Killing drone?!

PLAY_HRD · 07-10-2009, 02:00 PM

I'm sure many people are curious on good ways to kill some of the "drone" that is heard/felt in the car with an aftermarket exhaust.

I'm guessing that if I was to rap the pipes under the car with some kind of insulation/sound dampening rap it would greatly decrease to sound that is sent into the cabin of the car.

Would changing out the mufflers Riss Racing used to a larger (wider) muffler work for me?

Any info or lessons on exhaust frequencies and drone harmonics is greatly welcome!

askiles · 07-10-2009, 02:17 PM

Wrapping the pipes would have no affect at all. The sound is emitted from the rear of the exhaust, at the tips, not through the pipe. Drone is pretty inherent to the E9x M3, so most systems will just have it. The louder the exhaust most of the time means the louder and more present the drone will be. For the least amount of drone, go with the stock exhaust.

-Andy

Robo Squirrel · 07-10-2009, 02:26 PM

most aftermarket exhausts drone to some degree, pretty much on any car. even the stock exhaust on our cars has a little bit of low rpm drone

powertrip · 07-10-2009, 02:26 PM

Interesting scenario....my buddy and I both have AA signature exhausts. He's got the stock x-pipe, and I'm running Fabspeed's x-pipe which eliminates the secondary cats and resonators. His drone between 1700-2200 is twice as bad as mine. Now that my AA is breaking in it has quieted down noticeably. I have very little drone, but it still sounds wicked enough to turn heads and get you pulled over

.

PLAY_HRD · 07-10-2009, 02:51 PM

I found this randomly searching the net. Interested if adding a "dummy chamber" will lower the drone range.

Drone in the exhaust is due to the engine driving the exhaust system
at its resonant frequency. You can't get rid of it, any length of pipe has
a natural frequency, but you can change the frequency (RPM) it happens at.
Stock exhaust systems are tuned to put the resonant frequencies outside the
normal RPM range the engine is run in. Sometimes they add resonators for
this purpose. To raise the resonant frequency of a system, shorten its
length. To do this, you can try tail pipes that exit by the wheel (like
GN's have), or you can try a muffler with a shorter internal flow path. If
you have a true dual system, you can change the natural frequency of the
system dramatically by adding a balance tube. If you can't shorten the
system, then you can add slightly less than one wavelength of pipe. This
will also raise the resonant frequency of the system. The wavelength in a
single converter system (not true dual) is a little less than three feet at
3000 RPM. Shortening the system by a foot or so will move a resonance at
2000 RPM to about 3000 RPM.
To move a resonance, calculate the wavelength at the RPM that gives
the resonance you want to move. Then calculate the wavelength at the RPM
you would rather it be at. The difference is the length of pipe you need to
add or delete. Add to lower the RPM, delete to raise it. If you want to
raise it but you can't cut any pipe out, then add one wavelength of pipe
minus the amount you calculated. This will have the same affect. If you
add or subtract a multiple of a wavelength exactly, you will not change the
resonant RPM.

Wavelength = 1100 X 60 X 1/RPM X 1/4 X 1/2

or

Wavelength = 8250 / RPM

Wavelength = standing wavelength
1100 = speed of sound in air in feet per second
60 = convert RPM to Revs per second RPM = RPM
1/4 = four cylender firings per revolution (make this 1/2 for "true dual")
1/2 = standing wavelength is half the wavelength of a "normal" wave

If I got my math right, my "dummy chamber" needs to be 5.5inches on each.

askiles · 07-10-2009, 03:10 PM

AA's exhaust has this. They call it a noise canceling chamber.

-Andy

Subw00er · 07-10-2009, 04:11 PM

Its technically called a Helmholtz chamber. The OEM exhaust has two of them. Check out the thread in my sig for pics/diagram of them.

Lemans_Blue_M · 07-10-2009, 04:41 PM

The 'balance pipe' referenced above refers to an 'X' or 'H' configuration exhaust mid-pipe crossover. This effectively equalizes the exhaust gas pulses from two separate exhaust manifolds. This can help cancel out the drone of the exhaust system.

