HKS Mid Pipe Problem

[JB-370z]

So I got the hks exhaust installed a few weeks back and I am having a weird sound coming from my mid pipe! Its like a high pitched rattle. The shop put it on the lift and its comming from the mid pipe and not somthing else. Waiting on HKS to open monday! I also have berk high flow cats, does this make any difference?? Does anyone else have this ugly sound? I can really hear it the faster I go and it is mainly while the rpms are going down instead of up. They said they have never heard a sound like this in a mid pipe. What is in the mid pipe? I am going to record this sound and also send to HKS. Had a turbo hks rsx type s and none of there parts have ever failed till now, but it mught be somthing else!

[DannyGT]

Thats actually the infamous 'rasp' you will come across on these boards...almost all cars do it and depending on the config its either louder or quieter. You will hear it on decel and more defined in that 2-4k rpm range.

Now - you can go custom or with another exhaust but from what I can tell an FI exhaust with 18" is good and that invidia gemini exhaust nearly solved the issue all together by putting the resonators right before your typical H/X connection. Thats where the 'rasp' is heard and having the resonators in that early in the exhaust pretty much eliminates it.

Trust me, i exhausted myself months and months back trying to determine what it was...You can even find a youtube video that I made where you can clearly hear the sound.

Also, I forgot to mention...it gets worse with a HFC or Test pipe (downpipes) that are the main cause of that resonance right before the mid section.

[JB-370z]

DAnny you rock! I talked to berk yesterday and they guy talked my ear off 30min with great advice. Is there somthing a custom shop can do?

[DannyGT]

You can take a look at the pictures of the nvidia gemini exhaust and ask a custom shop to add 8-12 inch resonators in that similar location...but I have no clue how much it will quiet/ change your exhast note, so it's hard to say. It's up to you! I think FI has a down pipe that's resonated and HFC'd which would reduce the sound alot too!