BMW
M3 (M4) G80 / G81 / G82 · 2021 – present
Force the G8x flaps wide open whenever you want the S58 to actually sound like an M car.
- Works on M3, M3 Touring and M4 with OPF valved exhaust
- Cabin remote — no app, no Bluetooth, no subscription
- Doesn't override the ECU, never forces valves shut
- Slots into the existing actuator looms either side
Free UK shipping
2-year warranty
Fully reversible
The honest pitch
What this actually does to your M3 (M4)
BMW's OPF-era exhausts are clever and quiet. Almost too quiet. Sport Plus opens the flaps in narrow rev bands and then closes them again the moment the ECU thinks the neighbours might object.
Open Valve fixes that without an aftermarket back-box. You get the standard pipework, the standard sound character, just held permanently in its loudest state. The Sport+ pops, crackles and decel-bark all show up where the factory firmware tries to hide them.
Toggle off before you pull onto your street at midnight. Toggle on at the first roundabout the next morning.
Fitment
BMW M3 (M4) G80 / G81 / G82
Years
2021 – present
Install time
~10 minutes
Tools needed
None
Long read
The BMW M3 (M4) valve story
The G80 generation of M3 — and its M4, M3 Touring and M3 CS siblings — runs an OPF-equipped exhaust that BMW calibrated to be road-legal almost everywhere it sells. The S58 has plenty of noise to give. The valve map just doesn't let it. Sport plus opens the rear flaps in narrow RPM windows under load and shuts them again at the slightest hint of part-throttle cruise.
Open Valve overrides the close command at the actuator. Both rear flaps stay locked open the moment you press the fob, regardless of mode. The S58's twin-turbo voice — the off-cam burble at low revs, the metallic snarl past 5,500, the decel pops on overrun — all of it gets through the back-box at every throttle position.
We deliberately built this so the OFF button never forces the valves shut. The reason is engine-management: BMW occasionally opens the flaps at part throttle to manage back-pressure during certain DPF/OPF regeneration cycles. Forcing them closed would interfere with that. Our OFF state simply returns control to the ECU — the ECU is then free to open them when it wants, close them when it wants. The default behaviour you'd get without the module.
Install on the G80 takes us about fifteen minutes per car in the workshop. There are two actuator motors, one per side of the rear silencer. Both sit above the diffuser, accessible without dropping the bumper if you lower the rear of the wheel-arch liner. We supply heat-rated mounting for the module body because the silencer skin runs hot enough to soften standard tape.
Owners running aftermarket valved back-boxes — Akrapovic Slip-On, M Performance, Eisenmann — keep their connectors and the module works unchanged. Cars with full straight-through systems and no valves obviously can't use this.
Install — step by step
- 01
Cool the car. The S58 runs the back-box hot; give it 30 minutes after a drive before you go near the actuators.
- 02
Loosen the rear lower wheel-arch liner clips (T25 torx) on the offside. You don't need to remove it — folding it back gives access to the right-hand actuator.
- 03
Locate the grey 2-pin valve actuator connector on the motor body. Squeeze the lock tab, separate the two halves.
- 04
Plug the module inline: motor side into the OEM actuator, ECU side into the freed OEM harness. Repeat on the other side with the second module.
- 05
Velcro the module bodies to the chassis rail above each silencer, away from the heat-shield. Refit the wheel-arch liners.
- 06
Pair the fob: press and hold both buttons for three seconds — the module LED double-blinks to confirm. Test on idle: top button = audible click as flap opens, bottom button = click as control hands back.
In the box
- Two valve override modules (one per actuator)
- Two-button RF key fob (CR2032 pre-installed, spare in the box)
- OEM-pattern connectors — no cutting, no splicing, no scotch-locks
- Printed install card with model-specific photos and a workshop QR link
Fitment notes
- ·All G80 M3, G82 M4, G81 M3 Touring and G80/G82 M3/M4 CS supported.
- ·OPF cars only — the non-OPF rest-of-world spec from late 2020 uses a different actuator and is not supported.
- ·Compatible with all valved aftermarket back-boxes retaining OEM actuators (Akrapovic, BMW M Performance, Eisenmann, IPE).
BMW M3 (M4) — FAQ
Does it work on the M3 Touring?+
Yes. The G81 M3 Touring uses the same S58 powertrain and the same valve actuator hardware as the saloon. Same kit, same install procedure.
Will it work on the M3 CS?+
Yes. The CS runs the same actuator type, just with a different titanium back-box. We've fitted these on CS cars; the install location and connector are identical.
What about iDrive 8 noise warnings?+
iDrive doesn't monitor the valve position directly. It will show whatever the ECU thinks the valve state is — usually 'sport exhaust active' in M Sport modes. There's no warning popup and no message.
Will it throw a warning light on the dash?+
No. The module sits in the signal path between the ECU and the actuator motor. The ECU sees a normal actuator response back, so there's nothing to flag. We've shipped thousands of these and not had a single check-engine call linked to the module itself.
Is it reversible?+
Yes, fully. Unplug the module, plug the OEM connectors back into each other, refit the trim — about three minutes' work. There's no permanent change to the car, no part cut, nothing in the ECU. Dealer service visits, MOT, sale to a new owner — pull it out and it's like it was never fitted.
Does it work with an aftermarket exhaust?+
If the aftermarket back-box retains the OEM-pattern valve actuators (most do — Akrapovic, Milltek, IPE, Capristo all run the factory motors), yes. If the system is a straight-through with no valves, there's nothing for the module to override.
Does it interfere with the active sound design in the cabin?+
No. The cabin S58 'soundtrack' through the speakers is RPM/load driven and runs independently. It stays untouched. What changes is the real exhaust note from outside, which bleeds into the cabin more clearly.
Disclaimer
Open Valve modules are intended for off-road and motorsport use only. Please confirm your car has factory valve-actuated exhaust before ordering — if you're not sure, message us first. Professional installation recommended. Use at your own risk.