What AA is using is quite different...

They have designed a separate pipe that branches off the primary mid-pipe tube. They call it "NCC" technology. (noise canceling chamber)

As you can see, these pipes never crossover at any point. AA just went in a different direction to effectively achieve the same result.

mixja · 07-10-2009, 05:18 PM

Interesting - I guess that's why I got resonance drone with the AA X-Pipe/HFC and stock exhaust system at various points between 2000-4000RPM. Hence it makes sense to get a system that is either designed to work with factory exhaust/down pipe or a full aftermarket system.

Akrapovic owners still report resonance around 2000-2500RPM - I wonder why they didn't tune it lower...

MrHarris · 07-10-2009, 05:32 PM

Quote:

Originally Posted by PLAYHRD

I'm sure many people are curious on good ways to kill some of the "drone" that is heard/felt in the car with an aftermarket exhaust.

I'm guessing that if I was to rap the pipes under the car with some kind of insulation/sound dampening rap it would greatly decrease to sound that is sent into the cabin of the car.

Would changing out the mufflers Riss Racing used to a larger (wider) muffler work for me?

Any info or lessons on exhaust frequencies and drone harmonics is greatly welcome!

Your riss racing exhaust drones?

J08M3 · 07-10-2009, 05:33 PM

Quote:

Originally Posted by Lemans_Blue_M

The 'balance pipe' referenced above refers to an 'X' or 'H' configuration exhaust mid-pipe crossover. This effectively equalizes the exhaust gas pulses from two separate exhaust manifolds. This can help cancel out the drone of the exhaust system.

What AA is using is quite different...

They have designed a separate pipe that branches off the primary mid-pipe tube. They call it "NCC" technology. (noise canceling chamber)

As you can see, these pipes never crossover at any point. AA just went in a different direction to effectively achieve the same result.

OEM muffler has the same thing but you can't see it cause it's inside of the muffler housing

Bluesummer · 07-10-2009, 05:55 PM

hell, even stock exhaust has slight drone

Eugene-TAIWAN · 07-12-2009, 08:06 PM

I don't think its possible to kill the drone at all.

like people say in the thread the drone is also found in the stock set up.

I personally have the Eisenmann Race+customer header back including x-pipe and found the drone is there but goes away right after 2200rpm.

So for me, I just try to keep the gears over 2500rpm which is pretty easy.

Periokid · 07-12-2009, 10:35 PM

Quote:

Originally Posted by Lemans_Blue_M

The 'balance pipe' referenced above refers to an 'X' or 'H' configuration exhaust mid-pipe crossover. This effectively equalizes the exhaust gas pulses from two separate exhaust manifolds. This can help cancel out the drone of the exhaust system.

What AA is using is quite different...

They have designed a separate pipe that branches off the primary mid-pipe tube. They call it "NCC" technology. (noise canceling chamber)

As you can see, these pipes never crossover at any point. AA just went in a different direction to effectively achieve the same result.

So does the AA drone? Does the NCC work as advertised?

powertrip · 07-12-2009, 10:39 PM

The AA had very little drone combined with my x-pipe...it sounded so sexy.

Bluesummer · 07-12-2009, 10:47 PM

Quote:

Originally Posted by Eugene-TAIWAN

I don't think its possible to kill the drone at all.

like people say in the thread the drone is also found in the stock set up.

I personally have the Eisenmann Race+customer header back including x-pipe and found the drone is there but goes away right after 2200rpm.

So for me, I just try to keep the gears over 2500rpm which is pretty easy.

+1

Jonmartin · 07-12-2009, 11:41 PM

I shot mine with my Sig .45

powertrip · 07-13-2009, 12:31 AM

Quote:

Originally Posted by Jonmartin

I shot mine with my Sig .45

Sig, huh? Nice choice

.

MrHarris · 07-13-2009, 03:02 AM

RPi axle-back and AA axle-back have no drone at highway speeds which is where it matters most. Most exhausts will have drone pre 2.5k rpm.

