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      07-18-2018, 12:05 AM   #1
ZeD4Mr
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I've met a guy that built a J test pipe to a Z4M with RPi. He said it reduces the idling decibel from almost 100 to 88dB. The volume of the sound and tone stays the same but drone is minimized next to none.

Since he loved the RPi sound the best, out of all the other exhaust for the Z4M but can't bear with the drone, this is his solution with good results.

thoughts?
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      07-18-2018, 06:31 AM   #2
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I guess you'd really have to hear it to judge if it cured the problem of drone and sounded better quieter at idle. Can you post a video?
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      07-18-2018, 08:17 AM   #3
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Isn't the first time I've heard of this, and I have heard that it works very well. Called a Helmholtz chamber. Here's more pictures:

https://www.facebook.com/pg/flowauto...60298500704472













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      07-18-2018, 08:49 AM   #4
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Exhaust systems that are professionally engineered typically take into account for equal length headers (or not), length of piping to the mufflers, CATS, resonators, exhaust gas pulses, etc.

Curious how this app affects overall exhaust performance.
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      07-23-2018, 11:47 AM   #5
///Mcoupe
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So is the added piece just a resonator thats been capped ?
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      07-24-2018, 02:06 PM   #6
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Am I the only one not really bothered by the drone the RPI's make? I drive it like a grandma, sometimes like a grandma on an energy drink (not any more aggressive because rod bearings), and i just happen to always enjoy the sound at any given RPM, it's glorious!
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      07-24-2018, 03:11 PM   #7
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Quote:
Originally Posted by ///Mcoupe View Post
So is the added piece just a resonator thats been capped ?
Yes but the length of the pipe is the key as well as the capped resonator. They were able to weld it to hide the resonator behind the smaller tip so they are not as visible once installed. They try various length based on calculation and this works the best.

I will be able to hear this car next month and I'll report back.

Quote:
Originally Posted by RossBMWZseries View Post
Am I the only one not really bothered by the drone the RPI's make? I drive it like a grandma, sometimes like a grandma on an energy drink (not any more aggressive because rod bearings), and i just happen to always enjoy the sound at any given RPM, it's glorious!
Ross, Ear wax checked? I'll be recording trunk mounted video soon to compare with all other exhausts I've had to our Youtube Channel. It is very boomy at the wrong rpm.
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      08-04-2018, 02:27 PM   #8
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Quote:
Originally Posted by racerbruce View Post
Exhaust systems that are professionally engineered typically take into account for equal length headers (or not), length of piping to the mufflers, CATS, resonators, exhaust gas pulses, etc.

Curious how this app affects overall exhaust performance.
Since the end of the pipe is capped, the exhaust performance will be exactly the same. It's like having an electric circuit with an open going to nowhere -- all of the current/exhaust gas will flow out the only way it can.
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      12-18-2020, 11:00 PM   #9
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Quote:
Originally Posted by ZeD4Mr View Post
I will be able to hear this car next month and I'll report back.
Did you ever have a chance to hear how the car sounded with the j pipes?
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      12-19-2020, 12:59 AM   #10
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Quote:
Originally Posted by TurboDream17 View Post
Quote:
Originally Posted by ZeD4Mr View Post
I will be able to hear this car next month and I'll report back.
Did you ever have a chance to hear how the car sounded with the j pipes?
Yes, it sounded the same as the original Rpi and cut out 90% the drone..

It's still lound and raw but boominess while cruising is almost gone..

I'd go this route if I didn't score my current setup..
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      12-20-2020, 08:35 AM   #11
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Wonder how much something like this would cost / if someone would do that locally
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