buckmeister2

I can buy a 2012 factory Z06 exhaust (mainfolds, downpipes, x-pipe) for a very reasonable price. It looks to be in fine condition.

I have a 2008 base LS3 with an A6 auto. I am curious about what problems I will have installing it. I will use my stock non-NPP muffs and tailpipes.

I don't know if my car came with 2 or 4 cats. I know the 2012 system has 4, correct? What will I have to do to prevent codes from popping up?

Also, how much work will be involved in the install, considering I have the automatic trans? I know I will need a reducer from the x-pipe to my muffler connections...what else?

Need solid answers...thanks for all your help.

Jason.

...

Dcasole

I don't think you will pop any codes as long as all four sensors are hooked up.

But.... the angle of the pipes changed in 2009 and the 3 inch pipe will also need some massaging on the passenger side in order to clear your A6

Muffler shop should be able to make it work but it's not plug and play

Dave

Mike's LS3

The 2008 came with two cats. 2008-09 have a voluntary emissions recall, (mandatory in CA) replacing the existing cats and adding two smaller cats at the mid pipe like 2012+ corvettes. On the recall, the mid pipe cats do not have 02 sensors so the computer does not know they exist, so no codes.

Also, I would recommend two 02 sensor extensions for the front 02 sensors.

96GS#007

As mentioned above, your car came with 2 cats unless the recall was performed. In which case it has 4. Simply looking under the car will tell you what you have.

Other than the need to modify the mid-pipe to go from 3" to 2.5" to mate with your stock mufflers, the system is a true bolt in. If you have access to a lift and are a competent mechanic you can do it in a few hours or less. However, unless you have the tools to add the adapters you may want to take it to the shop. Note....you can install everything and then drive it to the shop sans mufflers and let the shop finish up the install.

The added cats aren't monitored. As long as you retain the existing 4 o2 sensors (1 in front of each primary cat and 1 aft of each primary cat) there will be no issues with codes of the CEL.

For an idea of the work and what the parts look like, search is your friend. My thread here should prove helpful.

RagTop69

OK, I'll show my stupidity. Doesn't putting the 2.5" reducers on the back of the system kind of negate the 3" system from the headers back to the exhaust pipes and will it create a backpressure problem? Just askin'.

ByRiver

If you are going to keep the stock mufflers, you need the reducers. If you are going to get new mufflers, then you won't need the reducers because you will be able to run 3" pipe all the way.

RagTop69

That was my point. If you do the 2.5" reducers you're defeating at least some of the advantage of the 3" Z06 exhaust system. So, whatdya think about the back pressure issue? If you're pumping 3" worth of exhaust down to a 2.5" CAT back, aren't you going to create some backpressure problems that neither a 3" system end to end or a 2.5" system end to end wouldn't experience? Might not be that big a deal, but it could also create gasket problems for the headers and heads. The engine is an air pump and won't operate optimally unless you can feed it air and exhaust air without restrictions.

buckmeister2

That is a good question, and one I also wondered. I did a search here, and elsewhere for the answers. Several things I found stated the following:

1. The 3" piping is used on the Z06 manifolds because it was easier to mate a larger pipe to the larger exhaust flange on the manifolds. Once the larger pipe was used, there was no purpose/sense in necking it down to a smaller pipe. 2. The 2.5" piping is sufficient to flow with no backpressure on any non-supercharged or not-highly-modded LS motor. The use of 3" pipe was chosen for reasons in #1. 3. Once the exhaust passes the cats, and flows as far rearward as the neck-down point, it has cooled enough so that no backpressure is created at the neck-down (not sure about this, but sounded possible). 4. Simply stated "No! Plenty of flow in 2.5" pipes x 2 for no backpressure worries.

For anyone who thinks this topic has been answered repeatedly, and that I am not using the search tools, that is incorrect. There is a lot of info on this site about this particular swap, but none of it addressed the 2010-later Z06 manifolds going into a 2008 A6 car. Also, there was no clear statement that the swaps cited were done before or after the 4-cat emission recall work. My car has not had the additional cats installed, and I will wait until after this swap is completed to consider that.

BTW....anyone who has had the recall cats installed, I would like to know if you feel there are any performance differences before vs. after the recall work.


thank you to everyone for your helpful answers.

Jim

Turbo6TA

Best answer yet .....

RagTop69

Thanks for the answer to the backpressure question I asked. As regards your questions above my answers are #1 yes and #2 no.