Exhaust advice
Thread Starter
Racer
Joined: Jul 2012
Posts: 341
Likes: 2
From: Elderslie, Scotland
Exhaust advice
Morning Gentlemen,
I've traversed the forum from the C3 pages to the C6 pages now that I've "upgraded" to the C6 generation.
Now have a 2008 model LS3 which has had an exhaust modification. Cats removed and straight through 2.5" stainless system with two separate boxes at the rear. There is also a small x pipe created which would be roughly under footwell.
My stainless guys says its a quality job but my issue is the noise. At the back its fine but accelerating and at certain speeds its a droning noise going up the box and at certain cruise speeds and accelerating up hills without dropping gear.
My guy has offered two options. 2 racing cats fitted, big job or an oval two in two out silencer half way down (roughly around the seat area).
It retains the look which I think is great.
What have you guys done and what do you think?
Cheers from Bonnie Scotland
I've traversed the forum from the C3 pages to the C6 pages now that I've "upgraded" to the C6 generation.
Now have a 2008 model LS3 which has had an exhaust modification. Cats removed and straight through 2.5" stainless system with two separate boxes at the rear. There is also a small x pipe created which would be roughly under footwell.
My stainless guys says its a quality job but my issue is the noise. At the back its fine but accelerating and at certain speeds its a droning noise going up the box and at certain cruise speeds and accelerating up hills without dropping gear.
My guy has offered two options. 2 racing cats fitted, big job or an oval two in two out silencer half way down (roughly around the seat area).
It retains the look which I think is great.
What have you guys done and what do you think?
Cheers from Bonnie Scotland
Melting Slicks
Joined: Sep 2008
Posts: 2,360
Likes: 59
From: San Jose California
If you want loud without the drone, you have a few choices.
Borla ATAK, or Corsa extremes, you will chase your tail trying to rid yourself of drone.
You could go a bi-mode system like the NPP or B&B fusion.
The best thing to do is try to find a corvette get together (Not sure if that would be possible for you.) and listen to some for yourself.
Drone is a big issue with these cars, I am on my 5th exhaust, (Looking for my 6th.) and can tell you that some systems drone awful. So take your time and Cooke wisely.
Good Luck,
DJ
Borla ATAK, or Corsa extremes, you will chase your tail trying to rid yourself of drone.
You could go a bi-mode system like the NPP or B&B fusion.
The best thing to do is try to find a corvette get together (Not sure if that would be possible for you.) and listen to some for yourself.
Drone is a big issue with these cars, I am on my 5th exhaust, (Looking for my 6th.) and can tell you that some systems drone awful. So take your time and Cooke wisely.
Good Luck,
DJ
Le Mans Master
Joined: Jun 2011
Posts: 8,049
Likes: 330
From: Charlotte NC
St. Jude Donor '14-'15
It IS your mufflers creating the drone, a CAT midway will kill the exhaust smell. I guess my first question will be what year is your car and did it come from the factory with the NPP option? If it came with NPP then it would be very easy to just replace the mufflers and have the Best of Both worlds. Your Corvette must be a rare find in Scotland, you must be a very Happy 
person. 
person.
Thread Starter
Racer
Joined: Jul 2012
Posts: 341
Likes: 2
From: Elderslie, Scotland
It IS your mufflers creating the drone, a CAT midway will kill the exhaust smell. I guess my first question will be what year is your car and did it come from the factory with the NPP option? If it came with NPP then it would be very easy to just replace the mufflers and have the Best of Both worlds. Your Corvette must be a rare find in Scotland, you must be a very Happy person.
person. I honestly don't know if the NPP option was on the car. It was a UK supplied car, not many on our roads especially up here in Scotland.
The only thing that I know is that the system has been changed completely from the manifold to the tips using 2.5 inch stainless. The cats have been removed and the pipes form an "X" just at the footwell area.
I should have got a photo when it was on the ramp. I'll try and get a video the next time I'm out, the resonance can even rattle the speakers
Tech Contributor
Joined: Jul 2002
Posts: 14,950
Likes: 266
From: St. Louis, MO
St. Jude Donor '08
Welcome to the c6 forum!
In my experience aftermarket cats won't help much at all with the drone. I had them with headers and Magnaflow 14336 mufflers and the drone drove me crazy.
