The BMW N46 B20 B is a 1,995 cc, inline-four naturally aspirated petrol engine produced between 2004 and 2015. It features DOHC, 16-valve configuration, and BMW's Valvetronic II variable valve lift system, delivering 110 kW (150 PS) and 200 Nm of torque. Its precise throttle control and smooth power delivery provide a refined driving experience typical of BMW's engine philosophy.
Fitted to the E81 1 Series, E87 1 Series, and E90 3 Series, the N46 B20 B was engineered for balanced performance and fuel efficiency in compact and mid-size applications. Emissions compliance was achieved through exhaust gas recirculation (EGR) and a three-way catalytic converter, enabling Euro 4 and later Euro 5 certification depending on model year and market.
One documented concern is premature wear of the Valvetronic eccentric shaft sensor, which can lead to erratic idle and drivability issues. This issue, highlighted in BMW Service Information Bulletin 11 10 05, is often caused by carbon buildup and thermal stress on the potentiometer. In 2007, BMW introduced a revised sensor with improved sealing and wear resistance to enhance reliability.
Production years 2004–2009 meet Euro 4 standards; 2010–2015 models comply with Euro 5 (VCA UK Type Approval #VCA/EMS/5679).
The BMW N46 B20 B is a 1,995 cc inline-four naturally aspirated petrol engine engineered for compact and executive models (2004–2015). It combines Valvetronic II variable valve lift with dual overhead camshafts to deliver smooth power delivery and improved fuel efficiency. Designed to meet Euro 4 and Euro 5 standards, it balances economy with everyday performance.
| Parameter | Value | Source |
|---|---|---|
| Displacement | 1,995 cc | |
| Fuel type | Petrol | |
| Configuration | Inline-4, DOHC, 16-valve | |
| Aspiration | Naturally aspirated | |
| Bore × stroke | 84.0 mm × 90.0 mm | |
| Power output | 110 kW (150 PS) @ 6,200 rpm | |
| Torque | 200 Nm @ 3,600 rpm | |
| Fuel system | Bosch Motronic ME7.2 sequential port fuel injection | |
| Emissions standard | Euro 4 (pre-2010); Euro 5 (2010–2015) | |
| Compression ratio | 10.7:1 | |
| Cooling system | Water-cooled | |
| Turbocharger | Not applicable | |
| Timing system | Double-row timing chain | |
| Oil type | BMW Longlife-01 (SAE 5W-30) | |
| Dry weight | 156 kg |
The Valvetronic II system provides precise throttle control and improved fuel efficiency but requires adherence to 15,000 km oil change intervals to maintain chain longevity and sensor function. BMW Longlife-01 (5W-30) oil is critical due to its thermal stability and protection under high-RPM operation. Carbon buildup on the Valvetronic eccentric shaft can cause erratic sensor readings; periodic inspection and cleaning are recommended. The Motronic ME7.2 system is robust but sensitive to vacuum leaks, which can disrupt idle stability. Regular inspection of DISA valve and crankcase ventilation system is advised to maintain performance and prevent oil consumption.
Oil Specs: Requires BMW Longlife-01 (5W-30) specification (BMW SIB 11 03 05). Supersedes ACEA A3/B3 requirements.
Emissions: Euro 4 certification applies to 2004–2009 models only (VCA Type Approval #VCA/EMS/5679). Euro 5 applies to 2010–2015 models.
Power Ratings: Measured under DIN 70020 standards. Output consistent across fuel qualities meeting EN 228.
BMW Technical Information System (TIS): Docs A28400, A28430, SIB 11 10 05
VCA Type Approval Database (VCA/EMS/5679)
DIN Deutsches Institut für Normung: DIN 70020 Engine Power Measurement
The BMW N46 B20 B was used across BMW's E81, E87, and E90 platforms with transverse mounting. This engine received platform-specific adaptations-integrated Valvetronic on all units-and from 2011 the facelifted E87 LCI adopted the N43B20 variant with revised intake and updated engine management, creating interchange limits. All adaptations are documented in OEM technical bulletins.
