Strange "LOW" noise at 3000rpm, droning?
 

Ok i have a 2001 Rx7

The car start and run perfect cold and hot, no flooding problem and other stuff

When i push gas around 3000-3500 rpm i ear a big "Bwhoooooom" for around 1/2 second (half) after this nothing strange happen.

Previous owned (in japan) istall a damn Big exaust (i can make photo if you need).

Do you have any idea to remove or reduce intensity of this noise? A silencer in terminal? other stuff? (withoud buy a new exaust)

Thank you.


PS Engine is stock except for aftermarket filters

http://imageshack.us/a/img152/1953/downloader1h.jpg

sure, put the stock airbox back in. the sound is probably your smog pump venting into the open intake just before it shuts down at 3k.

a less likely issue is within the turbos themselves, a stuck open charge pipe butterfly will force secondary turbo pressure out the primary turbo and out the intake before the twins actuate together at 3500-4k.

but the smog pump is quite noisy on open intake cars. generally the smog pump sounds like a "moooo"(cow).

Yeah it's like a Cow....

ATM i don't have original filter...

Can this create other problem or it's only a matter of acoustic confort?