An Experiment on Exhaust Noise Reduction

[Aaronbrook37]

Internet articles state that an increase of 8-10db is perceived as double the volume by the human ear, which makes sense with the testing I've done. I'm using my iPhone and an uncalibrated free iPhone app for testing purposes. Given that the legal limit for light duty vehicles in BC is 83db, the microphone is obviously far too sensitive given the data I've extracted from my two Festivas.

Car	Ambient	Interior idle	Exterior idle
White B6T	41db	72db	~92db
Gray B3	40db	70db	~83db

Essentially then, regardless of how loud each car actually is, the iPhone and my neighbours perceive the white car as about twice as loud as the grey one. What I need from you guys then is some help fabricating and designing the most effective means by which I can reduce that noise. It already has a turbo, high flow resonator, large cat, and full oval muffler... and I don't feel like replacing those parts as they're pretty new and were pretty expensive as well. I believe my muffler outlet is a straight 2.5" diameter hole.

Ideally I could bring that exterior level back into the mid-80s, but I don't expect it to ever be as quiet as the B3 car considering it has a brand new Walker muffler and a big middle resonator also. So I'd love some suggestions, links, or tricks people have for quieting down noisy cars. I realize the risks inherent to it and the loss of flow and power that comes with all silencers... but I've got my priorities. I'd really rather not just stuff ceramic fiber up the tail pipe when I could instead engineer some sort of sleeve or insert instead that could be removable, cheap, and effective.

As far as I know, there aren't any other simple ways to quiet things down other than putting the clutch in and shifting early.

[Micro Mudder]

I allwase just stright pipe my festivas haha sounds good and any extra hp and mpgs i like! but then again I live in the country so there is no one to disturb other then the cows

[rmoltis]

I used the largest resonator I could buy.
It seemed to help "quiet" a bit.
As well as the matching muffler.
Both quality units.

How does the packing in your resonator/muffler compare to other companies.
Sometimes one may have lower quality standards that don't muffle as well.

Also with turbo cars most of the engine pulses get muffled/trapped running through the turbo itself.
Making it less of a requirement for sound deadening with "turbo mufflers"

So if it says turbo muffler
I don't buy it because they skimp on deadening (sometimes)

Next option is to get an offset muffler so travelling diagonally it has more area to shed sound through the muffler.
The pipe is still straight just at an angle (you guys know what I mean)

You can also do that with resonators getting the offset in/out.

Just those might give you the little you may need.

Just my opinion though.

[TominMO]

For cheap and removable, you could put a reducer adaptor on the end of your tailpipe. Maybe even reduce it twice for a smaller tailpipe hole.

[rmoltis]

Lol that sounds good too.
I wonder if that would give you more torque
putting an exhaust reducer on the tailpipe when you want quietness?
But there are videos of wrx sti's with these and they work great on their chunky exhaust sounds.

[navdoc101]

I put FMS header, 2" pipes ,& turboII muffler on mine not loaud inside but tinny sounding on exceleration. So had a resonator put on , now just a nice mellow sound. Neither the muffler or the resonator had any "packing", just baffles.

[Aaronbrook37]

Gotta put this little experiment on hold... got an interested potential buyer for the car as is haha. If the price is right, expect a new member sometime in the near future. If not, I'll carry on with a silencer project!

[Tommychu]

Downturn on the outlet. Bouncing the sound off the asphalt is pretty effective at reducing perceived noise. Won't do much for cabin noise but much less obnoxious to everyone else.

[sketchman]

This design worked really well for me. Still flows well for the quietness it makes too. The higher you rev it, the better it works. On my old neon, at higher RPM you'd hear the engine up front over the exhaust. Mine was galvanized fence post for the center. Divider was a post cap. And the case was a stainless toilet brush holder with sheet metal end caps. Helps to have a drill press to perforate the pipe. Doing it by hand probably would be no fun.

[getnpsi]

Your neighbors need to drive a b3 festiva and then a b6t car that weighs the same. Delta of pissed off people before and after a joy ride...hard data is one thing, they look up and see your car coming...it could be back to stock and they will still hate you...no use throwing away money twice for no improvement of attitude

[Banana Bonanza]

I am old and grouchy and like a quiet car. I live with generic turbo muffler cause it was $20 new. Its not horrible, but if it could be even quieter, be really nice. Suppose real way to get quiet muffler is to go to a salvage yard that deals in late model cars and try to buy a used OEM muffler from small car. It will be quieter than anything you can buy aftermarket. Aftermarket mufflers are not really sold on basis of how ultra quiet they are.

Oh back in old days of cherry bomb mufflers and such, if cops started hassling you, you stuffed the muffler with fiberglass insulation. It would quiet it considerably , hopefully lasting long enough that cops stopped watching you so close. Course it could shoot out the back if you really stomped on the pedal.

Frankly the even older crowd had exhaust cutouts, sort of a Y configuration under car. One leg going to stock quiet muffler and the other capped with a sliding valve. You connected a long choke cable to the valve. When you wanted loud, you opened the valve and you got unmuffled loud. But if you saw cop, you closed it and got OEM quiet.