Stone Exhaust BMW S55 F80 F82 OPF-Back OEM Integrated Valved Exhaust System for M3 and M4
Transform your BMW M3 M4 with the Stone Exhaust OPF-Back OEM integrated valved exhaust system. Purpose-built for the BMW S55 engine in the F80 M3 Saloon and F82 M4 Coupe, this premium performance exhaust delivers an aggressive BMW M3 M4 exhaust note, dyno-proven gains, precision OEM fitment and true daily drivability with no drone. Designed through 3D scanning and reverse engineering of the factory system, the Stone Exhaust OPF-Back retains the factory valve control, so the ECU manages valves automatically for effortless, OEM-like operation and maximum performance sound when you want it.
If you are searching for BMW M3 exhaust, BMW M4 exhaust, BMW F80 exhaust upgrade, BMW F82 exhaust upgrade, S55 valved exhaust, OPF-back exhaust, GPF back exhaust, valvetronic exhaust, performance exhaust for M3 M4 or quad tip M3 M4 exhaust, this Stone Exhaust system is the premium, dyno-developed solution engineered to fit and perform flawlessly.
Why choose the Stone Exhaust OPF-Back for your S55 M3 M4
- OEM Integrated OPF-Back exhaust with factory valve control for seamless ECU operation
- Dyno-developed in-house for proven performance and enhanced Stone signature sound
- Eliminates drone commonly found on the standard exhaust system for comfortable cruising
- One-piece design with precision machine welding for strength and durability
- Developed using 3D scanning and reverse engineering for 100% OEM fitment
- Optional Stone Valvetronic System available with plug and play OBDII controller for remote dual-valve control
- In-house research and development backed by advanced manufacturing
- Dual exit with quad tailpipes look for a true M3 M4 presence
Real performance you can feel
Dyno-proven power gains:
- +12.2 PS at 6800 rpm
- +9.8 Nm / +7.2 ft-lb at 2500 rpm
Developed and validated on Stone’s in-house dyno, this OPF-Back system frees up flow and pairs the S55’s character with a deeper, richer tone. Enjoy a sharper throttle response and a more engaging drive without compromising refinement.
Engineering that makes the difference
Stone Exhaust engineers use comprehensive 3D scanning of OEM components to analyse pipe diameters, routing and bend angles, then simulate exhaust gas flow, thermal behaviour and pressure zones in advanced software. Iterative improvements lead to optimal flow and sound with perfect fitment on the BMW F80 M3 and F82 M4.
Built on a state-of-the-art 7-axis CNC bending machine, Stone achieves up to 98% roundness with minimal outer-bore wear at tight 180 degree bends, reducing turbulence and preventing weld fractures. Crisscross and overlapping welding techniques increase penetration and durability at high-heat junctions, while precise mechanical spot welding delivers consistent, robust joins. The result is a premium exhaust system engineered for endurance and performance.
Compatibility
BMW S55 engine
- BMW F80 M3 Saloon 2012-2015
- BMW F80 LCI M3 Saloon 2015-2018
- BMW F82 M4 Coupe 2013-2017
- BMW F82 LCI M4 Coupe 2016-2018
Best paired with
Often purchased together with the Stone Exhaust BMW S55 F80 F82 F87 Catless Downpipe (M2 Competition, M3 and M4) for maximum performance and the ultimate Stone Exhaust M3 and M4 sound.
Our experience at Nforcd
We have fitted and used Stone Exhaust systems on customer BMW M3 and M4 builds and the feedback is consistently excellent. Fitment is spot on thanks to the 3D scanned design, the tone is addictive with valves open and refined with valves closed, and the system genuinely removes the unwanted drone of the stock exhaust. If you want a BMW M3 M4 valved exhaust that performs, sounds right and fits like OEM, this is the one.
Fitting and installation
Professional installation available at Nforcd in Warwickshire. For a fitting quote or to schedule your upgrade, email Sales@nforcd.com.
Part number
AP507-OPFBack
Warranty
Stone Exhaust 2 Year Warranty
Media
Sound and product visuals
