bump for this, why does it only happen when im in gear? When i let it coast buzzing stops.

 

Its rasp.

Rasp sounds are unique to each exhaust system configuration.

 

But it only happens on deceleration around a specific rev range, i don't think it's considered as rasp? (correct me if im wrong)

Its a rattling sound which is extremely annoying.

Would removal of the flex pipe fix this?

 

ya this is the reason why im so confused. When i accelerate i get a different kind of rasp. But when i decelerate i get this buzzing noise not rasp. Again only when im in gear, once i let it coast it goes away. Can rasp sound different when accelerating/decelerating?

 

I could be wrong. Can't really know without hearing it but I've heard rasp happen a lot of different ways, with a lot of different and weird sounds.

The flex pipe is a possible cause.

Can you get under the car while someone revs it? Isolate the sound source. Get a vid of it if you can.

 

I have already done this and the noise is definitely coming from the flex pipe. I have changed the flex to a double walled one and the noise is still apparent.

I'm thinking of 2 scenarios that may possibly fix the issue:

1. Remove the flex and weld in a solid pipe.

2. Remove the X pipe and turn it into a true dual system and perhaps increase the resonator hot dogs to larger ones.

I don't know, but i've already gone through 2 exhaust systems to try and get rid of this bloody sound.

 

My new setup is making this awful sound. I have test pipes, x flow y pipe, I'm guessing its the flex joints because the sound is coming from there, I had a mechanic listen to the revs while on his lift.

Normal driving every time I shift it makes the sound. If I accel even cruising in 6th it makes the sound.

Decel it makes that sound around 2500-3000rpms when revving at idle it makes the sound anything over 2500rpms. I'm hoping the guys I bought the exhaust from can help me out. I'll post updates if I get a fix.

 

Rasp.

If you changed out the flex lines, if they are properly installed and the new flex lines have smooth internal liners, its not the flex line.

Rasp is caused by standing waves. That means there is a zone of a high intensity shock wave that is stagnet or unable to move downstream.

At that RPM (Hz). At that exhaust flow temperature (under decel) there is a wave of a specific wavelength.

Something about your exhaust system, as a whole, is reflecting the wave at that specific condition. So the wave nodes and anti-nodes are stuck in one location. The wave critical points are essentially hammering on the exhaust system walls.

In your case, it sounds like the flex lines are at the critical point.

The best way to address it is with resonators.

 

Wow! That's a very technical response!

Ok, so you're saying extra resonators will resolve this?

In that case, for people with true dual, X pipe and H pipe setups, should we have 4 resonators in total as they already come with 2 resonators standard.

 

okay the buzzing noise i have is similar to this. Only difference is mine happens when i deaccelerate the buzz starts at 2.5krpm. Also mine isnt as bad as this, his is more of a rattle mine is more of a buzzing noise but occurs when i deaccelerate.
http://www.youtube.com/watch?v=jJVVH9FE7fg

 

Possibly. Adding resonators will reduce the intensity of the standing wave and/or move it to a less critical location.

 

When it sounds like that, its hard to say if its a shockwave doing that or if its really is mechanical buzzing.

Either one can do it.

 

thanks hydrazine, i guess the only real way is to get it on stands. One more question, i have bassani and i really dont feel like changing exhaust. If i buy your resonators is there a way i can install them in my bassani or better yet my longtubes to reduce rasp? I also like your rolled ti tip, is there a way i can put use that with my bassani? I know ima have to get the ends cut if i switch tips. Thanks

 

Hi Tony,

I have an update on this, i replaced the flex pipes with stainless steel piping hoping that this would fix the issue...

It actually moved the sound down to my X-pipe!!! We even looked at the x-pipe to see if the welding inside was causing the noise... we cleaned up a few of the over welding material but its still there!

As JPE22 mentioned, its like buzzing noise on decel..

I'm going to wait and see how my tomei headers and cams will contribute to this noise, but hopefully they will make it disappear!!

Are you working on something to fix this issue Tony??

 

You're not the only one who has it. It's rasp. I recently recorded a less obnoxious noise which occurs for be just under 1k and at 1.5.. an annoying buzz. I have jic y pipe berks HFC and apexi... again, mine is softer, but it's rasp nonetheless. Had my setup checked at 3 different shops, taken apart, individual parts examined, but back together... considered patching up welds but most told me it wasn't worth it and i'd either have to change the setup or live with it.

I assume unfortunately you're in the same boat, resonators might work however.

 

DAMN IT!!! lol i guess ill have to take it to a muffler shop and have them put on some resonators on my exhaust

How much do they usually charge for those? And how much are the resonators? Do i buy them seperately??? Or i could just buy another exhaust system

 

I know this is a old thread but has anyone figured out how to get rid of the rattling sound? It makes me not want to waste money on TP's and have to live with that noise. Every video on YouTube has the same rattle once the rpms come down after reving the engine.