Who makes the best HFC's without rasp?
 

I have the Stillen HFC's and they took away back pressure and that left me with a hiss. I've seen on the Fast Intentions site for their HFC's and that said they free up back pressure. Can anyone say that their's don't have that hiss? I'm going to get the F.I. exhaust but want to make sure that both the exhaust and HFC's would be better than my set up now. Any help would be appreciated.

I don't have the FI HFCs, but I think the hiss is inherent in anything you buy. I've noticed that every addition I made that relieves outlet resistance leads to louder hiss. Nature of the beast.

:icon18: Agree. I have the Berk HFC's and they do the same thing, you are hearing the whoose of air through the lower cell count in the cat, more air flow, more whoose.
Not as noticeable when i put the Berk CBE on though.

Really?!! I just thought it was from loss of back pressure cuz when I put on my S-Tune exhaust, it sounded fine until I put on the Stillen HFC's. I can even hear it when I'm upshifting , not downshifting

Yeah but the catback has nothing to do with it. The hiss is from the cats because of the lower cell count inside the cat. (as mentioned before)

Yep. Hiss and rasp are inherent to the HFCs.

Stock cats have 400 cell count, F.I. 300

and others have 200 like berk and erz. Thats why im going ERZ, less cel count, way less price than FI, and same results. FIs being 300 count might help stop the cel tho.

Insofar as we can tell, there is no real difference between the 200/300 cell count in terms of performance. This is not surprising as the difference in peak power between the FI HFCs and Test Pipes is only about 3-4 whp.

For me, I would just choose ERZ because of the price.

Wow..so the Stillen has the most hp increase?!! Sucks I gotta deal with that nasty rasp sound

All of the HFCs are roughly in line with one another in terms of gains. There is no clear cut winner.

But yes -- you're going to have to deal with the rasp if you run any HFC.

I don't think the sound has anything directly to do with the cell count because I've been told and as far as I can tell the hiss is on Test Pipes also and even more noticeable and they are straight through..zero cell count. Maybe I'm wrong though and someone with TP can attest to the facts.

I just installed FI resonated test pipes along with the FI exhaust including the 18" CF resonators. There is a hiss with the whole system but it really is not that bad....very subtle compared to the low frequency growl...love that:tup:

Yea, the F.I. system is what I want; exhaust, and HFC's....but which would be better in terms of loudness/tone...12'' or the 18"?

The 18" resonators will provide some lower frequency noise reduction over the 12". The CF is a different build (material and modal response) than the SS and just responds a little differently so there is most likely a subtle sound difference. I've only driven mine two days but am liking what I hear.