Convertible Exhaust Butterfly Valve - Service Bulletin - Camaro5 Chevy Camaro Forum / Camaro ZL1, SS and V6 Forums

sswiss3000 · 02-05-2013, 08:58 PM

Convertible Exhaust Baffle - Bulletin

So I just came back from the dealership after dropping of my 2012 convertible 2SS (L99) for some warranty work as well as an issue I had with a squeaky noise coming from the back of the car.

Long story short they informed me that it was caused by a butterfly valve that was in the exhaust pipe right between the resonator and the muffler. This valve only exists on the L99s (convertibles only) in order to reduce exhaust noise during idle or low RPM operation (AFM). The service manager will give me the bulletin number tomorrow so that I can poste it. Basically it’s a valve that is held shut with a small spring and will only open during high exhaust flow situation. Thus the quick squeaky noise whenever I hit the gas

I was surprised to hear that the Automatic convertibles have such a valve installed, as I personally have never read or heard anything about it till now.
Has anyone ever removed this valve? Would be interested to hear the exhaust sound difference and how bad the AFM sound would be

update: My dealership told me that this noise is normal after all!! I have a hard time believing that

"The 2011 Camaro Convertible SS equipped with the 6.2L engine (RPO L99) and the 6-speed automatic transmission (RPO MX0) may have a metallic or spring-type rattle noise that is usually heard at idle when parked next to a wall or when pulling into or out of a garage.
The exhaust system for the 2011 model year has been revised to reduce exhaust noises heard during Active Fuel Management (AFM) mode. This revision includes a spring-loaded valve placed in the exhaust system before the muffler"

GnyaTek · 02-05-2013, 09:05 PM

Some folks have opened the butterfly a full turn to disable it. Have been tempted to try it to see how I'd like the exhaust note, but my guess is that it would be a royal pain to reset the spring to undo the mod if I didn't.

Anyone have experience with resetting the spring?

tonyko1 · 02-05-2013, 09:21 PM

I sure did notice how quiet my car was at idle, barely got a rumble at start up.

nukemustang · 02-05-2013, 09:28 PM

I think it also has to do with reducing resonations when the AFM kicks in.... I used to hear the valve cycle when it would transfer back and fourth from V8 to V4 mode. Anyone who has changed out the exhaust (cat back) has removed these valves.

CooG · 02-05-2013, 10:31 PM

I took mine in for this well over a year ago. Chevy dealership gave me a copy of the TSB and it says "no fix" for the problem.

I wasn't too worried about it since I was changing my exhaust anyway.

babytiger · 02-06-2013, 09:40 AM

Muffler delete will fix that problem real quick... cutting just in front of that butterfly.
One of the cheapest bang for your buck mods you can do.

HDRDTD · 02-06-2013, 09:47 AM

I thought those butterfly valves were on all L99's regardless if they were coupes or Verts.

Edwin320 · 02-06-2013, 09:49 AM

Is this an L99 thing only?

Bodih · 02-06-2013, 10:24 AM

Are you sure these are exclusive to the convertibles? I swapped out a cat-back system for a friend with an L99 coupe about a year ago, and could swear it had the valves as well. I was concerned at the time what impact it may have on the AFM, since I figured that was its purpose. She's never had an issue since removing it.

PDILLON · 02-06-2013, 10:32 AM

Dealer put O -rings on mine - I wired mine open and started it could not tell any difference so took the wires off but did not drive it with them wired open

melbourne_ls1 · 02-07-2013, 10:02 PM

It's definitely exclusive to the L99 verts. My 2010 L99 coupe did not have these but my 2011 L99 vert did (until I removed them :-). Local dealer also confirmed the butterflies are on the L99 verts only.

Convert-11 · 02-07-2013, 10:53 PM

Used a pliers to move the spring to hold the valve always open rather than always closed- I believe I moved it 4 positions. Gives it a little more popping! Also eliminated the slapping sound from the valve springing closed when revving the engine.

cam62 · 04-03-2013, 10:48 AM

Here's the info as written by GM for the 2011's. I was given a copy of it when I took my 2012 in for the same issue, but can't seem to find it now.

Here's a link to the service bulletin issue I was able to find on the web. And yes, acocrding to the document it is ONLY on the convertibles.

http://www.archivedsites.com/techlin...tle-noise.html

Text from article:
Exhaust Rattle Noise

By Blog Post on June 1, 2011 9:59 PM | No Comments

The 2011 Camaro Convertible SS equipped with the 6.2L engine (RPO L99) and the 6-speed automatic transmission (RPO MX0) may have a metallic or spring-type rattle noise that is usually heard at idle when parked next to a wall or when pulling into or out of a garage.

