Hissing from hfc, is it a rumor?
 

Hey everyone:

I have heard rumors that if you replace the hfc, or take out the oem, that you start hearing a "hissing" sound. Is this true?

I have also heard that the problem could potentially be an exhaust leak. If so, would it be possible to put an exhaust gasket?

I say exhaust leak because it seems like there are those chappy flanges on the end of the parts...maybe it could be it. If this is the case, should O just buy my own flange and replace them? (maybe a v-band clamp?)

Sorry for the long post with multiple questions, I just want to find someone who has had experience with this type of problem before I take the plunge.

Well I don't think it's so much a rumor as it is an aspect of our VQ engines. I get the hissing when I let off the gas and the engine is in gear and starts to decellerate. The sound doesn't bother me though, I'm not sure if anything can be done to make that sound quieter if that's what you're looking for, short of keeping stock cats on.

BTW: The sound is not present while accellerating at all.

Do you happen to know what in the engine is causing it? What system is it?

Well i don't know why the engine makes that sounds but yes it does. I have Ark r spec resonated hfc and it's makes the hiss in deceleration. I almost can't even hear it but the more you open up your exhaust the louder it gets. I had a 350hr with headers and straight pipes. The hiss was loud

Honestly I don't but if anyone on here does, please let us know because I've been wondering that myself. Curious what makes the engine have that unique sound, I think it would be cool to know.

Well then when I install my test pipes this week I can expect that hiss to louden also....oh well! :driving::vuvuzela:

Think the hiss is related to the VVEL operation with aftermarket exhaust. The exhaust changed the harmonics within the system and it's not tuned for it.

Perfect! That makes sense...Do you, or anyone else, happen to have a screenshot of the table that controls VVEL?

I have Berk HFCs and CBE and the hiss is definitely there. Does not bother me at all and actually sounds kind of 'exotic'. I tell everyone that it is the "snake" inside ready to pounce on some of those lesser vehicles :D.

Hiss will be present, but from a person who likes to tune their vehicle different noises will be present. It's not a big deal. I run test pipes to a CNT CBE.

VVEL controls are still limited, only certain Uprev Pro tuners have access & then ECUtek claims to control VVEL but you have to go to a tuner (no end user option yet).

IMO' HFC or Downpipes is a must
 

HFC really helps bring out some sound life to the Z. So due down pipes of course, if u can stand the smell. But after installing the Berk HFC using Ramps (no room under the car, barley squeeze under it with stock suspension) & doing it all buy my self (FML). Not to mention having a Cat back exhaust on the car already (have to remove the Y pipe on most aftermarket) I can truly say it was a bitch. No question...A whore like no other. But well worth it when you put her in her place and get it done. Glad that **** is done.:happydance:

Those who are experiencing a hiss with HFCs are experiencing it as a result of their exhaust and HFC pipes not mating. Some members are running a HFC with a 2.25 in outlet and then are running a 2.5" exhaust. Or some are running a 2.5" HFC and then a 2.25" inch exhaust. The variations in piping diameter at the flanges are causing air to seep out and creating a hissing sound.

That's a possibility. BUT, some have complete systems with matching diameters. And they still have it. The stock exhaust has it to some degree. If you look back to 2010 or there abouts. It was brought up then.

I'll be installing HFCs to compliment my Injen exhaust and I'll report back to you. They're both 2.25"

It would be great if you can post it. I am curious to see as well.