BY-PRODUCTS OF FUEL CHEMICALLY CHANGED TO HEAT ENERGY, EMISSIONS ARE KEPT UNDER TIGHT CONTROL BY TODAY’S SUBARU VEHICLES.
AUTOMOTIVE EMISSIONS ARE A HOT TOPIC. THEY’RE AT THE HEART OF CONVERSATIONS ABOUT EARTH’S OZONE LAYER, ALTERNATIVE FUELS, AND CONTEMPORARY AUTOMOTIVE TECHNOLOGY.
Every stage in the life of a vehicle produces emissions of one type or another. They are produced during manufacturing, utilization, maintenance, and disposal.
However, most people are concerned about emissions that result from an engine’s combustion process.
WHAT HAPPENS INSIDE AN ENGINE
During a gasoline engine’s four-stroke cycle, air is drawn into the cylinders with gasoline during intake, compressed, ignited, and pushed out through the exhaust system.1 That air is composed of nitrogen (79 percent), oxygen (20 percent), and inert gases (1 percent).
During complete combustion of gasoline (a hydrocarbon), oxygen joins with hydrogen to form water. Carbon joins with oxygen to form carbon dioxide (CO2).
Combustion is rarely complete. Contributing factors include uneven engine temperatures and impurities in the fuel. This results in hydrocarbons (HC) and carbon monoxide (CO) entering the exhaust system. Carbon monoxide is poisonous and, along with hydrocarbons, harmful to the atmosphere. The engine’s high pressure and temperatures greater than 2,500 degrees Fahrenheit produce oxides of nitrogen (NOX), which add to air pollution, acid rain, difficult breathing, and lung damage.
Subaru has implemented a number of designs and systems to help reduce emissions – so much so that some Subaru models have available Partial Zero Emission Vehicle (PZEV) engines.