Helmholtz Drone Solution - ModernCamaro.com - 5th Generation Camaro Enthusiasts
V8 Engine Discussion 6.2L LS3/L99 V8 | Exhaust | Ignition | Induction | Intakes

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post #1 of 12 Old 03-26-2011, 09:17 AM Thread Starter
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Lightbulb Helmholtz Drone Solution

Thought I'd share my drone solution with everyone here. I have a JBA 3" competition exhaust that sounds GREAT, however the drone in the 1800-2000 RPM range would make your ears bleed.

After doing some research it turns out there's a noise cancellation technique that works beautifully at resolving it. The concept was developed by a fellow named Helmholtz and if you're interested in the science behind it go here: http://www.phys.unsw.edu.au/jw/Helmholtz.html

Basically the idea is that sound waves are directed into a specifically sized "container" where they reflect back and cancel subsequent sound waves of the same frequency. The size of the container dictates the wave frequency that is canceled.

It turns out that for exhaust sound waves at the 1800-2000 RPM range, the size of this container should be a 2.25" x 28" pipe capped at one end. This pipe is to be connected to your exhaust at any point before the mufflers and can be bent in any shape, it's the length and diameter that are important.

I can attest 100% that this works, below are pictures of the Helmholtz resonator pipes I had added to my exhaust. So, if you love the sound of your exhaust, don't want to buy a new one that may still drone, this is your solution. It cost $140 to have the pipes made and welded onto my exhaust.
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Last edited by FrostBite; 03-26-2011 at 09:22 AM.
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post #2 of 12 Old 03-26-2011, 09:20 AM
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Interesting. No pics btw.

Do you have an L99 with or without a tune.

You need a sig son!

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post #3 of 12 Old 03-26-2011, 09:23 AM Thread Starter
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Quote:
Originally Posted by 54inches View Post
Interesting. No pics btw.

Do you have an L99 with or without a tune.

You need a sig son!
Hmmm, the pics should be there now
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post #4 of 12 Old 03-26-2011, 09:24 AM
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That's what GM did on the intake. Sound theory. It looks like you made sure they were angled a little so moisture wouldn't collect. Nice job. That's stainless, right?

James 1:25 Ordered from Faulkner Chevy #NKCF02 1100 5/8/9 2000, 3300 7/16/9 TPW 7/20,GOT MY (low) VIN! 4000 7/24/9 ,Picked up 8/7/9!!! Signed Litho #45. Car signed by FBodfather 2011. Service: Jennings Chevy in PA. We don't "drift", kiddies... we POWER SLIDE! MOTM/COTM Sept 2012 Pro Patria Vigilans.
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post #5 of 12 Old 03-26-2011, 09:28 AM Thread Starter
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That's what GM did on the intake. Sound theory. It looks like you made sure they were angled a little so moisture wouldn't collect. Nice job. That's stainless, right?
Good point....make sure your muffler shop installs them such that moisture will not collect in the resonator.

Yes, the exhaust and the resonator are stainless.
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post #6 of 12 Old 03-26-2011, 09:35 AM
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The resonators would be good places to hide cutouts too, if you can't see the ends.

James 1:25 Ordered from Faulkner Chevy #NKCF02 1100 5/8/9 2000, 3300 7/16/9 TPW 7/20,GOT MY (low) VIN! 4000 7/24/9 ,Picked up 8/7/9!!! Signed Litho #45. Car signed by FBodfather 2011. Service: Jennings Chevy in PA. We don't "drift", kiddies... we POWER SLIDE! MOTM/COTM Sept 2012 Pro Patria Vigilans.
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post #7 of 12 Old 03-26-2011, 02:36 PM
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Very nice!

2005 CTSV BLACK LS7 Clutch/Flywheel/Slave, Tick Speed Bleeder, Tilton Clutch MC, RevShift Bushings, Domestic V8 Solutions (shifter, 8.8 Diff conversion, srut tower braces, sub-frame connectors), SLP cats, no cags, xpipe, bullet mufflers, Volante, iPod dock, G-force tune; 379hp 381tq.

Killing 5th gens like it is my job.
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post #8 of 12 Old 03-26-2011, 06:37 PM
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I only get drone if my top is up which is rare.

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post #9 of 12 Old 03-27-2011, 09:13 AM Thread Starter
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Yes, a convertible is another solution for drone. LOL!

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post #10 of 12 Old 03-27-2011, 09:14 AM Thread Starter
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Quote:
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The resonators would be good places to hide cutouts too, if you can't see the ends.
That's actually not a bad idea, although I suspect most people with cutouts would want them placed closer to the engine.

2010 Camaro RS/SS M6, 641rwhp/558rwt

Edelbrock E-Force Super Charger, Comp Cams 224/236 .601/.608 117 LSA, Fastland "Duece" Fuel Pump, JBA 1 7/8" LT Headers, 4.10:1 Richmond gears, RPM Stage 6 TR6060 Transmission, ZR1 Twin Disc Clutch, Pfadt Coilovers, D2 MB2 Forged Wheels
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