Stone Exhaust BMW B58 G20 G21 OEM Integrated Valved Cat-Back Exhaust System — OPF Models (inc. M440i, M440i xDrive, M340i, M340i xDrive) | Part Number: AP546A
Unlock the sound and performance your BMW B58 deserves with the Stone Exhaust OEM integrated valved cat-back exhaust system for OPF models. Engineered for the BMW 3 Series G20/G21 M340i and 4 Series G22/G23/G26 M440i, this valved catback delivers a true OEM fit, a deeper tone, zero unwanted drone and proven gains on Stone’s in-house dyno. If you are searching for BMW M340i exhaust, BMW M440i exhaust, BMW G20 exhaust, BMW G21 exhaust, BMW G22 exhaust, BMW G23 exhaust or BMW G26 exhaust for OPF cars, this is the premium plug-and-play solution.
Why choose Stone Exhaust for your BMW B58
- Designed from 3D scans of the OEM system for a precise 100% OEM fit on OPF-equipped cars.
- OEM integrated valves maintain factory valve control via the ECU for seamless comfort to sport sound.
- Optional Stone Valvetronic System adds remote valve control and auto rpm-based opening via a plug-and-play OBDII controller.
- Refined daily driving with an aggressive, motorsport-inspired note on demand and an exhaust that eliminates drone found on many standard systems.
- In-house R&D and dyno development ensure real-world performance and repeatable quality.
Valve control options
- OEM Integrated Valves: Uses the factory valve actuators so the ECU controls opening and closing automatically, preserving all standard drive modes.
- Optional Stone Valvetronic System (Dual Valves): Remote controller lets you open or close valves at the press of a button, or use Auto Mode to open at a set rpm. Simple OBDII plug-and-play installation in minutes.
Key features
- OEM integration for OPF models
- Optional Stone Valvetronic remote valve control
- OPF exhaust design and compatibility
- Plug-and-play OBDII controller (Valvetronic option)
- One-piece design with precision machine welding
- In-house R&D, 3D scanning and reverse engineering
- Dyno developed in-house for measurable gains
- Eliminates drone compared to many stock systems
OPF solution
For OPF-equipped vehicles, Stone offers an OPF delete solution that can be included free of charge. This allows installation of the Stone cat-back on OPF cars without triggering an error code, so coding out the OPF warning on the ECU is not required.
Engineering that sets it apart
Stone Exhaust leverages advanced R&D to deliver unmatched fitment and flow on the BMW B58 platform:
- 3D Scanning & Reverse Engineering: OEM parts are 3D scanned to analyse routing, diameters and bend geometry for optimised performance.
- 7-Axis CNC Bending: Achieves up to 98% roundness with minimal outer bore wear at 180°, maintaining smooth flow and strength.
- Ultra-Precise Fabrication: Integrally moulded pipework with accuracy to under 0.025 mm reduces turbulence and ensures consistent quality.
- Advanced Welding Techniques: Crisscross and overlapping welds at high-stress points improve durability, with direct spot welding for superior strength and precision.
Compatibility
Engine: BMW B58
BMW 3 Series
- G20 M340i / M340i xDrive (2018–2020)
- G21 M340i xDrive (2018–2020)
BMW 4 Series
- G22 M440i / M440i xDrive (2020+)
- G23 M440i xDrive (2020+)
- G26 M440i xDrive (2020+)
Part number
AP546A
Warranty
Stone Exhaust 2-year warranty.
Installation and fitting
This system is designed for direct OEM fitment. For professional fitting, we recommend booking with Nforcd in Warwickshire. Request a fitting quote at Sales@nforcd.com.
What our customers say
We have installed Stone Exhaust systems on numerous BMW B58 cars and use them ourselves. Feedback is consistently excellent: perfect OEM-level fit, a deep refined tone with valves closed, an addictive, sporty sound with valves open and no annoying drone on the motorway.
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