AP506NSN26 Stone valve-controlled cat back for BMW F20 F21 125i N26
Transform the character of your 1 Series 125i with Stone’s flap controlled sports system for the N26 engine. This rear section upgrade delivers a rich, motorsport tone on demand and a refined OEM-plus note for everyday driving, with genuine plug and play control. Developed on the dyno and built for precise OEM fit, it sharpens throttle response, frees up flow and removes the cabin resonance that plagues the standard system.
- Part number: AP506NSN26
- Valve control with handheld remote - On, Off and Auto modes
- OBDII plug-in controller for quick installation and tidy wiring
- One-piece layout for optimal gas velocity and simple fitment
- 3D scanned from the factory layout for perfect alignment
- 7 axis CNC mandrel bends for exceptional roundness and flow
- Advanced overlapping weld techniques for strength and durability
- In-house dyno development for real-world performance gains
- Designed to eliminate unwanted drone at cruising speeds
- Backed by Stone’s 2 year warranty
What you will hear and feel
With the valve open you get a deeper, sportier soundtrack with crisp upshifts and a purposeful overrun. Close the valve and enjoy a calm, refined drive suitable for commuting and long motorway runs. Expect improved response, a freer revving feel and a more engaging drive without harshness.
Smart valve control
The supplied remote gives instant control of the exhaust flap. Choose On for maximum sound and flow, Off for neighbour friendly operation, or Auto to let the controller open the valve at a set engine speed. The control unit plugs into the OBD port for a clean, reversible, bolt-on installation.
Engineered the right way
Stone reverse engineers the factory layout using 3D scanning to nail pipe routing and clearances, then optimises gas dynamics and heat management. Precision 7 axis mandrel bending maintains up to 98 percent roundness through each bend, while meticulous weld methods withstand repeated heat cycles. The result is a premium BMW 125i cat back upgrade that fits like stock, flows better and lasts.
Compatibility
- BMW F20 125i 2014+ including LCI - requires M135i rear bumper
- BMW F21 125i 2010+ and 2014+ including LCI - requires M135i rear bumper
Why buy from MJ Modifications
We have installed and used this system at MJ Modifications and customer feedback has been consistently excellent for fit, finish and the controllable sound profile. If you would like professional fitting, we offer installation at our Warwickshire workshop. Request a quote at info@mjmodifications.co.uk.
Warranty
Stone Exhaust manufacturer warranty: 2 years.
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