If you install factory manifolds and cats then it will cut drone to a minimal level. When I had those with the 14336 mufflers it wasn't bad at all. But, you will lose HP with factory manifolds and cats.
I hate to say but the mufflers need to be designed for a Corvette to eliminate the drone.
I personally went to factory mufflers for nice and quiet and installed QTP cutouts when I wanted loud. As did my friend in Sweden.
Here is my thread if you're interested.
https://www.corvetteforum.com/forums...-on-my-c6.html
In my experience aftermarket cats won't help much at all with the drone. I had them with headers and Magnaflow 14336 mufflers and the drone drove me crazy.
If you install factory manifolds and cats then it will cut drone to a minimal level. When I had those with the 14336 mufflers it wasn't bad at all. But, you will lose HP with factory manifolds and cats.
I hate to say but the mufflers need to be designed for a Corvette to eliminate the drone.
I personally went to factory mufflers for nice and quiet and installed QTP cutouts when I wanted loud. As did my friend in Sweden.
Here is my thread if you're interested.
https://www.corvetteforum.com/forums...-on-my-c6.html
Had QTP cutouts installed by Florida Performance in Fort Lauderdale. Overall very pleased with the job Rob, the shop owner, did. This was his first C6 and he found a great place to put them and made the custom mandrel bent Y-pipes to maximize flow from the cutouts. We found no way to put them right after the collectors but they fit well by the trans. I have the DTE brace too but it wasn't in the way.
Installed the wiring myself along the drivers side rocker panel, behind seat then out the wheel well under the carpet. Removed the rear inner fender and drilled a small hole in the wheel well then ran the wire down to the cutouts. Hardest part is finding a hot wire when the ignition is on on these C6's. I ended up tapping the seat heater fuse as others here have done.
They are loud and DEEP when open at idle. I've actually heard louder exhaust though, I was kind of surprised they are not louder. I think it is because of the turn downs and the fact that I have cats and the pipes are pretty long before the cutouts. On the track they have a nice race car sound - I'd say like Borla Stingers plus 25%. When you open them at a stoplight you will turn heads, that's for sure.
Overall happy with the mod, it gives me quiet during my morning drive but loud when I'm at the track which is what I wanted.
Here is a video of idle with cutouts open and closed. The gain on the mike makes the closed sound much louder than it is, it's really quiet with factory mufflers even with my cam.
Here are some pics:
Installed the wiring myself along the drivers side rocker panel, behind seat then out the wheel well under the carpet. Removed the rear inner fender and drilled a small hole in the wheel well then ran the wire down to the cutouts. Hardest part is finding a hot wire when the ignition is on on these C6's. I ended up tapping the seat heater fuse as others here have done.
They are loud and DEEP when open at idle. I've actually heard louder exhaust though, I was kind of surprised they are not louder. I think it is because of the turn downs and the fact that I have cats and the pipes are pretty long before the cutouts. On the track they have a nice race car sound - I'd say like Borla Stingers plus 25%. When you open them at a stoplight you will turn heads, that's for sure.
Overall happy with the mod, it gives me quiet during my morning drive but loud when I'm at the track which is what I wanted.
Here is a video of idle with cutouts open and closed. The gain on the mike makes the closed sound much louder than it is, it's really quiet with factory mufflers even with my cam.
Here are some pics:
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Melting Slicks
Joined: Oct 2004
Posts: 2,863
Likes: 150
From: Woodland CA
To the OP, if you can find yourself a set of used NPP mufflers you should be in a good spot.
Tech Contributor
Joined: Jul 2002
Posts: 14,950
Likes: 266
From: St. Louis, MO
St. Jude Donor '08
I had the same setup on my 2005 and I actually loved the sound. It wasn't until I got a cam that the drone went insane. Could not hold a normal conversation on the freeway in 6th. I had to resort to putting the stock mufflers back on, drone gone.
To the OP, if you can find yourself a set of used NPP mufflers you should be in a good spot.
To the OP, if you can find yourself a set of used NPP mufflers you should be in a good spot.
I agree with you, NPP's are a great option for our newfound Scottish friend.
