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Canuck714

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Guys, I was having a discussion in another thread, and thought I would share this here.
I have a 14 Roush with Roush exhaust (no factory resonator) and it was unbearable to drive due to drone. I added a Helmholtz Resonator (J-Pipe) back in 2015 but thought I would share how easy this is for those suffering with the dreaded zone in the 1800-1900 RPM range. I think I was in the 27.5 inch range but should probably be 26.

Below is the calculation for the length you need to cancel the frequency at a specific RPM. As well as a picture under my truck to show how easy it was to run it along the side of the exhaust pipe.

upload_2020-5-26_11-46-30.png
J pipe.jpg
 
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Canuck714

Canuck714

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I was told that the cross section was not as important as length and radius of a bend. I settled on a 2.5 inch and it worked great. Others I have seen are 2 inch.

On Porsche and Mercedes, they use 1.5 inch j turns inside the muffler to accomplish this. Keep in mind, they are doing this on 2 mufflers with smaller inlet/outlet diameters than what we have.
 

richnot

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Awesome share of information, I was aware if it on certain foreign cars but never even thought about doing it to my Raptor because of all of the variables involved.

Now how do I fix the dreaded one rear passenger side window sub sonic whoom whoom??
 
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Canuck714

Canuck714

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Awesome share of information, I was aware if it on certain foreign cars but never even thought about doing it to my Raptor because of all of the variables involved.

Now how do I fix the dreaded one rear passenger side window sub sonic whoom whoom??
Crack sun roof or rear slider.. lol
 

richnot

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Ugh! So far neither of the above, it's just when you open one window or even both rear windows. I wonder if anyone has devised a fix for that other then leaving the windows up or cranking up the stereo to induce some crackling to go along with it. I did not even think about what part the rear slider would play in this??
 
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