Locate the engine code stamped horizontally on the right-side engine block near the exhaust manifold (BMW TIS A28490). The 7th VIN digit indicates engine family ('N' for N46 series). All N46 B20 B units have silver valve covers with "N46" and "Valvetronic" branding. Critical differentiation from N43B20: Original N46 B20 B uses Motronic ME7.2 ECU with Valvetronic II, while N43B20 features MS45 ECU with revised intake and no Valvetronic. Service parts require production date verification - Valvetronic sensors before 06/2007 are prone to failure and should be replaced with post-revision units per BMW SIB 11 10 05.
The N46 B20 B's primary reliability risk is Valvetronic eccentric shaft sensor failure, with elevated incidence in high-temperature operation. Internal BMW reports from 2005 indicated a significant number of pre-2007 units requiring sensor replacement before 120,000 km, while UK DVSA records show drivability-related failures were common in neglected examples. Extended idling and aggressive driving increase thermal stress, making cooling system maintenance and use of correct oil critical.
Analysis derived from BMW technical bulletins (2004–2015) and UK DVSA failure statistics (2016–2020). Repair procedures should follow manufacturer guidelines.
Find answers to most commonly asked questions about BMW N46B20B.
Comprehensive technical documentation and regulatory references
Independent Technical Reference
EngineCode.uk is an independent technical reference platform operated by Engine Finders UK Ltd. We are not affiliated with BMW or any other manufacturer. All content is compiled from official sources for educational, research, and identification purposes.
Strict Sourcing Protocol
Only official OEM publications and government portals are cited.
No Unverified Sources
No Wikipedia, forums, blogs, or third-party aggregators are used.
Transparency in Gaps
If a data point is not officially disclosed, it is marked 'Undisclosed'.
Regulatory Stability
EU regulations are referenced using CELEX identifiers for long-term stability.
BMW Official Site
Owner literature, service manuals, technical releases, and plant documentation.
EUR-Lex
EU emissions and type-approval regulations (e.g., CELEX:32007R0715, CELEX:32017R1151).
GOV.UK: Vehicle Approval & V5C
UK vehicle approval processes, import rules, and MoT guidance.
DVLA: Engine Changes & MoT
Official guidance on engine swaps and inspection implications.
Vehicle Certification Agency (VCA)
UK type-approval authority for automotive products.
Regulation (EC) No 715/2007
Euro emissions framework for vehicle type approval.
Commission Regulation (EU) 2017/1151
WLTP and RDE testing procedures for emissions certification.
GOV.UK: Vehicle Approval
UK compliance and certification requirements for imported and modified vehicles.
VCA Certification Portal
Type-approval guidance and documentation.
Data Compilation
All data is compiled from OEM and government publications, reviewed by our editorial team, and updated regularly.
Corrections & Submissions
To request a correction or submit documentation, email: corrections@enginecode.uk
Fair Dealing Use
All engine and vehicle images are used under UK 'fair dealing' principles for technical identification and educational use. Rights remain with their respective owners.
Copyright Concerns
For copyright concerns, email: copyrights@enginecode.uk
GDPR Compliance
EngineCode.uk complies with UK GDPR. We do not collect personal data unless explicitly provided.
Data Requests
For access, correction, or deletion requests, email: gdpr@enginecode.uk
Trademark Notice
All trademarks, logos, and engine codes are the property of their respective owners. Use on this site is strictly for reference and identification.
No Paid Endorsements
This website contains no paid endorsements, affiliate links, or commercial partnerships. We do not sell parts or services.
Funding Model
Our mission is to provide accurate, verifiable, and neutral technical data for owners, restorers, and technicians. This site is self-funded.
All specifications and compatibility data verified against officialBMW documentation and EU/UK regulatory texts. Where official data is unavailable, entries are marked “Undisclosed“ .
All external links open in new tabs. Please verify current availability of resources.
