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C6 Corvette ZR1 & Z06General info about GM’s Corvette Supercar, LS9 Corvette Technical Info, Performance Upgrades, Suspension Setup for Street or Track
Ahh the ol muffler mod. Fairly simple and big results in sound. Mine are actually Zr1 mufflers.. no need to make this modification. But am welding up a crack which is causing HORRIBLE rattles at certain RPM.
My question is, for those of you who have done this modification, do you recommend reinstalling the fiberglass packing or not? Is the difference huge in sound? I love the current sound through longtubes and offroad midpipe but would not mind it being a bit louder. I just cannot handle it being insanely vibrate-your-eyeballs loud like it sounds with the midpipe dumped and no axlebacks. The man at the muffler shop says he never reinstalls it when performing the muffler mod and there is no point in reinstalling. Have not been able to find much info on this exact subject.
I did the mod on my '09 Z and then on my current '07. Both rattled shortly after the mod. I didn't re-use the packing on either, but I don't know that it really matters. Perhaps in closed mode, but in open mode I'd not think it does anything. However, some have theorized that the lack of packing contributes to the internal cracking. This is interesting, and could be true, I don't know. Regardless, I don't think it affects the volume in open mode, so I'd say throw it back in. For me, I got sick of the rattle the second time around so I splurged for Borla Atak. Pricey yes, but I have zero regrets.
I did the mod on my '09 Z and then on my current '07. Both rattled shortly after the mod. I didn't re-use the packing on either, but I don't know that it really matters. Perhaps in closed mode, but in open mode I'd not think it does anything. However, some have theorized that the lack of packing contributes to the internal cracking. This is interesting, and could be true, I don't know. Regardless, I don't think it affects the volume in open mode, so I'd say throw it back in. For me, I got sick of the rattle the second time around so I splurged for Borla Atak. Pricey yes, but I have zero regrets.
I just went arh 2" headers and my mufflers rattle like crazy. stock mufflers and looking to do the muffler mod, so I guess the only way to get rid of the rattle is to get an axleback?
This is some information on the mod and the ZR1 rattle.
This photo is by member V8sten, he does the 3" muffler mods. This is a ZR1 muffler with the rattle.
The solid tube through the muffler is coming from the exhaust pipe, the exit for this pipe is the exit with the butterfly, On the gas it opens or if you have the switch you can open it. Now if the butterfly is closed the exhaust gas now has four 3/4" holes to exit in the rear chamber, the one that is broke, it then flows back to the rear chamber through the smaller solid pipe, and now through the perforated pipe and out, this would be the quiet side.Thinking is when the ZR1 is WOT and you lift your foot, the butterfly closes right now and the exhaust pressure is still there and flexes the bulkhead to the first chamber, after a while it fails.
Another V8sten picture, showing the pipes in the Z06 and ZR1 mufflers are the same size.
This is how I did my mufflers. I covered the perforated pipe. I then added two perforated pass through pipes. These were solid and I cut about 80% off of them than added the perforated sections. I did put the fiberglass back in. I've put over 8K on the car since I did the mod with no issues.
I like the quiet side now because it is really quiet. When my navigator is with me she can flip the switch and is happy. To tell you the truth I took a 400 mile trip alone one Saturday and I even closed the butterfly's. I have a video on TY of my muffler, I can't seem the get the link posted, but you can find it by my username, MIKE44460.
V8sten and Josh B. have a lot of information and pictures of the muffler internals and the mod.
i had a few mufflers and was never happy with any of them (Coras, Borla ATAK, B&B Fusion III) for different reasons, I decided to have my mechanic do the muffler mod on my 2011 Z06 mufflers and they sound great. Loud when you want them to be and very quiet when the valves are closed. I am almost certain that the packing was removed from my mufflers.
I just went arh 2" headers and my mufflers rattle like crazy. stock mufflers and looking to do the muffler mod, so I guess the only way to get rid of the rattle is to get an axleback?
You can fix the stock mufflers, it just requires pulling them, cutting them open, and welding up any cracked baffles internally. While in there, might as well do the mod. However, some have had them fail again, some have not. Sounds like some may have figured out a way to relieve pressure and prevent cracks if you read above.
For me, the trouble of pulling them a second time on this car with no guarantee that they wouldn’t rattle again was more than enough to convince me to fork out for Borla. The modded mufflers sounded great and would be on there still if they hadn’t rattled. That being said, my opinion is that the Borla sounds better everywhere. Not trying to justify the cost, I simply like the sound and volume so much better with the Ataks.
i had a few mufflers and was never happy with any of them (Coras, Borla ATAK, B&B Fusion III) for different reasons, I decided to have my mechanic do the muffler mod on my 2011 Z06 mufflers and they sound great. Loud when you want them to be and very quiet when the valves are closed. I am almost certain that the packing was removed from my mufflers.
Wouldn't 2011 mufflers already be modded from the factory? Just curious what mod they would have had to do to those since they’re already a solid pipe in stock form?
Also, thanks again for the push towards Borla. Could not be happier!
Wouldn't 2011 mufflers already be modded from the factory? Just curious what mod they would have had to do to those since they’re already a solid pipe in stock form?
Also, thanks again for the push towards Borla. Could not be happier!
The Borla does sound good but I wanted the functionality of the NPP back. The 2011 muffler still has the perforated pipe. My modded OEM exhaust is much louder than stock with the valves open and just as quiet with them closed.
Great info from everyone. Thanks to those who provided input on the packing especially.
