Exhaust

The last stroke of the Internal Combustion Engine is known as the Exhaust stroke, or "blow".  This is where the products of the chemical reaction are excreted from the system as a waste and blown out of the cylinder. It will go through a few processes to reduce its environmental impact such as going through the catalytic converter.  In 1975 the EPA required all cars to have a catalytic converter to reduce emissions by 75%. Previously, vehicles were releasing hydrocarbons and harmful carbon monoxides, damaging the environment and creating smog, leading to acid rains.  The Catalytic Converter basically consists of a simple redox reaction to convert the harmful molecules into less harmful molecules. using Palladium, Platinum, or some other metals.