BMW E90 320si Petrol N45B20A Engine Cylinder Head 7551120

BMW E90 320si Petrol N45B20A Engine Cylinder Head is an original component from the Cylinder Heads category, designed for the petrol unit used in the sporty 320si version. This used, factory-spec construction ensures a proper fit for the drivetrain while maintaining the operating parameters specified by the manufacturer. It is a solution for users who want to restore proper engine performance while maintaining compliance with BMW technology.

Specifications and technical data

• SKU: 7557932
• Mark: BMW (Genuine OE)
• Condition: Used
• OEM Part Number: 7557932
• Substitutable numbers: 11127557932, 7557932, 7551120, ŁS
• Fuel type: Petrol
• Category: Cylinder Heads & Valve Covers

Purpose and compatibility

The presented cylinder head has been designed for the N45B20A petrol engine used in the BMW E90 320si model. This ensures the correct geometry of the intake and exhaust ports, proper placement of valve seats, and compatibility with the engine's factory equipment. As a result, this component can be used as a base for repairing or rebuilding the engine in vehicles equipped with this specific unit.

Technical characteristics of the cylinder head

The cylinder head is responsible for managing the air-fuel mixture, exhaust gas discharge, and working with the timing system. In the case of the N45B20A petrol engine, it is crucial to maintain proper combustion chamber tightness, precise valve guidance, and stable spark plug mounting. The OEM construction ensures:

• factory placement of oil and cooling channels,
• correct positioning of camshafts and valve control elements,
• compatibility with standard gaskets and mounting components.

Thanks to this, the cylinder head serves as a solid base for further machining, regeneration, or assembly in accordance with BMW service procedures.

Application in a petrol engine

A petrol engine requires precise timing system operation and combustion chamber tightness, which is why a properly selected cylinder head has a direct impact on the engine's refinement, performance, and durability. In the case of the BMW E90 320si, using an original cylinder head allows you to:

• maintain proper cylinder filling parameters,
• ensure stable operation at higher RPMs,
• minimize the risk of leaks and compression loss.

For users who drive their cars dynamically, maintaining the factory specification of the cylinder head is particularly important from a reliability standpoint.

Component condition and assembly aspects

The offered cylinder head is a used part, which in practice means it requires standard verification before assembly – such as checking flatness, inspecting valve seats and guides, and potential regeneration in accordance with accepted workshop technology. This type of component most often serves as an economical base for engine rebuilding, allowing for cost reduction compared to purchasing a new cylinder head while maintaining the original BMW design.

Benefits of using an original BMW cylinder head

Using a factory cylinder head in a BMW E90 320si translates into several practical benefits:

• Full structural compatibility with the N45B20A unit, without the need for adaptation or modifications.
• The ability to use standard equipment components, gaskets, and mounting bolts.
• Better predictability of engine performance after repair compared to aftermarket replacements of uncertain origin.

For workshops specializing in the BMW brand and users who care about the technical consistency of their vehicle, this is a solution that allows for a professional engine rebuild.

If you are planning a comprehensive repair or upgrade of the engine area in your BMW and need other components from the same group, such as cylinder head housings, valve covers, or mounting elements, check out the available parts in the BMW Cylinder Heads category.

To better plan the repair of your BMW E90 engine, it is also worth familiarizing yourself with practical information regarding typical faults and weak points of these engines – you will find them in the article Troublesome BMW E90 engines: check what can ruin your budget!, which will help you assess the scope of work and choose the appropriate service strategy.