Single point injection

engine design

1. Single point injection system
 This is a system where a single injector or a group of injectors clustered together in one
centralized spot on the intake manifold.
 The throttle unit resembles a carburetor except that there is no fuel bowl float or
metering Jets.
 Fuel is sprayed directly into the throttle bores by the injectors.
Advantages of single point fuel injection
1. Only one fuel injector.
2. The system pressure is not dependant on the intake air pressure.
3. Reduced fuel consumption-there is precise adaptation of engine conditions.
4. Improved performance through greater latitude if the intake tracts.
5. Large distance of heat stressed parts which leads to fewer steam bubbles and a cheaper
delivery pump.
Disadvantage or challenges of single point fuel injection
1. There is time lag since the timing is done by the camshaft when a driver makes sudden
changes.
2. The amount of fuel delivered to the cylinder is not the same for all of them, one cylinder
side receives more fuel than the other due to the engine shape.
Operation
 There is only one electromagnetic fuel injector for all four cylinders
injecting fuel intermittently above the throttle valve.
 The injection amount is controlled by opening or closing of fuel injector.
 Since the supply pressure is low, a simple turbine pump is used which is
more efficient than a roller vane pump.
 The system pressure does not have to be regulated.
 The control unit keeps track of all essential data, speed, load, temperature
of the engine and also the throttle valve angle and position.
Construction
The single point fuel injection is made up of following parts.
 Fuel entrance

2.  Air intake
 NThrottle plate
 Admission
 Injector
 Engine







Some of the sensors used
 Inductive pick up- which determines the position
of the crankshaft and speed of the engine to
calculate injection time.
 Lambda probe-or Oxygen sensor help to
determine if the air fuel ratio of a combustion
engine is richer or lean by measuring oxygen
proportion.
 Temperature sensors
 Throttle potentiometer.