Stone Exhaust Valved Catback for BMW 3 Series F30 F31 & 4 Series F32 F33 F36 320i/420i (N

Stone Exhaust Valved Cat Back for BMW F30 F31 F32 F33 F36 320i and 420i - N20 Turbo

Transform the sound and response of your 3 Series or 4 Series with Stone’s factory-valve-compatible cat back. Developed specifically for the N20 turbo petrol platform, this performance rear section delivers a deeper, sportier note with civilised cruising and real-world refinement. It plugs straight into the original electronic flap system, so the car’s ECU controls the valve as standard. Comfort when you want it, more presence when you press on.

We have fitted and run this system on our own builds and customer cars. Feedback has been consistently positive - calm on the motorway with minimal cabin boom, crisp and aggressive under load, and excellent fitment thanks to precise engineering. If you are searching for a sports exhaust for F30 320i, F31 Touring 320i, F32 420i coupe, F33 420i cabrio or F36 420i Gran Coupe including xDrive, this is the direct-fit upgrade that keeps OE polish while adding excitement.

Key reasons to choose this Stone valved system

• Direct fit for BMW F30 F31 F32 F33 F36 with N20 2.0 turbo 320i and 420i including xDrive
• Factory valve integration - ECU controlled flap operation for seamless drive modes
• Refined tone with minimal drone compared to the stock back box
• 3D scanned and reverse engineered for exact OE-style alignment and hanger positions
• Dyno developed for improved flow and sharper throttle response
• One piece construction with precision mechanical welding for durability
• Engineered to cut unwanted cabin resonance while enhancing character

Optional Valvetronic remote control upgrade

Want to command the valve yourself at any time? Add the Stone Valvetronic single-valve kit. It includes a plug-and-play OBDII controller and remote, allowing you to open or close the flap on demand. Ideal if you want quiet start early in the morning and a more vocal soundtrack on a spirited drive.

Sound and development

How Stone achieves OE-level fit and finish

Stone designs each system using detailed 3D scanning of the original equipment to map pipe diameter, routing and bend angles. Flow, temperature and pressure are simulated to refine performance, then the final product is produced with a 7 axis CNC bending process that keeps up to 98 percent roundness. Critical joints feature overlapping and crisscross welds with mechanical arm spot welding for strength and long service life.

Installed photos

Vehicle compatibility - N20 2.0 turbo

3 Series

• F30 320i and 320i xDrive 2011 plus
• F30 LCI 320i and 320i xDrive 2014 plus
• F31 320i 2011 plus and 320i xDrive 2012 plus
• F31 LCI 320i and 320i xDrive 2014 plus

4 Series

• F32 420i and 420i xDrive 2013 plus
• F32 LCI 420i and 420i xDrive 2016 plus
• F33 420i 2013 plus and F33 LCI 2016 plus
• F36 420i and 420i xDrive 2013 plus
• F36 LCI 420i and 420i xDrive 2016 plus

Part numbers and outlet styles

• AP502 - Single left exit with twin tips - uses original bumper
• AP502N - Dual exit with twin tips - requires 335i or 435i rear bumper
• AP502NQ - Dual exit with quad tips - requires 335i or 435i rear bumper

Installation

Professional fitting recommended for best results. Book expert installation with MJ Modifications in Warwickshire. Request a quote at info@mjmodifications.co.uk.

Warranty

Stone Exhaust 2 year warranty.

Manufactured by

Stone Exhaust

Search terms to help you find this product

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