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

Exhaust Silencer BMW F20 F21 LCI M140i B58 Petrol Rear Back Box Muffler is an original, used exhaust system component designed for installation at the rear of a petrol-powered vehicle. Specifically engineered for the M140i version with the B58 engine, it ensures proper noise suppression while maintaining the characteristic sound and correct exhaust flow parameters. Thanks to its factory design, it fits factory mounting points, which facilitates installation and reduces the risk of improper fitment.

Specifications and technical data

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

Purpose and compatibility

The presented rear silencer is dedicated to BMW 1 Series F20/F21 LCI (facelift) models in the M140i version with the B58 petrol engine. The component operates in the rear section of the exhaust system, responsible for final sound dampening and exhaust flow stabilization. The OEM construction guarantees the preservation of factory acoustic parameters and proper fitment with other exhaust components.

Construction and function in the exhaust system

The rear silencer belongs to the Silencers and resonators category, responsible for noise control, vibration reduction, and backpressure optimization in the exhaust system. Its placement at the rear of the vehicle allows for:

• final silencing of the petrol engine while maintaining a sporty sound character,
• stabilization of exhaust gas flow across the entire rev range,
• reduction of resonances and unwanted vibrations transmitted to the chassis.

Thanks to the factory geometry of the silencer's interior, the exhaust system maintains the correct flow characteristics, which is essential for the proper operation of the B58 unit and compliance with factory engine control maps.

Benefits of using an original silencer

Using an original rear silencer in the BMW M140i brings a number of practical operational benefits:

• Factory fitment – no need for modifications to mounts, pipe diameters, or hangers, which shortens installation time.
• Stable acoustic parameters – maintaining the noise level and sound character intended by the manufacturer.
• Consistency with other exhaust system elements – the silencer works with factory catalytic converters and other exhaust sections.
• Seamless integration with the bodywork – proper positioning of the exhaust tips relative to the bumper and diffuser.

A used OEM component is a sensible choice for drivers who want to restore the proper operation of the exhaust system without interfering with the vehicle's construction and without the risk of unforeseen changes in engine performance characteristics.

Condition, verification, and selection by numbers

The silencer is offered as a used part, which allows for lower repair costs while maintaining the manufacturer's original specifications. Before installation, a standard visual inspection for leaks, the condition of mounts, and any signs of previous repairs is recommended. Proper selection of the component for a specific vehicle should be based on the OEM number and interchangeable numbers assigned to this model.

If you want to check the compatibility of the part with your VIN and OEM number step by step, our practical guide will be helpful: selecting the right part by VIN and OEM number, where you will find a procedure scheme, examples, and a list of questions for the seller.

Expanding the BMW exhaust system

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

Summary

Exhaust Silencer BMW F20 F21 LCI M140i B58 Petrol Rear Back Box Muffler is an original, used rear silencer designed for the rear section of the exhaust system in the petrol M140i version. It ensures factory-compliant sound, correct exhaust flow, and secure fitment to the bodywork and other exhaust components. It is a functional solution for users who want to restore the efficiency of the exhaust system while maintaining the character and parameters intended by the BMW manufacturer.