What does muffler sound have to do with performance?

Forgive the simplisity of this question but.....I can't drive up the street without hearing that ripping sound coming from somewhere. I understand how people can like that sound but I wonder, what does any of that have to do with performance? Isn't it possible to have an exhaust system that's quite and give the exact same result?

if it sounds deep and throaty its ususally more restrictive then a loud lawnmower muffler. those ones that are loud and annoying are more free flow so its less restrictive which usually results in more power

Quality cat-back systems make a nice deep, non buzzy sound. However, the ones that are loud and annoying are usually just a apc muffler and/or a tip. Cars that make that sound from lack of restriction dont pass emissions, so you dont see them on the street.

As exhaust flow is pulsating constantly, I would imagine it would have some affect on resonant frequency/tuning. Interesting question. Never seen a tech article or test on it though. :)

But can't sound be delt with without any effect to exhaust gas flow? For instance, I can't remember the name of these things, but for lack of a better term, aren't there reflector mufflers that are designed on the inside to reflect the sound waves to cancel each other out and there for cancell the sound while still allowing the exhaust gas to flow freely through the muffler? As I understand it, that's the idea behind some resonators as well, to cancel as many of the acoustics of an exhaust before the muffler which finishes off what's left of high frequency sound waves. A number of resonators to cancel certain frequencies of sound and the muffler to catch the leftovers.

...course, that's just my opinion...I could be wrong....
-wheel

(long live Dennis Miller)

If you go into a muffler shop and say "i want to get a catback exhaust" and they put it on right......Ok its nice and loud goes with your muffler, they cant take off cat because its illegal....But with that new 2 1/4 piping you still pass emissions correct??? Im just curious cause i want to go get 2 1/4 piping for my 5zigen muffler but i still have to take my emissions test.... And the guy i bought the car from still had the 5zigen FULL catback on there.....but its low sounding, so it looks like he bought the whole thing at one time shipped from the company????? So my ? is will you pass emissions if u get 2 1/4 piping on your car??

As long as you have the cat, and you clean and maintain your car regularly, you'll pass emission.

the cat is the only thing that has to do with emissions. the muffler has no effect on emissions

Actually, if your muffler is leaking, then it can fail emissions. i know cuz a guy wouldnt give me a brake tag on an old bucket i used to have.

Originally posted by wheel1856
But can't sound be delt with without any effect to exhaust gas flow? For instance, I can't remember the name of these things, but for lack of a better term,...

I read about this in my physics book but I'm unsure about its application to a muffler.

yeah, cancelling sound waves with sound waves is quite the delicate procedure, and a muffler application couldnt do it alone, not with all the bumps and such of driving. hence the resonators. Im still not sure about these things. I think I read an exhaust article in the FAQ once about it, or some book at Barnes and Noble I was purusing. Cant remember.

how do tunable mufflers work? arent those just mufflers with a cap that opens up or closes to change the sound...kinda like a plunger on a trumpet?

There are silencers you can get for some mufflers that cut down on the sound level, but they do decrease air flow; bringing down hp a little.

The post-cat pipe leading to the muffler is what makes most of the horsepower. A straighter exhaust with mandrel bends works great. That and how the muffler is designed internally. The actuall diameter of the tip hardly affects performance. (unless of course the diameter is something like 1 cm across ;) )

To answer the original post:

Most aftermarket exhausts are free-er flowing. A free-er flowing exhaust is larger in diameter (better flow) hence a louder exhaust. And with this freer flowing exhaust you have to exchange the resonator out for the aftermarket piece which comes with most cat-back systems. I've had so many different tones with the 5 different exhausts I've had.

One was a universal weld on type and that was buzzy - almost annoying. Had a Brospeed exhaust and that was quiet. Then I got a GReddy Evo and it was nice tone, but get on the throttle and it was loud screaming banshee. My RS*R Magnum exhaust was quiet and yet nice raspy tone to it. Now I have a A'PEXi N1 exhaust and it's pure LOUD! :)