Stone Exhaust BMW 1 Series M140i B58 Valved Cat-Back/Catback Performance Exhaust System (F20/F21) - Switchable Valvetronic Rear Section, OEM Valve Control, No Drone, OPF/GPF Friendly, Back Box + Mid Pipe | AP526A

Switchable Sports System for BMW 1 Series M140i B58 F20 F21

Give your B58-powered M140i the soundtrack it deserves. This Stone Exhaust switchable rear system delivers a deeper, crisper tone when the flap is open and calm refinement when it is shut, with no cabin boom at motorway speeds. Designed via full 3D scan of the factory layout, it bolts up cleanly, aligns perfectly and integrates with the original valve actuator for factory-style control.

What makes it a standout upgrade

• Factory valve integration. Uses the original actuator and ECU logic for quiet and loud modes, just as the car intended.
• Optional remote control. Add the Stone Valvetronic single valve kit for on-demand sound at the press of a button.
• Smooth, one-piece layout that promotes flow and makes installation straightforward.
• Plug and play OBDII controller available for enhanced control flexibility.
• Engineered to eliminate drone so daily driving remains relaxed and conversation friendly.
• 3D scanned and reverse engineered for true OEM-style fitment on the F20 and F21 chassis.
• In-house dyno development for response, tone and drivability that suit both road and spirited use.
• 7-axis CNC mandrel bending maintains up to 98 percent roundness at tight radii, reducing turbulence.
• Precision mechanical welds with criss-cross and overlapping techniques for long-term durability under heat.

Sound and drivability

Flap closed delivers an OEM-like hush for early starts and long journeys. Open it up and the turbocharged straight six comes alive with a rich, motorsport-inspired note and sharper character. No resonance, just a clean, purposeful voice that suits the B58 perfectly.

OPF and GPF compatibility

Running a particulate filter. An OPF solution is included free of charge to support fitment on OPF-equipped cars without warning lights, so no ECU coding is required.

Fitment

For BMW 1 Series M140i with the B58 3.0 turbo engine:

• F20 M140i 5-door
• F21 M140i 3-door

Recommended add-ons

• Stone Exhaust B58 Catless Performance Downpipe
• Stone Exhaust B58 Eddy Catalytic Performance Downpipe
• Stone Valvetronic System single valve remote kit

Pairing the system with a performance downpipe and the remote kit is a popular route to maximise flow, response and soundtrack.

Real-world results

We run this on our own cars and fit it for customers who want a premium M140i upgrade that sounds superb, lines up perfectly and stays civilised on longer trips. Feedback has been consistently positive on quality, valve operation and the absence of drone.

Installation and support

Professional fitting available at MJ Modifications in Warwickshire. For a fitting quote or advice, email info@mjmodifications.co.uk.

Warranty

Stone Exhaust 2 Year Warranty.

Manufacturer

Stone Exhaust

Part number

AP526A

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