{"product_id":"stone-exhaust-bmw-n55-f22-f23-m235i-cat-back-valvetronic-exhaust","title":"Stone Exhaust BMW 2 Series M235i (F22\/F23, N55, xDrive) Valved Cat-Back Exhaust System | OEM Integrated Valve | AP504B","description":"\u003cdiv class=\"product__description rte\"\u003e\n  \u003ch2\u003eStone Exhaust Switchable Cat Back for BMW M235i F22 F23 N55 including xDrive - Part No. AP504B\u003c\/h2\u003e\n\n  \u003cp\u003e\n    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.\n  \u003c\/p\u003e\n\n  \u003cp\u003e\n    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.\n  \u003c\/p\u003e\n\n  \u003ch3\u003eKey reasons enthusiasts choose this system\u003c\/h3\u003e\n  \u003cul\u003e\n    \u003cli\u003eFactory valve integration via ECU for seamless switchable sound control\u003c\/li\u003e\n    \u003cli\u003eOptional remote control with Stone Valvetronic OBD2 controller for manual open and close\u003c\/li\u003e\n    \u003cli\u003eTrue direct-fit geometry created from 3D scans of the original hardware\u003c\/li\u003e\n    \u003cli\u003eDyno-developed for improved flow and sharper response\u003c\/li\u003e\n    \u003cli\u003eTuned to reduce drone for comfortable motorway cruising\u003c\/li\u003e\n    \u003cli\u003eOne-piece layout for fewer joints and a clean, high quality finish\u003c\/li\u003e\n    \u003cli\u003ePrecision mechanical welding for durability and consistency\u003c\/li\u003e\n    \u003cli\u003e7-axis CNC bending that maintains roundness for smooth gas velocity\u003c\/li\u003e\n    \u003cli\u003eAdvanced overlap and crisscross weld techniques for heat resilience\u003c\/li\u003e\n    \u003cli\u003eDirect spot welding at critical points to enhance long-term strength\u003c\/li\u003e\n  \u003c\/ul\u003e\n\n  \u003ch3\u003eHow it sounds and drives\u003c\/h3\u003e\n  \u003cp\u003e\n    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.\n  \u003c\/p\u003e\n\n  \u003cdiv style=\"margin: 10px 0;\"\u003e\n    \u003cimg src=\"https:\/\/cdn.shopify.com\/s\/files\/1\/0284\/6300\/5795\/files\/Stone_Exhaust_BMW_N55_F22_F23_M235i_Cat-Back_Valvetronic_Exhaust_Stone_Exhaust_USA_600x600.png?v=1594116045\" alt=\"Stone Exhaust BMW M235i F22 F23 N55 valve-controlled cat back AP504B dyno-developed\"\u003e\n  \u003c\/div\u003e\n\n  \u003ch3\u003eValve control options\u003c\/h3\u003e\n  \u003cp\u003e\n    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.\n  \u003c\/p\u003e\n\n  \u003cdiv style=\"margin: 10px 0;\"\u003e\n    \u003ciframe width=\"1195\" height=\"672\" src=\"https:\/\/www.youtube.com\/embed\/V5c4VEyO1EM\" title=\"Stone Valvetronic System Installation\" frameborder=\"0\" allow=\"accelerometer; autoplay; encrypted-media; gyroscope; picture-in-picture\" allowfullscreen\u003e\u003c\/iframe\u003e\n  \u003c\/div\u003e\n\n  \u003ch3\u003eEngineering that makes the difference\u003c\/h3\u003e\n  \u003cp\u003e\n    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.