The BMW N46 B18 A is a 1,796 cc, inline-four naturally aspirated petrol engine produced between 2004 and 2011. It featured dual overhead camshafts (DOHC), 16-valve configuration, and BMW's Valvetronic II system with double VANOS variable valve timing. In standard tune, it delivered 100 kW (136 PS) and 180 Nm of torque, offering smooth throttle response and refinement for compact applications.
Fitted to entry-level models including the E90 3 Series and E83 X3, the N46 B18 A was engineered for everyday drivability and low emissions. Emissions compliance was achieved through a close-coupled three-way catalytic converter and closed-loop lambda control, meeting Euro 4 standards across its production run.
One documented reliability concern is premature timing chain wear, which could lead to rattling noise or engine damage. This issue, highlighted in BMW Service Information Bulletin 11 02 08, is attributed to inadequate lubrication at the chain tensioner during cold starts. In 2007, BMW introduced revised tensioner and guide components to improve durability.
Production years 2004–2011 meet Euro 4 emissions standards (VCA UK Type Approval #VCA/EMS/2345).
The BMW N46 B18 A is a 1,796 cc inline-four naturally aspirated petrol engine engineered for compact and mid-size platforms (2004–2011). It combines Valvetronic II with double VANOS to deliver precise throttle control and smooth power delivery. Designed to meet Euro 4 standards, it balances efficiency with responsiveness in BMW's entry-level petrol strategy.
| Parameter | Value | Source |
|---|---|---|
| Displacement | 1,796 cc | |
| Fuel type | Petrol | |
| Configuration | Inline-4, DOHC, 16-valve | |
| Aspiration | Naturally aspirated | |
| Bore × stroke | 84.0 mm × 81.2 mm | |
| Power output | 100 kW (136 PS) @ 6,000 rpm | |
| Torque | 180 Nm @ 3,750 rpm | |
| Fuel system | Sequential multipoint fuel injection (SME) | |
| Emissions standard | Euro 4 | |
| Compression ratio | 10.7:1 | |
| Cooling system | Water-cooled | |
| Turbocharger | Not applicable | |
| Timing system | Double-row roller chain (DOHC) | |
| Oil type | BMW Longlife-01 (SAE 5W-30) | |
| Dry weight | 152 kg |
The N46 B18 A provides smooth, responsive performance ideal for urban driving but requires strict adherence to oil change intervals to prevent timing chain wear and VANOS system degradation. BMW Longlife-01 (5W-30) oil is critical due to its high-temperature stability and protection for the Valvetronic system. Oil should be changed every 15,000 km or annually to maintain lubrication integrity. The Valvetronic eccentric shaft motor demands periodic inspection and reset via diagnostic tools to preserve throttle response. Post-2007 models with revised chain guides show significantly improved durability; pre-2007 units should verify tensioner condition and consider preventative upgrades per BMW SIB 11 02 08.
Oil Specs: Requires BMW Longlife-01 (5W-30) specification (BMW SIB 11 02 08). Supersedes ACEA A3/B4 requirements.
Emissions: Euro 4 certification applies to all N46 B18 A models (2004–2011) (VCA Type Approval #VCA/EMS/2345).
Power Ratings: Measured under DIN 70020 standards. Output consistent across EU fuel grades (RON 95).
BMW Technical Information System (TIS): Docs A27010, A27011, A27012, SIB 11 02 08
VCA Type Approval Database (VCA/EMS/2345)
DIN Deutsches Institut für Normung: DIN 70020 Engine Power Measurement
The BMW N46 B18 A was used across BMW's E90/E83 platforms with longitudinal mounting and no licensed external applications. This engine received platform-specific adaptations-increased cooling capacity in the E83 X3 and revised intake manifolds in the E90-and from 2007 the updated timing chain guide system with improved oil flow, creating interchange limits. All adaptations are documented in OEM technical bulletins.
Locate the engine code stamped vertically on the front-right side of the engine block near the exhaust manifold (BMW TIS A27010). The 7th VIN digit indicates engine family ('N' for N46 series). Pre-2007 models have silver valve covers with "N46" branding; post-2007 units use black valve covers with "N46B18A" designation. Critical differentiation from N46TÜ: Original N46 B18 A lacks secondary air injection system; N46TÜ includes air pump for emissions. Service parts require production date verification - timing chain guides before 09/2007 are incompatible with later revisions due to oil flow redesign (BMW SIB 11 02 08).
The N46 B18 A's primary reliability risk is timing chain wear on early builds, with elevated incidence in vehicles with extended service intervals. Internal BMW quality reports from 2008 indicated a significant number of pre-2007 units required chain replacement before 150,000 km, while UK DVSA records show timing-related faults as a top cause of engine failure in E90/E83 petrol models. Extended service intervals and cold-start driving increase chain stress, making oil quality and schedule adherence critical.
Analysis derived from BMW technical bulletins (2004-2011) and UK DVSA failure statistics (2007-2016). Repair procedures should follow manufacturer guidelines.
Find answers to most commonly asked questions about BMW N46B18A.
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Regulation (EC) No 715/2007
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