I would like to say that the phone does not really depict the sound well. iPhone 7plus and it is definitely louder in person. The silencer sounded loudest on video, due to being in the garage and no wind noise/external saturation to dampen the microphone. Doing the muffler cutoff is just fine at driving speeds. I will say there is a very deep vibrating loud drone between 2200-2900 RPM, that is obnoxious. I had to do something about that.
Home made silencer.
I took 1/4 inch stainless sheet and a 1 1/2 inch stainless tube. I cut the stainless sheet with a hacksaw to 2 1/4 x 2 1/4 inches (that’s approximately inside diameter of exhaust exit. I then punched and drilled out 1 1/2 inches of the sheet so the tube could faint in it. I wire wheeled and sanded every surface of the sheet when done.
I then took the tube and cut it to somewhere around 6-7 inches. I pushed it into the exhaust exit until it stopped, then held my finger in around an inch and cut there. Then I sanded the interior and exterior of the tube.
I put the tube into the sheet and welded it on the interior side. I took a 3/16tjs thick grinding wheel and ground corkscrewing grooves in the shaft of the tube. I happened to have a cap for this tube, so I sanded all surface of the cap, placed it on the tube, drilled a 5/16th hole. Took the cap off. Took a 1/2 inch long 1/4 inch shaft bolt and nut, and tightened the nut on the bolt through the shaft. I tack welded the nut in place. This way I could add/remove the cap with ease to restrict airflow on a whim more than just the silencer, and its just a bolt to screw in place to hold it together.
Next, on the face of the sheet I welded the tube to, I drilled and tapped a hole for a 4 inch long bolt (think it was 1/4 x 28 thread) so it would make installation and removal of the silencer into the exhaust easy. Then spray painted everything with all screws in to not paint threads and make tightening and loosing the bolts difficult.
Lastly I drilled two holes into the exhaust, one on each side. I took a nut and screwed it into a lag bolt, put the bolts through the holes, and tightened a nut on the inside of the exhaust (just put a piece of tape on the end of a box wrench to hold nut in place). Then I tack welded those in place. Now I have set screws to securely hold the silencer in place and prevent obnoxious vibration noises.
Lastly, if putting the cap on isn’t quiet enough (which it more than is. It’s stock volume with cap on silencer). You could always wrap the silencer with fiberglass Matt and hold it in place with chicken wire (or coat hanger, or whatever).
I’m running it with just the silencer, no cap, and it’s absolutely perfect. Has a great deep sound on acceleration, not loud at all unless you get the manifold pressure high (give it more than 1/5 throttle). And you cannot hear it at highway speeds. Pressure relief from the recirculating valve is still quite audible and nice. All in all; I am absolutely pleased. Total cost of all exhaust modification: 350 plus tax for catless downpipe. 20 dollars for muffler delete. Roughly six hours of work all told. Expression 328 CIn owners face as you gap them and your car growls...priceless.
Any questions shoot them my way. And yes, those welds are not pretty. I am not a welder. They are structurally functional and that’s all I care about. They are not visible unless you get underneath the car.
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