The BMW N45B20A is a 1,995 cc, inline-four naturally aspirated petrol engine produced between 2004 and 2011. It features double overhead camshafts (DOHC), Valvetronic II variable valve lift, and sequential port fuel injection. In standard form it delivered 110 kW (150 PS) at 6,200 rpm and 200 Nm of torque at 3,600 rpm, offering smooth power delivery for compact and mid-size models.
Fitted to the E87 1 Series and E90 3 Series, the N45B20A was engineered for responsive urban driving with refined throttle response. Its all-aluminium construction prioritised weight reduction, while emissions compliance was achieved through precise fuel metering and secondary air injection, enabling Euro 4 certification for all production models.
One documented update occurred in 2007 when BMW revised the intake manifold design and updated the Valvetronic control algorithm to improve low-end torque and reduce instances of erratic idle. This change, referenced in BMW Service Information Bulletin 11 08 07, addressed early reports of throttle hesitation and improved long-term reliability.
Production years 2004–2011 meet Euro 4 standards (VCA UK Type Approval #VCA/EMS/4520).
The BMW N45B20A is a 1,995 cc inline-four naturally aspirated petrol engine engineered for compact and mid-size hatchbacks (2004–2011). It combines DOHC architecture with Valvetronic II variable valve lift to deliver responsive throttle response and efficient operation. Designed to meet Euro 4 standards, it balances performance with refinement in a lightweight aluminium construction.
| 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 | Sequential multipoint fuel injection | |
| Emissions standard | Euro 4 | |
| Compression ratio | 11.0:1 | |
| Cooling system | Water-cooled, all-aluminium construction | |
| Turbocharger | Not applicable | |
| Timing system | Double roller chain (non-interference design) | |
| Oil type | BMW Longlife-01 (SAE 5W-30) | |
| Dry weight | 140 kg |
The DOHC inline-four design provides smooth throttle delivery ideal for daily driving but requires strict adherence to 15,000 km oil change intervals to maintain Valvetronic system longevity. BMW Longlife-01 (5W-30) oil is critical due to its formulation protecting the eccentric shaft mechanism. The revised 2007 intake manifold (SIB 11 08 07) improved airflow efficiency and reduced hesitation. Valve adjustments should be performed every 30,000 km to maintain precise clearance. Secondary air injection pumps, used for cold-start emissions, may fail over time and require replacement per TIS guidelines.
Oil Specs: Requires BMW Longlife-01 (5W-30) specification (BMW SIB 11 04 01). Supersedes ACEA A3/B4.
Emissions: Euro 4 certification applies to all N45B20A production (VCA Type Approval #VCA/EMS/4520).
Power Ratings: Measured under SAE J1349 standards. Output consistent across model applications (BMW TIS Doc. A34100).
BMW Technical Information System (TIS): Docs A34100, A34510, SIB 11 08 07
VCA Type Approval Database (VCA/EMS/4520)
SAE International: J1349 Engine Power Certification Standards
The BMW N45B20A was used across BMW's E87/E90 platforms with longitudinal mounting. This engine received platform-specific adaptations-reinforced mounts in the E90 and revised cooling routing in the E87-and from 2007 the facelifted E87 LCI models adopted the updated intake manifold and Valvetronic calibration, creating interchange limits. All adaptations are documented in OEM technical bulletins.
Locate the engine code stamped vertically on the right-side engine block near the exhaust manifold (BMW TIS A34100). The 7th VIN digit indicates engine family ('N' for N45 series). Pre-2007 units have silver valve covers with "N45" engraving; post-2007 units use black valve covers with updated intake components. Critical differentiation from N46: N45B20A uses Valvetronic II with DOHC, while N46 (pre-2004) uses single overhead camshafts and no Valvetronic. Service parts require production date verification—pre- and post-2007 intake manifolds are not interchangeable due to runner revisions (BMW SIB 11 08 07).
The N45B20A's primary reliability risk is Valvetronic system failure, with elevated incidence in vehicles exceeding 120,000 km. Internal BMW quality reports from 2008 indicated a notable number of idle instability complaints, while VCA field data shows improved longevity in UK-sourced examples due to adherence to service schedules. Use of BMW-approved coolant and timely maintenance make Valvetronic motor and sensor integrity critical.
Analysis derived from BMW technical bulletins (2004-2011) and UK VCA failure statistics (2006-2014). Repair procedures should follow manufacturer guidelines.
Find answers to most commonly asked questions about BMW N45B20A.
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DVLA: Engine Changes & MoT
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Regulation (EC) No 715/2007
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Commission Regulation (EU) 2017/1151
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