I am trying to put together some info on how to build a quiet exaust system without sacrificing power. Here are some of the things Iv'e learned and add to the list if you know something.

Run a thicker exaust tubing (gets rid of ringing and noise traveling out of the pipe)

Use a crossover tube (the x pipe is supossed to be the quietest)

 

I picked the components of my 89s exhaust because I wanted it as quiet as possible. Dynomax Super Turbo mufflers are very quiet, yet flow better than some "other" mufflers out there. I also used Monza tips which are like mini-glasspacks. They're 3", but not that big inside because of the resonator. It'll be a restriction when I drop in the larger motor, and anything bigger than 3" will look ridiculous, so they'll go eventually, but for now, they're a good addition. It's still a little louder than I would have liked, but sounds good.

Another technique for quieting the exhaust is to use turndowns (aim the outlet downwards). The ground will help mute some of the higher frequency sounds which is what really makes the exhaust loud. That also sort of enhances the lower frequency sounds which gives it that rumbly effect.

 

If you're really serious about staying quiet, don't get headers. They are worth the performance gain, but kiss the quiet exhaust idea goodbye. I have flowtech afterburners, 2.5" true dual exhaust with crossover pipe, dynomax super turbos and tailpipes exiting right behind the rear wheel's in the stock location on my malibu. I had always intended it to be a sleeper, which it still is, but the exhaust tone is a huge giveaway. The Megashifter isn't helping the image much either, but when you're spending the last few minutes you have to work inside on a lift beating the crap out of the column shift linkage in a hopeless effort to make it work with headers, the image loses importance. If I had more time and was a little more bent on making it a sleeper, porting the crap out of some TPI exhaust manifolds might have worked. If I was building an F-body sleeper, I'd port the hell out of TPI exhaust manifolds, use a dual cat Y pipe, and the flowmaster single exhaust. Maybe just get the intermediate pipe and use a dynomax muffler and have a tailpipe made.

 

I agree, headers toss the whole quiet issue out the window.