BMW S55 Cat Flange Gasket 18307848046 - Genuine OEM Exhaust Donut/Downpipe & Front Pipe Sealing Ring/Flange Ring - F8X Fits F87 M2 Competition, F80 M3, F82/F83 M4 Catalytic Converter Joint

BMW S55 Cat Flange Seal Ring 18307848046 for F87 M2 Competition, F80 M3, F82 F83 M4

Stop exhaust blow-by at the catalytic converter junction with the BMW part number 18307848046 seal ring. This factory-spec gasket ring is the precise replacement for the cat-to-front section interface on S55-powered F87 M2 Competition, F80 M3 and F82 F83 M4. Perfect when refitting catalysts, swapping front pipes, installing a mid pipe, or returning to stock after aftermarket work, it restores a tight, quiet and gas-tight joint.

Built for the heat cycles and pressure of the S55 turbo system, this flange ring delivers consistent clamping and alignment, helping prevent fumes, chuffing noises and MOT-unfriendly leaks. We use this part on our own shop cars and customer builds, and feedback has been excellent for fit, longevity and sealing performance.

Key benefits

• Direct replacement sealing ring for the catalyst flange on S55 models
• Correct thickness and profile for accurate flange alignment and clamp load
• Withstands high temperature and boost-related pressure at the joint
• Reduces exhaust leaks, ticking sounds and sulphur odours in the cabin
• Ideal during downpipe removal, catalyst replacement or mid section upgrades
• Trusted in-house and by our customers for reliable, long-term sealing

Compatibility

• BMW F87 M2 Competition, including LCI
• BMW F80 M3, pre-LCI and LCI
• BMW F82 M4, pre-LCI and LCI
• BMW F83 M4 Convertible, pre-LCI and LCI

Typical model years covered include 2014 to 2020 for M3 and M4 and 2018 to 2020 for M2 Competition. If unsure, please check with us.

Common search terms

S55 cat gasket, BMW M3 M4 exhaust seal ring, catalytic converter flange ring, F80 downpipe gasket, F82 F83 front pipe gasket, M2 Competition exhaust joint gasket, cat-to-mid pipe seal, S55 exhaust donut, BMW exhaust flange ring 18307848046.

Part number

18307848046

Fitment check

We will verify fitment before dispatch. Add your UK registration or the last 7 of your VIN at checkout so we can confirm suitability for your vehicle.

Installation

Professional fitting is recommended to ensure a perfect, leak-free seal. MJ Modifications offers expert installation in Warwickshire. For a fitting quote, email info@mjmodifications.co.uk.

Manufacturer

BMW original equipment specification.

Warranty

Two years manufacturer warranty for UK customers and one year for international customers when a VIN is provided on compatible vehicles.