Hey, this isn't a problem question or anything, I just like to learn as much about how automotive things work as possible. While doing some exhaust work the other day me and some buddies ran into a pipe that ran into the cat. If someone could give an explanation on the little pipe that runs into the cat that'd be great!

 

part of the smog pump system. pumps air or other crap into the cat for some reason that makes the EPA happy. you need that if your in a smog check zone.

 

Ohhhh ok, so it just pumps more dirty air into the cat to get cleaned. Thanks a lot man!

 

it pumps clean air (not exhaust) into the cat to make the catalyst do a better job at filtering.

 

In a perfect world with a perfect engine, emission gasses would consists of Nitrogen, C02, and water vapor. But since the combustion process is not perfect, the gases are carbon monoxide, nitrogen oxides, and hydro carbons. This is where your catalytic converter comes into play.

Basically, there are two stages of a catalytic converter. These are the reduction and oxidation stage.

In the reduction stage, Platinum and rhodium reduce emissions.

In the ocidation stage, that small pipe your talking about comes into play. It basically brings air(o2) into the catalytic converter to help burn the hydrocarbons. If you look closely, the pipe also has a one way check valve on it to ensure that gases travel in one direction only. And that is to the catalytic converter. This rules out the chance of exaust gases from coming up the tube and back into the smog pump.

Another good piece of information you should know is that your cat only works at high temperatures only. Hope this helps you out...

 

Thanks a lot! I love learning new stuff, especially parts that aren't usually noticed!