I swapped to resonated test pipes and now at 3k plus RPM there is resonance/rasp. I'm convinced it's the flex pipes as they are ribbed on the inside and when the increased exhaust flow is hitting it faster it's creating the noise. I really want it gone and I'm thinking about taking out the flex sections on my ark exhaust and putting straight pipes in. Fast intentions catbacks don't have flex sections. I have not read about cracking manifolds on this forum. I'm looking for some thoughts on this. All feedback appreciated.

 

There's most likely enough movement in the hanger system to absorb funky loads from the engine twisting. The flex sections on my IPL are pretty small but they are there for a reason. I'm getting some rasp with my FI RHFC's and the IPL exhaust unfortunately. Usually only down low at WOT.

 

It can be a leak, mismatched diameter piping. If the flex has a hole, then it can be contributed to that.

I wouldn't take out the flex sections in the ARK.

 

My Resonated TPs had zero rasp until I went to a a new Y-pipe. The new Y pipe has a 3" collector, and my Top Speed Y-back exhaust has a 2.5" mate to the Y pipe. I'm going back to my dented, scraped, and shredded OEM Y pipe, as I can't stand the ricey rasp, and the sound was perfect before (and TBH didn't notice any gain from going to the new Y). Maybe you also have a mismatched pipe fit along the way Upscale.

 

No leaks but having a specialist check it out next week and bring forth a solution. At least I hope.

 

Has anyone figured that the rasp is due to the design of the engine/heads? The rasp is far too common for me to think it is due solely to a particular exhaust setup. It probably is just more noticeable with more flow from a new exhaust.

 

Put my OEM Y-pipe back on and back to happy again, absolutely no rasp

 

I know exactly what you mean. I had the same problem. I put on resonated tp's with an upgraded y pipe. Before the resonated tp's I had no rasp/hiss. After I put the tp's on, I had rasp & hiss on deceleration. You would think the the resonator would heal the hiss but that was not the case. Just like you, I thought the sound was coming from the flex section & I wanted to chop it off. The flex sections are necessary for the movement of our engines. I ended up putting my stock cat's on & now looking for a hfc that doesn't hiss/rasp. I couldn't stand the hiss no matter how good my exhaust sounded.