Hey all,

Finally going to put HFC's on my X sedan. Do the Berks HFC have any rasp to them? I do not want any rasp out of my cats, and some of the videos I've seen of someone running the Berks seems to sound like there's rasp. I was also looking at Fast Intentions Resonated cats, but they're more expensive obviously. If I can get away with Berks for the cheaper price, I'd much rather do that.

 

Depends on what exhaust you'll be pairing them with, but almost always, HFCs will introduce some rasp but not as much as test pipes. When possible, opt for resonated versions that will help cut down the rasp, like the Fast Intentions (which are more expensive for a reason). Regardless of whether they are resonated or not, HFCs and test pipes will usually cause some rasp.

 

As of right now, I'm going to be running them on the stock exhaust. New exhaust system may be in the future. I might shoot for Fast Intentions resonated to stay on the safe side.

 

I had the FI resonated cats matched up to the OEM catback for about a year. The volume increase was negligible, and the tone was only slightly deepened when under load. All the while, there was a noticeable increase in power. Not dramatic change, but noticeable nonetheless.

That particular configuration... it's a stealthy mod.

 

How would it play with a Stillen gen 3 cold air intake? I was planning on installing the intakes and RHFC's at the same time. I'm not looking for a massive difference in sound, just a slightly noticeable change for the better.

I watched a video of someone with a Stillen gen 3 intake matched with Berks HFC's, and it seemed to be slightly louder than I wanted mine to be. I was hoping that with the new intake and with the RHFC, I would succeed in getting my desired result.

 

The air intake will add noticeable noise at WOT. With OEM exhaust components, you'll be keenly aware of that. If you're on the fence because you don't want the noise, I'd recommend the FI RHFC over the Gen3 intake... assuming you keep your OEM catback. Once you replace the catback, all those subtle considerations go out the window.

There are no modifications that come without compromise. Either you embrace the grunt of a loud car, or you redirect priorities elsewhere... like handling, or visuals, or creature comforts. Personally, I say do it all.

 

I've heard what the intake sounds like on a g37, and I actually like what it does to the noise. I just don't want to add the cats in with it and end up with something too loud. Since I like what the intake sounds like and the cats don't seem to add much, I might go for it. It's not that I'm extremely against the added noise, I just don't want to overdue it.

 

I've run BERK HFC's on my 06 M35 and it was a great combo with my exhaust set up. a few things you have to consider are the size (diameter) of the piping for the HFC's. I believe BERKs are 2.5" for the VHR so that my contribute to rasp and/or increased noise since your OE exhaust piping (Y Pipe inlet) is noticeably smaller in diameter (maybe 1.75" to 2.25"). The exhaust flow from the BERK cats will be slightly obstructed (going from larger diameter to smaller). I think the Fast Intentions HFCs (resonated or non-res) can be ordered as 2.5" or 2.25" (typically made to match diameters of their cat-backs). The 2.25" would be ideal for your OE set up.

The other item you have to consider is if you plan on getting the Stillen CAI and HFC's, you will be running your car on the "lean" side. If your car is your daily driver, I'd invest in getting your car tuned in the near future - search Uprev or Ecutek.

 

If I were to do both of those upgrades, the very next thing that I would do is a tune. I appreciate the feedback!

 

I ran the Berk HFC's along with the factory resonated mid-pipe and a Tanabe axle back for a couple of years and was VERY happy with the overall sound of the exhaust. Only slightly increased dB levels over stock and no noticeable rasp or drone. Now once I removed the factory mid-pipe that was a whole different ball game.