BMW F20 F21 LCI Exhaust Silencer Rear Back Box Muffler M140i B58 Petrol 8650846

Visual condition of the part

The product shows signs of use visible in the photos.

BMW F20 F21 LCI Exhaust Silencer Rear Back Box Muffler M140i B58 is an original exhaust system component designed specifically for the M140i petrol version with the B58 engine. Thanks to its factory design, it ensures proper noise suppression, maintains the characteristic acoustics of the B58 unit, and provides correct exhaust flow parameters. This solution is intended for users who want to maintain consistency with the factory BMW specification while ensuring the stable operation of the exhaust system.

Specifications and technical data

• SKU: 8638779-1
• Mark: BMW (Genuine OE)
• Condition: Used
• OEM Part Number: 8638779
• Substitutable numbers: 18308638779, 8638779, 8650846
• Location on the vehicle: Rear
• Fuel type: Petrol
• Category: Mufflers & Resonators

Purpose and compatibility

The presented rear silencer is an exhaust system component mounted in the rear part of the vehicle, dedicated to the BMW 1 Series F20/F21 generation after the facelift (LCI) in the M140i version with the B58 petrol engine. The construction was developed by BMW to maintain the appropriate backpressure, which is important for performance, engine refinement, and compliance with factory ECU maps.

As a part from the Silencers and resonators group, this component works with other exhaust system parts, such as center sections or resonators, creating a coherent exhaust gas discharge system in BMW cars with a petrol unit.

Construction and operating characteristics

The rear silencer in the M140i B58 performs several key technical functions:

• reduction of exhaust noise while maintaining the sporty, characteristic sound of the B58 unit,
• stabilization of exhaust flow in the final part of the system,
• limitation of vibrations and resonances transmitted to the body,
• maintenance of the appropriate backpressure level for the petrol engine.

Thanks to the factory design, the exhaust system retains its original acoustic and flow parameters, which is important both from the point of view of driving comfort and the durability of other components.

Application in service practice

The used rear silencer for the M140i B58 is a good choice in situations where the existing component has corroded, suffered mechanical damage, or no longer meets acoustic requirements. Compared to universal solutions, the original BMW silencer provides:

• a secure fit to the F20/F21 LCI chassis geometry,
• compliance with factory mounting points,
• no need for structural modifications during installation.

Such a solution facilitates workshop work and allows for maintaining the factory character of the exhaust system, which is important both for users who value originality and for those who pay attention to compliance with BMW service documentation.

Benefits of choosing an original BMW silencer

By choosing an original rear silencer for the M140i B58, you gain a component designed specifically for the petrol engine, vehicle weight, and suspension characteristics. This translates into:

• predictable vehicle behavior under various loads and speeds,
• maintenance of acoustic comfort in the interior,
• consistency with other BMW exhaust system components.

For many users, it is also important that using an original silencer facilitates subsequent diagnostics of potential exhaust system problems, as operating parameters remain consistent with the manufacturer's assumptions.

Additional information and exhaust system development

If you are planning a comprehensive repair or upgrade of the exhaust system area in your BMW and need other elements from the same group, such as tailpipe sections, center sections, or additional resonators, check the available parts in the BMW Silencers and resonators category.

For drivers interested in a broader context of modifications and the selection of used exhaust components, including legal aspects and practical differences in installation, an article describing performance solutions in performance segment cars may be helpful – you can find it here: Second-hand Mini John Cooper Works Pro sports exhaust – a legal way to get a racing sound and +7 HP.