How to build an exhaust resonator tube to eliminate drone
01-23-2013, 05:46 PM
#24
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04 2500 Avalanche 8.1, Magnaflow exhaust, 2 in 1 out 3 in. tail pipe, gutted cat's, all 4.
Added a 3 in diam. 32 inch long tube to the tail pipe. NO MORE DRONE
Added a 3 in diam. 32 inch long tube to the tail pipe. NO MORE DRONE
04-11-2013, 12:18 PM
#25
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How much would you charge for this i have the same problem, i live in the conroe area? thanks
This WORKS!!!! I did it on my 01 turbo truck with single 4" off the turbo split into duel 3" tail pipes and duel Mangnaflow offset, strait though mufflers. Droned BAD at highway speed, 65-75mph. So I built these. The first ones where about 22" and still had some drone, so extended them to 32" and NO DRONE!!! So much nicer! 
So last week, I put the new MBRP 4" down pipe back exhaust on my DuraMax with an Edelbrock strait though diesel muffler on it and damned if I didn't have a bunch of drone with it to at 62-75mph!
Since I have 7K miles to drive this month, I thought I'd give this a try again. Made the same 32" long 2 1/2" tube resignation tube like on my gas truck and welded it on the tail pipe after the muffler and it KILLED all the drone again!! The truck is barley louder then with the stock cat and muffler. 32" seem to be the magic number at least for an ECSB. 
So this work on both gas and diesels.
So last week, I put the new MBRP 4" down pipe back exhaust on my DuraMax with an Edelbrock strait though diesel muffler on it and damned if I didn't have a bunch of drone with it to at 62-75mph!
Since I have 7K miles to drive this month, I thought I'd give this a try again. Made the same 32" long 2 1/2" tube resignation tube like on my gas truck and welded it on the tail pipe after the muffler and it KILLED all the drone again!! The truck is barley louder then with the stock cat and muffler. 32" seem to be the magic number at least for an ECSB. So this work on both gas and diesels. 
04-21-2013, 02:04 PM
#28
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"Once again, grasshoppers, the "simplified" formula for determining the length of a Helmholtz quarter-wave chamber dealing with the elimination of a known resonance frequency is as follows:
The speed of sound in feet per second (say, 1072feet/second)
divided by
The frequency you wish to eliminate (say, 128cycles/second)
equals
8.375feet/cycle (numbers divide/seconds cancel out)
This is the length of a full wave form; much too big to work with under a vehicle.
To get a quarter-wave length, divide 8.373feet/cycle by 4 to get 2.09373feet/quarter-wave length.
Multiply 2.09373feet/quarter-wave by 12inches/foot to get the chamber length of 25.125".
Tube diameter does not affect frequency, only the amount of attenuation.
This worked back in 2009, and it still works today.
Be sure to use your own target frequency in the formula.
The speed of sound figure is not going to vary enough to worry about. We're not rocket scientists.
REMEMBER: Be sure to use your own target frequency in the formula."
The speed of sound in feet per second (say, 1072feet/second)
divided by
The frequency you wish to eliminate (say, 128cycles/second)
equals
8.375feet/cycle (numbers divide/seconds cancel out)
This is the length of a full wave form; much too big to work with under a vehicle.
To get a quarter-wave length, divide 8.373feet/cycle by 4 to get 2.09373feet/quarter-wave length.
Multiply 2.09373feet/quarter-wave by 12inches/foot to get the chamber length of 25.125".
Tube diameter does not affect frequency, only the amount of attenuation.
This worked back in 2009, and it still works today.
Be sure to use your own target frequency in the formula.
The speed of sound figure is not going to vary enough to worry about. We're not rocket scientists.
REMEMBER: Be sure to use your own target frequency in the formula."
05-04-2013, 01:20 AM
#29
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2003 Crown Victoria- Flowmaster 40 Series DRONE
I have been reading these posts and according to this analysis i made my DroneZONE is in the 287HZ range, it looks like.
Attached is the Frequency Analysis from Audacity.
I calculated 287hz or 275hz as the frequency desired to cancel.
((1072/287) / 4) * 12 = 11.2inches
((1072/275) / 4) * 12 = 11.69inches
What length should i go with? Is this correct?
Stock Dual Exhaust setup with the stock tail resonators removed and the mufflers replaced by 40 series Flowmasters.
2 inch to 2 1/4 inch range pipe.
4 Cats intact.
Any help would be much appreciated.
Frank
Attached is the Frequency Analysis from Audacity.
I calculated 287hz or 275hz as the frequency desired to cancel.
((1072/287) / 4) * 12 = 11.2inches
((1072/275) / 4) * 12 = 11.69inches
What length should i go with? Is this correct?
Stock Dual Exhaust setup with the stock tail resonators removed and the mufflers replaced by 40 series Flowmasters.
2 inch to 2 1/4 inch range pipe.
4 Cats intact.
Any help would be much appreciated.
Frank
"Once again, grasshoppers, the "simplified" formula for determining the length of a Helmholtz quarter-wave chamber dealing with the elimination of a known resonance frequency is as follows:
The speed of sound in feet per second (say, 1072feet/second)
divided by
The frequency you wish to eliminate (say, 128cycles/second)
equals
8.375feet/cycle (numbers divide/seconds cancel out)
This is the length of a full wave form; much too big to work with under a vehicle.
To get a quarter-wave length, divide 8.373feet/cycle by 4 to get 2.09373feet/quarter-wave length.
Multiply 2.09373feet/quarter-wave by 12inches/foot to get the chamber length of 25.125".
Tube diameter does not affect frequency, only the amount of attenuation.
This worked back in 2009, and it still works today.
Be sure to use your own target frequency in the formula.
The speed of sound figure is not going to vary enough to worry about. We're not rocket scientists.
REMEMBER: Be sure to use your own target frequency in the formula."
The speed of sound in feet per second (say, 1072feet/second)
divided by
The frequency you wish to eliminate (say, 128cycles/second)
equals
8.375feet/cycle (numbers divide/seconds cancel out)
This is the length of a full wave form; much too big to work with under a vehicle.
To get a quarter-wave length, divide 8.373feet/cycle by 4 to get 2.09373feet/quarter-wave length.
Multiply 2.09373feet/quarter-wave by 12inches/foot to get the chamber length of 25.125".
Tube diameter does not affect frequency, only the amount of attenuation.
This worked back in 2009, and it still works today.
Be sure to use your own target frequency in the formula.
The speed of sound figure is not going to vary enough to worry about. We're not rocket scientists.
REMEMBER: Be sure to use your own target frequency in the formula."
