[Billy_BMW]

Guys, here’s a new one. I have an EU spec M2C (S55)with the OPF software. I have an Eisenmann X-pipe deleting the OPF’s and center resonator.
Currently using BM3 with CS tune and while the burbles are like gunshots and obnoxious even in OTS form, my concern here is the lack of ignition-cut noise that’s evident in M3/M4’s. Basically, when you accelerate and let off, there’s this “thrum” and “PRRRTT” noise. Very obvious on F8X (brother has stock F80 ZCP and it’s very prominent), and possibly, US Spec M2C’s, which leads me to believe it could be OPF software related.

See what I mean in the M2C vid below.

Ive tried everything to get it (stock map/turning burbles off), however, I’m convinced that this effect isn’t programmed into the OPF software cars (just my hunch).

Question is, how do I get that sound? Can someone compare the software between OPF and non OPF S55’s and confirm what’s changed to remove that effect? How can I get it programmed in?

[bmwfan1234]

I think the OEM valve operation closes the valve when you release the throttle or downshift.
Can't you fully open the valve using BM3 so they stay open in sport/sport+?

[Billy_BMW]

Yes, you can have it fully open in Sport/Plus. It’s not the exhaust valve producing this sound.

[pz619]

S55 doesn’t have a blow off or bypass valve. I suspected this sound is the excess boost being blown through the cylinders into the exhaust.

[doughboy]

OP, my UK car makes that sound. (6MT)

I have OPFs swapped for hi flow secondary cats. It's more noticeable with standard back box than with the milltek i had on.

TBH that sound annoys me, does it more in sport than sport plus.

As above i think it is to do with the way the s55 has no dump valve.

[Billy_BMW]

Wonder why mine doesn’t. At first I thought the X-pipe would’ve equalized the exhaust pulses and stopped it. However, after some experimenting with burbles off and lots of YouTube vids, it’s clear it’s not in the software. At least for mine. 🤔

[doughboy]

Do you know what ISTEP version your car is at?

[Billy_BMW]

Not sure. But December ‘18 build. FWIW, I’ve yet to find a EU spec M2c or even M4 OPF spec that makes the noise as prominently as the older F8X S55 cars.

[doughboy]

It might not be as prominent as that US video (which has resonator delete too), and OPFs would muffle it more for sure, but mine does it - I know it does because I wish it didn't!