Hi everyone, I was wondering if I could get some insight/opinions regarding an issue I'm having, as I'm sure some of you guys will be able to diagnose the issue right away.

So I installed Fast Intentions Resonated High Flow Cats yesterday. Upon start up, the car sounded really good with my tanabe exhaust. When I started to rev it, I immediately noticed a distinct hissing noise around 2300-3000 rpm. It sounds as if there is something inside there that moves around, and as the rpms drop back down it sounds like a hissing noise, a metallic hissing noise (very abstract I know, but I'm trying to be as descriptive as possible). When driving, if I push the clutch in and take it out of gear the noise is gone instantly. It's only coming from the driver side cat. I would really appreciate any advice or insight anyone could provide.

Thanks alot in advance,

Calvin

 

may just be rasp which is to be expected from the loss of cats

 

I know what rasp is, definitely isn't rasp. Also, I did not remove cats, I installed HFCs, should be zero rasp and appropriately so there isn't (thank god). Just a metallic hissing noise and also gives the impression as if there is a loose piece of sheet metal inside.

 

Listen to this video and does it sounds like this hiss. When you step on it and then let go sounds like a vacuum leak type hiss.

 

sounds like you may have an exhaust leak. is it very noticeable when you're slowing down (off the brake) and down shift into a lower gear so that the engine brakes the car? or if you WOT? a quick easy way to check is to look at the flanges, do you see any soot / black discoloration this would be caused by and exhaust leak. also check the welds, i had a crack develop in my FI resonated test pipes. But to their credit FI took care of me and sent out a replacement. great customer service.

 

Hey,
Ya that noise is pretty similar, but that covers only half of the equation. That noise is definitely present but there's also a distinct sound as if there is a piece of metal loose inside there. So I would say it's a combination of the two noises. But to answer your question, yes, that noise is definitely present as well.

 

My mechanic told me its definitely not a leak in the exhaust, and that it is coming from the newly installed cats. I go to Simone performance btw, so I do believe his opinion is credible. But thanks, I will bring it up to him and take a look at the flanges as well, thanks.

 

Also forget that maybe I should mention I only replaced the two rear gaskets (oval shaped, with 2 bolts) when installing, and didnt replace the two front ones (triangular, with 3 bolts) that actually go "up" into the vehicle (used the originals). Just picked up the other two, hopefully some of the hissing can be solved with a faulty gasket.

 

the stock gasket between header and cats is better than any aftermarket option i've seen and can be reused appropriately

 

That sound happens to Z's/G's when you take out the cats. Most high flow cats and all resonated or non-resonated test pipes will make the noise audible. There are different y-pipes and cat-backs that combat it but it will never fully go away.

You either live with it or put your OEM cats back in.

 

I just got my Berk HFC's installed today. I also have the nice hissing rasp noise from at 2k on the deceleration. Typical side effect from the 100+ threads ive read...

 

i got mine installed last night. they are completely normal. gotta love the new enhanced sound

 

Both my friend and I have the same noise magen test pipes.

 

my .02,

I never had the hissing sound UNTIL recently when I scraped the mesh on my JIC Y pipe and damage the flex. Prior to that, for 8 months I was running on megan RTPs, JIC Y-pipe, stock mid and Greddy Elite. I never understood the hissing sound I see on youtube of ppl with after market tp, y-pipes right after they install their system. I always thought it was strange since mine doesn't make the hissing sound prior to flex scraping. I def notice it now since I took a good chunk of wire mess off my flex area on my y-pipe. I can honestly say it seems like there's a leak in that damage area although I can' feel it or see it when under the car. I can DEF hear it from the flex area. Now i'm thinking about wrapping the flex joint with exhaust wrap to get rid of the hissing. (i hate that hissing noise)

 

Well what did the mechanic say after all? Did you figure this whole thing out?? I just installed my INVIDIA HFCs and I have the same whistling sound with higher RPMs. It gets louder when you keep accelerating.
So I would like to know what your mechanic said.