Had a local muffler shop weld up all the cracks in mine today and remove packing. Reinforced the cracked walls with strips of steel. The muffler mod/Zr1 mufflers sound perfect with longtubes and offroad x. Had the same setup on my HCI z06 but with BB bullets. Unbearable drone. Worst I've ever heard. Usually ran around with open cutouts to alleviate the drone (yes it was that bad haha) Would love to try out some Corsas or Fusion 3's but have a hard time spending that much rather than a large snout for my LS9 blower!
Also, I have seen others complain of these same issues from corsa and sometimes borla. I am sure it is rare compared to the common cracking of the stockers though.
This is some information on the mod and the ZR1 rattle.
This photo is by member V8sten, he does the 3" muffler mods. This is a ZR1 muffler with the rattle.
The solid tube through the muffler is coming from the exhaust pipe, the exit for this pipe is the exit with the butterfly, On the gas it opens or if you have the switch you can open it. Now if the butterfly is closed the exhaust gas now has four 3/4" holes to exit in the rear chamber, the one that is broke, it then flows back to the rear chamber through the smaller solid pipe, and now through the perforated pipe and out, this would be the quiet side.Thinking is when the ZR1 is WOT and you lift your foot, the butterfly closes right now and the exhaust pressure is still there and flexes the bulkhead to the first chamber, after a while it fails.
Another V8sten picture, showing the pipes in the Z06 and ZR1 mufflers are the same size.
This is how I did my mufflers. I covered the perforated pipe. I then added two perforated pass through pipes. These were solid and I cut about 80% off of them than added the perforated sections. I did put the fiberglass back in. I've put over 8K on the car since I did the mod with no issues.
I like the quiet side now because it is really quiet. When my navigator is with me she can flip the switch and is happy. To tell you the truth I took a 400 mile trip alone one Saturday and I even closed the butterfly's. I have a video on TY of my muffler, I can't seem the get the link posted, but you can find it by my username, MIKE44460.
V8sten and Josh B. have a lot of information and pictures of the muffler internals and the mod.
wow, I really like this setup! Very nice with the addition of those perforated pass throughs. We cut mine open, used more steel to reinforce the walls to hopefully prevent any further issues. Left the packing out. May post of video once they are on for anyone looking for more of an idea on the difference like I am wondering
I have seen two different ways to doing the muffler mod. Pulling the packing out and welding it back up and closing up the perforated pipe closed. I heard a sound clip with the packing removed only and I think that’s the way I’m going
the packing will not effect the sound on the outside that much, may be a more "hollow" sound. Where it will make the greatest difference is in that drone area on the highway, around 60-65 mph on the highway in 6th gear. The drone will significantly increase without the packing. My suggestion is to leave the packing. The ZR1 mufflers have the fiberglass hairs just stuffed in the muffler, the older Z06 mufflers have a pillow with the same fiberglass material inside. When I do the 3" mod I unpack the pillow and install the fiberglass packing back in like the ZR1 mufflers. It will not catch fire when rewelding it back up. if that is your concern. Unless you like excessive drone I recommend putting it back in.
I have Borla mufflers. I was told by the seller one of them is rattling. When I have it welded will it be easy to find the area needing repair ? I won’t be doing the welding. A local welder will do this not a muffler shop.
I have Borla mufflers. I was told by the seller one of them is rattling. When I have it welded will it be easy to find the area needing repair ? I won’t be doing the welding. A local welder will do this not a muffler shop.
I am now using a set of borlas ataks. Honestly couldnt tell you for sure as i don't know much about the borlas other than that I love the sound of them on my car. Picked up my ataks used and traded my NPP's. My ataks actually have a slight rattle too similar to the rattle my NPP's had before repair but it is nowhere near as bad as the NPP rattle from the cracked baffle wall.
I'm interested to hear what you find out when you get your borlas opened up to repair in case my ataks get bad enough to need repair. With the straight through design of the borla mufflers, I would think the repair should be fairly straight forward.
Don't borla systems have a very good warranty or does it only cover defects rather than problems later on?
I had the mod for a few months the packing was removed and I could hear the “hollow” sound and I really didn’t like that. I sold the stocks to another for member I believe he put packing back in, I’d leave the packing in personally....once I heard the hollow sound it just stood out too much, most people may not have heard it but once I did it kinda just annoyed me. Picked up a set of Billy Boat Bullets(newest version) and never looked back! They sound amazing! Now I have no “mild/wild” function(don’t care) drone doesn’t bother me in the slightest and my Z isn’t a daily or a road trip car anyway. Best way to “fix drone issues” down shift and drive faster lol.
I had the mod for a few months the packing was removed and I could hear the “hollow” sound and I really didn’t like that. I sold the stocks to another for member I believe he put packing back in, I’d leave the packing in personally....once I heard the hollow sound it just stood out too much, most people may not have heard it but once I did it kinda just annoyed me. Picked up a set of Billy Boat Bullets(newest version) and never looked back! They sound amazing! Now I have no “mild/wild” function(don’t care) drone doesn’t bother me in the slightest and my Z isn’t a daily or a road trip car anyway. Best way to “fix drone issues” down shift and drive faster lol.
The newer BB bullets sound awesome. One of my favorite muffler setups and the horrendous drone of the first generation bullets has been improved a massive amount.
Imo, the stock modded or ZR1 mufflers have the hollow sound with or without packing. Good sounding mufflers but I much prefer aftermarket.
11-09-2018, 10:27 PM
Z06 muffler mod question
