We are proud to introduce you to the state of the art Stone Exhaust Valvetronic Cat-Back Exhaust System, to enhance the performance and sound of your BMW F22 Coupe & F23 Convertible M235i with the N55 engine.
Stone Exhaust has been developing world's best exhaust system since 1998, starting with 3D scanning and reverse engineering the OEM system, this allows the Stone engineers to design a 100% OEM fitment exhaust with precision. With our in-house dyno, your BMW exhaust system is proven to produce more power with the enhanced Stone signature exhaust sound.
The OEM Integred Valve option allows your exhuast system to operate as standard, where the onboard computer (ECU) will control the opening and closing of the valves automatically.
You can also add on Stone Cat-Back Valvetronic System. This product requires Single Valve System.
Features
- OEM Integration
- Available to add-on Stone Valvetronic System
- Plug and Play OBDII controller
- One Piece Design
- Mechanical Welding with Precision
- In House Research and Development
- 3D Scanning & Reverse Engineering
- Remote Control with On / Off / Auto settings
- Dyno Developed In House
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Eliminates drone found on the standard exhaust system
Dyno 
BMW F22 F23 M235i with Stone Exhaust Eddy Catalytic Downpipe & OEM Cat Back Exhaust Sound
OPF Delete
R&D and 3D Scanning
Stone Exhaust engineers use reverse engineering by 3D scanning OEM parts to understand their functionality and identify weaknesses. Data has been collected continuously in order to analyze factors such as pipe diameter, route and degrees of the bending angles of the N55 Exhaust Systems.
During R&D, Stone Exhaust utilizes the 3D simulation software to stimulate the exhaust gas flow movement, thermal and pressure rise zone. Progressive improvements were continually made until the optimal performance was achieved.
7 Axis CNC Bending Machine
Stone Exhaust System are constructed utilizing a 7 axis CNC Bending Machine which is the ultimate machine for high levels of precision delivery, necessary for industries such as the aerospace and defense industries.
With the state-of-the-art bending machine, Stone Exhaust has achieved the industry’s standard to an impressive 98% roundness, whilst maintaining the wear of the outer bore at only 25% at 180°. Airflow obstruction and welding fracture problems are prevented by utilizing this technology. With the combination of the CNC Bending machine, Reverse Engineering and 3D Design Scanning, Stone exhaust has created an integrally molded exhaust pipe with an accuracy error under 0.025mm.
Crisscross and Overlapping Welding Technique
The flange between the turbo and the downpipes reaches extreme temperatures (800℃ to 1100℃) which creates stress on the connection point. By utilizing both welding techniques to increases the width and penetration of welds. This increases the endurance and tolerance of these connection points, leading to quality products with reliable performance.
Direct Spot Welding
Our highly skilled engineers perform direct spot welding to increase product strength. This is undertaken by mechanical welding arms, proven to achieve greater precision and penetration in their welds compared to manual welding, resulting in an end product that is a work of art.
Compatibility - N55 Engine
BMW 2 Series
- F22 M235i (2012-2017)
- F22 M235i xDrive (2013-2017)
- F23 M235i/M235i xDrive (2014-2016)
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