[Gaviin]

As several people have noted in other threads, there's a series of popping or burping sounds from the exhaust when letting off the throttle, particularly when in Sport+ in first and second gears (I have a 6MT... not sure about the auto).

Does anyone have a technical explanation for what causes this? Someone asked me the other day, and I realized that I didn't have an answer.

[MTP335]

Idk, but i love it!

[Pray for Mojo]

Fuel burning in the exhaust manifold on deceleration.

[Glassjaw047]

it even burps in Comfort mode when manually shifting and going through the first few gears without decelerating. It sounds awesome!

[overcoil]

Exhaust gas pulses in a megaphone.

[abirmaher]

For some reason the term overrun comes to mind.

[ska///235i]

Back pressure

[velopod]

You guys must not be motorcycle enthusiasts ... you should hear my Ducati when snapping shut the throttle (or most Harleys)! Motorcycles typically run/are tuned more lean than cars with more sophisticated fuel injection, but as mentioned, the "backpressure" when letting off the gas (especially in a turbocharged car) increases resistance before the fuel is burned off and pop pop snap. A nice sound me thinks ;-)

[3.0L]

I'm not sure either, but I really, really like the sound

I did read on some other BMW forum that there might "valving" changes somewhere in the exhaust plumbing that enhance sound between Comfort and Sport modes. Also, another poster thought the BMW engineers designed in a system where a "light" dabble of raw gasoline was injected somewhere in the exhaust to create the popping sounds.

[SJL]

Did a couple of experimenting with the different modes for the popping.

Seemed like it crackles the most on Sport+ mode coupled with gearstick shifted left to DS mode .

Also just a side note, the interior cabin is filled with a soft deep humming only exclusively on sport+ mode which I can't seem to replicate it on the other modes or with just pure manual shifting.

Am on ER downpipe and M Performance Exhaust.

[Killramos]

Originally Posted by SJL

Did a couple of experimenting with the different modes for the popping.

Seemed like it crackles the most on Sport+ mode coupled with gearstick shifted left to DS mode .

Also just a side note, the interior cabin is filled with a soft deep humming only exclusively on sport+ mode which I can't seem to replicate it on the other modes or with just pure manual shifting.

Am on ER downpipe and M Performance Exhaust.

That's because the pops happen above 3500 rpm, in normal d it won't shift as aggressively (power on) or as high.

I do find sport plus drones a TOUCH in regular city driving.

[SJL]

Originally Posted by Killramos

That's because the pops happen above 3500 rpm, in normal d it won't shift as aggressively (power on) or as high.

I do find sport plus drones a TOUCH in regular city driving.

Oh my bad, I kinda meant on how the exhaust "crackles" & "gurgles" sound characteristics on the different modes .

But yes, exhaust blips wise , only happens from 3.5k rpm onwards.

[ItsSammyBoi22]

I'm not really sure if this fits here under this thread or not, but I am new to the app and have not found my way to creating a new thread. I recently just got a downpipe installed to my 2014 435i and flashed to BM3 stage 2. I had it running on the stock exhaust sound which I loved. It had some pretty decent pops when shifting from 3rd gear down the 2nd. I was not too sure about this because the person who installed my downpipe said to avoid the pops because it can destroy my turbo. If I recall correctly he said something about "fuel drip" being added to create the pops. I removed all burbles and pops on BM3 and I kind of miss the burbles. Does anyone know anything about the pops and any relationship it has to turbo? The guy who installed had pretty good credentials so I did not question him but I wanted to see if anyone else knew anything about it. Thank you!

[High Desert]

Perhaps I can shed some light on this. I have been running BMW MINIs for 17 years. It is probably your tune. Who made it?

BMW engines have a turbo "blow off" valve on their turbos which releases pressure on the turbo. On the 3 and especially 4 cylinder engines, the "pops and gurgles" comes from an extra amount fuel injected into the exhaust system. You can hear the valve release on the Mini Coopers, haven't heard it on my 228i.

With the 2019 model (LCI) new EU regulations on "noise pollution" required BMW to eliminate these sound makers. Most MINI owners are not happy with this.

There is a lot of discussion on it in the US Mini Cooper forum "North American Motoring."

[ItsSammyBoi22]

Originally Posted by High Desert

Perhaps I can shed some light on this. I have been running BMW MINIs for 17 years. It is probably your tune. Who made it?

BMW engines have a turbo "blow off" valve on their turbos which releases pressure on the turbo. On the 3 and especially 4 cylinder engines, the "pops and gurgles" comes from an extra amount fuel injected into the exhaust system. You can hear the valve release on the Mini Coopers, haven't heard it on my 228i.

With the 2019 model (LCI) new EU regulations on "noise pollution" required BMW to eliminate these sound makers. Most MINI owners are not happy with this.

There is a lot of discussion on it in the US Mini Cooper forum "North American Motoring."

Gotcha. So can the pops cause any sort of damage to the car? According to the BM3 Stage 2 OTS tune, I had just the stock exhaust sound set.

[chattanooga240]

Mr. Pibb

[tcollier91]

A LOT of misinformed answers here...

[High Desert]

Originally Posted by ItsSammyBoi22

Gotcha. So can the pops cause any sort of damage to the car? According to the BM3 Stage 2 OTS tune, I had just the stock exhaust sound set.

No damage and covered by warranty. In the MINIs, a John Cooper Works factory tune (for the S model) came with an exhaust that has a solenoid valve that bypasses the muffler for a straight exhaust. The JCW had no factory tune (already had software/modes) and the exhaust was an option. No more tune from BMW and no longer available. The justa, S, and JCW also made great noises before the new EU regs, varying by mode and temperature. They all have "B" BMW series engines. Some are doing resonator deletes on their exhausts on the LCIs and say it helps a little with the sounds. After market tunes (2 and 3) did (does) have issues with turbo pressures which causes failures and many upgraded them plus intercoolers. Maybe search for a different tune?

[TrboMike]

Didnt you see the leaked video where PETA snuck into a BMW factory which was growing snap crackle and pop clones and installing them in cat converters?

[BetweenTheWheels]

Originally Posted by High Desert

Perhaps I can shed some light on this. I have been running BMW MINIs for 17 years. It is probably your tune. Who made it?

BMW engines have a turbo "blow off" valve on their turbos which releases pressure on the turbo. On the 3 and especially 4 cylinder engines, the "pops and gurgles" comes from an extra amount fuel injected into the exhaust system. You can hear the valve release on the Mini Coopers, haven't heard it on my 228i.

With the 2019 model (LCI) new EU regulations on "noise pollution" required BMW to eliminate these sound makers. Most MINI owners are not happy with this.

There is a lot of discussion on it in the US Mini Cooper forum "North American Motoring."

This is correct - fuel that doesn't burn on the normal compression stroke is released into the exhaust and causes the pops.

Mercedes even goes so far as to call it 'a controlled misfire'. I get how some municipalities have outlawed it and why some don't like it. Done well with the right exhaust tone, I think it sounds amazing. Too loud and aggressive and it sounds like crap.

[Throttlesteer14]

Pizza and beer before bed. Oh wait, thats my pops and burps.