\n  \u003c\/p\u003e\n\n  \u003cdiv style=\"margin: 10px 0;\"\u003e\n    \u003cimg src=\"https:\/\/cdn.shopify.com\/s\/files\/1\/0284\/6300\/5795\/files\/1_9336c8b0-c9ea-4822-891c-83490f630707.jpg?v=1572705528\" alt=\"Stone Exhaust 3D scanning reverse engineered fitment for BMW M235i\"\u003e\n  \u003c\/div\u003e\n\n  \u003cdiv style=\"margin: 10px 0;\"\u003e\n    \u003cimg src=\"https:\/\/cdn.shopify.com\/s\/files\/1\/0284\/6300\/5795\/files\/bending.jpg?v=1572739395\" alt=\"7-axis CNC bending for smooth flow M235i F22 F23 exhaust\"\u003e\n  \u003c\/div\u003e\n\n  \u003cdiv style=\"margin: 10px 0;\"\u003e\n    \u003cimg src=\"https:\/\/cdn.shopify.com\/s\/files\/1\/0284\/6300\/5795\/files\/Stone_Exhaust_Art_of_Welding_-_1_1024x1024.jpg?v=1572828150\" alt=\"Precision welding Stone Exhaust BMW 2 Series M235i\"\u003e\n  \u003c\/div\u003e\n\n  \u003cdiv style=\"margin: 10px 0;\"\u003e\n    \u003cimg src=\"https:\/\/cdn.shopify.com\/s\/files\/1\/0284\/6300\/5795\/files\/Stone_Exhaust_Art_of_Welding_-_2_1024x1024.jpg?v=1572828178\" alt=\"Direct spot welding strength Stone Exhaust M235i cat back\"\u003e\n  \u003c\/div\u003e\n\n  \u003ch3\u003eHear it on the car\u003c\/h3\u003e\n  \u003cp\u003eBMW F22 F23 M235i with Stone Exhaust Eddy Catalytic Downpipe and OE cat back sound example:\u003c\/p\u003e\n  \u003cdiv style=\"margin: 10px 0;\"\u003e\n    \u003ciframe width=\"1195\" height=\"672\" src=\"https:\/\/www.youtube.com\/embed\/L4t5NLCtFYg\" title=\"BMW M235i Stone Exhaust Sound\" frameborder=\"0\" allow=\"accelerometer; autoplay; encrypted-media; gyroscope; picture-in-picture\" allowfullscreen\u003e\u003c\/iframe\u003e\n  \u003c\/div\u003e\n\n  \u003ch3\u003eCompatibility\u003c\/h3\u003e\n  \u003cul\u003e\n    \u003cli\u003eBMW 2 Series F22 M235i 2012+\u003c\/li\u003e\n    \u003cli\u003eBMW 2 Series F22 M235i xDrive 2013+\u003c\/li\u003e\n    \u003cli\u003eBMW 2 Series F23 M235i and M235i xDrive Convertible 2014+\u003c\/li\u003e\n  \u003c\/ul\u003e\n\n  \u003ch3\u003ePart number\u003c\/h3\u003e\n  \u003cp\u003e\u003cstrong\u003eAP504B\u003c\/strong\u003e\u003c\/p\u003e\n\n  \u003ch3\u003eInstallation and fitting\u003c\/h3\u003e\n  \u003cp\u003e\n    Designed for a direct, bolt-on replacement. Professional fitting recommended. For expert installation, book with MJ Modifications in Warwickshire. Request a quote at \u003ca href=\"mailto:info@mjmodifications.co.uk\"\u003einfo@mjmodifications.co.uk\u003c\/a\u003e. We have installed this system for customers and on our own vehicles with excellent alignment and results.\n  \u003c\/p\u003e\n\n  \u003ch3\u003eWarranty\u003c\/h3\u003e\n  \u003cp\u003eStone Exhaust 2 year warranty.\u003c\/p\u003e\n\n  \u003ch3\u003ePopular search terms\u003c\/h3\u003e\n  \u003cp\u003e\n    BMW M235i sports exhaust UK, BMW 2 Series M235i cat back UK, F22 M235i exhaust upgrade, F23 M235i exhaust, switchable exhaust M235i, valve flap exhaust BMW N55, xDrive M235i exhaust system, M235i performance rear section, BMW M235i loud exhaust with valve, BMW 2 Series coupe exhaust, BMW 2 Series convertible exhaust, ECU controlled flap exhaust, OBD2 remote valve controller, drone free M235i exhaust, performance exhaust for N55 M235i, Stone Exhaust M235i UK.\n  \u003c\/p\u003e\n\u003c\/div\u003e","brand":"Stone Exhaust","offers":[{"title":"Flat Cut Gloss Carbon Fiber (82mm)","offer_id":56008709570946,"sku":null,"price":2584.32,"currency_code":"GBP","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0871\/5445\/8937\/files\/1020CG_FlatCutGlossCarbonFibre_102mm-2_300x300_ef8c51a3-ae8f-4312-bdc0-a77dc8fb6870.png?v=1764091150","url":"https:\/\/mjmodifications.co.uk\/products\/stone-exhaust-bmw-n55-f22-f23-m235i-cat-back-valvetronic-exhaust","provider":"MJ Modifications","version":"1.0","type":"link"}