Why does different types of engines i.e. petrol/diesel produce different exhaust emissions?
Both diesel and gasoline contain only carbon and hydrogen. They each do produce H2O and CO2 on burning. There is about a much greater compression ratio between the 2. A diesel must be above a 22 to 1 ratio. A gas can be from 6 to 10 to 1. The compression of the air causes the nitrogen and the oxygen in the air to combine causing nitrous and nitric oxides such as found in smog. Partially burned hydrocarbons are found in gas engines. Unburned carbon more often in a diesel. Each can make carbon monoxide because of a shortage of oxygen in the cylinders. A properly tuned diesel will not have the black smoke of carbon particles. The catalytic converter on a gas engine tries to burn more of the partially burned hydrocarbons which also contribute to smog.
