Reducing exhaust sound levels Z06
Thread Starter
Instructor
Joined: Apr 2009
Posts: 155
Likes: 0
From: South of France
Reducing exhaust sound levels Z06
Good morning.
As posted in my intro, i have an 02 Z06 which and i'm in the process to get it homologated in France. Not an easy job!
Nearly everything on the car is done regarding lights, side blinkers, etc.
There is one problem that remains, the exhaust is way too loud!!
At least for the homologation 
Right now i'm trying to figure out how i can reduce the sound levels, the homologation service needs 75dB, measured at 4m distance flooring it in third.
I installed the standard air box from an 02 C5 which reduces intake noise.
The plan is to install the stock C5 rear mufflers with 2 exhaust valves installed at the entrance of the mufflers silimar on what they do on the new Z06. I'm hoping this will reduce the sound levels by a fair bit.
These are the valves i'm talking about:
So.... my question is, does anybody know if the standard C5 mufflers fit without modifications and if this is even a good idea to do.
Any other ideas would be more than welcome.
Many thanks in advance.
Xav
As posted in my intro, i have an 02 Z06 which and i'm in the process to get it homologated in France. Not an easy job!
Nearly everything on the car is done regarding lights, side blinkers, etc.
There is one problem that remains, the exhaust is way too loud!!
At least for the homologation Right now i'm trying to figure out how i can reduce the sound levels, the homologation service needs 75dB, measured at 4m distance flooring it in third.
I installed the standard air box from an 02 C5 which reduces intake noise.
The plan is to install the stock C5 rear mufflers with 2 exhaust valves installed at the entrance of the mufflers silimar on what they do on the new Z06. I'm hoping this will reduce the sound levels by a fair bit.
These are the valves i'm talking about:
So.... my question is, does anybody know if the standard C5 mufflers fit without modifications and if this is even a good idea to do.
Any other ideas would be more than welcome.
Many thanks in advance.
Xav
Thread Starter
Instructor
Joined: Apr 2009
Posts: 155
Likes: 0
From: South of France
You might be right, i think it has high flow cats.
Is this what i would need to convert to the stock C5 exhaust?
And the mufflers:
dont worry about performance, everything goes straight back off once homologated!!
Pro
Joined: May 2004
Posts: 551
Likes: 19
From: Morgantown WV
Getting the high flow cats off the car and adding the stock exhaust will make it whisper quiet.
Thread Starter
Instructor
Joined: Apr 2009
Posts: 155
Likes: 0
From: South of France
Ok, thanks Ajay, i think i'll give it a try, stock airbox, stock C5 exhaust + 2 the valves that should reduce the noise a lot. !
I did have a stock C5 so i know how it sounds like but not sure if it exceeds 75dB. 75dB is verry verry low.
Does anybody know the outer wall diameter of a stock C5 exhaust?
Is is 2 1/2" ?
I did have a stock C5 so i know how it sounds like but not sure if it exceeds 75dB. 75dB is verry verry low.
Does anybody know the outer wall diameter of a stock C5 exhaust?
Is is 2 1/2" ?
Pro
Joined: May 2004
Posts: 551
Likes: 19
From: Morgantown WV
Ok, thanks Ajay, i think i'll give it a try, stock airbox, stock C5 exhaust + 2 the valves that should reduce the noise a lot. !
I did have a stock C5 so i know how it sounds like but not sure if it exceeds 75dB. 75dB is verry verry low.
Does anybody know the outer wall diameter of a stock C5 exhaust?
Is is 2 1/2" ?
I did have a stock C5 so i know how it sounds like but not sure if it exceeds 75dB. 75dB is verry verry low.
Does anybody know the outer wall diameter of a stock C5 exhaust?
Is is 2 1/2" ?
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Le Mans Master
Joined: Jan 2004
Posts: 6,801
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From: Anywhere where Cones need hit
Cruise-In 9-10 Veteran
CI-X Auto-X Champ (race tires)
St. Jude Donor '07-'09
How about a set of supertrap mufflers??... cut the tips off the C5 exhuast, and have these put on the ends... there are 'wafers' on the inside you can add or delete for sound, and the flow doesn't suffer.
