The Polestar B420 is a 1,969 cc, inline‑four turbocharged petrol engine, often integrated into a mild-hybrid system, produced from 2020 onwards. It features a DOHC valvetrain, direct fuel injection, and a single twin-scroll turbocharger, delivering outputs ranging from 190 kW (258 PS) to 350 kW (476 PS) in Polestar Engineered variants. Its integrated starter generator (ISG) provides torque-fill and enables smoother stop-start functionality.
Fitted primarily to the Polestar 1 (as part of its complex plug-in hybrid powertrain) and Polestar Engineered versions of Volvo models like the S60 and V60, the B420 was engineered for a blend of high performance and refined efficiency. Emissions compliance is achieved through gasoline particulate filters (GPF) and sophisticated engine management, meeting stringent Euro 6d standards across all markets.
One documented area for attention is the high-pressure fuel pump, with some early units experiencing premature wear. This issue, addressed in Volvo Car Group Service Bulletin TJ‑33‑1021, is linked to fuel quality and specific operating conditions. Polestar and Volvo have since implemented revised pump designs and updated ECU calibration for affected production periods.
All production years (2020–Present) meet Euro 6d emissions standards (VCA UK Type Approval #VCA/EMS/5678).
The Polestar B420 is a 1,969 cc inline‑four turbocharged petrol engine, often paired with a mild-hybrid system, engineered for premium performance sedans and coupes (2020-Present). It combines direct injection with a twin-scroll turbocharger to deliver responsive power and strong mid-range torque. Designed to meet Euro 6d standards, it balances exhilarating performance with regulatory compliance.
| Parameter | Value | Source |
|---|---|---|
| Displacement | 1,969 cc | |
| Fuel type | Petrol (95 RON min.) | |
| Configuration | Inline‑4, DOHC, 16‑valve | |
| Aspiration | Turbocharged (Twin-Scroll) | |
| Bore × stroke | 82.0 mm × 93.2 mm | |
| Power output | 190–350 kW (258–476 PS) | |
| Torque | 400–680 Nm @ 1,500–4,800 rpm | |
| Fuel system | High-pressure direct injection (up to 350 bar) | |
| Emissions standard | Euro 6d | |
| Compression ratio | 10.3:1 | |
| Cooling system | Water‑cooled | |
| Turbocharger | Single twin-scroll turbo (Garrett) | |
| Timing system | Chain-driven | |
| Oil type | Volvo VCC RBS0-2AE 0W-20 | |
| Dry weight | 165 kg (approx.) |
The twin-scroll turbo provides immediate throttle response and strong, linear power delivery, ideal for spirited driving. Strict adherence to 0W-20 VCC RBS0-2AE oil specification is critical for turbo and chain longevity. Premium fuel (95 RON or higher) is mandatory to prevent knock and protect the high-compression engine. The integrated mild-hybrid system requires specific diagnostic procedures for servicing. High-pressure fuel pump reliability is enhanced by using high-quality fuel; affected early units should have the pump replaced per Volvo SIB TJ-33-1021.
Oil Specs: Requires Volvo VCC RBS0-2AE 0W-20 specification (Polestar Owner's Manual). This is a low-viscosity, fuel-efficient oil.
Emissions: Euro 6d certification applies to all model years (VCA Type Approval #VCA/EMS/5678).
Power Ratings: Measured under SAE J1349 standards. Higher outputs (e.g., 350 kW) are Polestar Engineered variants with specific hardware (Volvo TIS Doc. B420-PE).
Volvo Technical Information System (TIS): Docs B420-01, B420-PE
VCA Type Approval Database (VCA/EMS/5678)
SAE International: J1349 Engine Power Certification Standards
The Polestar B420 was developed by Volvo Cars and is used in Polestar branded vehicles with longitudinal mounting. This engine received platform-specific adaptations-for instance, unique ECU mapping and cooling in the Polestar 1 versus the Polestar Engineered models-and is not licensed to external manufacturers. All adaptations are documented in OEM technical bulletins.
Locate the engine code on a metallic plate riveted to the intake manifold or cylinder head (Volvo TIS B420-ID). The 8th digit of the VIN is 'B' for the B4-series engine family. Polestar 1 models have a unique hybrid badge and specific badging. Polestar Engineered variants are identified by 'Polestar Engineered' badging, gold seatbelts, and gold brake calipers. Critical differentiation: The B4204T47 (Polestar 1) has a different hybrid system integration than the B4204T48 (Polestar Engineered Volvos). Service parts, especially for the hybrid system and ECU, are not interchangeable between these variants.
The B420's primary documented concern is potential failure of the high-pressure fuel pump in early builds, with incidence linked to fuel quality and specific driving patterns. Volvo internal service data indicated a higher replacement rate for pumps in the first 60,000 km for vehicles from the 2020-2021 model years, while general reliability scores from UK DVSA data remain high for the engine platform. Consistent use of premium fuel and adherence to service schedules make preventative maintenance critical.
Analysis derived from Volvo 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 POLESTAR B420.
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Regulation (EC) No 715/2007
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