BMW 320si E90 2.0L N45B20S Petrol Engine

BMW 320si E90 2.0L N45B20S petrol engine

High-Performance Replacement Engine for Sale

BMW 320si E90 2.0L N45B20S petrol engine is a rare, motorsport-inspired power unit designed for drivers who demand sharp throttle response, lightweight engineering, and superior rev-happy performance. Originally developed to meet WTCC homologation requirements, the N45B20S stands apart from standard BMW engines with its high-compression ratio, modified cylinder head, and enhanced intake system. If you’re looking to restore factory performance to your BMW 320si or want an authentic replacement engine that maintains the car’s original pedigree—this N45B20S unit offers an exceptional balance of precision engineering and genuine BMW reliability.

This engine is compatible exclusively with the BMW E90 320si sedan (2006–2007) and is not interchangeable with typical N46 or N43 engines due to its unique design and motorsport-derived components. Built as a 2.0-litre naturally aspirated four-cylinder, it produces approximately 173 hp (127 kW) and is paired with a short-stroke configuration for quick acceleration and high-revving capability. Key features include Valvetronic control, double overhead camshafts, a redesigned cooling system, and lightweight construction that reduces front-end weight for improved handling.

The N45B20S boasts distinctive technical specifications. It includes an all-aluminium block, a high 11.0:1 compression ratio, ported cylinder head, enlarged valves, and a performance-oriented intake manifold for improved airflow. The engine’s robust internals were engineered to withstand spirited driving while maintaining BMW’s signature smoothness and refinement. When sourced in good condition and maintained correctly, this engine delivers engaging performance and a uniquely raw driving experience compared to modern turbocharged units.

Common weaknesses and Maintenance.

However, as with any performance-focused engine, the N45B20S has known weaknesses that buyers should be aware of. The most common issue involves cylinder-head cracking, often caused by overheating or inadequate coolant circulation. Regular monitoring of coolant levels, prompt replacement of thermostats, and ensuring the radiator is functioning properly are essential preventive measures. Timing-chain wear can also occur over higher mileage, making periodic inspection vital to avoid noise, stretching, or potential failure. Additionally, carbon buildup on valves is possible due to the engine’s high-rev nature, so maintaining clean fuel injectors and using premium petrol helps preserve long-term efficiency.

With proper care—consistent oil changes, cooling-system maintenance, and attentive monitoring the N45B20S engine remains a rewarding and reliable performance asset. Whether you’re rebuilding a BMW 320si, replacing a worn-out motor, or restoring the car’s original power, this engine represents an authentic and high-quality solution for enthusiasts seeking precision engineering and genuine BMW performance.

Each BMW 320si E90 2.0L N45B20S petrol engine is inspected, compression-tested, and imported directly to our warehouse, guaranteeing high quality and long-term reliability.