The Remus race has terrible drone at highway speeds, and the only way to remove it was to drive in 5th at 70-75mph. Quite annoying.

PLAY_HRD · 07-13-2009, 08:53 AM

Quote:

Originally Posted by MrHarris

Your riss racing exhaust drones?

From my understanding of sound waves, I'd say that the sound that i'm hearing is what people refer to as drone. At 2000 rpm the exhaust is so intense that it vibrares throughout the car and sets off car alarms next to it. It does sound sweet when you get on it.

NFDoms2k1 · 07-13-2009, 05:08 PM

Quote:

Originally Posted by Eugene-TAIWAN

I don't think its possible to kill the drone at all.

like people say in the thread the drone is also found in the stock set up.

I personally have the Eisenmann Race+customer header back including x-pipe and found the drone is there but goes away right after 2200rpm.

So for me, I just try to keep the gears over 2500rpm which is pretty easy.

+2 I just downshift - keeps me in the powerband

!Xoible · 07-13-2009, 05:10 PM

what's funny is i think stock has more drone than some of the aftermarket ones lol

when i got straight pipes the drone kicked my ass.. but the more i drive it, the less i notice the drone. BUT bumping the music up so fucking loud makes my head bump as i get out of the car... for the next few hours

07-10-2009, 02:00 PM	#1
PLAY_HRD GOT M 15 Rep 138 Posts Drives: 2023 BMW M550i xDrive Sedan Join Date: Jun 2009 Location: Triangle, VA iTrader: (0)	Killing drone?! I'm sure many people are curious on good ways to kill some of the "drone" that is heard/felt in the car with an aftermarket exhaust. I'm guessing that if I was to rap the pipes under the car with some kind of insulation/sound dampening rap it would greatly decrease to sound that is sent into the cabin of the car. Would changing out the mufflers Riss Racing used to a larger (wider) muffler work for me? Any info or lessons on exhaust frequencies and drone harmonics is greatly welcome! __________________
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07-10-2009, 02:17 PM	#2
askiles Major 56 Rep 1,164 Posts Drives: 2008 M3 Sedan - Alpine White Join Date: Apr 2009 Location: Phoenix, AZ iTrader: (2)	Wrapping the pipes would have no affect at all. The sound is emitted from the rear of the exhaust, at the tips, not through the pipe. Drone is pretty inherent to the E9x M3, so most systems will just have it. The louder the exhaust most of the time means the louder and more present the drone will be. For the least amount of drone, go with the stock exhaust. -Andy __________________ 2008 M3 Sedan- Alpine White
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07-10-2009, 02:26 PM	#3
Robo Squirrel Major 70 Rep 1,008 Posts Drives: 991.2 GT3 Join Date: Mar 2009 Location: MI iTrader: (1)	most aftermarket exhausts drone to some degree, pretty much on any car. even the stock exhaust on our cars has a little bit of low rpm drone __________________
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07-10-2009, 02:26 PM	#4
powertrip Scared money don't make money. 67 Rep 1,448 Posts Drives: 2009 E92 M3 DCT Join Date: Apr 2009 Location: Irvine, CA iTrader: (3) Garage List 2009 E92 M3 [0.00]	Interesting scenario....my buddy and I both have AA signature exhausts. He's got the stock x-pipe, and I'm running Fabspeed's x-pipe which eliminates the secondary cats and resonators. His drone between 1700-2200 is twice as bad as mine. Now that my AA is breaking in it has quieted down noticeably. I have very little drone, but it still sounds wicked enough to turn heads and get you pulled over . __________________ 2009 E92 M3/DCT/Alpine White/Fox Red/Carbon Leather OE Tuned 402 whp & 303 wtq/Gintani X-pipe/MXP Axle Back/Rogue Pulley/AFE Stage 2/Cosmetics By IND & EAS HUGE THANKS: Gintani, OE Tuning, and EAS
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07-10-2009, 02:51 PM	#5
