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 for M135i, M235i, 335i, 435i, X3 35i xDrive, X4 35i xDrive & M40i xDrive with N55 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 N55 Exhaust System found on the BMW F20 F21 F22 F23 F30 F31 F32 F33 F36 manufactured with the Electronic Wastegate and Pneumatic Wastegate.

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.

Dyno 

N55 Engine

BMW 1 Series 

• F20 M135i /M135i xDrive (2011+)
• F20 LCI M135i /M135i xDrive (2015+)
• F21 M135i (2011+) /M135i xDrive (2012+)
• F21 LCI M135i /M135i xDrive (2015+)

BMW 2 Series 

• F22 M235i/ (2012+)
• F22 M235i xDrive (2013+)
• F23 M235i/M235i xDrive (2014+)

BMW 3 Series

• F30/F31 330e/335i/ 335i xDrive (2011-2015)

BMW 4 Series

• F32 435i/435i xDrive (2012+)
• F33 435i/435i xDrive (2013+)
• F36 435i/435i xDrive (2013+)

BMW X Series

A201P (PWG)

A202P (EWG)

Manufactured by

Stone Exhaust

Warranty

Stone Exhaust 2 Year Warranty

Stock V.S Stone Exhaust Catless DP

Fitted Photos

Video 

BMW N55 F30 335i Stone Exhaust Sound