Click here to visit LS1Tech
Click here to visit Performance Trucks
Click here to visit Mod Motor Tech
Click here to visit Modern Hemi

PerformanceTrucks.net Forums  

Go Back   PerformanceTrucks.net Forums > GENERAL MOTORS SPECIFIC FORUMS > GM Engine & Exhaust Performance
Sign in using an external account
Register Forgot Password?
Register Albums FAQ Members Calendar Search Today's Posts Mark Forums Read VendorsUsed CarsGarageStore TSBs & Recalls
Welcome to PerformanceTrucks.net Forums

Reply
 
LinkBack Thread Tools Search this Thread
Old 09-28-2011, 01:20 AM   #1
Trader Rating: 16
TECH Senior Member
 
smokeshow's Avatar
 
Join Date: Feb 2009
Location: Tucson, AZ
Posts: 6,237
Default How to build an exhaust resonator tube to eliminate drone

The concept behind drone is pretty simple; nearly everything has a resonant frequency...exhaust systems, electronic RLC circuits, even gravitation has resonance. At peak resonance, the amplitude of the wave at the resonant frequency shoots up to many times higher than normal amplitude. With sound resonance, it pops up when a certain frequency emitted from the engine resonates with the exhaust system and muffler to create that nasty in-cab drone. Unfortunately this resonance often has its peak right in the area where you want to cruise, between 55-75mph.

The solution is a 1/4 wave resonator tube. Simply put, it is a small piece of exhaust pipe with a flat capped end welded nearly perpendicular to the exhaust flow post-muffler that serves to take some of the resonant amplitude and shoot it back into the exhaust pipe out of phase with the resonant frequency to bring down the amplitude. If you've ever taken a physics class, this is in the 'standing wave dynamics' chapter. Mufflers are designed to bring down the amplitude or volume of the exhaust note at all RPMs, but they typically can't do anything about resonance. Corsa mufflers have a built-in resonator that works decent, but only with the entire exhaust kit. Sometimes you'll run across a setup that drones at an RPM the Corsa muffler and exhaust wasn't designed to combat, so theres a chance the internal resonator will do little to no good.

Things you need to know to build the resonator:

-RPM that drone occurs at
-Number of cylinders (engines with simultaneous firing cylinders like the SRT-10 truck will divide this number by two)

You will also need to know the speed of sound. It varies with temperature, but is generally accepted to be 343m/s.

Say your V8 truck resonates at 2000rpms, right at cruising speed. You'll need to find the frequency of the drone. Units here are pulses per second, or Hertz.

f = RPM * pulses/rev * (1/60)

f = 2000 rev/min * 4 pulses/rev * (1/60)

f = 133.34 pulses/second = 133.34Hz

At 2000rpms, your V8 fires 4 times per revolution. RPM is in minutes, so divide by 60 to reduce to seconds. Now you need to find the length of the wave at the frequency you just calculated. Wavelength is denoted by lambda (λ), units are meters.

λ = v/f = speed of sound / frequency

λ = (343m/s)/(133.34Hz)

λ = 2.572 meters

This gives you the length of a full sound wave. The idea here is to reintroduce a sound wave into the exhaust that is 180 out of phase with your drone frequency. To do this, you build your resonator tube at exactly one-fourth the length of the resonant wave. By the time the sound wave enters the resonator tube, bounces off the end and re-enters the exhaust stream, the amplitude is exactly opposite of the drone frequency and will lower or eliminate the volume of the drone.

Dividing the wavelength by 4 gives you 0.643m, or about 2.1 feet. Its long and kind of awkward, but someone who has had to deal with a droning truck on a road trip will likely sacrifice the space to make it fit

The diameter of the tube you'd need is debatable, as I haven't tried different sizes of tubing. When I built mine, I took a shot in the dark and went with 2" pipe on my 3" exhaust. It gives about half the surface area at the end of the tube to bounce off of. I assume a larger resonator tube would allow more sound to bounce back and cancel more of the drone noise. However, space is somewhat limited when you are sending an exhaust pipe off of your existing pipe at some odd angle. You can bend the resonator tube to some extent, but it needs to be mandrel bent, not more than one bend or more than ~30. If the bend is too sharp, the sound will bounce back too early and the resonator will work poorly or won't work at all.

