Automobile Blog May Archive

• Fuel injection is a means of metering fuel into an internal combustion engine
• The primary difference between carburetors and fuel injection is that fuel injection atomizes the fuel by forcibly pumping it through a small nozzle under high pressure. A carburetor relies on the vacuum created by intake air rushing through it to add the fuel to the airstream
• The objectives for fuel injection systems can vary. All share the central task of supplying fuel to the combustion process, but it is a design decision how a particular system will be optimized
• Here are some of the noted design objectives:
  • power output
  • fuel efficiency
  • emissions performance
  • ability to accommodate alternative fuels
  • durability
  • reliability
  • driveability and smooth operation
  • initial cost
  • maintenance cost
  • diagnostic capability
  • range of environmental operation
  • Engine operation
• Benefits to the driver of a fuel-injected car include smoother and more dependable engine response during quick throttle transitions; easier and more dependable engine starting; better operation at extremely high or low ambient temperatures; reduced maintenance intervals; and increased fuel efficiency
• Emissions, efficiency, and power: Fuel injection generally delivers a more accurate and equal mass of fuel to each cylinder of the engine than can a carburetor, thus improving the cylinder-to-cylinder distribution
• A fuel injected engine often produces more power than an equivalent carbureted engine
• The ultimate combustion goal is to match each molecule of fuel with a corresponding number of molecules of oxygen so that neither has any molecules remaining after combustion in the engine and catalytic converter. Such a balanced condition is known as stoichiometry
• The process of determining the amount of fuel, and its delivery into the engine, are known as fuel metering. Early injection systems used mechanical methods to meter fuel
• The fuel injector acts as the fuel-dispensing nozzle. It injects liquid fuel directly into the engine's air stream
• Prior to 1969, it was rare for a gasoline engine to be equipped with fuel injection, and those few extant systems were generally low-pressure mechanical designs incorporating rather primitive technology
• Central to an EFI system is a computer called the Engine Control Unit (ECU), which monitors engine operating parameters via various sensors
• Throttle-body injection: (called TBI by General Motors and CFI by Ford) was introduced in the mid 1980s as a transition technology toward individual port injection
• Port fuel injection (CPFI): It uses tubes with poppet valves from a central injector to spray fuel at each intake port rather than the central throttle-body