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 d…
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 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.
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.
The most common questions about engine codes, what they mean, how to find them and how this database works
The N45B20A is generally robust when maintained, with the primary concern being Valvetronic system wear. Pre-2007 models are more prone to hesitation, while post-2007 revisions improved low-end torque and idle stability. Using BMW-specified oil (Longlife-01 5W-30) and changing it every 15,000 km greatly enhances longevity, especially in high-mileage applications.
Key issues include Valvetronic eccentric shaft sensor failure, intake manifold vacuum leaks, aging ignition coils leading to misfires, and coolant leaks from the thermostat housing. These are well-documented in BMW service bulletins and affect high-mileage examples most. Proper maintenance significantly reduces failure rates.
The N45B20A was used in the E87 1 Series (120i) from 2004 to 2011 and the E90 3 Series (320i) from 2005 to 2011. It was superseded by the N43 naturally aspirated four-cylinder engine. The 2007 intake manifold update improved throttle response and low-RPM performance.
Yes, the N45B20A responds well to tuning. ECU remaps can safely increase output to 125–135 kW (170–185 PS) on stage 1, as the stock internals handle moderate increases. Intake and exhaust upgrades enhance responsiveness. Always maintain proper cooling and fuel system condition to support modifications.
In combined driving, the N45B20A achieves approximately 7.0–8.0 L/100km (40–35 mpg UK). Highway efficiency improves to ~6.0 L/100km (47 mpg UK), while city driving may reach 9.0 L/100km (31 mpg UK). Real-world figures depend on driving style, vehicle weight, and transmission type.
Yes. The N45B20A is an interference engine, meaning that if the timing chain fails or jumps, the pistons can contact the valves, causing severe internal damage. However, the double roller chain design is durable and non-serviceable under normal conditions. Chain replacement is only recommended if wear is detected.
BMW specifies SAE 5W-30 oil meeting BMW Longlife-01 standard. This viscosity ensures proper lubrication of the Valvetronic system and cylinder heads under high-temperature operation. Oil changes every 15,000 km or annually are recommended to maintain engine health and prevent sludge buildup.
Comprehensive technical documentation and regulatory references
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DVLA: Engine Changes & MoT
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Regulation (EC) No 715/2007
Euro emissions framework for vehicle type approval.
Commission Regulation (EU) 2017/1151
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