The reason for this is simply the fact that sound waves do not necessarily 'flow' with whatever medium they are travelling in. Sound is a pressure wave, and any obstacle (bends) will return the wave prematurely. To minimize 'obstables' in the resonator tube, the straighter it is, the better it will work. The intent is not to randomly scatter the sound wave as a radius will tend to do, but to send it back to the exhaust precisely when it is needed.

So, you just need to mock up your resonator tube in a place that it will fit, cut a hole into the exhaust pipe and weld the tube to it and enjoy a drone-free ride.
Attached Thumbnails
How to build an exhaust resonator tube to eliminate drone-resonator-jpg  
__________________
Jake

2012 Chevy Cruze...turbo warpig
2004 Silverado RCSB...with power adders. All slow and no go.

Last edited by smokeshow; 11-15-2011 at 06:15 AM.
smokeshow is offline   Reply With Quote
Old 09-28-2011, 01:41 AM   #2
Trader Rating: 1
TECH Veteran

 
ak2007r6's Avatar
 
Join Date: Aug 2011
Location: Alaska
Posts: 4,088
Default

Excellent write up, I feel like I am back in my ultrasonic class again.
__________________
2011 GMC Sierra.......SOLD
2011 GMC Sierra 6.2L Procharger Build

2004 Chevy Silverado Joe Gibbs RCSB
http://www.performancetrucks.net/for...-gibbs-519496/

08 Chevy Impala...The DD
ak2007r6 is offline   Reply With Quote
Old 09-28-2011, 11:41 AM   #3
Trader Rating: 21
11 Second Hall Moniter
 
AKlowriderZ71's Avatar
 
Join Date: May 2008
Location: Wyoming
Posts: 10,412
Default

Stickied.
__________________
AKlowriderZ71 is offline   Reply With Quote
Old 09-28-2011, 12:09 PM   #4
Trader Rating: 95
Baltimore Whore
 
Mangled03gmc's Avatar
 
Join Date: Apr 2004
Location: In a van DOWN BY THE RIVER
Posts: 16,765
Send a message via AIM to Mangled03gmc
Default

Ok now stop posting Roger, go do the damn thing and let us know how it worked..
__________________
JOHN
RIP brother
Artificial Intelligence is no match for natural stupidity.... You can't fix stupid
*Approved *** Seller*
Mangled03gmc is offline   Reply With Quote
Old 09-28-2011, 12:25 PM   #5
Trader Rating: 1
TECH Veteran

 
ak2007r6's Avatar
 
Join Date: Aug 2011
Location: Alaska
Posts: 4,088
Default

Quote:
Originally Posted by Mangled03gmc View Post
Ok now stop posting Roger, go do the damn thing and let us know how it worked..
+1 I remember you telling me how you got a welder in your shop recently and wanted to see if you remembered how to use it
__________________
2011 GMC Sierra.......SOLD
2011 GMC Sierra 6.2L Procharger Build

2004 Chevy Silverado Joe Gibbs RCSB
http://www.performancetrucks.net/for...-gibbs-519496/

08 Chevy Impala...The DD
ak2007r6 is offline   Reply With Quote
Old 09-28-2011, 12:46 PM   #6
Trader Rating: 36
Tin Foil Hat Wearin' Fool
 
1slow01Z71's Avatar
 
Join Date: Oct 2004
Location: Austin, TX
Posts: 22,953
Send a message via MSN to 1slow01Z71
Default

Only thing wrong with your post is the postulation about corsa mufflers. This whole subject was discussed a few years ago on here. I had a corsa muffler for a stock 5.3 and it didn't resonate with catless longtubes, a 418 donkey dick cammed stroker, a baby cam 420 or a head and cam 6.0. Bends, tubing thickness, and valve events of an engine factor into the equation. My recommendation would be to start long if possible and adjust accordingly to get best results which is what guys did back in the day.

