#fartcan

After igniting fuel and burning it to power an engine, the engine needs to get rid of the gases that are left over in the combustion chamber. At the end of the power stroke, the exhaust stroke starts with the exhaust valves opening to allow the burnt fuel to leave and allow room for a new amount of the fuel mixture to enter the chamber in the next intake stroke. After leaving the cylinder the gases enter the exhaust system where the gases would be directed out of the vehicle through various systems to clean up the gases and make the engine operate quieter.

First, the gases leave from the engine and enter from each individual cylinder into the exhaust manifold. The exhaust manifold collects the gases through tubes that are connected to each cylinder and are brought together into usually one pipe where they will enter other systems. After exiting the exhaust manifold there will be an oxygen sensor to check the air/fuel mixture from the engine and see if it is burning too rich or too lean. A lean air/fuel mixture is when there is too much air than the desired ratio of air and fuel. A rich mixture is the opposite of a lean mixture where there is too much fuel than then the desired ratio. The sensor checks if there is a problem like leftover air or if there is none, it then sends data to the engine management system to correct the problem by injecting more or less fuel into the mixture before entering the chamber.

Then the gases enter the catalytic converter where it will eliminate harmful gases. In a three-way catalytic converter, it tries to eliminate nitrogen oxide(NOx) emissions, carbon monoxide(CO) emissions, and hydrocarbon(CxHx) emissions. Inside a catalytic converter, there are two blocks, a reduction catalyst that is made out of platinum and rhodium, and an oxidation catalyst that is made out of platinum and palladium. The gases first pass through the reduction catalyst that is made up of thousands of little micro ducts to maximize surface area. In here the nitrogen oxides are passing through but the bond of the nitrogen with the oxygen isn't as strong as the bond of the nitrogen and the catalyst so the nitrogen is pulled away from the two oxygen molecules and sticks to the catalyst while leaving the two leftover oxygen to bond together or find other oxygen molecules to bond together. The individual nitrogen molecules that are bonded with the catalyst will keep moving and bond with another nitrogen molecule and detach from the catalyst. At the end of the block, there will only be oxygen and nitrogen which are harmless. In the oxidation catalyst, carbon monoxide and oxygen will bond with the catalyst surface. Then the oxygen molecules will separate and bond with the carbon monoxide to create carbon dioxide and the carbon dioxide will have a weaker bond with the catalyst and separate away. The leftover oxygen molecules will then mix with the hydrocarbon emissions to create more carbon dioxide and H2O gases. Overall you are then left with mostly nitrogen(N2), oxygen(O2), carbon dioxide(CO2), and H2O gases. After the catalytic converter, there will be another oxygen sensor to check the efficiency of the converter.

Then there will be a resonator but not all vehicles are equipped with this. A resonator is used to drown out certain engine rpm ranges by breaking up sound wavelengths and bouncing them back onto each other to cancel each other out. In the end, there will be a muffler that reduces noise overall. These are three types of mufflers that are used, a chambered muffler, straight muffler, and a turbo muffler. In a chambered muffler the purpose of it is to cancel out the sounds by splitting the sound then bouncing them off the wall and turning them onto each other. In a turbo muffler, it uses perforated pipes and a sound deadening material to eliminate the noise. The gases just pass through the perforated pipes but the sound goes out of the pipes and into the sound deadening material where it will be eliminated. In a straight muffler, the pipe is also perforated but the materials used around the pipe is steel wool and a fiberglass insulator where the sound is then converted into heat.