The exhaust system for the 2011 model year has been revised to reduce exhaust noises heard during Active Fuel Management (AFM) mode. This revision includes a spring-loaded valve placed in the exhaust system before the muffler. (Fig. 15)

t is characteristic of this spring-loaded valve to make some noise during engine operation or when tapping on the exhaust pipes. No parts should be replaced or repaired for this noise.

photo from article

sswiss3000 · 04-15-2013, 12:24 AM

Do you guys also get a short squeak right before the exhaust butterfly valves pop open? its super annoying on mine, but the dealer is telling me that this is normal.

02-05-2013, 08:58 PM	#1
sswiss3000 Drives: 2012 Camaro 2SS Vert, L99 Join Date: Sep 2011 Location: Dekalb IL Posts: 360 View My Garage	Convertible Exhaust Butterfly Valve - Service Bulletin Convertible Exhaust Baffle - Bulletin So I just came back from the dealership after dropping of my 2012 convertible 2SS (L99) for some warranty work as well as an issue I had with a squeaky noise coming from the back of the car. Long story short they informed me that it was caused by a butterfly valve that was in the exhaust pipe right between the resonator and the muffler. This valve only exists on the L99s (convertibles only) in order to reduce exhaust noise during idle or low RPM operation (AFM). The service manager will give me the bulletin number tomorrow so that I can poste it. Basically it’s a valve that is held shut with a small spring and will only open during high exhaust flow situation. Thus the quick squeaky noise whenever I hit the gas I was surprised to hear that the Automatic convertibles have such a valve installed, as I personally have never read or heard anything about it till now. Has anyone ever removed this valve? Would be interested to hear the exhaust sound difference and how bad the AFM sound would be update: My dealership told me that this noise is normal after all!! I have a hard time believing that "The 2011 Camaro Convertible SS equipped with the 6.2L engine (RPO L99) and the 6-speed automatic transmission (RPO MX0) may have a metallic or spring-type rattle noise that is usually heard at idle when parked next to a wall or when pulling into or out of a garage. The exhaust system for the 2011 model year has been revised to reduce exhaust noises heard during Active Fuel Management (AFM) mode. This revision includes a spring-loaded valve placed in the exhaust system before the muffler" Attached Images Last edited by sswiss3000; 04-06-2016 at 08:18 PM.

02-05-2013, 09:28 PM	#4
nukemustang Drives: 2017 Raptor, 2017 SS Join Date: Feb 2010 Location: Charleston, SC Posts: 277	I think it also has to do with reducing resonations when the AFM kicks in.... I used to hear the valve cycle when it would transfer back and fourth from V8 to V4 mode. Anyone who has changed out the exhaust (cat back) has removed these valves. __________________ Saving for: 2019 ZL1 convertible..... SOLD:2016 2SS Red Hot Convertible with black metallic rally stripes SOLD:2011 Silver Ice Metallic 1SS/RS Convertible. Completed modifications: installed factory HUD, deleted AFM/DOD, Dynatech LT coated headers with high flow cats, Solo Cat back exhaust, CAI inc. intake, Vmax ported TB, SIM quarter flares/splash guards, steering wheel radio controls, PDIM iPod interface in center console, RX catch can, JRE cold air scoop, windshield washer bottle relocation.

02-06-2013, 09:49 AM	#8
Edwin320 Drives: 2018 Camaro ZL1 Convertible A10 Join Date: Mar 2012 Location: Miami, Fl Posts: 427 View My Garage	Is this an L99 thing only? __________________ Ed 2018 ZL1 A10 'Vert

02-06-2013, 10:24 AM	#9
Bodih I Got My Orange Crush Drives: it like I stoles it... Join Date: Jan 2011 Location: Tucson, AZ Posts: 2,079	Are you sure these are exclusive to the convertibles? I swapped out a cat-back system for a friend with an L99 coupe about a year ago, and could swear it had the valves as well. I was concerned at the time what impact it may have on the AFM, since I figured that was its purpose. She's never had an issue since removing it. __________________ My love is in league with the freeway. Its passion will ride, as the cities fly by, and the tail-lights dissolve in the coming of night. And the questions in thousands take flight ~Robert Plant - Big Log~

