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

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

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In order to get even better efficiency for the section of exhaust turbine, as well as to prevent multiple welding positions in the downpipe section, which generates ash in the pipe while welding, causing bad exhaust efficiency, and then generates vaper lock and thus inability to exhaust, Stone Exhaust uses a variety of smart ideas in downpipe design. The company employs flow velocity measurement software in 3D and the technique of one-piece bend pipes, along with mechanical arms which accurately welds without generating ash in the pipe wall in order to further exhaust efficiency of Catless Downpipe. It is a perfect and effective product which has surpassed all similar products in the market.

  • Catless downpipe Inc. X3 20i xDrive, X4 20i xDrive, X3 28i xDrive & X4 28i xDrive with N20 engine.
  • Unique Flex design to prevent breakage caused by extreme heat 
  • Crisscross welding to strengthen turbo flange
  • One Piece Design
  • Machine Welding
  • In House Research and Development
  • 3D Scanning & Reverse Engineering
  • 100% OEM Fitment

    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 28i & X4 28. 

    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

      • E84 X1-X4 20i/28i (2008 - 2015)
      • F25 X3 20i (2013-2017)/ X3 20i xDrive  (2011-2017)
      • F25 X3 28i (2013-2017)/ X3 28i xDrive  (2009-2017)
      • F26 X4 20i xDrive (2013-2018)
      • F26 X4 28i xDrive (2013-2018)

      BMW Z Series

      • E89 Z4 20i/30i (2008 -2016)




      Manufactured by

      Stone Exhaust



      Stone Exhaust 2 Year Warranty



      BMW N20 F26 X4 28i xDrive With Stone Exhaust Catless DP + Valvetronic Cat-back Exhaust System Sound