Stock Exhaust System

[The Tech]

Here are some more photos of the stock system. This is how the Manifold and Catalytic Converter look as they come off as a unit.



In the pipe that connects the two pieces you can see the bung for the first O2 sensor.



This is the middle section of the system that goes from the Cats back to just behind the rear axle.



Near the front of this section you can see the bung for the second O2 sensor.



Then comes the first resonators or mufflers immediately followed by the crossover box.



Following that is the second set of resonators



And then the OEM connectors for the axle back system followed by the muffler/tailpipe assembly

[Pursuit]

FYI, the first set of "resonators" are actually the secondary catalytic converters, sometimes called "Pup Cats".

Maurice

[The Tech]

That is surprising as there are no sensors following them.

[Pursuit]

Not really, The first set of O2's see AFR and the second set of O2's look at the effeciency of the first set of Cat's and measure Cat temp. The secondary Pup Cat's add to the cleaning effect/catalytic conversion of the exhaust gasses.

Maurice

[ImpalaPPV]

Overall the stock exhaust system looks pretty good. I mean it looks like 2.25" stainless steel. The mufflers look like they are restrictive as do the cats. I think if one was to replace the stock mufflers with aftermarkets (to get a little more growl and flow) and lose the "pup" cats it would make some (economical) performance improvements on a mildly modified car. Add headers and hi-flow cats and I think it would be a noticeable gain. The whole kooks set up is no doubt the clear performer (and it sounds great) if you can afford it. Again for me one downside to a full on kooks system is noise. I want my police car to fit in with the other police cars so that perhaps they won't notice me. lol

[Pursuit]

There are two main restrictions in the stock system. the biggest is in the flex joint just before the mufflers. It narrows down to less than 1-3/4" inside the flex joint and the area up front near the resonator, that both pipes go through, narrows down to 2".

Maurice,

[ImpalaPPV]

I see. That makes it a little more complicated to modify the original set up. I'd have to weld in larger diameter flex joints and replace the first resonator. How big is that first resonator (about)? I was contemplating the feasibility of replacing it with a Dynomax Ultra Flo "X" muffler. But upon examining the pictures of the stock exhaust I don't think it would fit the pipes or the trans/exhaust tunnel. Then again, if I am cutting and welding that much maybe I should just have a shop make me what I want in 2.5". Eh, I should probably get a Caprice before I worry about replacing the exhaust. Here's to wishful thinking.

[leadfart]

You should also be aware, that if you modify the OEM exhaust, ie, louder mufflers, and don't disable AFM, it will sound like crap, switching from 8-4-8. It's pretty annoying.

[ImpalaPPV]

How bad does it sound? I can imagine considering all the muffling they are using...How much does AFM help mileage? My car would ideally be a warmed up daily driver so many mpg would be a factor...

[sardillim]

a little off topic but have you guys noticed how easy it is to remove the transmission?