I have an 04 z and for some reason when I rev up and just let the rpms fall the car makes a very annoying raspy sound from which seems to be possibly coming from the resonated part of the dual exhaust. Info on my car, it's a 2004 automatic with an injen cai, fast intentions non resonated test pipes and a true dual borla exhaust. Plz help me figure this out, the noise is driving me crazy.

 

My friend is a great mechanic and helps me do all my installs. He screwed around with it for over 3 hour today and still can't 100% figure it out. I was hoping someone else has ran into this problem. And unfortunately I had to sell my manual for an auto because I have 3 slipped disks in my back which cause pain when I use a clutch........ I miss manual.

 

is it a raspy noise or does it sound like hissing air? if you have test pipes, when you let off the gas the the rpms drop you'll definitely hear a hissing. my test pipes do that.

 

My HFC's make a hissing noise on deceleration around 2000rpm. I was under the impression all test pipes and HFC's will have this noise on our cars. I just put the Motordyne XYZ resonated y pipe on my car and it got rid of a lot of the hiss

 

Is there perhaps a hole or leak in the exhaust?

 

I have a borla and Z1 test pipes. Want test pipes? Get hiss. Its just how it is!

 

Well I had resonated test pipes on it up till today when I replaced them with non resonated thinking maybe the resonator went bad but the noise stayed. So in a nutshell it's a noise I'll live with forever? I mean I love the true dual H pipe so I'm not going back to a Y pipe. I've taken the exhaust on and off in many places checking for leaks but still had the noise no matter what. Has anyone else tried to get rid of this sound while still using an H or X pipe?

 

You are stuck with it as long as you have test pipes on.

 

I had TopSpeed Pro1 resonated test pipes with the stock exhaust and had the hiss anytime the RPMs would drop back to 2,500 or 2,250 RPM. It drove me crazy because it does sound like something is leaking and just cheap.

When I went with full Nismo S-Tune catback still with the pipes, the hiss went away from what I could tell, but it was too loud for my liking, so I went back to stock catalytic converters, which is slightly too quiet but fine.

Getting a X-pipe fabricated in there may solve it so it may be worth a try, but I'm with NiLL on that, as long as you have the test pipes you can expect that hissing noise.

 

Its hard to know how the noise sounds like. My guess would be its because the TPs are non-resonated. Dont think it's an exhaust leak, that usually sounds like a rattle when you're giving it gas not letting off.

 

So if I was to go with a big name hfc like stillen or something, do yal think the hiss/rasp would go away? I never heard the sound when I had the borla and just the normal cats on cuz I assumed they had to much restriction and were quieter but Idk what to think at this point.

 

It really isnt a big deal. I cared more about the rasp between 3400-4k with the borla then the hiss on decel. Then I got my CAI and now its gone. Pull in the clutch if you don't like the hiss. It's just a noise the engine makes, that required you to jam a potato in your exhaust to get rid of.

 

It's the Borla H (X) pipe. Normal turbulence. When you add test pipes/high flow cat, the turbulence increases which increases the raspy sound.

I think some members have eliminated the sound by installing a magnaflow x-pipe. There's threads around on that.

 

are your sure you're not low on oil? my car made a "hissing/machine gun noise" when decelerating, then i changed the oil, and it went away!

 

Thx a lot man I'll buy one as soon as I get I chance. I looked up videos and other threads and this seems that it will totally help me.

 

I get a nasty rasp rite at the H pipe with my test pipes and Borla setup. I despise this noise but the sound when accelerating outweighs it so...