Stone Exhaust
Stone Exhaust BMW 2 Series M235i (F22/F23, N55, xDrive) Valved Cat-Back Exhaust System | OEM Integrated Valve | AP504B
Stone Exhaust BMW 2 Series M235i (F22/F23, N55, xDrive) Valved Cat-Back Exhaust System | OEM Integrated Valve | AP504B
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Stone Exhaust Switchable Cat Back for BMW M235i F22 F23 N55 including xDrive - Part No. AP504B
Transform the character of your BMW 2 Series M235i with this valve-controlled rear section from Stone Exhaust. Built for the F22 coupé and F23 convertible with the N55 turbo engine, this system integrates with the factory flap so you get quiet when you want it and a fierce, motorsport soundtrack when you demand it. It is a direct fit, developed with precise 3D scanning, reverse engineering and in-house dyno validation for genuine performance and everyday refinement.
Looking for a BMW M235i sports exhaust upgrade in the UK, a switchable exhaust for F22 M235i, a valve flap cat back for N55, or an xDrive compatible M235i rear section? This Stone unit delivers the aggressive tone, crisp throttle response and OE-quality fit enthusiasts expect, with the convenience of plug-and-play valve control.
Key reasons enthusiasts choose this system
- Factory valve integration via ECU for seamless switchable sound control
- Optional remote control with Stone Valvetronic OBD2 controller for manual open and close
- True direct-fit geometry created from 3D scans of the original hardware
- Dyno-developed for improved flow and sharper response
- Tuned to reduce drone for comfortable motorway cruising
- One-piece layout for fewer joints and a clean, high quality finish
- Precision mechanical welding for durability and consistency
- 7-axis CNC bending that maintains roundness for smooth gas velocity
- Advanced overlap and crisscross weld techniques for heat resilience
- Direct spot welding at critical points to enhance long-term strength
How it sounds and drives
With the flap open you get a deep, hard-edged tone that suits spirited driving. Close the flap and it calms down for neighbours, long journeys and daily commuting. The sound profile is purposeful without being boomy, and the flow improvements help the N55 feel keener through the revs. We run Stone systems on our own cars and customer feedback has been consistently excellent for fit, finish and the way the exhaust transforms the driving experience.
Valve control options
Standard: the original ECU manages the flap automatically, just like from the factory. For on-demand control, add the Stone Valvetronic System Single Valve with plug-and-play OBD2 controller and remote so you can switch between quiet and loud at the touch of a button.
Engineering that makes the difference
Stone engineers map the OEM system with 3D scanning, then optimise tube diameter, routing and bend angles. Flow simulation helps target pressure and heat zones. The result is smooth gas transition, reduced turbulence and the reliability you want from a daily-driven performance exhaust. 7-axis CNC bending keeps pipe roundness high, while overlapping and crisscross welds plus direct spot welding shore up the hottest connection points.
Hear it on the car
BMW F22 F23 M235i with Stone Exhaust Eddy Catalytic Downpipe and OE cat back sound example:
Compatibility
- BMW 2 Series F22 M235i 2012+
- BMW 2 Series F22 M235i xDrive 2013+
- BMW 2 Series F23 M235i and M235i xDrive Convertible 2014+
Part number
AP504B
Installation and fitting
Designed for a direct, bolt-on replacement. Professional fitting recommended. For expert installation, book with MJ Modifications in Warwickshire. Request a quote at info@mjmodifications.co.uk. We have installed this system for customers and on our own vehicles with excellent alignment and results.
Warranty
Stone Exhaust 2 year warranty.
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