Exhaust Flaps Always Open — keeping the exhaust flap open

Exhaust Flaps Always Open is an ECU software setting for petrol engines that keeps the flap in a sports exhaust open at all times. The car sounds equally loud in every mode, including idle and gentle driving. For tuners: send us the original file and get a ready-to-flash file with corrected checksums, on average in 30–60 minutes.

How an exhaust flap works

Many sports exhausts give the gas two routes. Through the silencer chambers it is quieter. Through a straight pipe, which a flap closes off, it is louder. The flap is controlled by the engine ECU: it uses engine speed, load and the selected drive mode to decide when to open it.

On stock software the flap is usually closed at idle and in gentle driving, and opens when driving hard or in sport mode. On the Jaguar F-Type, for example, the active exhaust valves open above 3,000 rpm. On cars with a sound button the driver can open them manually.

The actuator is either vacuum or electric. A vacuum actuator works through an electropneumatic valve that applies vacuum to a diaphragm when the ECU commands it. According to Pierburg (MS Motorservice), on-board diagnostics only check the electrical circuit of such valves. If a hose cracks or water gets into the vacuum line, the ECU may not notice, while the flap stops moving.

Why keep the flap open

What changes in the software

Only the flap control changes: the ECU stops choosing the position by rpm and mode and keeps the flap open.

Stock opening conditions differ from car to car; the table shows the typical picture.

This also explains a common owner question: the exhaust is sometimes quiet and sometimes loud. Usually that is by design: the flap is doing its normal job. After flashing, the sound stays the same all the time.

The rest of the calibration is unchanged and checksums are recalculated. Pop & Bangs and Stage 1 can go in the same file. If the flap is faulty or removed, you need a different option, EXT Flaps Off: it disables flap control and its diagnostics on both petrol and diesel ECUs.

What to do with the flap and actuator

• Before ordering, check that the flap moves: in a mode where it opens on stock software, for example when revving in Sport, you should hear and see it working. Software will not open a flap seized by corrosion.
• With a vacuum actuator, check the hoses and the electropneumatic valve: vacuum has to reach the diaphragm.
• If the car has a sound button or an exhaust sound setting in the menu, after flashing they will no longer close the flap: it stays open all the time.
• If the flap has been removed or the new exhaust has none, mention it in the order. The actuator may then set a circuit fault, and we will check what can be done on your ECU.

How to order the file

1. Read the original file via OBD or on the bench with the tool you use. We need an unmodified stock file.
2. Upload it to the portal and select EXHAUST FLAPS ALWAYS OPEN FIX. In the comment, say which exhaust is fitted and whether the flaps are in place.
3. Get the finished file with recalculated checksums, on average within 30–60 minutes.
4. Flash the file and check: the flap is open already at idle and there are no faults.

Supported ECUs are listed below. If yours is not there, send the file with a request and we will check whether there is a solution for that software.

With the flap permanently open the car is louder than the manufacturer intended. In the UK it is illegal to modify the exhaust system to make a vehicle noisier, and the police can act on excessive noise on the road. In Germany a change that makes a car noisier voids its operating permit. Similar rules apply in many countries. Use the option where the law allows it, for example on track and at closed events. Responsibility for using the file lies with the vehicle owner.