Can someone explain why my exhaust is so much deeper/throatier on start?

[Karlooch]

Have valves opened all the time on stock exhaust. Not talking about a cold start either im talking about after the car has been warmed up and say I have to go run some errands and turn the car off for half an hour/hour I find that right after I turn the car on and for the first minute or so of driving the exhaust note is so much deeper and has more of a rumble and then after a minute or so it reverts back to that raspier bmw exhaust note.

[horsepower_and_hounds]

I think there is some kind of turbo bypass ting at start up/warm up the tone always changes after 30 sec

[RoundelM3]

It's the cold-start routine - wastegates open (turbos bypassed), which removes the muffling effect of the turbos, and fast idle. Shortly after the idle settles back to normal, the wastegates close and the exhaust quiets down. If you change modes to Sport or Sport+ before hitting the start button, the muffler valves will open up and it'll be even louder during that same 90 seconds or so.

[sna66]

Yeah I like opening the valves before starting in the morning to piss off my neighbors 😂

[Karlooch]

Originally Posted by RoundelM3

It's the cold-start routine - wastegates open (turbos bypassed), which removes the muffling effect of the turbos, and fast idle. Shortly after the idle settles back to normal, the wastegates close and the exhaust quiets down. If you change modes to Sport or Sport+ before hitting the start button, the muffler valves will open up and it'll be even louder during that same 90 seconds or so.

The thing is its not the cold start. Its mid day after turning the car on and off and driving throughout the day and I have the flaps open and disconnected all the time anyways. Unless im misunderstanding something.

[RugbyBro]

Originally Posted by Karlooch

The thing is its not the cold start. Its mid day after turning the car on and off and driving throughout the day and I have the flaps open and disconnected all the time anyways. Unless im misunderstanding something.

Still the startup sequence - the car will do this even if it's warm from being driven. The cats cool down much quicker than the engine.

The only time I've noticed it won't do it is if I turn off the car and then turn it on again within, say, 5 minutes or so.

If you don't like this sound (I know I don't) then AFAIK the only way to avoid it is to code out the cold start sequencing

[Karlooch]

Originally Posted by RugbyBro

Still the startup sequence - the car will do this even if it's warm from being driven. The cats cool down much quicker than the engine.

The only time I've noticed it won't do it is if I turn off the car and then turn it on again within, say, 5 minutes or so.

If you don't like this sound (I know I don't) then AFAIK the only way to avoid it is to code out the cold start sequencing

No I actually love the sound so much I want it to sound like that all the time and not for just the first few.

[RugbyBro]

Originally Posted by Karlooch

No I actually love the sound so much I want it to sound like that all the time and not for just the first few.

I remember with the stock exhaust it didn’t sound too bad, kind of refreshing in a way actually since stock is a little quiet.

If you have the resonator and secondary cats removed (I do) it sounds really awful IMO. I drive with the valves closed until it settles down lol

[Tecnniqe]

Originally Posted by RugbyBro

If you have the resonator and secondary cats removed (I do) it sounds really awful IMO. I drive with the valves closed until it settles down lol

It sounds straight piped during the cold start but worth it for the rest of the drive