[Cavpilot2k]

Question: The other day I drove a friend's 435 with Perf. Exhaust.
When letting off the accelerator, the car would give three brief "pops" that sounded like coughs. It sounded good, and I'm sure it was meant to do that, but every time, it was the same exact three pops- same volume, same I reevaluate, same duration. Every time. It was so consistent that it sounds "manufactured", like it isn't a natural function of the engine/exhaust combo, but rather in order to give the car a sportier sound, BMW programmed the sound in because everybody loved the sound in our E8x and E9x N54/55s. My 135 with PE has a lovely aggressive burble on overrun, but it sounds natural, whereas this car sounded artificial.

So my question is this (and forgive my ignorance because I am new to the F-series 3/4): who else notices this and has it been discussed that it sounds programmed and artificial?
Just curious.

[ahero4eternity]

It's the combustion of unburned fuel in the exhaust caused by the injection of oxygen into the exhaust system by either the A.I.R. system or by cessation of fuel flow during deceleration. Much more appreciable with something other than stock exhaust like MPE. MPPK exaggerates it even more.

[Zel335]

I wouldn't say it's manufactured directly like they did for the transmission shift burbles on the Dual clutch and auto cars. A lot will say it's the cause of un-burnt fuel in the exhaust system.

[Cavpilot2k]

I agree with you both on what causes it-it's just that in comparison to previous generations, it is almost too exactly consistent to be natural. Like I said, it is always exactly three pops. Never two, never four, and always at the same interval and duration. It seems unlikely that the mere coincidence of some excess fuel burning off on overrun would produce exactly the same effect every time.
My N55 135 with PE seems much more natural about it.

[Cavpilot2k]

It just makes me think that BMW said "people love those overrun burbles, so lets make sure we program that in on the next (F) generation."