Stone Exhaust BMW N55 F22 F23 M235i OEM Integrated Valved Cat-back Exhaust System - Part Number AP504B
Upgrade your BMW M235i with the Stone Exhaust OEM integrated valved cat-back exhaust system. Engineered for the BMW 2 Series F22 and F23 with the N55 engine, this premium performance exhaust delivers an aggressive, motorsport-inspired tone with refined cruising manners and OEM-level fitment. Developed using 3D scanning, reverse engineering and in-house dyno testing, the Stone Exhaust cat-back enhances flow, sharpens throttle response and removes the factory drone for daily usability.
Searching for BMW M235i exhaust, BMW F22 M235i catback, BMW F23 M235i catback, valved exhaust M235i, BMW N55 cat back, F22 M235i performance exhaust, or UK BMW 2 Series M235i exhaust upgrade? This Stone Valvetronic-ready system is the proven choice for sound, performance and quality.
Why choose Stone Exhaust for your BMW M235i
- OEM integrated valve control - the factory ECU opens and closes the valve as standard
- Optional Stone Valvetronic System - remote valve control with plug and play OBDII controller
- True OEM fitment - 3D scanned and reverse engineered for precise installation
- In-house dyno developed - performance-focused design and flow optimisation
- Eliminates drone - confident daily driving with a strong, sporty tone on throttle
- One piece design - fewer joints for reliability and a clean, high quality finish
- Mechanical welding with precision - strength, durability and consistency
- 7-axis CNC bending - up to 98 percent roundness and minimal outer bore wear for smooth flow
- Advanced welding techniques - crisscross and overlapping welds for high temperature endurance
- Direct spot welding - increased structural integrity and long-term reliability
Real-world results and sound
The Stone signature sound is deep and purposeful with the valve open, and civilised with the valve closed. Backed by in-house dyno development, this cat-back is designed to unlock performance from your N55 while keeping motorway cruising comfortable. We run Stone systems on our own cars and customer feedback has been consistently excellent for build quality, fitment and sound.
Valve control options
OEM integrated valve - uses the car's ECU to manage valve operation, just like factory. For full manual control, add the Stone Valvetronic System - Single Valve - with the plug and play OBDII controller and remote, allowing you to switch sound levels on demand.
Engineering that makes a difference
Stone engineers use 3D scanning and reverse engineering of OEM parts to optimise pipe diameter, routing and bend angles, then validate with flow simulation for thermal and pressure zones. The 7-axis CNC bending process achieves outstanding roundness, minimises turbulence and prevents welding fracture issues. Crisscross and overlapping welds plus direct spot welding boost strength at high temperature connection points for long-term reliability.
Hear it on the car
BMW F22 F23 M235i with Stone Exhaust Eddy Catalytic Downpipe and OEM cat-back exhaust sound example:
Compatibility - BMW N55
- 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 direct OEM fitment. Professional installation recommended. For expert fitting, choose Nforcd in Warwickshire - request a quote at Sales@nforcd.com. We have installed this system for customers and on our own cars with superb results and perfect alignment.
Warranty
Stone Exhaust 2 year warranty.
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