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Automotive Emissions and Onboard Diagnostics

by John West & Mark Stachew

Start ý Why Onboard Diagnostics? ý Major Components ý Catalytic Converter ý Oxygen Sensor ý EGR ý Fuel System Adaptive Learning ý Misfire Detection ý The Need for Speed ý New Regulations ý 0 to 100 KB in 6 Seconds ý Sources and PDF

Automobile emissions have a great effect on our environment, contributing to air pollution problems such as global warming, smog, ozone depletion, and acid rain. Gasoline and diesel fuels are mixtures of hydrocarbons. In an ideal engine, oxygen in the air would convert all the hydrogen in the fuel to water and all the carbon in the fuel to carbon dioxide. Nitrogen in the air would remain unchanged. However, in a real engine, fuel is not pure and combustion is not perfect, therefore automotive engines emit several types of pollutants.

Typical engines convert the hydrocarbons and air into carbon monoxide (CO), unburned hydrocarbons (HC), nitrogen oxides (NOx), sulfur dioxide (SO₂), carbon dioxide (CO₂), and water (H₂0), just to name a few. These products of real combustion affect the environment in many ways. Carbon monoxide reduces the flow of oxygen in the bloodstream, unburned hydrocarbons react in the presence of nitrogen oxides to form ground-level ozone, and nitrogen oxides and sulfur dioxides contribute to the formation of acid rain and smog. Even carbon dioxide, while a product of perfect combustion, is a greenhouse gas and contributes to global warming.

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