BMW M4 F82 Competition: DCE Parts exhaust system and Stage 2 engine reprogramming (S55 engine)

On the BMW M4 F82 Competition produced after the introduction of the petrol particulate filter, the sound is much more muffled than on the first generations. The exhaust system has to comply with stricter emission and noise constraints, which greatly reduces the engine's sound character.

In the video, this is immediately apparent on start-up: even with the valves open, the sound remains very discreet. With the windows closed, it even becomes difficult to really enjoy the six-cylinder engine. For a car with over 400bhp and a very distinct sporting identity, the contrast is quite striking.

In fact, this is one of the points most often made by owners of BMW M3s and M4s equipped with the S55 engine: the car drives very well, but it lacks sonic presence. The engine has real potential, but the original design severely limits what you can hear.

So the idea is not simply to make more noise. The aim is above all to obtain a more rewarding sound, more in keeping with the car's character, while avoiding the extreme configurations that quickly become tiresome on the road.

To improve the sound without completely transforming the car, the solution was deliberately simple: free up the exhaust line while retaining the original silencer and BMW valve system. In the video, the part installed comes from DCE Parts, a brand with which we are working more and more on this type of preparation.

The modification consists of replacing the intermediate section with a stainless steel monotube, which frees up the exhaust flow considerably. The S55 engine breathes better and the sound is immediately more present, without having to install a much more expensive complete line. The original rear silencer and valves are retained, ensuring that the car remains perfectly usable on a daily basis. Once the system has been fitted, the difference is immediate when the car is started up: the M4 has a greater sonic presence, the pops become audible and the six-cylinder finally sounds more in tune with the car's character.

The car is then mounted on the axle to replace the original section. This is a relatively standard operation on a BMW M4 F82 Competition, but as is often the case with this type of work, certain fasteners can complicate dismantling. In the video, a nut has to be cut off before being replaced because it broke during dismantling.

Once the original section has been removed, the DCE Parts monotube is installed and adjusted to avoid any contact with the thermal protectors and the bottom plate. The assembly ends with a check on the positioning of the line to avoid any vibrations or parasitic noises once the car has been lowered from the deck.

Once the line has been hauled up and the car lowered from the bridge, it's time for the first start. The difference is immediately perceptible. Even with the valves closed, the BMW M4 F82 Competition becomes much more present than in its original configuration.

When the valves are opened, the transformation is even more marked. The S55 engine gains in character, revving up becomes more audible and the pops on deceleration are clearly apparent. Without touching the rear silencer, the car finally sounds sportier.

Paul's reaction was immediate on first start-up: "It's crazy. The difference between open and closed valves is enormous. "

After installation of the exhaust system, the BMW M4 F82 Competition is placed on the power bench to measure its performance before any engine reprogramming. This run enabled the health of the engine to be checked and a reliable basis for comparison to be established.

The car developed 494bhp and 580Nm of torque, already higher than the 450bhp originally announced. The analysis also highlights an important point made in the video: on a turbo petrol engine like the S55, a perfectly healthy ignition is essential to obtain the best performance. Spark plugs and coils must be in excellent condition, because as soon as turbo pressure and ignition advance increase, imperfect ignition can quickly limit gains.

The car then undergoes Stage 2 engine reprogramming to optimise the main engine parameters (turbo pressure, torque management and ignition advance). After calibration, a further run on the test bench measures the results.

Beyond the power figures, it is above all the increase in torque that changes the car's behaviour. The engine loads up considerably more at low and mid-range speeds, relaunching more quickly and pushing off much more strongly when driveability permits.

Once the preparation is complete, the car goes out for a test drive to check how it really behaves on the road. The difference is immediately apparent. The M4 becomes more responsive under acceleration, and acceleration is much more responsive thanks to the extra torque.

The sound also benefits from the new exhaust system. In open-valve mode, the S55 engine is much more present, while in closed-valve mode the car remains perfectly usable for normal driving without excessive cabin noise.

With around 700 Nm transmitted to the rear wheels, driveability is obviously something to keep an eye on, especially on wet roads. But when conditions allow, the M4 reveals a much sportier character and a real improvement in driving sensations.