KISS

Does anyone else have this problem. I have Rt cats, JIC y-pipe and Magnaflow exhaust. The car sound fine but when I'm at 2500-3000 rpm's it buzzes. Sometimes I'll hear it on the highway at full throttle. I've heard some other Z owners have this problem.

lotus

I had the same set up with Nismo exhaust and had the same problem. It might be the JIC Y but not sure what was causing it so I sold the RT cats.....

jeffery

I have the same problem between 3 and 4 thousand rpms.
nismo cams, headers, rt cats, stillen exhaust.

barrybell

Such sound occur when thin sheet metal vibrates or oscillates
due to harmonic pulses.

NY 350Z

iTrader: (9)

yo i got just the helix pipes...and same thing...3-4k sounds like GARBAGE. so ricey,im embarassed to drive it!

dollar99

I got the kinetix test pipes and Borla, I agree with the rest of you 3-4k sounds like a civic fart can. It almost sounds like I got BB's rattling in my muffler.

KISS

WOW. I'm glad I'm not the only one. What's going on? I was thinking of replacing my exhaust with the Invidia system.

Beaker02

Had the same thing. Fixed it. Get the car in the air and check to see if the pipe going to the back is coming in contact with the crossmember in the frame about midway back. Another sure sign is when it buzzes worse when the car is cold. The fix: Have your installer heat the pipe and put a small indentation (1/4in.) in the pipe as it goes over the crossmember. Goodluck, hope it solves your problem.

Ultimateone

Its most likely the cats...seems like after ech person install Hi flo's or test pipes we get the rasp

Juztin

iTrader: (9)

very high exhaust flow which can also cause exhaust vibrations. But in general it's simply the fact that you have a much more open exhaust. Adding a secondary pre-silencer helps as well. But me personally I have exhaust vibrations which I need to fix, but I also have raspyness from like 3k-3.8k, so I try to stay outta that range as much as possible, or just gun it, which makes the exahust sound a lot better. Otherwise just put your stock cats back on and problem solved.

mpol99

Its the cats, I had that on my old car when i put test pipes in.

ajk4

yea its definetly the cats. i have checked, checked, and re-checked every clearance area from heat shields to the cross member, rear sway bar, etc., etc. and have come to the conclusion that its the cats. from what i've read the rt cats use a composite metal filter, whereas the carsound cats use a ceramic type, and consequently dont experience the rasp that the random techs produce at 3-4k rpms. however, the carsound cats dont flow quite as well as the rt cats, but agruably thats at best 1-2hp from midrange to the top (as seen from the recent ts flow charts).

Z PHAT Z

iTrader: (46)

It's 100% is the test pipes or some RT cats also contribute to that raspiness sound. I used to have a long tube catless headers and I also got that annoying sound. The fix is that get a different hi-flow cats or test pipes with resonator.

Rizzness

iTrader: (2)

So this does not occur with the Kinetix Hi-flows??? or what??
ZZ

KISS

I called RT. They said that high flow cats can only effect the sound by making it deeper. More flowing air, louder, deeper exhaust. That none of their cats could cause this. They make cats, to make cars perform and sound better than stock. It is all in the exhaust. So has anyone ever run without a muffler?

FLY BY Z

Yep, I have had two custom exhausts without mufflers before I went for the NISMO. The first with test pipes had an H-Pipe (true dual) and one set of resonators and was very loud and very raspy.

The second I ran with cats and it had an X-Pipe and two sets of resonators (no mufflers again). When I installed the XERD headers it got very loud and raspy.

Now I have the XERD headers and the NISMO exhaust. It sounds excellent but from 2.8K to about 3.3K it has a metallic metal sound (no it's not rubbing there is plenty of clearance everywhere) that is the new version of the raspy sound. It doesn't go away by taking away or adding the muffler.

I used to think that it was weird metal vibrations on the exhaust system but now, after all these exhausts, I am starting to think otherwise. It may just be the way the motor sounds. When you open the exhaust as much as test pipes and some HF cats, you are going to hear different things that are not as muffled. Could the raspiness be the RPM area where the valve timing begins to change? Or some other weird aspect of the motor? Is it simply a characteristic of a V6?

My LS1 with test pipes and high flow exhaust was not raspy, just loud. Something is different. Only thing I can think of is different number of cylinders or different technology/firing order/etc.

2FST4U

KISS-

What you are describing is a common occurance with these cars (G35s & 350Zs) when you replace the cats with high-output cats. It is an unfortunate side effect of the gains you receive. A custom cat will have to be developed specifically tuned for these vehicles in order to control the sound. Short of putting batting into the RT Cats (or other model) - until someone develops this, it is what it is - unfortunately.

AC

hfm

iTrader: (1)

First thread I've read where rasp was a problem with Random Tech cats. The rasp will definitely occur with any testpipe with the notable exception of the LaBree Motorsport testpipes with resonator. The resonator effectively reduces the rasp to make it virtually unnoticable. I have heard no rasp complaints for the LBMS highflow cats, Kinetix or Crawford cats.

If you're having problems with the RTs, I would recommend you try the LBMS, Kinetix or Crawford cats after doing a search for both.

lsdunique

iTrader: (3)

I know the test pipes have a large amount of raspiness, and I have heard some of the RTs have had somewhat similar raspiness.

The RTs probably have the highest flow of the high flow converters out there right now. I havent heard of any such raspiness though on any of the high flows that use the magnaflow/carsound cats like ours.

Zship

iTrader: (1)

When I tried the Test Pipes with the Borla TD, I had the same raspiness. It obviously is not the test pipes because it is just straight thru tubing. I think when the exhaust gas velocity is increased through the use of a less restrictive exhaust (cats or test pipes), something is making the noise in the exhaust track. As I tried to diagnose where the noise was coming from, it sounded like it was before the test pipes. I am starting to think it might be the O2 sensors. They have a thin metal cage around them that might be rattling with the increase in exhaust gas velocity. Hopefully someone can try plugging up the O2 bung and see if the raspiness is gone. I would try it, but my car is off the road for the winter.