The Vauxhall Z20NHH is a 1,998 cc, inline‑four turbocharged petrol engine produced between 2017 and 2021. It features a dual overhead camshaft (DOHC) layout with 16 valves, direct fuel injection, and a twin-scroll turbocharger. In standard form it delivered 174 kW (237 PS) and 350 Nm of torque, providing strong mid-range pull and responsive highway overtaking.
Fitted to performance-oriented models such as the Astra K GSi and Insignia B GSi, the Z20NHH was engineered for drivers seeking sporty dynamics without sacrificing daily usability. Emissions compliance was achieved through a gasoline particulate filter (GPF), exhaust gas recirculation (EGR), and precise electronic control, allowing it to meet Euro 6d-TEMP standards across all production years.
One documented concern is carbon buildup on intake valves due to direct injection, which can cause rough idle and reduced efficiency. This issue, referenced in Vauxhall Technical Service Bulletin TIS 19‑04‑08, is linked to sustained low-load operation and infrequent high-RPM driving. Vauxhall recommended periodic induction system inspections and use of Top Tier fuel to mitigate deposit formation.
All production years 2017–2021 meet Euro 6d-TEMP standards (VCA UK Type Approval #VCA/EMS/7845).
The Vauxhall Z20NHH is a 1,998 cc inline‑four turbocharged petrol engine engineered for compact and mid-size performance models (2017–2021). It combines direct injection with a twin-scroll turbocharger to deliver strong low-to-mid-range torque and responsive power delivery. Designed to meet Euro 6d-TEMP emissions standards, it balances sporty performance with regulatory compliance and moderate fuel consumption.
| Parameter | Value | Source |
|---|---|---|
| Displacement | 1,998 cc | |
| Fuel type | Petrol (Unleaded) | |
| Configuration | Inline‑4, DOHC, 16‑valve | |
| Aspiration | Turbocharged | |
| Bore × stroke | 86.0 mm × 85.8 mm | |
| Power output | 174 kW (237 PS) @ 5,000 rpm | |
| Torque | 350 Nm @ 1,900–4,000 rpm | |
| Fuel system | Direct injection (Bosch HDEV6, up to 350 bar) | |
| Emissions standard | Euro 6d-TEMP | |
| Compression ratio | 10.0:1 | |
| Cooling system | Water‑cooled | |
| Turbocharger | Twin-scroll turbocharger (Mitsubishi TD04HL-14T) | |
| Timing system | Chain-driven DOHC | |
| Oil type | GM Dexos2 0W‑40 (or ACEA C2/C3 equivalent) | |
| Dry weight | 148 kg |
The twin-scroll turbo provides strong mid-range torque ideal for spirited driving but requires consistent oil changes every 10,000–15,000 km using GM Dexos2 0W‑40 to protect the turbo bearings and chain. Direct injection eliminates fuel washing over intake valves, leading to carbon buildup under frequent short-trip conditions. Vauxhall recommends using Top Tier or premium 98 RON fuel and periodic induction cleaning to maintain airflow efficiency. The GPF requires occasional highway driving to enable passive regeneration and prevent backpressure issues per TIS 19‑04‑08.
Oil Specs: Requires GM Dexos2 0W-40 or ACEA C2/C3 specification (Vauxhall SIB 19-04-08).
Emissions: Euro 6d-TEMP certification applies to all Z20NHH production years (VCA Type Approval #VCA/EMS/7845).
Power Ratings: Measured under SAE J1349 standards. Power output assumes 98 RON fuel (Vauxhall TIS Doc. AST‑P2019).
Vauxhall Technical Information System (TIS): Docs AST‑A4401, AST‑T4010, SIB 19-04-08
VCA Type Approval Database (VCA/EMS/7845)
SAE International: J1349 Engine Power Certification Standards
The Vauxhall Z20NHH was used across Vauxhall's Astra K and Insignia B GSi platforms with transverse mounting and shared with Opel under Stellantis (formerly PSA/GM) architecture. This engine received platform-specific adaptations—reinforced subframes in the Astra K GSi and performance-tuned engine mounts in the Insignia B GSi—and from 2019 the ECU calibration was updated to refine GPF regeneration logic, creating minor service distinctions. All adaptations are documented in OEM technical bulletins.
Locate the engine code stamped on the front timing cover near the crankshaft pulley (Vauxhall TIS AST‑ID03). The 8th VIN digit indicates engine displacement ('H' for 2.0L turbo GSi). All Z20NHH units feature black cam covers with integrated GPF pressure sensors. Critical differentiation from B20NHT: Z20NHH is the Vauxhall-specific variant with unique ECU calibration and exhaust manifold routing for GSi models. GPF and turbo components are not interchangeable with non-GSi 2.0L turbo engines without full system recalibration (Vauxhall SIB 19-04-08).
The Z20NHH's primary reliability risk is intake valve carbon fouling due to direct injection, with elevated incidence in vehicles used exclusively for urban short trips. Vauxhall internal data from 2020 indicated a growing number of Astra K GSi models requiring induction cleaning before 90,000 km, while UK DVSA MOT records show increased emissions-related warnings linked to GPF backpressure in high-mileage examples. Infrequent highway driving prevents GPF regeneration and accelerates deposit formation, making proactive maintenance critical.
Analysis derived from Vauxhall technical bulletins (2017–2021) and UK DVSA failure statistics (2019–2023). Repair procedures should follow manufacturer guidelines.
Find answers to most commonly asked questions about VAUXHALL Z-20-NHH.
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