Never ending quest for the best C4 ZR-1 exhaust system- Stainless Works-UPDATED
 

Been back and forth with a few different pipe combos- but the long story made short is that the 3" all the way back with the SW 3" X-Pipe makes great top end with plenty mid range torque using LS7 cats from a C6 Z06. It is faster than the stock mufflers on 2.7" pipe without cats. It's Freaking Loud, but then running stock muffs catless on longtube headers was a bit obnoxious too. There is drone, I will probably go to turbo mufflers again when I get some more money to spend. Additionally, I really like running catalysts again. Birds don't fall out of trees when you drive by, you don't get dirty looks from the beach hippy in a Prius, and it quiets things down and quells those decel backfires quite a bit. Lastly, I priced various aftermarket bullet cats with a 3" slip connect, but how can you beat factory Cats from a 505 hp car? You can tell it is running clean, the pipes aren't even blacked up yet and there is no odor at all. OEM parts FTW.

http://i29.photobucket.com/albums/c2...ps4fe8968e.jpg

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I had recently installed some LT5 headers and I found these 2" longtubes that were already setup for air injection. These aren't SW headers, but a mystery brand- maybe made by Morrison Motorsports in GA is the best guess I have so far. Anyhow, they fit perfectly and really woke up the car.
http://i29.photobucket.com/albums/c2...ps3c4a2ec2.jpg

I was running cat-less for a couple of months after the header install (using stock mufflers), but I got tired of my eyes watering every time I pulled up to a stop light with my windows down. Since I had some oem LS7 exhaust that was a stillborn modification on my C6 that I decided to not go through with, I put those nice 3" piped cats to use. They are pretty compact and just fit under the heat shields in the tunnel.
http://i29.photobucket.com/albums/c2...psb358eb2e.jpg
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Notice that we were able to retain the use of the clamping system so the pipes can be separated for service.
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Factory air injection still in place. Does this car even have headers?? Stealth- Because California.
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Also I got a good lesson in installation technique at my local muffler place. Check out the diff clearance. Perfect 1/4" spacing at rest. My old B&B sure wasn't able to achieve this, but it does have a lot to do with jacking up the center piping in place with a jack of some kind, then tightening the clamps before letting it hang.
http://i29.photobucket.com/albums/c2...ps643aa02b.jpg


more pics:

http://i29.photobucket.com/albums/c2...psdcccae37.jpg

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I considered that one long ago, and those mufflers tips are the reason I didn't buy them. I think they are hideous, but if they are working great for your Z-good for you. :seasix:

A Vette tuner told me that SW is the muffler system he get the most HP at his mainline dyno.

I'm passed Muscle Car Rumble. I want to get there, able to have a phone conversation, listen to my tunes, and drive.

I foresee buying Turbo S mufflers for both Vettes in the future. I care less I loose 5-15 RWHP. Dynomax sells a 3" resonator with an X inside. That baby looks pretty cool to me.

I'm not sure on the mono-tips either. The mufflers look ok to me- I don't need to have a chromed-out can, but they do look pretty nice if you can get one. If I decide to keep it loud, I can just take the mono-tip off and buy 4 generic chrome tips. Most likely I will get the S-turbo style muffler a little later on. Maybe I should dyno it before then because there is little doubt this is the most powerful combination I've had on this car to date. It has been about 90 degrees around here and the car still hauls ass even in this air. We've all done some bolt-on's that you couldn't really tell for sure by the seat-of-your-pants if it was better or not...the headers and the big 3" catback on the LT5 isn't one of those mods.

I actually bought the car with a B&B x-piped system which is pretty similar. I foolishly got rid of that early on, but I should have kept it and thrown some different mufflers on it. Well, I tried a couple of combos and could never get the good top end rev so here I am in the same place 2 years later.

I'm predicting 115+ mph in the quarter. I should also say that I got this thru a group buy on the ZR1 net registry so the price was really attractive ($735).

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Wow, They do drone :99pewtercoupe:

New Style SW chrome rectangular Outlets.
 

Great photos and nice writeup mike. :seasix:

I really like the new style SW chrome rectangular pipes. I have those on my 90'z and the older style dual circular chrome pipes on my 91' Z.

I tried to listen to my radio, but turned it off after a few minutes. The good news is I can't hear my targa top squeak anymore

I guess I didn't feel that I had spent enough money on this thing so here's the update:

So I got some C6-Z06 mufflers with the NPP exhaust flapper valves (vacuum actuated).
http://i29.photobucket.com/albums/c2...psdc20a86d.jpg
Note that the inside pipes are the loud, high flow straight thru section. This will be blocked during cruise conditions.

