Yup - WIFE IS LOUD!!! (exhaust acoustics)

[Schrade]

Jeff was right - THis thing is LOUD! (http://www.zr1.net/forum/showthread.php?t=20910)

Outside sounds great. I let a neighbor do a lap around the block after he helped lock down clamps. Sounded great driving off; I couldn't hear it on the back side of the block.

Inside is a different story. What I'm not diggin' so much is drone. It's loud between about 1,200 RPM's, to about 1,800, give or take. Gotta' be way below 40 Hz...

So I'm thinkin' on a few things here, individually, or in combination, to 'interfere' with the harmonic resonance:

https://lh5.googleusercontent.com/-rac1zrFZ2e8/U3-3CNj9TSI/AAAAAAAAETw/QSlpBSH2p_o/s1024/IMG_6542.JPG

1) Pipe wrap the 2 sections where the resonator was, and the X-pipe.

2) New (or additional) sound material under the carpet interior. I stayed with the original material because it 'smelled' new when I uncovered it for Black conversion.

3) Fitting / welding in a free flowing resonator behind the X-pipe (or 2 individual units, space permitting)


Where's Jeff T here; Jeff - did you consider option 3 here? Seems it would be an easy task, if a resonator could be modded for 2 x 3" inlets / outlets...

Of course, option 'b' would work too - turn up the radio ;)

What did you do to take the edge off of interior noise, without hampering exhaust flow?

[mike100]

Single outlet mufflers will quell the worst of the resonance. The oem resonator was for a slightly higher harmonic and not going to do a lot for the hatchback drone.

I hacked NPP exhaust tips from a C6 and made a control scheme for the vacuum actuation. You'd be surprised at how well it actually works even on louder muffler designs.

[mike100]

Catalysts help a little too.

[Karl]

Get the high temp red RTV out. I had a couple of leaks at the collector area.

I plan on using sound deadening material on my interior.

I may also swap the b&b mufflers for the dynomax with the built in noise valve.

[Schrade]

Single outlet mufflers will quell the worst of the resonance. The oem resonator was for a slightly higher harmonic and not going to do a lot for the hatchback drone.

I hacked NPP exhaust tips from a C6 and made a control scheme for the vacuum actuation. You'd be surprised at how well it actually works even on louder muffler designs.

Any snappics of your hardware there Mike?

Karl - 'Get it out'? You mean 'get some hi-temp RTV put IN'? I can see how that might effect harmonics, but all the slip-joints are sealed now...

[Shrek]

My first plan was a resonator or resonators in place of the X-pipe.
That is until she said "put the Flowmaster system back on"
So I had no choice but to go with her option on her car!!

[Karl]

Yes after putting some miles on the car the slip fit connectors began to leak exhaust. Certainly not loud enough to cause drone and resonance, but it became audible.

[KILLSHOTS]

It's loud? Do you have mufflers on it? Is it a daily driver? Mine is wide open, except for the cats, and I can't wait to put headers on it so those "mufflers" are gone too. Still too quiet for me. Oh well, different strokes...

A resonator should help with sound but my understanding is that getting rid of resonance is a VERY difficult thing to do, unless you're installing a "complete" system, such as a Corsa. When we design our own, we can muffle sound but resonance is hit or miss. Best of luck with it, Schrade!

[Paul Workman]

Any snappics of your hardware there Mike?

Karl - 'Get it out'? You mean 'get some hi-temp RTV put IN'? I can see how that might effect harmonics, but all the slip-joints are sealed now...

Really not trying to be a schmart azz, but featured in the current edition of HOTB is an excellent article WITH PIX that Mike wrote, detailing the entire setup. That article alone is worth your $35 membership - which is required to see the magazine.

Just a thought....;)

[mike100]

I may repost some form of the information in the HoTB write-up after it has had a chance to be exclusive for a bit longer.

Here's a video of it working on Stainless Works muffs:
http://i29.photobucket.com/albums/c265/mschrameck/exhaust%20system%20clips/th_MOV02832_zps97199d80.jpg (http://i29.photobucket.com/albums/c265/mschrameck/exhaust%20system%20clips/MOV02832_zps97199d80.mp4)

[XfireZ51]

Mike,

I ride around w the actuators closed nearly all the time. It really is a pronounced difference between full open and full closed. W tuning it actually Is quite a mellow note at cruise.

[Paul Workman]

Mike,

I ride around w the actuators closed nearly all the time. It really is a pronounced difference between full open and full closed. W tuning it actually Is quite a mellow note at cruise.

I am a student of the progress being made by everyone employing the NPP valve concept to our cars. So, now that my other little "immediate concern" is behind me, I'm looking forward to getting back to "finalizing" (whatever that is?) my exhaust. Hearing about the mitigation of the droning issue is "music to my ears" - so to speak! And, I like your adaptation to Mike's approach especially.