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.

Off topic, but i see your from snoqualmie Nikon! I just moved from Everett few months ago, i used to ride stevens, baker, and snoqualmie! Anyways your picture reminds me of all the trees! we don't have them down here in Texas : (

That's exactly why the hiss is louder with test pipes. The lower the cell count the louder the hiss. This is why the test pipes have the loudest hiss.

Dont forget you can get the resonated HFCs from FI too, I dont know if that will help stop the rasp or not but combined with the CBE resonators that should keep it more quiet than those without the HFC resonators. I thought about theirs but the price is too steep for me so I will be going ERZ HFCs combined with my FI CBE. Should sound good. With the way my FI CBE with 12 resonators sounds right now, which is about perfect, not too loud but loud enough that it gets noticed and no rasp, if you go FI CBE 12 resonaotrs and FI resonated HFCs you will like the sound as it should be loud but not ricer loud.

Since you stated that you plan on going with our exhaust system I have a recommendation. If you really want to keep a HFC of some sort but want to cut down on the hiss during deceleration here is what I recommend.

First and foremost go with our stainless steel muffler option and 18" resonators in the x pipe itself. As far as the high flow cats, ours are 300 cell just like the Berk as well as Stillen. However, we offer a resonated high flow cat that no one else does. What this does is give you a high flow cat and resonated test pipes all in one. The beauty is, they do not make any less power than our 300 cell high flow cats. The resonator is straight through perforated core and in my opinion will help cut down that hiss that you are hearing.

It is there even when the exhaust is stock and if you listen real closely you can hear it ever so faint that it is. By removing the stock cats which use higher cell count cores and thicker exterior material, you eliminate what is absorbing most of that sound. All of the HFC's on the market are less restrictive than stock and much lighter because we use thinner wall tubing. This is why this sound becomes so much prevalent.

If you have any questions, please do not hesitate to ask...

Thank you, Tony

Be careful going with a HFC that uses a 200 cell cat. They are less restrictive and will be LOUDER than ours. I know that ours are more expensive but when you first came to me you told me that you wanted the quietest option available. Our resonated high flow cats are it. In the end whatever you decide to go with, I do hope that it works for you. I just wanted to put my 2 cents in...

Thanks, Tony

No problem, I dont want too loud (which is why I wont do test pipes or LTHs) but I dont want too expensive either. For me price is at the top of the priority list with performance and quality. Id love to have the res HFC but its just too steep for me for the gains. Love the CBE tho.

berk and stillen are 300 cell counts too? I thought they were 200 cell counts.

If the money is the top priority then go with just a high flow cats. They are $120 less than the res. HFC's...

Thanks, Tony

Thanks for the info, clears up quite a bit of questions for me!

Thanks, Tony for all that information! But which would be better as far as the deep tone: the res. HFC or the regular HFC? I want to cut down on the hiss but I'd like a nice deep tone too if that's possible. If there isn't a way to do that than maybe I'll just deal with that hiss.

The FI CBE will take care of that. It's the deepest there is, even with HFCs or Test Pipes... it's nuts.

Do a search for a post by forum member "Valentino". He has some high speed pass clips with his FI test pipes and 18" CBE... it sounds so wicked!!!

The Res HFC's are deeper and smoother. It is the resonator itself that attributes to most of that.

Thanks guys!!!! Now that I know I'm going for the res HFC's and CBE..now I just gotta sell my stock exhaust and the Nismo S-tune exhaust with Stillen HFC's. If yall know of anyone who's looking for either, let me know.

Also..for the res HFC, placing my order for them it says pick one Extra O2 bung: passenger, driver, or both pipes. What are these 02 bungs?

One other thing you also might want to consider is whether or not the HFC will give a CEL. I have had the F.I. HFCs on for about 8000 miles now and not a single CEL.

Passenger side first, to the best of my knowledge it runs leaner of the two banks on this car. However, when in doubt run two.

Hey bud, hope that all is well.

Look at that, 8000 miles and no CEL. I do not expect you to get one in 8000 more...

Tony

Extra bungs are placed before the cat core and are used for wide-band tuning. You may never need them.

There are plenty of threads about this. The more of a brand's HFCs that are out there, the more likely you are to hear about CELs. Berk has probably sold the most to our community and theirs have the most CEL reports. ERZ has only sold a couple to a few of us on here, and there haven't been any CELs. FI hasn't outfitted that many of our 370Z community members, so the numbers are still relatively low to get a good feel for CELs. They make nice products with a lot of R&D though, so I imagine they've done their homework in preventing CELs. Good to know that 8k miles are CEL free for you.

Sophia you are going to LOVE the sound!

Actually we have sold somewhere between 50-70 sets of HFC for the 370Z. If you include the G37 as well as HR 350Z we have sold hundreds of sets. Those cars are different than the 370 but the engine is virtually the same. What I am getting at is that we have plenty out there.

speaking of cats, i got a CEL a bit ago thats been off and on intermittent, I'm going to try the steel wool trick and see if that works, how much of it should I use? should I pack in as much as possible, or just a pinch or two?

Bought GTM test pipes off a forum member, had the L stem for the sensor, great sound no cel, but you will get a smell in the cabin. I think the rasp is primarily caused from a 2.5 HFC/TP going into a less than 2.5" y-pipe.

So it won't hurt to get both 02 bungs? I should just get them to be safe I guess

I make the best HFC's without rasp!

Nah won't hurt, I just didn't think they were necessary though if I throw a CEL i'll rescind this statement.