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Old 01-09-2018, 07:00 PM   #1
element91
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Default Custom muffler design ideas

I am driving a 2004 FXT.

I recently scored a Chinese 3 inch cat back exhaust. I added a 20 inch resonator parallel to the driveshaft and a Borla pro XS 19 inch muffler. The car is simply too loud. Ive been searching high and low for muffler that will fit in the stock location and be a decent volume and sound deadening. I have not come up with much other then straight through designed mufflers with perforated pipe stuffed with a sound deadening material. Spending hundreds of dollars searching for the right muffler is not appealing. I am a decent welder and fabricator. I am considering building a muffler with same dimensions as the stock unit with a 3 inlet and outlet.

My goal is to be stealth! !!!!

I am in the break-in stage of a new motor and will be getting a pro tune in coming weeks , I am imagining that it will put out approximately 350 wheel horsepower.

Does anyone have any prior experience with such a project? Materials used for stuffing? Shapes for internal baffles that allow for decent flow and excellent noise cancellation?

Thanks for any input you may have,
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Old 01-11-2018, 02:31 PM   #2
TopElement
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Take a look at Summit Racing mufflers made from 304 SS. For the price, you can't build a higher quality, nicer looking muffler, that will sound as good.
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Old 01-30-2018, 07:53 PM   #3
NicEJ25
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one of the quiestest muffler for the flow is the dynomax superturbo. I used it as stock location muffler on my 2002 impreza wagon and it wasn't too loud

I later used a dynomax VT muffler, and I'm sad they don't make them anymore. excellent noise control at idle/low throttle/cruise while being aggressive at WOT
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Old 02-01-2018, 03:20 PM   #4
v2rocket_aka944
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yeah, a turbo muffler would go a long way and they are usually pretty inexpensive.

there's no magic to mufflers - some brands charge $500 or whatever, because they can, not because they do anything any better.

also, make sure the exhaust tip sticks out to be even with or maybe slightly beyond the rear bumper - this puts the "loud spot" well enough behind you that it's not resonating under the trunk floor.
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Old 02-01-2018, 09:32 PM   #5
element91
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Thanks v2rocket extended tip,



been collecting materials 16g stainless sheet,stainless wool, high temp fiber packing, and a flex coupler for the dp to cb,

end caps cut to match the factory muffler dimentions, at this point I am going to create a straight through perf tube with a high volume muffler,..

No luck finding 3" perf stainless SOOOOOO....
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Old 02-01-2018, 10:08 PM   #6
Vancouver98STi
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Quote:
Originally Posted by element91 View Post

No luck finding 3" perf stainless SOOOOOO....
Drilling all those holes would be a helluva job for an OCD person to do. Way too difficult to get them all perfectly equidistant.

Years ago I made a resonator for a car of mine. I did much the same as you've done there... drilled a lot of holes. If I was to do it again, I think I'd instead get a relatively heavy gauge SS Perforated Sheet, roll it, and use that inside the muffler/resonator.


Last edited by Vancouver98STi; 02-02-2018 at 03:07 AM.
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Old 02-01-2018, 10:49 PM   #7
2slofouru
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What about a flat magnaflow with 3" in/out? They are quality and with a long resonator it should be fairly stealth. To quiet it down a lot, you either need a large volume muffler (like the oem sti single tip) with plenty of room for the high freq waves to cancel, or something similar. You could even use something like the apexi noir black and mod the exit for a straight 3". The apexi is pricey though, and you have to weld all supports on and hope the s bend isn't too sharp because of its inlet location.
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Old 02-04-2018, 11:08 AM   #8
element91
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Stainless wool

HIGH Temp fiberglass



Success , car is now super stealthy no drone at all. mild noise above 4k WOT otherwise sounds stock! ~

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Old 02-04-2018, 03:43 PM   #9
2slofouru
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Did you use any internal bracing between the center section and the tube? Seems like those walls would be doing a lot of flexing. Looks like you used all of the available space as well, like oem, very good plan. Be sure to put a sound clip or two on youtube if you can, curious to see how it turned out.
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Old 02-04-2018, 05:44 PM   #10
Vancouver98STi
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Quote:
Originally Posted by element91 View Post

Success , car is now super stealthy no drone at all. mild noise above 4k WOT otherwise sounds stock!
Great!

Just curious... do you still have cat(s) installed? If so, I suspect that also helps keep the noise down with this straight-through muffler design.
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Old 02-04-2018, 07:14 PM   #11
element91
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Grimmspeed DP with catted -> 3" with a 20" resonator -> 3" straight through muffler
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