[cyam]

Those upshift sounds are actually coming from the TCU (transmission). They are ignition cuts and are used in certain situations (high revs, high load) during gearchanges to reduce torque ("torque reduction"). This lessens stress on gearbox at the gearchange.

It has nothing to do with the exhaust. Aftermarket exhausts do not change this - only makes whatever is there louder.

Ignition cuts are "instructions" from the TCU to tell the DME to cut the ignition in one or more cylinders to reduce torque. This results in the fuel in that/those cylinders to remain unburnt. When the exhaust is hot enough this fuel ignites when it enters the turbo due to the heat and cause the "upshift fart" noise you hear. So its actually the fuel igniting in the ehaust instead of in the cylinders.

This technique of torque reduction is one of several ways, and it is usually used under high load/high rpm - and usually only present in the more aggressive sport modes. This method of torque reduction has the advantage of not needing to close the throttle during the gearchange so the turbo doesn't drop in rpm. Thus it is typically reserved as a method of torque reduction when performance is of the utmost importance.

Seems the newer models are programmed to not use ignition cuts as a method of torque reduction (there are several other ways that can be done).

A gearbox tune (using XHP) can add that back in. An engine tune can also add this in depending on the tune. But its actually a gearbox request and for the benefit of the gearbox.

[cyam]

Originally Posted by Narek_M4

Just to chime in, I have a 2020 m340i and when I first got it I was on the best software version pre de tune so around 400hp my car was fuckin loud as shit massive crackles pops bangs you name it. I took it in for service one day, all of that glorious sound was gone. Be careful out there they are putting new software updates to make the 2020s sound super quiet

Not true. I have an early 2020 and had a s/w update. It went quiet immediately after the update. The reason for this is NOT that they "programmed the sounds away" - its because all the engine adaptations were reset. But one tank full of gas driving the car super hard in the Sport modes, and the glorious sounds all came back. Drive the car like a grandma and it will adapt to that and remain quiet.

[LexusEater]

Originally Posted by SaltyPickle

Probably not. BMW did their best to take all the fun out of 2021+ cars.

Agreed. I literally found out about their extra limiting speed limiter in a race. It wasn't disclosed at the dealership about the different tire packages, etc. I didn't see it on the sticker either. Pretty shady if you ask me. All they did was try to speed shame me when I asked about it.