Race Director
Joined: Apr 2007
Posts: 14,062
Likes: 602
From: Henderson Nv-Rohnert Park/Sonoma C o. ca/born in NY Rockaway Beach.
I did full z06 exhaust to the mufflers and did the muffler mod, and the car was loud when open ,,, would drone at some rpms,,,but could just hit the button and drone is gone....loved it.....ill be doing the same setup on my new GS when I get it .
Race Director
Joined: Oct 2005
Posts: 14,555
Likes: 1,255
From: Saint Albans, WV
I certainly respect Joe G but kind of disagree on the offroad. I had the offroad installed with my blower over 10 years ago. I was totally shocked at the volume when I got it back. I dealt with it for a few years and put hi-flow cats on. Suddenly it was like a silencer. Switched from Sport to Xtreme to pick some sound back up but was nowhere near the monstrous sound I had. Just my take on it.
Last edited by saplumr; Dec 14, 2015 at 06:53 PM.
Tech Contributor
Joined: Jul 2002
Posts: 14,950
Likes: 266
From: St. Louis, MO
St. Jude Donor '08
I certainly respect Joe G but kind of disagree on the offroad. I had the offroad installed with my blower over 10 years ago. I was totally shocked at the volume when I got it back. I dealt with it for a few years and put hi-flow cats on. Suddenly it was like a silencer. Switched from Sport to Xtreme to pick some sound back up but was nowhere near the monstrous sound I had. Just my take on it.
Do you have manifolds? I'm referring to high flow cats with headers. The headers are a lot louder than manifolds.
Tech Contributor
Joined: Jul 2002
Posts: 14,950
Likes: 266
From: St. Louis, MO
St. Jude Donor '08
Excellent. Well what can I tell you, my headers with high flow cats droned me to death with the Magnaflow 14336 mufflers.
Now oddly enough, you'd think my cutouts would drone but they don't. Perhaps because the sound is directed toward the ground? For whatever reason, they don't drone on the highway
Now oddly enough, you'd think my cutouts would drone but they don't. Perhaps because the sound is directed toward the ground? For whatever reason, they don't drone on the highway
Race Director
Joined: Oct 2005
Posts: 14,555
Likes: 1,255
From: Saint Albans, WV
Excellent. Well what can I tell you, my headers with high flow cats droned me to death with the Magnaflow 14336 mufflers.
Now oddly enough, you'd think my cutouts would drone but they don't. Perhaps because the sound is directed toward the ground? For whatever reason, they don't drone on the highway
Now oddly enough, you'd think my cutouts would drone but they don't. Perhaps because the sound is directed toward the ground? For whatever reason, they don't drone on the highway
I have noticeable drone with my current setup in the 1700 range but it's tolerable. Cutouts are on my to do list.
Tech Contributor
Joined: Jul 2002
Posts: 14,950
Likes: 266
From: St. Louis, MO
St. Jude Donor '08
On my c5 my first mod was Borla Stingers. Sounded great. Then I installed headers and high flow cats. Probably 50% louder but ok. Then I installed a big cam....forget it, 50% louder again and way too loud. People looked at me like my car was broken at stop lights. It was too much. That's why I went with cutouts and stock mufflers on my C6. I get the choice.
NPP's or Z06 mufflers are a good choice too but won't work with my trailer hitch.
Thread Starter
Racer
Joined: Jul 2012
Posts: 341
Likes: 2
From: Elderslie, Scotland
Lots to think about. I did a wee video last night so will post that up.
Won't hold it against you that you were born in Ayr
Its a bit more difficult getting bits and bobs sent over here. Can be done but the shipping costs are horrendous. Checked out the glovebox label. No NPP fitted to the car. Not sure what that will mean to me but its heading into a exhaust specialist locally who is gonna look at a solution. He does rally, race and drag racing systems. I'll let you know what he comes up with and hopefully get a few photos.
Lots of modding to come methinks
Won't hold it against you that you were born in Ayr
Its a bit more difficult getting bits and bobs sent over here. Can be done but the shipping costs are horrendous. Checked out the glovebox label. No NPP fitted to the car. Not sure what that will mean to me but its heading into a exhaust specialist locally who is gonna look at a solution. He does rally, race and drag racing systems. I'll let you know what he comes up with and hopefully get a few photos.
Lots of modding to come methinks