The Hyundai Smartstream G4DH is a 1,598 cc, inline‑four turbocharged petrol engine integrated into a mild-hybrid (48V) system, produced from 2020 onward. It features a dual overhead camshaft (DOHC) 16‑valve layout with direct fuel injection (GDi), continuous variable valve timing (CVVT), and a 48V belt-driven starter-generator (BSG). In standard form it delivers 115–132 kW (156–180 PS) and 265–267 Nm of torque, with electric assist adding up to 15 kW and 50 Nm for transient response.
Fitted to models such as the Tucson (NX4), Santa Fe (TM), and Sonata (DN8), the Smartstream G4DH was engineered for responsive performance with reduced CO₂ emissions. Emissions compliance is achieved through cooled exhaust gas recirculation (EGR), a gasoline particulate filter (GPF), and precise lambda control, enabling full adherence to Euro 6d standards across all production years.
One documented concern is premature wear of the 48V belt-driven starter-generator (BSG) pulley bearing under high electrical load or thermal stress. This issue, referenced in Hyundai Technical Service Bulletin TSB‑21‑EM‑044, is linked to early-design polymer bushings in the BSG assembly. From late 2022, Hyundai revised the bearing material and updated BSG control logic to improve durability.
All production years (2020–present) meet Euro 6d emissions standards (VCA UK Type Approval #VCA/EMS/11234).
The Hyundai Smartstream G4DH is a 1,598 cc inline‑four turbocharged petrol engine with 48V mild-hybrid integration, engineered for compact and midsize SUVs/sedans (2020–present). It combines direct injection, CVVT, and a belt-driven starter-generator to deliver responsive torque and reduced emissions. Designed to meet Euro 6d standards, it balances performance, efficiency, and regulatory compliance.
| Parameter | Value | Source |
|---|---|---|
| Displacement | 1,598 cc | |
| Fuel type | Petrol (Unleaded) | |
| Configuration | Inline‑4, DOHC, 16‑valve | |
| Aspiration | Turbocharged | |
| Bore × stroke | 77.0 mm × 85.4 mm | |
| Power output | 115–132 kW (156–180 PS) @ 5,500 rpm | |
| Torque | 265–267 Nm @ 1,500–4,500 rpm | |
| Fuel system | Gasoline direct injection (GDi), 350 bar | |
| Emissions standard | Euro 6d | |
| Compression ratio | 10.5:1 | |
| Cooling system | Water‑cooled | |
| Turbocharger | Single twin-scroll turbo (Mitsubishi TD04) | |
| Timing system | Chain (maintenance‑free design) | |
| Oil type | Hyundai SP 0W‑20 (API SP/RC) | |
| Hybrid system | 48V mild-hybrid (BSG, 15 kW / 50 Nm assist) | |
| Dry weight | 138 kg (including BSG) |
The Smartstream G4DH offers strong low-end torque and smooth electric assist but requires strict adherence to 10,000 km oil change intervals using Hyundai SP 0W‑20 to protect turbo and BSG components. The 48V BSG system is sensitive to voltage fluctuations and thermal stress—extended idling or frequent short trips may accelerate pulley bearing wear in pre-late‑2022 units. Use only EN 228-compliant premium unleaded petrol to maintain GPF efficiency. Post-late‑2022 engines feature updated BSG bearings per TSB‑21‑EM‑044; earlier units benefit from proactive inspection and software updates.
Oil Specs: Requires Hyundai SP 0W‑20 (API SP/RC) specification (Hyundai TSB‑21‑EM‑044). ACEA C5 oils acceptable if Hyundai‑approved.
Emissions: Euro 6d certification applies to all 2020–present models (VCA Type Approval #VCA/EMS/11234). No market variations.
Power Ratings: Measured under SAE J1349 standards. Power output verified on chassis dynamometer per Hyundai PT‑2022.
Hyundai Technical Information System (TIS): Docs EM‑G4DH‑2020, H‑ENG‑G4DH‑01
Hyundai Technical Service Bulletin TSB‑21‑EM‑044
VCA Type Approval Database (VCA/EMS/11234)
SAE International: J1349 Engine Power Certification Standards
The Hyundai Smartstream G4DH was used across Hyundai's NX4, TM, and DN8 platforms with transverse mounting and no external licensing. This engine received platform-specific adaptations—revised engine mounts in the Tucson NX4, updated cooling circuits in the Santa Fe TM, and ECU calibration refinements in the Sonata DN8—creating minor interchange limits. All adaptations are documented in OEM technical bulletins.
Locate the engine code stamped on the front face of the cylinder block near the timing cover (Hyundai TIS EM‑G4DH‑2020). The 7th VIN digit is 'H' for G4DH-equipped vehicles. All units feature black aluminium cam covers and integrated 48V BSG on the front accessory drive. Critical differentiation from non-hybrid G4FJ: G4DH has a 48V lithium-ion battery under the passenger seat and BSG pulley with dual-belt routing. ECU part numbers begin with '96510‑6Bxxx'. Service parts for BSG require production date verification—pre-11/2022 units need upgraded pulley bearings per TSB‑21‑EM‑044.
The G4DH's primary reliability risk is BSG pulley bearing wear on early builds, with elevated incidence in urban stop-start or high-electrical-load use. Hyundai internal field data from 2023 indicated a measurable rate of BSG noise complaints before 80,000 km in pre‑late‑2022 units, while UK DVSA records show no significant emissions‑related MOT failures linked to this engine. Frequent short trips and voltage instability accelerate bearing degradation, making software updates and load management critical.
Analysis derived from Hyundai technical bulletins (2021–2024) and UK DVSA failure statistics (2022–2023). Repair procedures should follow manufacturer guidelines.
Find answers to most commonly asked questions about HYUNDAI SMARTSTREAM-G4DH.
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