Okay guys, I think I found the cause of our hideous raspiness, (the sound of a thin piece of aluminum vibrating). The sound is coming from exactly that, a thin piece of aluminum. Read on...

I've been driving with the test pipes for a week now and I couldn't stand the 3k+ sound anymore so I decided to remove the testpipes today. As we removed the pipes, I noticed the markings on the exhaust gaskets. The pipes did not line up EXACTLY with the hole on the gasket leaving about 1/3 inch of thin aluminum exposed to the inside of the pipe. After examing the gasket a little more, I noticed that it was not 1 piece of aluminum but 4-5 peices of very thin aluminum. This is the cause of our raspiness. The thin peices of aluminum vibrating at high frequencies against eachother when the exhaust gases are flowing over it. So if you guys have this problem, check to make sure your exhaust gaskets are PERFECTLY centered between the two pipes. Better yet, throw away the stock gaskets and buy some new ones thats made out of a single piece of thicker metal.

 

So when you installed new gaskets that lined up perfectly it went away? Good detective work. I think I have a little raspy action with my cats, though some of it seems to have dissipated a little bit.

 

I dont know man, I had my exhaust shop install brand new gaskets thats fit ***** on and I still have the rasp?

 

I had the rasp really bad, but it was due to rattling around the crossmember. For about a week, I was burning through gaskets daily, all due to alignment issues. I think the RT angle is slightly off from stock cats or my NISMO/RT combo was the culprit. Anyway, I had the problem permanently fixed by welding the Y pipe to the cats, removing flanges from both. I now have NO raspiness and NO rattling and the fitment is perfect. This is in combination with a fabricated midpipe hanger that alleviated a lot of problems also.

 

anyone else try this???

 

I used the Nismo gasket set that came with my exhaust. One piece not like the stock "stacked" metal gaskets. Still got the "buzz" when decelerating in gear.

 

anyone know where i can get these gaskets?

 

[QUOTE]Originally posted by dollar99
[B]Okay guys, I think I found the cause of our hideous raspiness...

Mine still has the raspiness at certain rpm range 3600 - 4400. It's not the anoying coffee can exhaust sound either - I am not sure it is even audible to people outside of the vehicle.

I used the nismo gasket kit - but did anyone else notice when the cats were removed, it appeared as though the exhaust manifold had an insulated thin piece of metal inside - almost like a very small diameter exhaust system within the manifold. I've never seen anything like it before, but wonder if it is contributing as the metal was not a very thick guage and it may be vibrating in sympathy at certain rpms.

I guess the question would be does anyone have the rasp that has headers installed?

On another note - anyone with the RT's and Nismo exhaust have buzzing from interior plastic panels? That is my next battle.

Cheers!

 

so you had it before when accel, BUT now it is gone when accel, but there under decel???

 

I had the same problem with my xerd racepipes and borla exhaust and it took me about two weeks to adjust both of them to get rid of annoying noise.

 

But I still have raspiness noise on high rpm.

 

So the solution is to line up the gaskets?


It is going to fix the buzzing sound ?

 

My cats make a metallic rattling sound at lower RPM's both accelerating and decelerating, but that might be due to some heat shields, so I'll take a look this weekend.
There's more noise with the high flow cats than stock--metallic sounds here and there.

 

People have replaced every part in the exhaust except the O2 sensors. They still have the rasp. I'm not sure it is the sensors, however they have a thin metal cage around them that might be causing the rasp/buzz.

Hopefully someone can try taking out the O2 sensors and see if the buzz goes away. It will throw a CEL but it will go away when you plug the sensors back in. It is the only part left that no one has replaced.