PLAY_HRD GOT M 15 Rep 138 Posts Drives: 2023 BMW M550i xDrive Sedan Join Date: Jun 2009 Location: Triangle, VA iTrader: (0)	I found this randomly searching the net. Interested if adding a "dummy chamber" will lower the drone range. Drone in the exhaust is due to the engine driving the exhaust system at its resonant frequency. You can't get rid of it, any length of pipe has a natural frequency, but you can change the frequency (RPM) it happens at. Stock exhaust systems are tuned to put the resonant frequencies outside the normal RPM range the engine is run in. Sometimes they add resonators for this purpose. To raise the resonant frequency of a system, shorten its length. To do this, you can try tail pipes that exit by the wheel (like GN's have), or you can try a muffler with a shorter internal flow path. If you have a true dual system, you can change the natural frequency of the system dramatically by adding a balance tube. If you can't shorten the system, then you can add slightly less than one wavelength of pipe. This will also raise the resonant frequency of the system. The wavelength in a single converter system (not true dual) is a little less than three feet at 3000 RPM. Shortening the system by a foot or so will move a resonance at 2000 RPM to about 3000 RPM. To move a resonance, calculate the wavelength at the RPM that gives the resonance you want to move. Then calculate the wavelength at the RPM you would rather it be at. The difference is the length of pipe you need to add or delete. Add to lower the RPM, delete to raise it. If you want to raise it but you can't cut any pipe out, then add one wavelength of pipe minus the amount you calculated. This will have the same affect. If you add or subtract a multiple of a wavelength exactly, you will not change the resonant RPM. Wavelength = 1100 X 60 X 1/RPM X 1/4 X 1/2 or Wavelength = 8250 / RPM Wavelength = standing wavelength 1100 = speed of sound in air in feet per second 60 = convert RPM to Revs per second RPM = RPM 1/4 = four cylender firings per revolution (make this 1/2 for "true dual") 1/2 = standing wavelength is half the wavelength of a "normal" wave If I got my math right, my "dummy chamber" needs to be 5.5inches on each. __________________
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07-10-2009, 03:10 PM	#6
askiles Major 56 Rep 1,164 Posts Drives: 2008 M3 Sedan - Alpine White Join Date: Apr 2009 Location: Phoenix, AZ iTrader: (2)	AA's exhaust has this. They call it a noise canceling chamber. -Andy __________________ 2008 M3 Sedan- Alpine White
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07-10-2009, 04:11 PM	#7
Subw00er Bates '08 Interlagos Launch 126 Rep 1,230 Posts Drives: 440i xGC, ZL1, JCW Join Date: Nov 2005 Location: NY iTrader: (2)	Its technically called a Helmholtz chamber. The OEM exhaust has two of them. Check out the thread in my sig for pics/diagram of them. __________________ Custom Exhaust Project: Bates Valvetronic exhaust: http://www.m3post.com/forums/showthread.php?t=253661 -- Exhaust Mod pics in here: http://www.flickr.com/photos/40236795@N03/ DON'T BUY Race Ready Performance electronic cutout valves. Here's why: http://www.m3post.com/forums/showthr...40#post9589740
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07-10-2009, 04:41 PM	#8
Lemans_Blue_M Automotive Industry Insider 462 Rep 1,948 Posts Drives: Lemans Blue M3 Join Date: Aug 2007 Location: Texas iTrader: (0)	The 'balance pipe' referenced above refers to an 'X' or 'H' configuration exhaust mid-pipe crossover. This effectively equalizes the exhaust gas pulses from two separate exhaust manifolds. This can help cancel out the drone of the exhaust system. What AA is using is quite different... They have designed a separate pipe that branches off the primary mid-pipe tube. They call it "NCC" technology. (noise canceling chamber) As you can see, these pipes never crossover at any point. AA just went in a different direction to effectively achieve the same result. __________________ The best is yet to come...
