Friend and I installed the borla true dual exhaust, and it has been a nightmare ever since.

Okay, the pipes are install fine, all clamps tightened, I even took it to a nissan dealer who check for leaks, but there are these two noises and a smell and I cannot imagine what it is.

First noise: Raspy buzzing, happens during the downfall of revs, appears to be coming from gaskets at the cats. Also happens during coasting and sometimes acceleration but not always, like in 1st or second gear.

Second noise: Vibration/Sound. Very loud, seems to be coming from the same spot but unsure. Only happens at 1500 rpms exactly, whenever you hit the gas lightly. It's like a deep, hollow sound, sort of like running over the middle line on a road with those tiny divots, yet deeper . I check the rear hangars and they don't appear to be hitting anything, and it only happens at this rpm.

Smell: Smells like, well.. not gas, but more of a chemical smell.


Yea, so something's up

My assumptions:

A: I need to replace the cats, as the flanges are rusted and are now aligned with the new flanges. The gaskets are in place, though. During the first start up of the car, water was leaking from each side of the gaskets though, a sign of it not being tight, but we went ender and tightened it more. This is why I think the stock flange may either be bent or damaged.


B: I need new gaskets? I don't see how complicated the little things are, and they were undamaged in the process, but perhaps it could mean the difference?


Any ideas?

 

How many miles ago did you install the exhaust? First week or so after i put on my catback there was a horrible smell also even with the windows rolled up gone now though. Just drive it around for a cpl of days if it's a fresh install.

No idea what the buzzin sound could be

 

Buzzing could be the little borla grimlins that have been reported on the loose

 

i had the same smell for a while but it went away after a few days. maybe during all the install you torqued something else out of place, did you use hand tools or power?

 

Buzzing, and harsh vibration/noise... still yet to be diagnosed.

@ Combat: It's spelt gremlins, and thanks. Your ability to determine the opportunity to give advice or waste a post provided me with ample amusement.

 

Hand tools. Tighted it good, then drove around about 20 miles, and had it tightened again. The problem is very very distinct, not something light that could be blamed on it being new.

The vibration noise is abnoxious, the buzzing is annoying, and we can't think of anything it could be.

I did order kinetix test pipes to replace the cats. Hopefully this will solve any leak between the flanges, or any tinny backfire inside the cats themselves.

 

You're welcome and I was just waiting to see when the spelling **** would come out.

It never ceases to amaze me how we have so many internet English teachers. Don't give me this its simple English because I have written so many papers, essays, and reports and the last thing I get hit on is grammatical errors

 

I think borla has to be the poorest design. Just the fact that it uses clamps as oppose to other exhausts sucks.

 

@ combat: k. Nice life story, yet this topic isn't about you.

@ above: Yea, I was thinking the same, yet I don't think the clamps are causing the problem. Possibly the vibrations, but not the buzzing...

 

Dude call down. It was a ****ing joke. Gimme a break.

 

I am not sure if this is it but if I remember correctly, there are some heat shields above the cats, these might be what is causing your noise. Take a look at them and make sure they are not to close to the exhaust or body. If they seem close to anything, try bending them a bit to give them some clearance and see if that helps.

Chris

 

Thank you very much for your advice. However, I am wondering why they would hit now and not before, seeing as the piping is the same same size, and I never moved the cats themselves. This could explain the raspy noise though, however the vibration is still unexplained. I think it may be either the middle hangar, or the opposite side, where the exhause goes above a rod, and it may be leaning on it. Still, the fact that it only happens (and I mean ONLY) at 1500 rpms leads me to beleive it is an air flow problem.

 

Normally when noise happens only at a particular RPM, it is due to harmonic resonance. Basically, a sound being produced at 1500 rpm is exactly the frequency necessary to cause vibration. The vibrating part does not need to be in contact with anything, just exposed to the sound. There are a few more thin aluminum heat shields under the Z as well. One where the stock resonator was, and another where the back box was.

The Borla is known to produce a lower tone than stock so it is possible this tone just happens to hit the frequency for some random part while the stock does not.

Chris

 

i have the same problem!!! i learned to live with it. i think the second noise you are talking about is normal the noise coming only at low rpms. had that since day one. the 1st noise you are talking about only came after installing my kinetix hfc. (by the way you are going to love the sound w them) except the hissing nose. its like a hissing noise that comes from backpressure on the exaust i only get it when i hit the gas and let off quick.. like when i rev at some one. (can hear it when the rpm comes back down).. i think. i have also been told that its the stupisd clamp on "H" PIPE" i love borla cause ive always had it on all my cars and trucks but the exhaust for the Z is a very bad badly designed.

 

i have borla true duals, bought second hand and without the resonators they are loud and without stock cats and either deletes/test pipes or high flows, OH BOY!!!
theres resonators on mine and glad to have them. I out the exhaust right about 500 miles on the car and a CAI right about 900 miles, so I know just by when I pass a stock equipped Z much difference!
i cant complain about the borlas, good deal i found, sound great, feels great.


my set is basically quiet until i get to right around 3000 rpm and then "there she goes" !

if i get to my other computer, i can find a link for the pic of the underbody.
there is a chance that the exhaust is hitting onto the side skirt.

 

I am absolutely not going to learn to live with this. Your low rpm noise may be a light bass, like hitting it in 6th at 25 mph, maybe a little more, this is a jarring knock-type.

Secondly, the hiss (which is more of a snare), happens with backpressure as well, but also at coasting speeds, and sometimes when accelerating. With echo of parked cars or walls, it is substantially audible. If it really is the H-pipe, then this means a leak. Leak = loss of hp. Not an option. My car is a project sleeper. This is step two of about 7-8 overall mods that I am working with to try and top the N/A power of this car. I'm not moving forward till this is fixed.


Anyways, I though of an idea as to why this may be happening. In order to take the nuts off the flange for the cats, we had to use a breaker bar. This broke one of the screws off the flange, and we then had to saw the rest of the screw off, and drill through it to the head of the bolt. The use of the breaker bar and the amount of tension, pulling (See: enough for car to shake), it may have bent or warped the flange on both sides of the car.

Thanks for the tips in this topic, keep them coming and I will definately update the topic as the situation progesses.

 

i had the same noise when i installed my invidia catback system which sounds great my noise was coming from the gas tank shield my exhaust would rub the gas tank shield at certain rpm

 

Did you have to adjust the exhaust, or was the shield able to be moved or bent? I think that could be what the vibration noise is. Thanks for you input.

 

man you need to get it checked... i thought you were just complaining about little stuff . what you are saying is a real problem. i dont mind living with a little noise from performance glitches(borla td, jwt fly and clutch but what you are saying sounds major.

 

I have the exact same problem with the rattle at a specific rpm. Mine was actually at 1100 rpms. I asked some friends of mine (senior UC berkeley engineers) what to do and they said harmonic resonance also. I think the only thing to do is to change the vibration frequency... but I actually have no idea how to do that.

Sorry for the kinda useless post... but just wanted to agree with hypersprite if you get it fixed please let us know!

ChiShi