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Aims and ObjectivesAim
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 engineBe able to recognize a single point injection system and a multi-point injection systemIdentify how fuel and air is atomized within a fuel injection systemFuel Injection Systems
The role of the InjectorsThe 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
InjectorsThe 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
Fuel AtomisationDuring 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
QuestionHow is fuel atomized in injector fuelling systems?
Fuel Injection Systems
Simultaneously and SequentialSimultaneous injectors will operate all (or groups of injectors) at the same timeSequential will operate independently and open at close at different times (determined by the ECU) Fuel Injection Systems
Single point injection systemSingle 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
Single point injection systemFuel Injection SystemsGives 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)
Multi point injection systemIndividual 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
Multi point injection systemThe 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
QuestionName three advantageous of a single point injection system ?
Name three advantageous of a multi-point injection system ?
Fuel Injection Systems
Types of injectorsPintle 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
Hole type injectorWas introduced on later engine models, initially to reduce the reduce concerns with injector depositsFuel 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
High and low resistance injector windingsTwo different types of injector windings are usedThis is dependant on the type of drive circuit used,And is also dependant of weather an external resistor is being used.
Fuel Injection SystemsLow resistance injector windings
Range between 2-3 at 21.1 C
Used with an external resistor in a voltage controlled circuit
High Resistance circuits
Range around 13.8 at 21.1 C
Do not require the use of an external resistor in a voltage controlled driver circuit.
QuestionWhat resistance should you expect a high resistance circuit to operate at ?
Fuel Injection Systems
Injector driver circuitsFuel Injection Systems
Summary have we ?Fuel Injection SystemsBeen 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