BMW M135i Owner Discovers Engine Sound is Artificially Enhanced [Video]
At first, we thought it was just the M5 which had the system installed, but a British owner of a M135i discovered that his car too featured a similar system.
He was able to unplug the sound synth device, and after doing so and powering up the car, he discovered that the radio had stopped working, and the deep low rumble of the straight-six was gone, and what was left sounded more like a one-liter three cylinder engine, found in some city cars.
The difference in engine note reportedly becomes a lot more obvious after 2,500 rpm. After fiddling around with the system, the owner reconnects the sound enhancement device, the radio starts working again, and the car sounds like it should have, but without electronic aids.
BMW could have at least made this public knowledge, and not kept it hidden and be ashamed of it - which they are, because otherwise they would have let owners know that the device is installed.