I have a FI RCBE for a 09 S sedan Tony from FI recommended the 2 1/4 exhaust for the sedan. car sounded perfect only had a hiss at higher rpm when letting off the gas and it was gone in an instant.. no problem at all.


Purchased F.I. RHFC for the system during a group buy a few months ago...after the install I could keep the car in park... step on the gas and hold rpm at 1200-1600 and there would be a hiss coming from the xpipe.. had the car checked at many shops and there was no leak... made a clip for tony to listen to and he thought most likely it was the xpipe.. he replaced the xpipe sound still there.. original xpipe was fine...


A few weeks ago I swapped my cats back to stock hiss is totally gone.. I measured the cats and they were 2 1/2.. matched to a 2 1/4..shop that did the swap was 99.9% sure that is why the hiss at lower rpm.. exhaust turbulence...
the cats are in perfect condition


does anyone make a 2 1/4 HFC for the g37?

 

I'm not sure on whether anyone makes a 2 1/4 for the sedan. At times I've wondered how that works as many guys run the FI RHFC's with the stock exhaust and we all know that it's mighty restrictive and is definitely less than the 2 1/2 coming off the cat.

I guess I cured myself of that issue because I have a FI CBE on order and just contacted Lance this week to upgrade to 2 1/2 piping so it should be a smooth fit.

Is it possible that the step down from 2 1/2 to the 2 1/4 x-pipe is causing the hiss? That would be my guess.

Did you use any high temperature silicone RTV when sealing the gaskets between the flanges? I've never done a CBE on any of my cars and this one will be the first so I'm a little green on knowledge of that aspect.

 

I have 2 1/4 the whole way from my FI HFC into my exhaust depot ypipe, then finally into my top speed mids and mufflers.