Quote:
Originally Posted by TeamARK
we believe that the sound is generated from the flanges that meet at the HFC and headers. The sizes of these two pipes are different and by looking at some HFC's they do not taper down, but instead create a step between the two piping sizes.
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I would like to *think* I'm a pro now since I have been down this road and hacked my exhaust to death just to try and eliminate that sound.
There only seems to be a couple of ways of eliminating that rasp...From some old sources I have heard from in G37's etc etc - going 'true' dual seems to stop the rasp. But of course, we all know it makes less power.
The other way that seems to work is when you place resonators before the H/X setup - think Invidia Gemini - which is where I have verified the dreaded sound is at its worse. I was planning on adding some resonators at that spot but I haven’t done anything because I wanted to wait for a SC/TT kit so I can make the needed changes to the exhaust at that point.
Additionally - I want to point out that the GTM Res test pipes I have definitely killed alot of the rasp but it’s still there for a brief second around 2500rpms. Instead of hearing it from 2-4kish and all throughout decel it only quickly 'pings' around 2500 and quickly goes away and almost zero on deceleration. So, I was happy with the improvement but I've always been bugged by it.