i just put on a dynomax super turbo muffler last thursday, but haven't been on the highway, until today. i had it at around 70mph for about 15-20min and i sounded nice. then when i got back on to normal streets it seemed louder. am i losing it or is there a "break in period" for the muffler?

 

I have a Magnaflow racing series muffler (straight-through design). Sometimes it seems louder than other times, and without obvious reason. In general though, the obvious factors are RPMs (mine is loudest between 3,000-4,000 RPMs and much quieter at other RPMs), wind and road noise which would drown out some of the noise, and throttle. When I touch the throttle very gently, the noise almost completely goes away. Moderate to full throttle is louder, as it is during engine braking/deceleration in gear.

I don't know of any "break-in" period. And I'm not familiar with Dynomax products, but I thought I'd share my experience and see if that helped.

 

rpm's didn't really have anything to do with it though. after i got off the freeway, where the rev's were at about 4grand for 15min straight, i got onto normal city roads. then my revs stayed between 2-3grand. even if i blipped the throttle it seemed louder. i'm not sure if because the engine was running at that high of a rev for that long, that it "warmed up" the muffler at all, maybe? that's my guess, but i wanted to ask all of you and get your opinions.

 

your muffler got really warm from the hot running and its cold outside so when it slowed down the car it gets louder cuz more flow thro a hot muffler
thats my guess, it happens to me, i find it alot louder on coler days

 

I was told that my Borla muffler would get louder after about 1,000 miles. I'm not sure if the person who told that really knew what they were talking about, but I thought I'd mention it. Personally, I don't *think* it's gotten any louder and I have almost 4K miles on it now. One thing did start happening though after a couple thousand miles and it sounds similar to what semtex said - when it's cold (well, that's a misnomer in FL ) it makes a raspy noise akin to a hornet on acid for just a couple minutes until it warms up. It usually does it when I'm shifting from 1st to 2nd while the clutch is in and the revs are going down (backflow noise?).

 

break-in? the welds i would imagine on the muffler could expand at higher temperatures, as well as letting the metal expand at the joints in your muffler, but either than that, it's normal, when i drove my car away from meineke, the car didn't seem that loud, and comparing the loudness of the echos i get from the houses in my neighborhood now and when i first got the thing installed a month and a half ago, it'doesn't seem any louder. i've never heard of a break in period, and seeing as there are NO moving parts what so ever, i don't see where you would need a break in period.
peace