General Question About an Exhaust System

I dont know if this would be the right place to post this question but I have a 92 Park Ave and I wanted to do a Custom True Dual Exhaust with 2 Cats and 2 Glass packs with custom headers. I have done custom exhausts in the past before on friends cars but they didn't care about the inspection stickers. Since I would be putting two cats on a car that originally had one would it still pass a NJ State Inspection for emissions. Any help on this subject would be greatly appreciated.

Actually this is a very specific question about exhaust. :)

IMO there are two separate tests you need to be concerned about. One is visual, in that some states require stock exhausts or aftermarket components that have been manufactured and approved by the state government. If your exhaust does not meet these two criteria, it may fail, even before testing.

Specifically, for older cars like yours, the concern is the placement of the oxygen sensor and the size, placement and type of converter. Changes from stock spec may change how these components work. So long as you keep it all stock to the cat, you can do what you want downstream, including dual mufflers etc.

Obviously the other test is actual function of the system. If you do dual cats, imo the problem will be operating temp. Dual cats might not get as hot as a single, and thus not work as efficiently, causing a failure for CO and hydrocarbons. However, if this is an issue, you could always use some fabric header wrap around the manifolds and downpipes to hold the heat in and keep the cats warm.

I would suggest going to a NJ testing facility and ask them what they look for in terms of visual tests and efficiency. If they do not care about the visuals, you could try building a system and hope it passes.

FWIW I have done many dual exhaust, and single exhausts over the years. IMO a dual system is not necessarily better. It is heavier, tends to rust-out faster, often is noisier, more expensive, and does not always produce more power. These days I find a well-designed single to be just as good as duals.

The Exhaust system on the 92 Park Avenue is quite good and you will not be able to outflow it.. Even the Supercharged 91.5 - 95 3800s could not outflow this exhaust unless pretty well modded..

If you do anything it would be simpler to use a Camaro/Firebird Muffler with the dual outs..