Exhaust drone elimination by j pipe (helmholtz 1/4 wave resonator)

Elias_E90 · 05-17-2018, 12:27 AM

Hello,
My custom exhaust is droning between 1500 rpm and 2300 rpm.
After doing research, i found a good solution which involves installing j pipes. I need to calculate the length of this pipe.
The pipe would be installed before the muffler in a 90 degrees angle.

https://www.performancetrucks.net/fo...-drone-489463/

This is a good website that explains the calculations, however i have 1 question.
Are the pulses per revolution of our n52 6? (6 sparks per revolution?)

Once i finish this project ill share the results. I cant find a used pe in my country (the best solution) and i find a new pe expensive. So i have headers, replaced secondary cats with bullet resonators (eliminated rasp after deleting secondaries) stock resonator Y and custom muffler.
The j pipes (helmholtz res) are effective for drone elimination and the dont affect the flow, i have seen them on 370z and muscle cars. Also any idea about the section of these pipes ? I didnt find a recommended section in my research

Biginboca · 05-17-2018, 03:48 AM

The AA Gen 2 muffler has one of these, I’m running one and it works great no drone at all. You might want to have a look at their website to see pics of how they made theirs.

Elias_E90 · 05-17-2018, 04:05 AM

Yes i saw it, it inspired me to look into this btw. But i am in lebanon that s like the other end of the world. So 700$ + shipping will be expensive and vat and customs tax, i dont think it will arrive here under 1100$. I will consider it if i am in the states sometime.. but for now my solution would cost under 100$.

On second thoughts i think an inline 6 engine have 3 sparks per revolution.. (i said 6 because a dude on revit said so) but come to think of it, if every 360 degrees the piston do 2 strokes (down and up) it needs 720 degrees to complete the full 4 strokes, i think it would be 3 pulses per revolution.. i need this to calculate the frequency and ill try to get something to measure the frequencies in the cabin while droning. I should get close numbers

Edit : each exhaust will make its own drone depending on piping and mufflers so i must figure out the length of my j pipe depending on the frequency where my whole exhaust is resonating

05-17-2018, 12:27 AM	#1
Elias_E90 Private 25 Rep 94 Posts Drives: E90 328i Join Date: Apr 2018 Location: Lebanon iTrader: (0)	Exhaust drone elimination by j pipe (helmholtz 1/4 wave resonator) Hello, My custom exhaust is droning between 1500 rpm and 2300 rpm. After doing research, i found a good solution which involves installing j pipes. I need to calculate the length of this pipe. The pipe would be installed before the muffler in a 90 degrees angle. https://www.performancetrucks.net/fo...-drone-489463/ This is a good website that explains the calculations, however i have 1 question. Are the pulses per revolution of our n52 6? (6 sparks per revolution?) Once i finish this project ill share the results. I cant find a used pe in my country (the best solution) and i find a new pe expensive. So i have headers, replaced secondary cats with bullet resonators (eliminated rasp after deleting secondaries) stock resonator Y and custom muffler. The j pipes (helmholtz res) are effective for drone elimination and the dont affect the flow, i have seen them on 370z and muscle cars. Also any idea about the section of these pipes ? I didnt find a recommended section in my research __________________ E90 328i n52 auto, 3 stage IM, k&n drop in, charcoal delete, silicone boot, ebay headers, secondary cats delete, bpc tune. MILVs (soon), MT swap (planning)
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05-17-2018, 03:48 AM	#2
Biginboca Colonel 3764 Rep 2,738 Posts Drives: 2009 E92 328i 6MT Join Date: Jun 2017 Location: Boynton Beach, FL... USA iTrader: (3)	The AA Gen 2 muffler has one of these, I’m running one and it works great no drone at all. You might want to have a look at their website to see pics of how they made theirs.
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05-17-2018, 04:05 AM	#3
Elias_E90 Private 25 Rep 94 Posts Drives: E90 328i Join Date: Apr 2018 Location: Lebanon iTrader: (0)	Yes i saw it, it inspired me to look into this btw. But i am in lebanon that s like the other end of the world. So 700$ + shipping will be expensive and vat and customs tax, i dont think it will arrive here under 1100$. I will consider it if i am in the states sometime.. but for now my solution would cost under 100$. On second thoughts i think an inline 6 engine have 3 sparks per revolution.. (i said 6 because a dude on revit said so) but come to think of it, if every 360 degrees the piston do 2 strokes (down and up) it needs 720 degrees to complete the full 4 strokes, i think it would be 3 pulses per revolution.. i need this to calculate the frequency and ill try to get something to measure the frequencies in the cabin while droning. I should get close numbers Edit : each exhaust will make its own drone depending on piping and mufflers so i must figure out the length of my j pipe depending on the frequency where my whole exhaust is resonating __________________ E90 328i n52 auto, 3 stage IM, k&n drop in, charcoal delete, silicone boot, ebay headers, secondary cats delete, bpc tune. MILVs (soon), MT swap (planning)
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