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РусскийRUKey takeaways
- The exhaust flap is positioned by ECU maps of RPM, load, speed and drive mode.
- Carbon and corrosion jam the mechanism — a stored DTC and a stuck sound character follow.
- Software can open the flap earlier, change mode behaviour or cleanly retire the diagnostics when hardware is removed.
Exhaust flap control is where sound design meets emissions and comfort rules. The flap — a valve in the rear silencer or mid-pipe, driven by a vacuum actuator or an electric motor — is positioned by the ECU according to maps of RPM, load, vehicle speed and selected drive mode.
Why manufacturers fit it
- Noise regulations — keeping drive-by sound levels legal in the tested ranges
- Comfort — closed at low speed and steady cruising, quiet cabin
- Character — open under load or in Sport mode for the intended sound
- Backpressure tuning — on some platforms the closed flap also shapes low-end torque behaviour
The control loop
Electric flaps report their position; the ECU compares target and actual and stores faults when the valve jams, the motor draws implausible current or the feedback goes open-circuit. Carbon build-up and a corroded mechanism are the usual killers — a jammed flap means either a permanently quiet exhaust or a permanently open, droning one, plus a stored DTC and in some cases reduced-power operation.
Calibration options
At software level the flap strategy is just another actuator map set: opening thresholds can be moved (open earlier, or always-open behaviour), the mode dependency can be changed, or — when the hardware is removed on a build — the diagnostics for the missing actuator can be cleanly deactivated so no fault codes and no fallback reactions remain.
What happens when the exhaust flap fails?
Can the flap stay open permanently via software?
Related: To change or deactivate flap behaviour, see the Exhaust Flap deactivation service. See also: the emissions strategy overview.