Hissing from hfc, is it a rumor?

Nick M · 04-28-2015, 11:46 AM

Quote:

Originally Posted by Jordo!

Switching to a larger diameter Y pipe will create a very load hiss.

Replacing OEM cats with unreasonated HFC's or TP's will result in farty rattle.

Both will be primarily on decel around 2.5 K or so RPM.

Only solution is to go OEM diameter Y (or Nismo OEM H), and resonated HFC/TP or LTH. Other than that its hit or miss to fix. Good luck...

None of this is true.

I did not have a hiss when I replaced my OEM y-pipe with my AAM y-pipe and catback.

I did not get a farty rattle when I swapped my OEM cats for FI test pipes.

Resonated test pipes can and will usually hiss just like non-resonated will.

Jordo! · 05-08-2015, 08:24 PM

Quote:

Originally Posted by Nick M

None of this is true.

I did not have a hiss when I replaced my OEM y-pipe with my AAM y-pipe and catback.

I did not get a farty rattle when I swapped my OEM cats for FI test pipes.

Resonated test pipes can and will usually hiss just like non-resonated will.

If the diameter was wider on the Y pipe, it almost certainly hissed.

If your test pipes were resonated, it didn't rattle significantly.

If the AAM Y pipe is about the same diameter as OEM then that's why it didn't hiss.

The cat-back muffler is not the issue -- all the noises are coming from diameter transitions and resonance from everything just past the headers. Whoever optimistically hoped it could be dialed out via VVEL, unfortunately, is mistaken. No one's found a way to do that and it most likely just isn't possible.

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