Once the fuel and air mixture is ignited and burned in the engine cylinders, there is a residue left of poison gases such as carbon monoxide (a key ingredient of smog). Each cylinder has an exhaust valve for expelling this residue.

A pipe is connected to each of the exhaust valves and these four pipes combine into one pipe. This is known as the exhaust manifold. ("Mani" = many and "fold" = parts, thus manifold literally means "many parts.")

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Catalytic converter

The residue is channeled from here to a piece of machinery known as the catalytic converter. ("Catalytic" means acts as a catalyst. A catalyst is something that speeds up a chemical reaction. In this case the chemical reaction is the converting of the poisonous gases in the exhaust to reduce the level of poisons and harmful chemicals released into the air). The catalytic converter consists of a honeycomb of holes made of platinum and ceramic. When the exhaust hits the catalytic converter some of the poisons are burned off.

Muffler and tailpipe

What is left is passed through the muffler to the tail-pipe and is expelled out the back of the vehicle. By no stretch of the imagination does the catalytic converter entirely take care of the environmental destruction caused by the poisons that are emitted, but it would be worse yet without these converters. When a smog test is done it determines if the catalytic converter is performing to the required standard as set by state and federal regulations. The muffler is simply a box with packing inside that deadens noise. It's just a sort of "silencer" for your car.