Modifying NPP quiet side??
Thread Starter
Drifting
Joined: Apr 2007
Posts: 1,543
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From: NorCal @SithLordGS
Modifying NPP quiet side??
Has anyone modified the "quiet" side of thier NPP muffler to get a little more noise out of that side? Similar to what has been done to a stock non-NPP muffler??
I want to get a little more sound out of the quiet side...
I want to get a little more sound out of the quiet side...
Thread Starter
Drifting
Joined: Apr 2007
Posts: 1,543
Likes: 157
From: NorCal @SithLordGS
I saw that, but I was thinking of a "FREE" mod.. 
I know that drilling a hole in the Stock C6 muffler gains more sound, but I don't know what the inside of an NPP (non-ZO6) muffler looks like...
thanks for the link though!
I know that drilling a hole in the Stock C6 muffler gains more sound, but I don't know what the inside of an NPP (non-ZO6) muffler looks like...
thanks for the link though!
Safety Car
Joined: Sep 2007
Posts: 3,502
Likes: 82
I sure as heck wouldn't start drilling holes in my mufflers!...a bit hard to undo! You could probably replicate the idea I linked to with a pair of 25 cent fuel line clamps..not quite as elegant but same results.
Thread Starter
Drifting
Joined: Apr 2007
Posts: 1,543
Likes: 157
From: NorCal @SithLordGS
Yeah, clamps would work. You really can see there anyways.
I did the drilling on my stock C6 exhaust prior to installing the ZR1 NPP mufflers. I was thinking of doing the same to the NPPs, but will try the clamps first.. :-)
I just wanted to see if anyone has modded the quiet side of their NPPs and read about their sound results
I did the drilling on my stock C6 exhaust prior to installing the ZR1 NPP mufflers. I was thinking of doing the same to the NPPs, but will try the clamps first.. :-)
I just wanted to see if anyone has modded the quiet side of their NPPs and read about their sound results
Team Owner
Joined: Nov 2006
Posts: 21,136
Likes: 212
From: Long Island New York
$25 isnt alot to get the sound you want w/o permanantly damaging the cans. If you can do it for a buck or so even better. Im going to order the SOD's clamps this week. The NPP's are quieter than stock mufflers. Open its FEROCIOUS! Need a little more testosterone when closed.
Advanced
Joined: Jul 2009
Posts: 54
Likes: 1
From: St. Louis MO
Related question: Since I don't have NPP on my car and I am installing z06 mufflers is there a cheap and easy way to simply keep the butterflies open?
Ideally this mod would be something I could undo pretty easy when I finally install the M2W kit.
Thanks
Ideally this mod would be something I could undo pretty easy when I finally install the M2W kit.
Thanks
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Thread Starter
Drifting
Joined: Apr 2007
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From: NorCal @SithLordGS
Safety Car
Joined: Sep 2007
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Actually it's the opposite. When there is no vacuum the butterflys are open, the spring actually keeps them open. Vacuum closes the valves.
Bumblebee06- The butterflies will be open if you don't have vacuum source hooked up. They will be constant "LOUD" with a mild drone..
Bumblebee06- The butterflies will be open if you don't have vacuum source hooked up. They will be constant "LOUD" with a mild drone..
I stand corrected...you are right...vacuum pulls the butterflys shut
Last edited by Motorhead-47; Aug 18, 2009 at 08:31 PM.
Thread Starter
Drifting
Joined: Apr 2007
Posts: 1,543
Likes: 157
From: NorCal @SithLordGS
I'm going to try the hose clamp first, if I can find one that small.
I looked at the exhaust exits. The butterfly side has four ~.75" holes (top, bottom, sides) at the rear chamber just inside of the perforated tips, rear of the butterfly valve. I was thinking if the clamp thing doesn't get the desired sound, then I will drill at the 6-oclock position of the "muffled" side, at the rear chamber of the muffler can, thrugh the inner pipe. This is similar to the mods done with non-NPP mufflers. I did this to my stock mufflers and got the sound that I wanted. I will then weld in a patch on the outer skin of the can to plug the hole there.
