Fuel injection is a system for admitting fuel into an internal combustion engine. It has become the primary fuel delivery system used in automotive engines, which replaced carburetors during the 1980s and 1990s. A variety of injection systems have existed since the first use of the 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, while a carburetor relies on suction created by intake air rushing through a venturi to draw the fuel into the airstream.
Modern fuel injection systems are designed specifically for the type of fuel being used. Some systems are designed for multiple grades of fuel (using sensors to adapt the tuning for the fuel currently used). Most fuel injection systems are for gasoline or diesel applications only.
There are a variety of functional objectives for fuel injection systems. Each share the task of supplying fuel to the combustion process, but it is a design decision how a particular system is optimized. There are several competing objectives such as:
- Power output
- Fuel efficiency
- Emissions performance
- Ability to accommodate alternative fuels
- Driveability and smooth operation
- Initial cost
- Maintenance cost
- Diagnostic capability
- Range of environmental operation