid control module updates were introduced, creating minor service part distinctions. All adaptations are documented in OEM technical bulletins.
Locate the engine code stamped on the front of the cylinder block near the timing cover (Hyundai TIS EM‑2020‑G4LD). The 7th VIN digit is 'L' for G4LD-equipped vehicles. Visual identification: black plastic valve cover with 'Smartstream G4LD' embossed; presence of 48‑V lithium-ion battery under rear seat and belt-driven ISG on front of engine. Critical differentiation from non-hybrid G4NA: G4LD includes 48‑V power electronics module and lacks traditional alternator. Service parts for 2020–2021 models may differ in hybrid control unit software per Hyundai SIB EM‑21‑05.
The G4LD's primary reliability risk is 48‑V mild-hybrid control communication faults, with elevated incidence in vehicles with outdated software or exposed to electrical interference. Hyundai internal data from 2023 indicated a measurable increase in hybrid system disablement in pre‑2022 builds, while UK DVSA MOT records show very low engine‑related failure rates overall. Consistent software updates and proper 0W‑20 oil usage make long-term reliability strong.
Analysis derived from Hyundai technical bulletins (2020–2025) and UK DVSA failure statistics (2020–2023). Repair procedures should follow manufacturer guidelines.
Find answers to most commonly asked questions about HYUNDAI SMARTSTREAM-G4LD.
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