I'm off to get some clamps...
I looked at the exhaust exits. The butterfly side has four ~.75" holes (top, bottom, sides) at the rear chamber just inside of the perforated tips, rear of the butterfly valve. I was thinking if the clamp thing doesn't get the desired sound, then I will drill at the 6-oclock position of the "muffled" side, at the rear chamber of the muffler can, thrugh the inner pipe. This is similar to the mods done with non-NPP mufflers. I did this to my stock mufflers and got the sound that I wanted. I will then weld in a patch on the outer skin of the can to plug the hole there.
I'm off to get some clamps...
Thread Starter
Drifting
Joined: Apr 2007
Posts: 1,543
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From: NorCal @SithLordGS
OK, I did the clamp mod today and I'm VERY happy with the sound. Just a tad louder than stock, with more rumble. No drone at at cruise speeds, a little when accelerating, but goes away quickly.
I purchase some 1/2" diameter hose clamps and clamped them to the rod that actuates the butterfly valves.
The clamp keeps the butterfly door open just a tad, enough to let some sound out..
Here's a pic inside the "loud" side. You can see some holes just inside of the tips that open up to the rear chamber in the can. I was going to drill the "quiet" side similar to this and then weld a patch plate to the hole in the can. I'm going to leave well enough alone because I'm happy with the sound achieved with this $1.50 mod
Here's a pic of the "quiet" side
Here's a pic of my car
I purchase some 1/2" diameter hose clamps and clamped them to the rod that actuates the butterfly valves.
The clamp keeps the butterfly door open just a tad, enough to let some sound out..
Here's a pic inside the "loud" side. You can see some holes just inside of the tips that open up to the rear chamber in the can. I was going to drill the "quiet" side similar to this and then weld a patch plate to the hole in the can. I'm going to leave well enough alone because I'm happy with the sound achieved with this $1.50 mod
Here's a pic of the "quiet" side
Here's a pic of my car
Racer
Joined: Jun 2006
Posts: 410
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From: Berwick Louisiana
That one's easy, don't hook up a vacuum source to the butterfly accuator. They're spring loaded to be normally open and need vacuum to close, that's what the M2W unit controls. I ran mine with the butterflies open for a while before I put the M2W kit on and didn't like it. They drone pretty bad at lower RPMs. If you keep the car in 5th on the highway you'll be ok, but in 6th the drone gets a bit annoying
Le Mans Master
Joined: Dec 2005
Posts: 6,999
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From: Southeast TX
With the butterflies open just slightly, does it sound anything like an exhaust leak? What do you have forward of the NPP's? Cats/no cats, headers or stock manifolds? Stock cam?
For just an instant, before my NPP's are completely closed, mine does sound like it has a big exhaust leak. This "sounds" like a good idea. The cost numbers look VERY impressive. Guess I'll have to play with the clamp placement when time allows.
For just an instant, before my NPP's are completely closed, mine does sound like it has a big exhaust leak. This "sounds" like a good idea. The cost numbers look VERY impressive. Guess I'll have to play with the clamp placement when time allows.
Thread Starter
Drifting
Joined: Apr 2007
Posts: 1,543
Likes: 157
From: NorCal @SithLordGS
With the butterflies open just slightly, does it sound anything like an exhaust leak? What do you have forward of the NPP's? Cats/no cats, headers or stock manifolds? Stock cam?
For just an instant, before my NPP's are completely closed, mine does sound like it has a big exhaust leak. This "sounds" like a good idea. The cost numbers look VERY impressive. Guess I'll have to play with the clamp placement when time allows.
For just an instant, before my NPP's are completely closed, mine does sound like it has a big exhaust leak. This "sounds" like a good idea. The cost numbers look VERY impressive. Guess I'll have to play with the clamp placement when time allows.
The best part, the mod was dirt cheap, and reversable. I personally don't think I will move the clamp over any more than where it's placed now for fear of creating drone as this is my daily driver
Safety Car
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From: Los Alamitos California
St. Jude Donor '09
