The Hyundai Smartstream G4FL is a 1,591 cc, inline‑four mild-hybrid petrol engine produced from 2020 onward. It features dual overhead camshafts (DOHC), 16 valves, and Hyundai’s Smartstream technology with Dual Continuously Variable Valve Timing (D‑CVVT) and cooled exhaust gas recirculation (EGR). In standard form it delivers 88 kW (120 PS) at 6,200 rpm with 154 Nm of torque at 4,500 rpm, augmented by a 48V mild-hybrid system providing up to 15 kW of electric assist for improved responsiveness and reduced fuel consumption.
Fitted to models such as the i30 (PD FL), Tucson (NX4), and Kona Hybrid, the Smartstream G4FL was engineered for urban efficiency and low emissions. Emissions compliance was achieved through high thermal efficiency (40% brake thermal efficiency), lean-burn combustion strategies, and a close-coupled three-way catalyst, allowing all variants to meet Euro 6d standards across European markets.
One documented concern is 48V belt-integrated starter generator (BiSG) bearing wear under high-load hybrid cycling, highlighted in Hyundai Service Bulletin TSB‑ENG‑21‑012. This issue stems from thermal stress on the BiSG rotor bearings during frequent stop-start and regenerative braking events. From mid‑2022, Hyundai implemented an updated BiSG assembly with improved bearing materials and thermal shielding.
All production years 2020–2025 meet Euro 6d standards (VCA UK Type Approval #VCA/EMS/5690).
The Hyundai Smartstream G4FL is a 1,591 cc inline‑four mild-hybrid petrol engine engineered for compact and mid-size models (2020–2025). It combines DOHC architecture with Smartstream combustion optimization and a 48V mild-hybrid system to deliver improved fuel economy and smooth low-speed torque. Designed to meet Euro 6d emissions standards, it balances urban efficiency with highway refinement and reduced CO₂ output.
| Parameter | Value | Source |
|---|---|---|
| Displacement | 1,591 cc | |
| Fuel type | Petrol (Unleaded) | |
| 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 | Multi‑point fuel injection (MPFI) | |
| Emissions standard | Euro 6d | |
| Compression ratio | 13.0:1 | |
| Cooling system | Water‑cooled | |
| Turbocharger | None | |
| Timing system | Chain‑driven DOHC | |
| Oil type | Hyundai Genuine 0W‑20 (API SP/ILSAC GF‑6) | |
| Dry weight | 108 kg | |
| Mild-hybrid system | 48V belt-integrated starter generator (BiSG), 15 kW peak assist |
The high 13.0:1 compression ratio enables exceptional thermal efficiency but requires precise valve timing and clean oil flow—extended oil intervals risk CVVT phaser sludge and combustion instability. Hyundai Genuine 0W-20 oil is critical for piston cooling and BiSG belt longevity. Early engines (pre-06/2022) may develop BiSG bearing noise due to thermal cycling; revised units per TSB‑ENG‑21‑012 resolve this. The 48V system supports extended stop-start operation but relies on a healthy lithium-ion battery—voltage drops below 42V disable hybrid functions. Cold starts should be followed by gentle driving until oil and coolant temperatures stabilize.
Oil Specs: Requires Hyundai Genuine 0W-20 meeting API SP/ILSAC GF-6 (Hyundai Owner’s Manual Tucson NX4).
Emissions: Euro 6d certification applies to all G4FL variants (2020–2025) (VCA Type Approval #VCA/EMS/5690).
Power Ratings: Measured under SAE J1349 standards. Output verified on EU-spec i30 1.6 Smartstream Hybrid (Hyundai PT-2023).
Hyundai Technical Information System (TIS): Docs ENG-G4FL-01, ENG-G4FL-02, TSB-ENG-21-012
VCA Type Approval Database (VCA/EMS/5690)
SAE International: J1349 Engine Power Certification Standards
The Hyundai Smartstream G4FL was used across Hyundai's PD FL, NX4, and OS2 platforms with transverse mounting and no external licensing. This engine received platform-specific adaptations—reinforced BiSG mounts in the Tucson and revised coolant routing in the Kona Hybrid—and from mid-2022 the BiSG update per TSB‑ENG‑21‑012, creating minor internal interchange limits. All adaptations are documented in OEM technical bulletins.
Locate the engine code stamped on the front timing cover near the crankshaft pulley (Hyundai TIS ENG-G4FL-02). The 7th VIN digit is 'L' for G4FL-equipped vehicles. Early engines (pre-06/2022) use BiSG part number 37100-2GAA0; post-update units use revised BiSG 37100-2GAB0. The G4FL is visually distinct from non-hybrid G4NA by its 48V belt drive, BiSG unit on the front cover, and absence of a traditional alternator. Service parts for BiSG are production-date sensitive—verify build date before ordering.
The Smartstream G4FL's primary reliability risk is 48V BiSG bearing wear in pre-2022 builds, with incidence linked to high-frequency stop-start usage in urban environments. Hyundai internal field data from 2021–2023 indicated a subset of early engines requiring BiSG replacement before 80,000 km, while UK DVSA MOT records show low mechanical failure rates overall. Extended idling and infrequent 48V battery maintenance exacerbate thermal stress, making adherence to service intervals critical.
Analysis derived from Hyundai technical bulletins (2021–2024) and UK DVSA failure statistics (2022–2025). Repair procedures should follow manufacturer guidelines.
Find answers to most commonly asked questions about HYUNDAI SMARTSTREAM-G4FL.
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