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Stone Exhaust

Stone Exhaust BMW M135i xDrive F40 & M235i xDrive F44 B48E Valved Valvetronic Cat-Back/GPF-Back Performance Exhaust | Switchable OBD2 Plug & Play Remote | OPF/GPF Solution | 1 Series & 2 Series Gran Coupe Sports Catback | No Drone

Stone Exhaust BMW M135i xDrive F40 & M235i xDrive F44 B48E Valved Valvetronic Cat-Back/GPF-Back Performance Exhaust | Switchable OBD2 Plug & Play Remote | OPF/GPF Solution | 1 Series & 2 Series Gran Coupe Sports Catback | No Drone

£3,256.03
£3,427.40 £3,256.03
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Model
Tailpipe Finish

Heads-up on cancellations & returns: if you cancel an order or return an item, you won't get back 100% of what you paid. We apply a 10% restocking fee, the outbound shipping is non-refundable, and we have to pass on Shopify / PayPal payment processing fees; these aren't returned to us when we refund you. International orders also lose on exchange-rate spread in both directions. If the original packaging is damaged or missing, a reboxing charge applies. For international orders specifically, if you refuse to pay our shipping invoice or supply a prepaid label after placing the order, the same deductions apply. We're upfront about this — please be sure of your purchase before ordering.

Stone Valvetronic system for BMW F40 M135i xDrive and F44 M235i xDrive - B48E platform

Give your BMW 1 Series M135i xDrive F40 or BMW 2 Series Gran Coupe M235i xDrive F44 the soundtrack and response it deserves with the Stone switchable rear section. Purpose built for the B48E engine cars, this premium catback upgrade delivers a rich, motorsport-inspired tone, tangible performance gains verified on Stone’s in-house dyno, and a perfect, OEM-style fit achieved through precise 3D scanning and reverse engineering.

We run this hardware on our own builds and have fitted it for many happy customers. Feedback is consistent - outstanding sound with the valves open, refined and calm with them closed, easy control through the plug-in OBD module, and no intrusive motorway drone. If you are hunting for a high quality, valve-controlled sports system for your M135i or M235i, this is the one to choose.

Key reasons to choose this Stone system

  • Vehicle specific design for BMW F40 M135i xDrive and F44 M235i xDrive cars using the B48E engine
  • Dual valve, switchable sound control with remote - ON, OFF and AUTO modes
  • OBDII plug-in controller for quick installation and simple valve management
  • Developed to remove the cabin boom common with the factory setup for relaxed cruising
  • One-piece layout with precision machine welding for strength and longevity
  • 3D scanned and reverse engineered for true direct-fit installation
  • Dyno tested by Stone for proven performance improvement

Switchable valves - quiet when you need it, aggressive when you want it

The included remote puts you in control. Open the valves for maximum flow and a deeper, sportier character, close them for near OE levels of civility, or use AUTO so the system opens at a preset RPM. The supplied OBD plug-in controller makes operation intuitive and installation straightforward.

Built with precision for smooth flow and reliability

  • Seven-axis CNC mandrel bending - up to 98 percent roundness for optimised gas speed
  • Crisscross and overlapping welding on high heat joints for durability
  • Direct spot welding with mechanical arms for strong, consistent welds
  • Integrally moulded pipework with accuracy down to 0.025 mm

OPF - GPF support

Running an OPF - GPF equipped car. A free-of-charge OPF delete solution is available on request, allowing fitment on OPF vehicles without fault codes - no ECU coding required. Ask us to include it when ordering.

Recommended pairings

For an even more pronounced tone and additional flow, many owners add either the Stone BMW B48E F40 M135i xDrive Catless Downpipe or the Stone BMW B48E F40 M135i xDrive Eddy Catalytic Downpipe.

Compatibility

Engine: BMW B48E

  • BMW 1 Series F40 M135i xDrive 2018+
  • BMW 2 Series F44 M235i xDrive 2018+

Part numbers

  • AP548AS - F40 M135i xDrive
  • AP548BS - F44 M235i xDrive

What you will love

  • Sporty, characterful soundtrack with valves open - calm and comfortable with valves shut
  • Real-world performance uplift backed by Stone dyno development
  • Direct-fit installation thanks to accurate scanning and precision welding
  • Reliable, plug-in OBD control for instant valve operation

Warranty

Stone Exhaust 2 Year Warranty.

Professional fitting

Prefer expert installation. MJ Modifications offers professional fitting in Warwickshire. Request a tailored quote at info@mjmodifications.co.uk.

Videos

Stone Valvetronic System Installation


BMW B48E F40 M135i xDrive - Stone Catless Downpipe plus Valvetronic catback sound

Image gallery

Stone Valvetronic catback for BMW F40 M135i xDrive - MJ Modifications UK

Stone switchable exhaust BMW M135i F40 - MJ Modifications UK

BMW B48E F40 M135i catback rear section by Stone - MJ Modifications UK

Stone valve-controlled system for BMW M135i xDrive - MJ Modifications UK

Stone rear section BMW F40 M135i xDrive - MJ Modifications UK

Close up Stone Valvetronic BMW F40 M135i - MJ Modifications UK

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