Stone Exhaust
Stone Exhaust Valved Cat-Back Exhaust for BMW N20 F30 F32 F33 F36 (328i 428i) OEM Integrated Valve, Quad/Dual/Single Exit UK
Stone Exhaust Valved Cat-Back Exhaust for BMW N20 F30 F32 F33 F36 (328i 428i) OEM Integrated Valve, Quad/Dual/Single Exit UK
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Stone Exhaust Switchable Catback for BMW F30 F32 F33 F36 328i 428i, UK supplied
Transform the character of your BMW N20-powered 3 and 4 Series with Stone’s valve-controlled rear system. This premium, direct-fit upgrade delivers a richer tone on throttle and refined cabin manners on a cruise, with seamless plug-in operation using the factory flap control. If you are searching for a sports exhaust for 328i, a switchable flap system for 428i, a performance back box for F30 or F32, quad tip conversion for 4 Series, or a dual exit setup for xDrive models, this is the high quality choice for UK enthusiasts.
Key reasons enthusiasts choose Stone
- Factory flap integration uses the car’s ECU to manage the valve for everyday refinement and a more aggressive note when you want it.
- Optional Stone Valvetronic System Single Valve upgrade for remote flap control via a simple plug in OBDII controller.
- One piece construction for strength, consistent flow and precise alignment.
- 3D scanned and reverse engineered from the original system for genuine bolt-on fitment and perfect tip placement.
- Developed on the dyno to optimise gas speed and deliver that signature Stone tone without motorway drone.
- 7 axis CNC mandrel bending maintains roundness through tight radii to reduce turbulence.
- Advanced welding techniques, including crisscross and overlapping in high heat zones, for durability under sustained load.
- Automated spot welding ensures consistent penetration and a clean, premium finish.
- In house R&D focusing on flow, temperature management and back pressure balance.
How the factory-controlled flap behaves
The integrated valve works with your car’s electronics, keeping things civilised at light throttle then opening to unlock a deeper, sportier soundtrack as you push on. Want manual control at any time? Add the Stone Valvetronic System Single Valve for remote operation using the plug and play OBDII controller.
The sound and response upgrade your BMW deserves
Expect a deeper idle, sharper response and a crisp, motorsport-inspired note under load, all without the intrusive cabin boom that spoils long journeys. Ideal for daily use, weekend drives and show car builds with quad tips.
Compatibility, N20 2.0 turbo models
BMW 3 Series
- F30 328i, 2011 onwards
BMW 4 Series
- F32 428i and 428i xDrive, 2012 onwards
- F33 428i and 428i xDrive, 2013 onwards
- F36 428i and 428i xDrive, 2013 onwards
Options and part numbers
- AP501, single left exit with twin tailpipes
- AP512, dual exit with single tailpipe each side
- AP512Q, dual exit with quad tailpipes
In the metal
Installed examples of the Stone system on N20 F30 F32 F33 F36:
Engineering detail
Stone engineers 3D scan the original components to map diameters, routing and bend angles, then simulate flow, heat and pressure to refine performance and fit to within 0.025 mm.
7 axis CNC bending preserves up to 98 percent roundness through tight bends, keeping gas speed high and welds stress free. High heat areas receive crisscross and overlapping welds, while automated spot welding adds consistency and strength.
What owners say
We have fitted and tested these systems in house and feedback has been excellent. Customers love the perfect alignment, premium build, deeper soundtrack and the lack of motorway boom. It is the sound your F30 328i or F32 428i should have had from the factory.
Fitting and installation
Professional installation recommended. MJ Modifications, based in Warwickshire, can fit this system. Request a quote at info@mjmodifications.co.uk.
Warranty
Stone Exhaust 2 year warranty.
Search-friendly terms customers use
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