Stone Exhaust BMW N20 E84 E89 F25 F26 Eddy Catalytic Downpipe (Inc. X3 20i xDrive, X4 20i xDrive, X3 28i xDrive & X4 28i xDrive)

Stone Exhaust BMW N20 E84 E89 F25 F26 Eddy Catalytic Downpipe (Inc. X3 20i xDrive, X4 20i xDrive, X3 28i xDrive & X4 28i xDrive)

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Meet the latest technology that adheres to the world's increasingly stringent environmental regulations at the same time enhances performance to another level. In comparison to commercially available linear frustums, the "eddy catalytic technology" adopts an arc-packaging method. The turbine emissions process produces a vortex effect which purifies the exhaust gases while maintaining an equal amount of back pressure. When compared to a variety of horsepower tests and straight downpipes, our patented eddy catalytic technology can effectively increase horsepower and torque.


  • Patented O2 sensor technology design provides real-time data performance by accurately sensing every rotating displacement.
  • No more delayed in power delivery
  • No error code nor check engine light
  • Using one of the rare noble metal to help efficiently filter out exhaust gas.
  • Computer simulation to obtain the best diameter.
  • Special 3D design to achieve 100% OEM fitment, no modification required.
  • SUS304 Premium Grade Stainless steel.
  • Dual Cross-Welding Technology providing substantial increase durability at the turbo Flange.
  • UK MOT friendly and Euro 6 Compliant


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 N20 Exhaust System found on the BMW F25 F26 X3 20i xDrive, X4 20i xDrive, X3 28i xDrive & X4 28i xDrive. 

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.

Stone Exhaust System 3D Scanning Reverse Engineering UK - Nforcd UK


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.

    Stone Exhaust System UK Bending - Nforcd UK


    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.

    Stone Exhaust Art of Welding - Nforcd UK


    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.

    Stone Exhaust Art of Welding - Nforcd UK


    N20 Engine

    BMW X Series

  1. E84 X1-X4 20i/28i (2008 - 2015)
  2. F25 X3 20i (2013-2017)/ X3 20i xDrive  (2011-2017)
  3. F25 X3 28i (2013-2017)/ X3 28i xDrive  (2009-2017)
  4. F26 X4 20i xDrive (2013-2018)
  5. F26 X4 28i xDrive (2013-2018)

    BMW Z Series

  7. E89 Z4 20i/30i (2008 -2016)


    Manufactured by

    Stone Exhaust


    Stone Exhaust 2 Year Warranty