The document describes the operation of fuel injection systems. It explains that fuel is atomized when it is pressurized and turned into a vapor in the injector, allowing it to burn easily. It discusses single-point and multi-point injection systems, noting advantages like easier control for single-point but better fuel burning for multi-point. Multi-point systems use individual injectors for each cylinder near the inlet valve for precise control of air-fuel ratio and emissions compliance.

1. Aims and Objectives
Aim
•To be able to describe the operation of an injection system within an internal combustion engine
Objectives
•Be able to describe the operation of an injection system within an internal combustion engine
•Be able to recognize a single point injection system and a multi-point injection system
•Identify how fuel and air is atomized within a fuel injection system
Fuel Injection Systems

2. The role of the Injectors
The injector delivers a finely atomized spray of fuel
into the inlet port
The injectors also vary the amount of fuel delivered to
suit the engines conditions
The spray is obtained by passing fuel (that is
pressurised) through the nozzle of the injector
It is located in the inlet manifold near the cylinder
head intake port
Fuel Injection Systems

3. Injectors
The opening of the injector is controlled by the vehicles ECU
The injector is supplied with the battery voltage via a relay, the earth circuit is controlled by
the ECU
When the circuit is completed by the ECU a solenoid operates, the injector valve opens, fuel
is then able to be sprayed into the inlet manifold
The valve moves roughly 1.5-10 milliseconds. This is known an injector duration or opening
time
The ECU will make amendments to the duration depending on engine temperature, loading air
temperature and battery voltage
Fuel Injection Systems

4. Fuel Atomisation
During fuelling of a cylinder the fuel is pressurised
which causes the fuel to become a vapour, allowing it
to burn easily (compared to the fuel being delivered to
the cylinder in liquid form)
Fuel Injection Systems

5. Question
How is fuel atomized in injector fuelling systems?
Fuel Injection Systems

6. Simultaneously and Sequential
Simultaneous injectors will operate all (or groups of injectors) at the same time
Sequential will operate independently and open at close at different times (determined by
the ECU)
Fuel Injection Systems

7. Single point injection system
Single point injection or throttle body injection system uses a single injector to spray fuel in
the air intake side of the throttle butterfly (where the carburettor is situated)
Fuel Injection Systems

8. Single point injection system
Fuel Injection Systems
Gives poor atomization of the fuel
Does not give precise control of the
air/fuel ratio to meet emission regulations
However, it is easier to control
electronically than a carburettor
The fuel pressure is less then that of a
multi point injection system (usually 1 bar)

9. Multi point injection system
Individual injectors are used for each cylinder
An injector is positioned near the inlet valve of
each cylinder
This system was originally used on diesel engines
but is also now widely used on petrol engines
Fuel Injection Systems

10. Multi point injection system
The multi point injection system is the most common type of fuelling system that is used on
modern vehicles today
This is mainly due to the fact that this injection system can be controlled easily by the
vehicles ECU
Furthermore, this type of fuelling system provides a better method of burning the fuel
without much wastage. Compared with other fuelling systems
Fuel Injection Systems

11. Question
Name three advantageous of a single point injection system ?
Name three advantageous of a multi-point injection system ?
Fuel Injection Systems

12. Types of injectors
Pintle Type Injector
Original injector design
Offers good atomization of fuel
Prone to deposit build up on the Pintle valve (deposits can reduce the
amount of fuel flow, and therefore the vehicle will run leaner than
recommended
Fuel Injection Systems

13. Hole type injector
Was introduced on later engine models, initially to reduce the reduce
concerns with injector deposits
Fuel is delivered through holes drilled in a director plate at the injector
tip.
Offers good fuel atomization and gives better resistance to deposit
build-up.
Fuel Injection Systems

14. High and low resistance injector windings
Two different types of injector windings are used
This is dependant on the type of drive circuit used,
And is also dependant of weather an external resistor is being used.
Fuel Injection Systems
Low resistance injector windings
Range between 2-3Ώ at 21.1 ◦C
Used with an external resistor in a voltage
controlled circuit
High Resistance circuits
Range around 13.8Ώ at 21.1 ◦C
Do not require the use of an external
resistor in a voltage controlled driver
circuit.

15. Question
What resistance should you expect a high resistance circuit to operate at ?
Fuel Injection Systems

16. Injector driver circuits
Fuel Injection Systems

17. Summary – have we ?
Fuel Injection Systems
Been able to describe the operation of an injection system within an internal
combustion engine
Been able to recognize a single point injection system and a multi-point injection
system
Identified how fuel and air is atomized within a fuel injection system