Ok well I was washing my car and everything im like I wonder what will happen if my muffler gets full of water...lol I made sure it didnt go any farther than the muffler I parked backwards on a hill so the water would all come out anyway. Well I did this and then I started it up and now it sounds better. Its louder!!!!!!

 

Only possible theory I could have as to why it would do something like that is because during the course of normal operation, on the inside of your exhaust pipes/mufflers, a blackish deposit develops (as anyone who has ever ran their finger inside their exhaust pipe can attest to)...if you flushed it out with water, it probably just cleaned the muffler out and it resonates better cause the deposit isnt absorbing the sound. Thats my theory about it.

 

however, that theory is supposively the exhast opposite on wut happends on the flowmaster 80 series. but maybe it was really clogged up.

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- David
88' GTA 5.7L TPI MODS---> air foil, K&N, Shift Kit, 180* therm, TB bypass, Gutted CAT, Flowmaster 80 Series

 

If your muffler actually "filled" with water, I think what you're experiencing is probably similar to what happens when you blow across the top of a bottle, then put some water in it, and the pitch gets higher. It's probably not really louder, just that the predominant sound frequency has moved into a higher range, giving the perception of being louder. I imagine it would return to it's normal characteristics as the water blew out or evaporated.

Just one theory.

 

yeah now my muffler is back to normal. I heard that if u buy those thrush glass packs and drive for a while then when u turn the car off spray water inside it and it breaks up all the glass inside making it louder. I dunno if this is true or not, but that is what I heard.