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Hacked them off to put them on my loud-ass SW mufflers.
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Working out the fit- had to rotate them a touch to fit the vacuum can.
Also the diaphragm comes loose and you can reposition it so the vacuum nipple points in any direction.
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Got the staggered tip the same on both sides- sort of follows the fascia curve.
http://i29.photobucket.com/albums/c2...ps331fc03a.jpg

I have not completed the vacuum circuit yet, but plan to trigger a vacuum solenoid using the vacuum secondary signal for the LT5 secondary throttle blades in the intake. It is computer controlled and works on throttle position and engine rpm- so the algorithm is already perfect as it exists stock on the ZR-1 model. I'm piggy backing that function for sure

I could only manually pump up the valves to test them for now, but it is REALLY quiet! This IS the solution to the C4 drone on the typical aftermarket system. I can see why they offered this on the C6 vettes- it is the only way to make dual outlet mufflers quiet.

I drove the car with the NPP valves hooked up to the plenum. They close at idle and very light cruise, but if you even barely crack 30% throttle or go up a hill, it gets loud quickly. never the less- it works and is very mellow!

Got an EGR solenoid from the junkyard for $7.95 It was from an early 90's cadillac with a 4.9 I think. Same egr solenoid that comes on most of those cars before they went to the electric one. It vents to the atmosphere and has a little foam filter on the 3rd port. I think I will hook it up to the vacuum ball in the right front ahead of the tire.

Need to figure out how to get switched 12v power into the engine compartment though.

We have the Mild to Wild switch on our 07 using an 08 NPP exhaust. I love it. We can push the button and go to full open or closed. When closed the car is quiet like stock and open it sounds great with headers. Installation was a breeze.

I won't be getting fancy with a remote control key fob like the M2W. As it stands, my adjustable vacuum switch was lost in the mail and the seller is going to send me another. I want to wire it to be automatic based on engine load, but if i can hide a switch, I was considering using a relay to force the function on, off, or automatic (dual-mode).

recall on C6's, there is an actual control box that interfaces with the ecm. Mine is more manually plumbed in and monitoring the secondary throttle plate vacuum signal

ON EDIT: How did you adapt an '08 NPP onto your 07 C6? Did you only get the M2W box or did you get the GM controller along with the mufflers?

There wasn't a controller. I wasn't aware of one. I always thought the only thing that made them work was strictly intake vacuum. There was a control box that came with the M2W. All we did was run a vacuum line from the intake to the control box and then from the box to the exhaust. Then ran a hot wire from the fuse panel to the box.

Wired this way the exhaust only works full time open or full time closed which isn't the way it was intended to work. GM designed the exhaust to open at 2000 rpm if I remember correctly. I also don't know if the Z06 Bi-mode works exactly the same as the NPP but I assume it does.

I am really impressed. You guys are actually discussing a C4 technical problem! What is this forum coming to?
http://abe.midco.net/~barondeau1/Vet...ep%20right.jpg
:hurray:

yeah, there is a factory vacuum control box. looks like the M2W substitutes for that in the case of cars that did not come with it. On the factory equipped cars, it never comes on before 3000-3500 or so. It monitors engine speed and throttle position presumably.

Mine is working similarly now.

We only have winter in January here. Plenty of good car working days still.

So I finally received the adjustable vacuum switch. When the vacuum controlled secondary throttle is activated on the LT5, so is my loud valve. I set it to 12" of vacuum (12 in Hg).

http://i29.photobucket.com/albums/c2...8.jpg~original

The switch powers a junkyard EGR vacuum solenoid. This couples the vacuum to the muffler valves. It either connects the vacuum to the valve, or vents the vacuum to the atmosphere thru the little foam filter on the 3rd port. It never has a vacuum leak on the source end. Perfect $8 solution (I should have pocketed it but I was feeling honest). The vacuum source is the nearby vacuum ball used for the a/c and air injection diverter valve. The 12v was easy too- I tapped into the under hood lamps which of course aren't even connected anyhow.
http://i29.photobucket.com/albums/c2...c.jpg~original

This is actually a second MAP sensor just to monitor the secondary throttle system. I 'T'-ed into it. Vacuum here means all 16 runners and injectors are working on the LT5 and it was a simple idea to switch the NPP valve off of this computer controlled load function.
http://i29.photobucket.com/albums/c2...a.jpg~original

Here it is idling- the loud section of the muffler is blocked off (left pipe). Will try to get a video on Saturday.
http://i29.photobucket.com/albums/c2...a.jpg~original

The only idea I have is to get a second solenoid and run a dedicated line to each vacuum actuator. It would help them to open and close a little more quickly than running both muffs off of one teeny 15' vacuum line. But it does work and is sooo much more driveable on longer runs.

ZR1 exhaust
 

Hi,
I live near you and own a 90 ZR-1 like yours. I was hoping I might be able to hear your ZR-1 before I buy a new exhaust.
Thanks Larry Huff :seasix::

I can (usually) be found at the Carlsbad cars & coffee on Saturday mornings at the cbad outlet mall from 7-9am.

I don't know if you have ever bought an aftermarket cat-back for a C4 before, but it gets ugly real quickly if you are even a little sensitive to noise. I would have loved this stuff when I was 23 years old, but now I have to result to such retrofits and modifications to keep my sanity.

here's a video of the system in action- even my cheap camera video picks up the audible resonance- it does work.

http://s29.photobucket.com/user/mschrameck/media/MOV02832_zpsbfcf3c58.mp4.html