I read that HFCs can create rasp because the HFC piping is 2.5" in diameter and the Y-pipe piping is 2.25" in diameter (a 1/4 inch smaller) at the HFC flange connection. And that sudden reduction in piping size is what primarily causes the rasp. I have a Nismo, and I like the look and sound of the stock exhaust + HFC, but I have finally gotten fed up with the rasp.

My question is, would replacing the Y-Pipe with one that is 2.5" at the cat flanges help the rasp? Would that create problems since then there would be two 2.5" pipes joining into one 2.5" pipe?

Just looking for a solution here that would allow me to keep the stock cat-back and get rid of the rasp, without removing the HFCs.

 

Rasp is as old as this forum. It is the result of putting together mismatched exhaust components. How many exhaust variations do you think Nissan went though to get the classic 350Z sound? Alter the exhaust and you will alter the sound. Better or worse no one can guarantee.

 

I'm just looking for suggestions. I am not all that experienced and figured someone would have some knowledge that could be useful for me.

 

WHat y pipe have you been considering to mate with what brand of hfc?

 

I have no idea. I was hoping someone would have tried it before.

I have AAM HFCs and stock a Y-Pipe. Don't have any experience with Y-Pipes.

 

I just ordered the Motordyne XYZ pipe, should sort out that restriction

 

I read about that one recently, I believe I may try it.