Miata and Mini guys use these all the time to decrease noise @ tracks when they don't want to run a full exhuast.
http://www.supertrapp.com/product_se...auto/index.asp
Miata and Mini guys use these all the time to decrease noise @ tracks when they don't want to run a full exhuast.
http://www.supertrapp.com/product_se...auto/index.asp
Tech Contributor
Joined: Oct 1999
Posts: 41,066
Likes: 9,829
From: Charlotte, NC (formerly Endicott, NY)
The SuperTrapps are still to loud. I had them on my 97. At the quietest setting you couldn't hear yourself think inside the cabin. No way will they pass a 75 db test while revving in third.
I don't think the valves will work. If the exhaust is going completely through the mufflers the valves will not help reduce the sound.
If the car you purchased had a lot of track time where it was run at Wide Open Throttle quite a bit of the time the Tis may be louder than stock Tis. I know the Tis on my 03Z have gotten a lot louder than they were when I bought the car 6 years ago.
One thing to think about: How fast do you have to be going when you pass by the meter? If your speed is lower and the rpms are around a thousand rpms in third or about 50 kph when you floor it the sound will be a lot less.
Bill
I don't think the valves will work. If the exhaust is going completely through the mufflers the valves will not help reduce the sound.
If the car you purchased had a lot of track time where it was run at Wide Open Throttle quite a bit of the time the Tis may be louder than stock Tis. I know the Tis on my 03Z have gotten a lot louder than they were when I bought the car 6 years ago.
One thing to think about: How fast do you have to be going when you pass by the meter? If your speed is lower and the rpms are around a thousand rpms in third or about 50 kph when you floor it the sound will be a lot less.
Bill
Last edited by Bill Dearborn; Apr 15, 2009 at 04:32 PM.
Thread Starter
Instructor
Joined: Apr 2009
Posts: 155
Likes: 0
From: South of France
Hi guys,
thanks for the replies.
This is a pic indicating how the measurement is taken.
I know it's in french but basically the green dots are the mics and the car passes at 50hm/h. that's eeuuuh 35miles in third gear. 10 metres before the mic's they floor it.
Problably welding in a tube after the cats with a reduced diameter will reduce the noise as well.
thanks for the replies.
This is a pic indicating how the measurement is taken.
I know it's in french but basically the green dots are the mics and the car passes at 50hm/h. that's eeuuuh 35miles in third gear. 10 metres before the mic's they floor it.
Problably welding in a tube after the cats with a reduced diameter will reduce the noise as well.
Pro
Joined: May 2004
Posts: 551
Likes: 19
From: Morgantown WV
Hi guys,
thanks for the replies.
This is a pic indicating how the measurement is taken.
I know it's in french but basically the green dots are the mics and the car passes at 50hm/h. that's eeuuuh 35miles in third gear. 10 metres before the mic's they floor it.
Problably welding in a tube after the cats with a reduced diameter will reduce the noise as well.
thanks for the replies.
This is a pic indicating how the measurement is taken.
I know it's in french but basically the green dots are the mics and the car passes at 50hm/h. that's eeuuuh 35miles in third gear. 10 metres before the mic's they floor it.
Problably welding in a tube after the cats with a reduced diameter will reduce the noise as well.
Tech Contributor
Joined: Oct 1999
Posts: 41,066
Likes: 9,829
From: Charlotte, NC (formerly Endicott, NY)
Bill
Burning Brakes
Joined: Feb 2005
Posts: 1,201
Likes: 14
From: Honolulu, HI
I tried this in my car yesterday after looking at the diagram you provided and the description of how the test is run. Tach was reading about 2K rpms in third with 50 kph showing on the HUD. Not as much noise as I would have thought. Maybe just adding the stock manifolds and H pipe with stock cats will work. GM must have had to pass this same test when they homologated the Z06 for original sale in France.
Bill
Bill
Le Mans Master
Joined: Sep 2007
Posts: 7,604
Likes: 8
From: Belleville Il
Another idea,,there are several(cherry Bomb comes to mind) that make 3"body straight tube glass pack mufflers. You could place 1 in each side replacing the straight section of the H pipe. this would make a small reduction in the sound level before it gets to the stock mufflers,,enhancing their sound reduction ability. These additional mufflers should not have any impact on performance as well. These should be easy to splice into your system,,not cost much,,and no significant HP loss if any. I've seen them in Jeg's and Summit cheap and are available in several lengths,,should be able to find one to fit with a 2 1/2" inlet/outlet. They have a reasonable sound level when run by themselves,,so placing them upstream from your stock mufflers should make it very quiet!!
