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Stone Exhaust

Stone Exhaust BMW Toyota B58D Eddy Catalytic Downpipe GPF (Inc. A90 Supra, G29 Z4 M40i, G20 M340i & G20 M340i xDrive)

Stone Exhaust BMW Toyota B58D Eddy Catalytic Downpipe GPF (Inc. A90 Supra, G29 Z4 M40i, G20 M340i & G20 M340i xDrive)

Regular price £1,887.84 Inc. VAT
Regular price £1,987.20 Sale price £1,887.84 Inc. VAT On sale

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Meet the latest patented technology that adheres to the world's increasingly stringent environmental regulations, at the same time enhances performance to another level on your BMW G20, G21, G29 G29, Z4 M40i, M340i & M340i xDrive and Toyota A90 Supra with B58D engine. 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 conventional straight downpipes, the patented eddy catalytic technology can effectively increase horsepower and torque. In the lower rpm you will be immerse with vast amount of torque until you reach higher rpm where the vortex effect really comes to life and opens up the Catalytic, resulting in a performance similar to a 100 CELL Catalytic. However in the lower rpm, the catalytic will produce efficient and clean emission similar to a 400CEL Catalytic and produce no Check Engine Lights, completely error free.


  • Patented O2 sensor technology design provides real-time data performance by accurately sensing every rotating displacement. No more delayed or error code problem.
  • Using one of the rare noble metal to help efficiently filter out exhaust gas.
  • Computer simulation of the best diameter.
  • A special 3D design able to achieve a perfectly matching model with the original pipe. the same installation applies, no need to modify.
  • SUS304 Stainless steel.
  • Dual Cross-Welding Technology providing substantial increase durability.
  • 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 B58D Exhaust System found on the A90 Supra, G29 Z4 M40i, G20 M340i & G20 M340i 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 - ML Performance 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 - ML Performance 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 - ML Performance 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 - ML Performance UK


      B58D Engine


      2 Series

      • G42 M240i xDrive (2022+)

        3 Series

        • G20 340i/340i xDrive (2018+)
        • G21 340i xDrive (2018+)

          BMW Z Series

          • G29 Z M40i (2019+)
          • A90 Supra (2020-Present)



          Manufactured by

          Stone Exhaust



          Stone Exhaust 2 Year Warranty

          BMW G29 B58D Z4 M40i / Stone Eddy Catted Downpipe

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