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Discussion Starter #1
I have a 1990 BMW 525i, i bought it used recently. Seems to be a great car so far, but it is very loud, the exhaust note is deep, real deep. It's not tooo loud as a driver, but passengers in the backseat complain (lol) and when its started, it can be heard in the house. (the depth of the tone, not necessarily how loud it is).

I noticed that it had a K&N performance air filter. I dont think the box was changed (but im not sure either), just the filter. The previous owner said that it did bring in some noise though.

My question is just how much noise can a filter bring in? If I were to buy another filter, would it be noticeably quieter? Would a fram air filter do the trick (since its the most widely available).

The car really quiets down at about 4k RPM, and the idle is the loudest part, even louder idle in drive and as it revs more it quiets down. -- just some background info incase it helps.

Thanks much
Your time is greatly appreciated.
 

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An air filter closer to stock would quiet it down some but it sounds like this is mostly the exhaust. Try the Frma fileter for a little improvement but you must have an a/m exhaust on there. You have an exhaust issue
 

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Discussion Starter #3
Thanks for the advice, i think i'll go pick up the fram filter tomarrow morning then. You suggested that maybe my exhaust is aftermarket... how could I tell? it looks stock and appears to be the same as other e34s. no chrome no flash, two short, straight outlets. Maybe its just old and beat up?

Thanks again.
 

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I'm in agreement with SoonerE39 in that it's an exhaust issue. However, if the passengers in the back of the car are the ones complaining I wouldn't worry so much about changing the air filter as that's not really causing the tone and noise you're trying to remedy. Considering the age of your car (1990) you may have some holes rotted into your exhaust system somewhere possibly in either your muffler, the connecting pipes, or your cats. Have it checked out by a muffler shop (they don't have to do any work if you don't want them to, but they can look it over and tell you if there are any holes).

Good luck.
 
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