Q: Are Harmful Emissions Reduced by a Car's Exhaust System?

The automobile exhaust system has been around as long as the car itself. The purpose of the original exhaust system was to divert gases from the the combustion process away from the engine and operator. The purpose of today’s exhaust systems is the same but with added tasks.

During combustion, the air and fuel mixture are burned under high pressure and with the aid of a spark plug. This process creates gases that are expelled via the exhaust system. These gases are made up of hydrocarbons, nitrogen, carbon monoxide, nitrogen oxides, and oxygen. Several decades ago, the government realized that some of these gases are quite harmful. They don’t just affect us, but also the planet as a whole through what we now know as the greenhouse effect. This led to stricter emission regulations, which led to the birth of the catalytic converter.

Today’s exhaust systems consists of piping, exhaust manifold (bolted to the cylinder head), muffler, tail pipe, oxygen sensors, and as of 1975, a catalytic converter. The exhaust gases are pushed out of the combustion chamber by the piston through the exhaust manifold. It is then sampled by an oxygen sensor which tells the vehicle’s computer if there was too much or not enough fuel, before going through the catalytic converter. Then it is sampled by yet another oxygen sensor, which is for catalytic monitoring. The next component is the muffler, which minimizes noise, and then it goes out the tailpipe.

As stated earlier, it is in the catalytic converter that emissions are controlled. There two kinds of converters: two-way and three-way converters. Two-way converters have two tasks. One is the oxidation of carbon monoxide to carbon dioxide. The other is the oxidation of hydrocarbons (unburned fuel) to carbon dioxide and water. The three-way does much the same but also controls the emission of oxides of nitrogen (NOx), which is the precursor to acid rain and smog.

It is the catalytic converter (which is part of the exhaust system) that is responsible for reducing harmful emissions. Therefore, if you notice any problems with the catalytic converter, you should have it replaced by a certified mechanic.