Most converters I've seen had two seperate sections of honeycomb inside. There was a front honeycomb 'brick' and a rear brick.

I noticed on my maxima (when doing the Warpspeed b-pipe) that it looked like the rear section was gone. I could see a perfect front honeycomb, but just a large empty space toward the rear.

Are the pre-cats in the stock y-pipe the 'front brick' in this system? After installing the WS y-pipe, I did notice that the exhaust was a bit 'stinky' until the car had been run for a LONG time.

Thanks!

 

Here's something I just found on the web...

Most converters produced in recent years contain two monolith "bricks" spaced several inches apart from each other. The washcoat on the forward brick typically contains rhodium which causes nitrogen oxides to break down into nitrogen and oxygen. After passing through the first brick, exhaust gasses pass through an air chamber before entering the second brick. In some converters, known as “oxidation” types, a small tube passes through the chamber and injects air pumped in by an engine-driven “smog pump”. (In some vehicles, the "smog pump" incorporates an electric motor, which reduces accessory drive complexity and also allows for remote mounting.) Injected air simply brings additional oxygen into the exhaust stream to assist in the oxidation process.

It came from the following site...

http://www.hyper-flow.com/technical.htm

Thanks!