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07-10-2009, 05:18 PM	#9
mixja Captain 51 Rep 780 Posts Drives: 2011 E90 DCT Silverstone Join Date: Jun 2008 Location: Beverly Hils, CA iTrader: (1)	Interesting - I guess that's why I got resonance drone with the AA X-Pipe/HFC and stock exhaust system at various points between 2000-4000RPM. Hence it makes sense to get a system that is either designed to work with factory exhaust/down pipe or a full aftermarket system. Akrapovic owners still report resonance around 2000-2500RPM - I wonder why they didn't tune it lower...
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07-10-2009, 05:55 PM	#12
Bluesummer Lieutenant General 588 Rep 15,818 Posts Drives: slower than Ayrton Senna Join Date: Dec 2006 Location: SoCal iTrader: (15) Garage List 2017 BMW X5M [0.00] 2015 M4 [0.00] 2011 E82 135 [0.00] 2011 M3 [0.00] 2007 335 [0.00]	hell, even stock exhaust has slight drone __________________ IG:d.violet.m3
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07-12-2009, 08:06 PM	#13
Eugene-TAIWAN Brigadier General 249 Rep 3,157 Posts Drives: E92 M3 Coupe Join Date: Jun 2009 Location: Taiwan iTrader: (4)	I don't think its possible to kill the drone at all. like people say in the thread the drone is also found in the stock set up. I personally have the Eisenmann Race+customer header back including x-pipe and found the drone is there but goes away right after 2200rpm. So for me, I just try to keep the gears over 2500rpm which is pretty easy. __________________ Past: Gintani stage3 M3, Cayman GTS present: Porsche 993RWB, 964RS America,996 cupcar, 964 turbo 3.6,Macan Turbo,997GT2,930 turbo,i3, MINI JCW
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07-12-2009, 10:39 PM	#15
powertrip Scared money don't make money. 67 Rep 1,448 Posts Drives: 2009 E92 M3 DCT Join Date: Apr 2009 Location: Irvine, CA iTrader: (3) Garage List 2009 E92 M3 [0.00]	The AA had very little drone combined with my x-pipe...it sounded so sexy. __________________ 2009 E92 M3/DCT/Alpine White/Fox Red/Carbon Leather OE Tuned 402 whp & 303 wtq/Gintani X-pipe/MXP Axle Back/Rogue Pulley/AFE Stage 2/Cosmetics By IND & EAS HUGE THANKS: Gintani, OE Tuning, and EAS
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07-12-2009, 11:41 PM	#17
Jonmartin Banned 123 Rep 2,097 Posts Drives: E90 M3 Join Date: Nov 2005 Location: Los Angles (818) iTrader: (1)	I shot mine with my Sig .45
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07-13-2009, 03:02 AM	#19
MrHarris yodog 197 Rep 5,025 Posts Drives: '86 Corolla Join Date: Jun 2007 Location: Diamond Bar, Ca iTrader: (5) Garage List 2009 BMW [10.00]	RPi axle-back and AA axle-back have no drone at highway speeds which is where it matters most. Most exhausts will have drone pre 2.5k rpm. The Remus race has terrible drone at highway speeds, and the only way to remove it was to drive in 5th at 70-75mph. Quite annoying. __________________ 2009 E92 M3 \| Alpine White \| Black Extended \| Advan RS \| Turner Test Pipes \| Dinan Axle-Back \| OETuning \| Eibach Springs \| UUC SSK \| VRS Front Lip \| VRS Type I Diffuser \| Matte Black \| RPi Scoops \| MS Filter \| Yokohama AD08 \| F1 Pinnacle Special Thanks: Gintani \| OETuning \| eAs
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07-13-2009, 05:10 PM	#22
!Xoible Banned 839 Rep 46,029 Posts Drives: .... Join Date: Nov 2006 Location: . iTrader: (4) Garage List 2008 M3 [4.00] 2007 335i [9.00] 2008 528i [8.00] 2006 Infiniti - G35 ... [8.00]	what's funny is i think stock has more drone than some of the aftermarket ones lol when i got straight pipes the drone kicked my ass.. but the more i drive it, the less i notice the drone. BUT bumping the music up so fucking loud makes my head bump as i get out of the car... for the next few hours
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