The resonator chamber doesn't have to be perpendicular to work either and can have a 90* bend, it just has to be mandrel bent with a decent sized radius.
Exhaust Drone Fix

Once this thread has ran its course I'll add it to the sticky thread up top. Good info for sure.

Last edited by 1slow01Z71; 09-29-2011 at 07:57 AM. Reason: added link and more info
1slow01Z71 is offline   Reply With Quote
Old 09-28-2011, 03:56 PM   #7
Trader Rating: 12
11 sec. Truck Mod

 
TIM Z's Avatar
 
Join Date: Dec 2005
Location: OH IO :(
Posts: 8,930
Default

My head hurts now thankyou.
__________________

Carlos Danger
President of the Dirty Sanchez Club
2000 ECSB Z71 LT
LQ4 / TVS 1900@15psi/2barSD Dyno tuned by TJ.
Blower Cam- AlkyControlMeth-Long tubes. LC32 8Rib
4L80E . PI 2600 triple disc
11.6@114@12psi no meth 1.6 60'-new times coming.
627rwhp-615tq 2nd gear dyno pull .

2009 Sierra Denali AWD- blk on blk / 6.2-6speed

2007 CCSB LT3 2500HD 4x4 DURAMAX LBZ-SOLD
05' Tahoe Z71/ 04' 2500 Express 6.0/80E 241k!
Big thanks to Pat(03sierraslt),Mark, and TJ @ BEI
TIM Z is offline   Reply With Quote
Old 10-10-2011, 08:37 PM   #8
Trader Rating: 7
9 Second Club

 
Rhino79's Avatar
 
Join Date: May 2005
Location: Cabot, AR
Posts: 3,124
Default

I know a similar style "j" shaped pipe is popular too, seems to be very effective! Some make the pipe where it has a sliding section to keep it adustable. Great info!!
__________________

2010 Camaro 1SS L99
GPI Custom SS4 VVT Cam, CAI, LT'S, Circle D 1E, GM 3.91's TUNE
All work and tuning performed at Gwatney Performance Innovation
10.75 @126.33 and 9.99 @ 138.56 on the juice
Rhino79 is offline   Reply With Quote
Old 11-15-2011, 05:52 AM   #9
Trader Rating: 0
Teching In

 
Join Date: Oct 2011
Posts: 19
Default

Ok, aside from all the math and physics. The range of drone you were suggesting is exactly what I very uncomfortably deal with, especially uncomfortable at distance.
Now since what you suggested is the range I experience, what have you done in size (diameter, dont need any length and size jokes, lol) ) and length?..... (for me physics was somewhere between ummm... and DOH)
__________________
Blake
2004 2500 , lb7, 5 stage tune. 4", MBRP no dyno or numbers but...wanna try me? (now gone.. a moment of silence please) (fire hydrants are not as you see in the movies)... 2000 Ext. Cab, 5.3, 2wd...2005 Ford Explorer 4.0, 2wd...1992 Toyota 4Runner, 4x4



Honey Badger don't care
Blake did it is offline   Reply With Quote
Old 11-15-2011, 06:20 AM   #10
Trader Rating: 16
TECH Senior Member
 
smokeshow's Avatar
 
Join Date: Feb 2009
Location: Tucson, AZ
Posts: 6,237
Default

When I built mine, I was targeting a 2200rpm drone, so the tube ended up being about 22" long..
__________________
Jake

2012 Chevy Cruze...turbo warpig
2004 Silverado RCSB...with power adders. All slow and no go.
smokeshow is offline   Reply With Quote
Old 11-15-2011, 06:20 AM
PerformanceTrucks
Ford F150




Paid Advertisement
Reply

Tags
building, built, drone, eliminate, exhaust, f150, ford, home, location, make, resonator, resonators, sound, stop, tube


Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are On
Pingbacks are On
Refbacks are On



All times are GMT -5. The time now is 01:42 PM.

 



Powered by vBulletin® Version 3.7.4
Copyright ©2000 - 2014, Jelsoft Enterprises Ltd.
SEO by vBSEO ©2010, Crawlability, Inc.

PerformanceTrucks.net and InternetBrands, Inc. are not affiliated with the Ford Motor Company