remedy for hissing sound?

TPrelude-370z

Basically long story short, I have erz test pipes, little rasp no hiss. I just installed an obx y pipe and let the hiss begin. It starts at the exact same rpm and the same way everyone else' does. I love the boost in power, makes a big difference. This hiss drives me insane.

picture of obx y pipe for reference 2.5" inlets, 3" outlet. Prime suspect is that transition from 3" outlet to 2.25" mid pipe



I was already going to piece together a custom exhaust, so I found some options I would like opinions on for conquer the hiss completely. Nobody has gone this route before to my knowledge so it will be a learning experience.

Here are the options



-- easiest and cheapest has a 3" inlet with either a 2.25 stock outlet, or 2.5" outlet for custom exhaust all the way back to the axle. Easy transition couple welds, who knows what it will sound like 2.5" with resonators or 2.25" exit to stock exhaust.





-- more expensive - 75$ for just the piece, then more complicated welding from the y pipe removing collector and having 2 pipes from the y converging to the x. this comes in 2.5 inlet or 2.25 same principal can go 2.5 and go custom mid pipe or 2.25 and match oem piping

Now ideally I would like to run the 3" inlet u pipe to the 2.5" outlet and continue that to the midpipe all the way to the muffler attachment at the axle. This seems like it would be the cheapest most direct rout to having a cat back minus muffler portion. I have 2 somewhat large resonators already that I would weld on each of the 2 sides of the u pipe to help with the sound Everything would match up right minus the 3" to 2.5" y pipe collector to u pipe collector which should be just fine.

Other option would be cut obx y pipe before collector and use the x pipe to connect y pipe to x pipe to mid pipe, again with resonators. This would cost a significant amount more money and my budget for this is 150$ (x pipes alone are like 75$ where u pipe is 15$

Simplest and cheapest temporary option would be u pipe from 3" outlet of y pipe and matching the 2.25" outlet to the rest of the exhaust.

My thoughts are, will this 3" transition from y pipe to mid pipe do the job to eliminate the hiss, and does it make a difference if I go 2.5 all the way back, or leave the 3" transitioning u pipe and connect to the stock exaust matching 2.25?

I will be replicated a number of after market exhausts so you can see what I am looking at, here are pics.



-- magnaflow which I could replicate through the mid pipe at a 3" transition from the obx collector to 2.5" outlet and add 2 resonators w/ the mid pipe at 2.5" This would be a y pipe back exhaust minus the muffler portion.



this option would chop the y pipe collector and install the x pipe for a dual 2.5" inlet and outlet to the mid pipe with resonators.


this example would be y pipe hacked and use no x pipe, connect the mid pipe then resonators without transition


Thoughts? Ideally I would like to have a y pipe back exhaust his free that sounds great and uses stock muffler section (for now).

Cell

Nice, you're from chicago too. Which part?

You may have wanted to buy a full catback with resonators instead of just a y-pipe.

TPrelude-370z

I live in Schaumburg a mile away from the woodfield mall. Yeah, I went the "buy one thing at a time route" and assumed the hiss wouldn't happen to me. In hindsight getting a full exhaust would have been a better call. I am having a muffler shop put together a custom axle back for me in which I already have the large resonators and exhaust tips (same as stock).

I doubt that will do anything but make the sound more audible. I can get longer resonators and have them custom make me a y pipe to axle piece to make it a full test pipe back exhaust. I can also play with the outlet from the 3" y pipe outlet to a matching 3" piece/another resonater with a 2.5" outlet to the axle back portion. It would definitely be a long shot, but whats the worst that can happen, I put it back to the way it is now.

christian370z

I get hiss from my HFCs and FI exhaust on deceleration too, but the hotter the exhaust gets the exhaust hisses. I plan to eventually wrap my x pipe with some exhaust header wrap to see if that makes a difference.

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TPrelude-370z

I like the username. I am going to my exhaust guy to so some work, I will see what he can do first before I wrap it. Is the outlet the single pipe that goes to 3" I also thought about wrapping the flex pipes. I will know more this weekend and update.

Steve

fuct

i have the CNT/ERZ (same ****) res TP's... to get rid of the hiss, get rid of the TP's... :\ high flow cats would make it go away...... sry

TPrelude-370z

Thanks for replying. Did you have an aftermarket y pipe also? I had no hiss with the test pipes and stock exhaust. There is no way I am taking off those test pipes just out of principal.

It took a shop 8 hours while I sat there, and then an 02 sensor went bad (they replaced it, great guys). The power I get from the test pipes is more substantial than the y pipe.

I know there is some way to fix this. I am going to try some different options and see what I can come up with. I have faith in my exhaust place that they will figure something out. I still plan on installing my own muffler/resonator and tip combination as an axle back exhaust (already have the parts).

I planned on doing one thing at a time to feel the power increase and hear the sound improvement. Hindsight I would have been better off with HFC and exhaust. But hey, what would be the fun in that.

Cell

You should of went to project X to get your test pipes put in. Don't have some random shop do it. project X has tons of experience with the vq motor. The reason that shop took 8 hours was because of the demon bolt.

All the time and money that you will put into this will cost a pretty penny if you decide to go that route of piecing it together one by one.

Dembflyr

Add turbos.

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efuseakay

Yes. Next time you need any work done, call Eli at Projext X.

Trips

Please Stay on Topic!!

Thank You

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TPrelude-370z

I agree to stick with knowledgeable shops. I took it to Genesis racing development whom is well known and respected in the z and wrx community. I just moved here and was referred by ams I believe whom work on gtr and other higher end cars (they wouldn't even do it for me).

they had done the job on a z many times without issue. I knew the bolt would be a problem that is why I took it to them. Regardless they never quit until is was done, charged me 140$ for 8hrs worth of work, paid for and installed at 180$ o2 sensor. How many shops would do that?

I may have found a solution to the hiss, I will post a more detailed thread about options I have found and custom exhaust work. In hind sight I would have just ordered a name brand one, but this is going to be a fun journey. I have multiple options to try and fix the hiss and make the exhaust sound good. It will be a trial and error type thing but it will eventually end up great.

Dembflyr

Are you serious?

Because even though I was being facetious, there is no hiss with turbos installed. Isn't that what the topic was about?

Sorry for trying to be funny. It won't happen again.

__________________
2012 G37S Sedan 6MT - Project Practicality

2009-6MT-Sport/Touring-Dembflyr's Journal-TT Build Thread-CAR IS SOLD

Methodical4u

ART pipes with F.I. set-up and decel hiss here too. I don't really care since it's normal. I suppose it's a little annoying.. but I don't even know what area it comes from to even begin to know what to do about it.

TPrelude-370z

Update:

At the exhaust shop now. Going from 3" outlet of obx y pipe to a matching 3" inlet y/u pipe as in the picture above. Then from the y pipe 2.5" straight to the muffler without resonators. I will keep you posted and put up some sound clips soon. I really feel this will improve or eliminate the his.