Just started noticing this after installing an Invidia 60mm test pipe on my ASM 60mm exhaust. Very hard to explain the sound, but best way is a soft "whistle" sound. Mostly faint and is only heard from about 2500-3800 RPM. Sound is not high pitched by any means, mostly sounds like the exhaust flowing over something. Am I just experiencing this due to more flow?

 

If you are handy with the tools.... swap your OEM cat back in there and see if it goes away.

 

Yeah, I'm definitely gonna try that. Almost positive it wasn't doing it before the test pipe.

 

slight exhaust leak. did you put in a new gasket or reuse the old one?

 

Could be a slight weld burr on the inside of the flange. If you take it off, run your finger over the inside and if you feel anything suspicious, file it down a little. On the other hand, if it's inaudible during a drive and doesn't bother you, leave it as is. It probably sounds pretty cool outside the car.

 

Thanks for the replies guys.

Yes, the gaskets are all brand new. Only reason why I don't think it could be an exhaust leak, is because it goes away after 4k RPM. Wouldn't a leak be present throughout the entire RPM range?

 

you are correct. I think the noise you are hearing is a common problem with test pipe installs. I have the same thing.

 

mine does the same thing, i have a t.p. aswell

 

Same here but my test pipe is resonated, its sounds kinda neat actually

 

oh that's a good point.

i actually have the same thing on my car, with the 63mm high flow cat. happens in the same spot.

i always assumed small exhaust leak, but the car never showed any problems on the dyno or in the 3x its been tuned, so that's good news for us.