Stone Exhaust BMW 328i/428i F30 F32 F33 N26 Valved Cat-Back (Catback) Performance Exhaust | Switchable Valvetronic OEM Valve Control | Twin/Dual/Quad Tips | Drone-Free Direct-Fit Sports Back Box/Muffler Upgrade for 3 Series & 4 Series | Rear Section

BMW 328i 428i F30 F32 F33 N26 valve-controlled performance exhaust by Stone Exhaust

Give your turbocharged N26 3 Series or 4 Series the soundtrack and response it deserves. This switchable performance system is a direct replacement for the factory rear section, using the car’s original valve control for quiet cruising and a richer, sportier tone when open. Designed around the OEM layout for factory-style fit and finish, it delivers a deeper note, cleaner flow and crisp throttle response without unwanted cabin resonance.

Prefer manual control on demand? Add the optional Stone Valvetronic single-valve kit with simple OBDII plug-in controller for instant loud or quiet at the touch of a button.

Key reasons enthusiasts choose this upgrade

• Factory valve integration for seamless ECU control, smooth in Comfort, full character in Sport
• Optimised flow from Stone’s 3D-scanned, OEM-referenced design for real-world gains on their in-house dyno
• Refined, drone-free cruising with a deeper, more engaging tone under load
• Optional Valvetronic remote valve control via OBDII for plug-and-play switching
• One-piece layout for strength, leak resistance and consistent performance
• Precision CNC bending with up to 98 percent roundness to reduce turbulence at tight radii
• Robust mechanical welds with crisscross and overlap techniques for durability at high temperatures
• Direct replacement using factory mounting points for a hassle-free install

Compatible BMW models with the N26 engine

• BMW 3 Series F30 328i saloon 2011+
• BMW 4 Series F32 428i coupé 2013+
• BMW 4 Series F33 428i convertible 2013+

Tip layouts and part numbers

• AP501N26 Left single exit with twin tailpipes
• AP512N26 Dual exit with one tailpipe each side
• AP512QN26 Dual exit with quad tailpipes

Engineering detail that makes the difference

Stone engineers 3D-scan the factory exhaust to map diameters, routing and bend angles, then iterate with flow, thermal and pressure simulations to refine the design. A 7-axis CNC bending process maintains exceptional roundness through bends for stable gas speed and reduced turbulence. Crisscross and overlapping welds increase penetration and width, while precision spot welding by mechanical arms ensures consistent strength and a clean finish.

What drivers say

We have fitted this system to our own cars and for many customers, and the feedback is consistently positive. Fitment is spot on, the cruising refinement is excellent, and when the valve opens the car gains a properly sporty tone without cabin boom. It is a brilliant upgrade for daily use that still brings the weekend excitement.

Fitting and support

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

Warranty and manufacturer

Stone Exhaust 2 year warranty. Manufactured by Stone Exhaust.

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