Fox Quiet/sleeper muffler

I’ll be the third or fourth one to recommend Dynomax super turbos
Those should sound Really smooth with a turbocharger

only thing is you have to make sure you get the biggest one that will fit.
Also. The off set /off set configuration is the best flowing one as it has the curved deflectors
When you look at pics of super turbo mufflers they all show the curved plates in cutaway BUT it’s only the larger offset / offset configuration that has those plates.
The others only have dimples in case to redirect the flow back to the next pipe.
Hope my rambling helps

Dynomax super turbos ......

Couple questions -

• What kind of x-pipe crossover are you using ( brand matters due to location)?
• Cats - are you opposed?
• Sound deadening - do you have any?

X-pipe design matters. Without getting too deep into standing waves and speed, the practical side is that X-pipes like the BBK have a resonance with the 302w. This will change once you introduce a turbo to the exhaust stream.

Cats def take the edge/sharpness off of the exhaust sound too. If you look for the 6cyl Jeep Cherokee replacements that are CARB EO certified, the bodies are short (4") and 1 is certified for more GVWR than any mustang. Why this particular cat? It's small, can handle the heat, isn't junk, doesn't require AIR like the stone age cats that came with our cars. And because of how small it is, you can work it into the stream wherever you want.

Mufflers - Pretty much any non-chamber muffler will be good here. The larger the case volume, obviously the better. The Fox platform is limited with muffler space under the car. I'm a fan of the Borla ProXS line personally. Pick the sound you want* (see my last point below)

Sound deadening. Our mufflers sit up under the rear seats and have a sheetmetal wall that they can resonate through. Fix THAT. Add some sticky mass like Vibro to change the panel resonance, lay some MLV like Second Skin on top of that, and then stuff under the rear seats w/ some denim insulation. Do the same for the trunk/spare tire area. Done right and you won't hear the fuel pump from inside the car anymore.

Lastly...once you get your turbo's plumed and the car tuned, download a spectrum analyzer on your phone and go drive around. You'll very quickly find the resonate frequency that is annoying (it will spike, in Hz), note the RPM that it's the worst. Use a fancy web calculator to come up with the pipe length for a 1/4 wave resonator (aka a side branch). Go to an exhaust shop, have them weld that into the mid-pipe. You mentioned cut outs....put the cut out at the end of the resonator pipe and you'll get the best of both worlds.

I really like this idea. I still get too much drone. After the torque boxes get reinforced, some sound absorption and a res. pipe and cutout sound great. Space is tight. Any approximations on the size of one to help kill the drone?

Here is the a very simple version of the formula:

1100ft/sec (speed of sound) divided by drone frequency (in Hz) = full wave length.
Full wave length divided by 4 = quarter wave length.
Quarter wave length multiplied by 12 = length in inches of the Helmholtz chamber required to deal with your particular drone frequency.

This is a great thread that goes way deep into the theory & some exhaust pics:

As far as attenuation goes, generally speaking the larger volume the chamber is, the greater the reduction. It would prob be easiest to use the same diam pipe as your current exhaust. Best part is, once you get outside of that frequency band/exhaust velocity, it will get much louder again. The resonator only impacts the frequency that it's designed around.