04-03-2013, 10:48 AM	#13
cam62 Drives: 2012 IBM Vert 2SS/rs Join Date: Jul 2011 Location: Tampa, FL Posts: 1,157 View My Garage	Here's the info as written by GM for the 2011's. I was given a copy of it when I took my 2012 in for the same issue, but can't seem to find it now. Here's a link to the service bulletin issue I was able to find on the web. And yes, acocrding to the document it is ONLY on the convertibles. http://www.archivedsites.com/techlin...tle-noise.html Text from article: Exhaust Rattle Noise By Blog Post on June 1, 2011 9:59 PM \| No Comments The 2011 Camaro Convertible SS equipped with the 6.2L engine (RPO L99) and the 6-speed automatic transmission (RPO MX0) may have a metallic or spring-type rattle noise that is usually heard at idle when parked next to a wall or when pulling into or out of a garage. The exhaust system for the 2011 model year has been revised to reduce exhaust noises heard during Active Fuel Management (AFM) mode. This revision includes a spring-loaded valve placed in the exhaust system before the muffler. (Fig. 15) t is characteristic of this spring-loaded valve to make some noise during engine operation or when tapping on the exhaust pipes. No parts should be replaced or repaired for this noise. photo from article Attached Images __________________ rx catch can;vmax ported throttle body;bowtie delete;SLP SS emblem;CAI cold air intake

02-05-2013, 09:05 PM	#2
GnyaTek Drives: 2011 SIM 2SS/RS Vert Join Date: Jul 2011 Location: Middle TN Posts: 1,128	Some folks have opened the butterfly a full turn to disable it. Have been tempted to try it to see how I'd like the exhaust note, but my guess is that it would be a royal pain to reset the spring to undo the mod if I didn't. Anyone have experience with resetting the spring?

02-05-2013, 09:21 PM	#3
tonyko1 Banned Drives: 2012 Camaro 2SS/RS Convertible, IBM Join Date: Jun 2012 Location: Oregon Posts: 1,015	I sure did notice how quiet my car was at idle, barely got a rumble at start up.

02-05-2013, 10:31 PM	#5
CooG RIP - Convertible SS Drives: '13 Mustang Boss 302 - RED Join Date: Apr 2011 Location: Houston, TX Posts: 960	I took mine in for this well over a year ago. Chevy dealership gave me a copy of the TSB and it says "no fix" for the problem. I wasn't too worried about it since I was changing my exhaust anyway.

02-06-2013, 09:40 AM	#6
babytiger it's hers... Drives: 2011 Camaro 2SS/RS Convertible Join Date: Jun 2012 Location: katy, tx Posts: 1,202	Muffler delete will fix that problem real quick... cutting just in front of that butterfly. One of the cheapest bang for your buck mods you can do.

02-06-2013, 09:47 AM	#7
HDRDTD Drives: 2013 Triple Black ZL1 Vert M6 ECF Join Date: Mar 2011 Location: Trenton, Michigan Posts: 7,047	I thought those butterfly valves were on all L99's regardless if they were coupes or Verts.

02-06-2013, 10:32 AM	#10
PDILLON Drives: GMC Slycone - 2011 SS Camaro conv. Join Date: Sep 2012 Location: ST. Charles, Mo. Posts: 68	Dealer put O -rings on mine - I wired mine open and started it could not tell any difference so took the wires off but did not drive it with them wired open

02-07-2013, 10:02 PM	#11
melbourne_ls1 Drives: 2011 2SS Red Jewel Tintcoat Vert Join Date: Mar 2010 Location: Florida Posts: 160	It's definitely exclusive to the L99 verts. My 2010 L99 coupe did not have these but my 2011 L99 vert did (until I removed them :-). Local dealer also confirmed the butterflies are on the L99 verts only.

02-07-2013, 10:53 PM	#12
Convert-11 Drives: 2011 Convertible Camaro 2SS/RS Auto Join Date: Aug 2011 Location: MN Posts: 145	Used a pliers to move the spring to hold the valve always open rather than always closed- I believe I moved it 4 positions. Gives it a little more popping! Also eliminated the slapping sound from the valve springing closed when revving the engine.

04-15-2013, 12:24 AM	#14
sswiss3000 Drives: 2012 Camaro 2SS Vert, L99 Join Date: Sep 2011 Location: Dekalb IL Posts: 360 View My Garage	Do you guys also get a short squeak right before the exhaust butterfly valves pop open? its super annoying on mine, but the dealer is telling me that this is normal.